LIBRARY     OF 


1685-1056 


AN  INTRODUCTION  TO  ENTOMOLOGY 


AN 


INTRODUCTION 


TO 


ENTOMOLOGY 


BY 

JOHN   HENRY    COMSTOCK 

PROFESSOR    OF    ENTOMOLOGY    AND    GENERAL    INVERTEBRATE 
ZOOLOGY,  EMERITUS,   IN    CORNELL    UNIVERSITY 


FIRST  COMPLETE  EDITION 
THIRD  EDITION  OF  PART  I 


ITHACA,  N.  Y. 

THE   COMSTOCK   PUBLISHING   CO. 

1920 


COPYRIGHT  1920 

BY 

THE  COMSTOCK  PUBLISHING  CO. 


COPYRIGHT  1924 

BY 

J.  H.  COMSTOCK 


PRESS  OF 

W.  F.  HUMPHREY.  GENEVA.  N.  Y. 

PRINTED  IN  U.  S.  A. 


TO 

MY  OLD  STUDENTS 

"WHOSE  YOUTHFUL  ENTHUSIASM  WAS  A  CONSTANT  INSPIRATION  DURING 
THE  LONG  PERIOD  OF  MY  SERVICE  AS  A  TEACHER  THIS  EFFORT 
TO  CONTINUE  TO  AID  THEM  IS  AFFECTIONATELY 
INSCRIBED 


PREFACE 

IT  IS  now  nearly  thirty  years  since  "A  Manual  for  the  Study  of 
Insects,"  in  the  preparation  of  which  I  was  aided  by  Mrs.  Corn- 
stock,  was  published.  The  great  advances  in  the  science  of  ento- 
mology during  this  period  have  made  a  revision  of  that  work  desirable- 
In  the  revision  of  the  "Manual"  so  many  changes  and  additions  have 
been  foimd  necessary  that  the  result  is  a  book  differing  greatly  from 
the  original  work;  for  this  reason,  it  is  published  imder  a  different 
title.  The  title  selected  is  that  of  an  earlier  work,  an  "Introduction 
to  Entomology"  published  in  1888  and  long  out  of  print. 

Part  I  of  the  present  volume  was  published  separately  in  19 19,  in 
order  that  it  might  be  available  for  the  use  of  classes  in  insect  mor- 
phology and  also  that  an  opportunity  might  be  offered  for  the  sugges- 
tion of  desirable  changes  to  be  made  before  the  incorporation  of  it  in 
the  completed  work.  Such  suggestions  have  been  received,  with  the 
result  that  some  very  important  changes  have  been  made  in  the  text. 
In  the  preparation  of  this  work  I  have  received  much  help  from 
my  colleagues  in  the  entomological  department  of  Cornell  University, 
for  which  I  wish  to  make  grateful  acknowledgment,  and  especially 
to  Dr.  J.  G.  Needham  for  aid  in  the  study  of  win-g-venation,  to  Dr. 
O.  A.  Johannsen  for  help  in  the  preparation  of  the  chapter  on  tfee 
Diptera,  to  Dr.  W.  T.  M.  Forbes  for  help  in  the  preparation  of  the 
chapter  on  the  Lepidoptera,  to  Dr.  J.  C.  Bradley  for  help  in  the  prep- 
aration of  the  chapter  on  the  H\TTLenoptera,  and  to  Dr.  J.  T.  Llovd 
for  the  use  of  his  figures  of  the  cases  of  caddice  worms. 

From  the  published  works  of  Professors  Herrick,  Crosby  and 
Slingerland,  Crosby  and  Leonard,  Sanderson,  and  Matheson  I  have 
gleaned  much  information;  references  to  these  and  to  the  more  im- 
portant of  the  other  sources  from  which  material  has  been  drawn  are 
indicated  in  the  text  and  in  the  bibliography  at  the  end  of  the  volimie. 
References  to  the  bibliography  are  made  in  the  text  by  citing  the 
name  of  the  author  and  the  year  in  which  the  paper  quoted  was 
published. 

The  wood  cuts  used  in  the  text  were  engraved  from  nature  by 
Mrs.  Anna  B.  Comstock  for  our  joint  work,  "A  Manual  for  the  Study 
of  Insects."  The  other  original  figures  and  the  copies  of  published 
figures  were  drawn  by  Miss  Anna  C.  Stryke,  Miss  Ellen  Edmonsor, 
Miss  Mary  McKeel,  Mr.  Albert  Force,  Mrs.  Louise  Nash,  and  Miss 
E.  L.  Keyes.  I  am  deeply  indebted  to  each  of  these  artists  for  the 
painstaking  care  shown  in  their  work. 


As  an  aid  to  the  pronunciation  of  the  technical  terms  used  and 
of  the  Latin  names  of  insects,  the  accented  sjdlable  is  marked  with  a 
sign  indicating  the  quahty  of  the  vowel  according  to  the  English  sj-s- 
tem  of  pronouncing  Latin. 

Two  objects  have  been  kept  constantly  in  mind  in  the  preparation 
of  this  book:  first,  to  aid  the  student  in  laying  a  firm  fotmdation  for 
his  entomological  studies;  and  second,  to  make  available,  so  far  as 
possible  in  the  limited  space  of  a  handbook,  a  knowledge  of  the  varied 
phenomena  of  the  insect  world.  It  is  hoped  that  those  who  use  this 
book  will  find  delight  in  acquiring  a  more  intimate  acquaintance  with 
these  phenomena. 

John  Henry  Comstock 
Entomological  Department 

Cornell  University 
August  ig24 


TABLE    OF    CONTENTS 

PART  I.     THE  STRUCTURE  AND  METAMORPHOSIS 
OF  INSECTS 

CHAPTER  I 

Pages 

The  Characteristics  of  Insects  and  Their  Near  Relatives i 

Phylum  Arthropoda i 

List  of  the  classes  of  the  Arthropoda 2 

Table  of  the  classes  of  the  Arthropoda 3 

Class  Onychophora 4 

Class  Crustacea 6 

•    Class  Palaeostracha 8 

Class  Arachnida 9 

Class  Pycnogonida 10 

Class  Tardigrada 12 

Class  Pentastomida 14 

Class  Diplopoda 15 

Class  Pauropoda 14 

Class  Chilopoda 28 

Class  Symphyla 23 

Class  Myrientomata 26 

Class  Hexapoda 20 


CHAPTER  II 

The  External  Anatomy  of  Insects 29 

I.   the  structure  of  THE  body- WALL 

a.     The  three  layers  of  the  body- wall 29 

The  hypodermis 29 

The  trichogens 30 

The  cuticula 30 

Chitin  30 

Chitinized  and  non-chitinized   cuticula 30 

The  epidermis  and  the  dermis 31 

The  basement  membrane 31 

h.     The  external  apophyses  of  the  cuticula 31 

The  cuticular  nodules 3^ 

The  fixed  hairs ^  3^ 

The  spines 32 

c.     The  appendages  of  the  cuticula 32 

The  spurs 32 


TABLE   OF   CONTENTS 

The  setae ,2 

The  taxonomic  value  of  setae ,^ 

A  classification  of  setae ■,■, 

(1)  The  clothing  hairs ^3 

(2)  The  glandular  hairs -jj 

(3)  The  sense-hairs jj 

The  segmentation  of  the  body ,4 

The  body-segments,  somites  or  metameres ^4 

The  transverse  conjunctiva 34 

The  segmentation  of  the  appendages 34 

The  divisions  of  a  body-segment 34 

The  tergum,  the  pleura,  and  the  sternum , 34 

The  lateral  conjunctivae 35 

The  sclerites 35 

The  sutures 35 

The  median  sutures 35 

The  pilif erous  tubercles  of  larvae 35 

The  homologizing  of  sclerites 35 

The  regions  of  the  body 36 


2.      THE  HEAD 

The  corneas  of  the  eyes 36 

The  corneas  of  the  compound  eyes 36 

The  corneas  of  the  ocelli 37 

The  areas  of  the  surface  of  the  head 37 

The  front 37 

The  clypeus ^',8 

The  labrum 38 

The  epicranium 38 

The  vertex 39 

The  occiput 39 

The  genae 39 

The  postgenae 39 

The  gula 39 

The  ocular  sclerites 39 

The  antennal  sclerites 39 

The  trochantin  of  the  mandible 40 

The  maxillary  pleurites 40 

The  cervical  sclerites 40 

The  appendages  of  the  head 40 

The  antennae 40 

The  mouth-parts 42 

The  labrum 42 

The  mandibles 42 

The  maxillalae 42 

The  maxillae : ; 42 

The  labium  or  second  maxillae 45 


TABLE   OF   CONTENTS  xi 

The  epipharynx 46 

The  hypopharynx 47 

d.     The  segments  of  the  head 47 

3.      THE  THORAX 

a.     The  segments  of  the  thorax 48 

The  prothorax,  mesothorax,  and  metathorax 48 

The  alitrunk 49 

The  propodeum  or  the  median  segment 49 

h.     The  sclerites  of  a  thoracic  segment 49 

The  sclerites  of  a  tergum 49 

The  notum 49 

The  postnotum  or  the  postscutellum 50 

The  divisions  of  the  notum 50 

The  patagia 50 

The  parapsides 5^ 

The  sclerites  of  the  pleura 51 

The  episternum 51 

The  epimerum 5^ 

The  preepisternum 51 

The  paraptera 5^ 

The  spiracles 52 

The  peritremes 52 

The  acetabula 52 

The  sclerites  of  a  sternum 52 

c.  The  articular  sclerites  of  the  appendages 53 

The  articular  sclerites  of  the  legs 53 

The  trochantin 53 

The  antecoxal  piece 54 

The  second  antecoxal  piece 54 

The  articular  sclerites  of  the  wings 54 

The  tegula 54 

The  axillaries 54 

d.  The  appendages  of  the  thorax 55 

The  legs 56 

The  coxa 56 

The  styli 56 

The  trochanter 57 

The  femur 57 

The  tibia 57 

The  tarsus 57 

The  wings 58 

The  different  types  of  wings 59 

The  margins  of  wings 60 

The  angles  of  wings 60 

The  axillary  cord 60 

The  axillary  membrane 60 

The  alula 60 

The  axillary  excision 61 


TABLE    OF   CONTENTS 

The  posterior  lobe 6i 

The  methods  of  uniting  the  two  wings  of  each  side 6i 

The  hamuli 6i 

The  frenulum  and  the  frenulum  hook     6i 

The  jugum 6i 

Thefibula 62 

The  hypothetical  type  of  the  primitive  wing- venation 62 

Longitudinal  veins  and  cross- veins 64 

The  principal  wing- veins .- 64 

The  chief  branches  of  the  wing- veins 64 

The  veins  of  the  anal  area 65 

The  reduction  of  the  number  of  the  wing- veins 65 

Serial  veins 67 

The  increase  of  the  number  of  the  wing- veins 68 

The  accessory  veins 68 

The  intercalary  veins 69 

The  adventitious  veins 70 

The  anastomosis  of  veins 70 

The  named  cross-veins 71 

The  arculus 72 

Theterminologyof  the  cells  of  the  wing 72 

The  corrugations  of  the  wings 73 

Convex  and  concave  veins 73 

The  furrows  of  the  wing 73 

The  bullae 74 

The  ambient  vein 74 

The  humeral  veins 74 

The  pterostigma  or  stigma 74 

The  epiplurae 74 

The  discal  cell  and  the  discal  vein 74 

The  anal  area  and  the  preanal  area  of  the  wing 75 


4.       THE  ABDOMEN 75 

a.  The  segments  of  the  abdomen 75 

b.  The  appendages  of  the  abdomen 7^ 

The  styli  or  vestigial  legs  of  certain  Thysanura 76 

The  collophore  of  the  Collembola 76 

The  spring  of  the  Collembola 76 

ThegenitaUa 7^ 

The  cerci 77 

The  median  caudal  filament 7^ 

The  prolegs  of  larvae 7^ 


5.      THE  MUSIC  AND  THE  MUSICAL  ORGANS  OF  INSECTS 78 

a.  Sounds  produced  by  striking  objects  outside  of  the  body 79 

b.  The  music  of  flight 80 


TABLE  OF  CONTENTS                            .  xiii 

c.      Stridulating  organs  of  the  rasping  type 8i 

The  stridulating  organs  of  the  Locustidae 82 

The  stridulating  organs  of  the  Gryllidae  and  the  Tettigoniidie 83 

Rasping  organs  of  other  than  orthopterous  insects ; .  87 

d.  The  musical  organs  of  a  cicada 89 

e.  The  spiracular  musical  organs 91 

/.     The  acute  buzzing  of  flies  and  bees 91 

g.     Musical  notation  of  the  songs  of  insects 92 

h.     Insect  choruses ^3 


CHAPTER  III 
The  Internal  Anatomy  of  Insects 94 


I.   THE  HYPODERMAL  STRUCTURES. 


The  internal  skeleton 

Sources  of  the  internal  skeleton . 


95 

Chitinized  tendons 95 

Invaginations  ofthe  body- wall  or  apodemes 95 

The  tentorium 06 

The  posterior  arms  of  the  tentorium 96 

The  anterior  arms  of  the  tentorium 97 

The  dorsal  arms  of  the  tentorium 97 

The  frontal  plate  of  the  tentorium 97 

The  endothorax 97 

The  pragmas 97 

The  lateral  apodemes 98 

The  furcae 98 

b.     The  hypodermal  glands 98 

The  molting-fluid  glands 99 

Glands  connected  with  setse 99 

Venomous  setas  and  spines 100 

Androconia 100 

The  specific  scent-glands  of  females 100 

Tenent  hairs 1 00 

The  osmeteria 1 01 

Glands  opening  on  the  surface  of  the  body 102 

Wax-glands 102 

Froth-glands  of  spittle  insects 102 

Stink-glands 102 

The  cephalic  silk-glands 103 

The  salivary  glands ' 104 


2.      THE  MUSCLES. 


104 


3.      THE  ALIMENTARY  CANAL  AND  ITS  APPENDAGES I07 

The  more  general  features 107 

The  principal  divisions 108 

Imperforate  intestines  in  the  larvae  of  certain  insects 1 08 


TABLE   OF   CONTENTS 

b.  The  fore-intestine I09 

The  layers  of  the  fore-intestine 109 

The  intima log 

The  epithelium 109 

The  basement  membrane 109 

The  longitudinal  muscles 109 

The  cirailar  muscles 109 

The  peritoneal  membrane    109 

The  regions  of  the  fore-intestine 109 

The  pharynx 109 

The  oesophagus i  to 

The  crop 110 

The  proventriculus no 

The  oesophageal  valve 1 1 1 

c.  The  mid-intestine in 

The  layers  of  the  mid-intestine in 

The  epithelium 112 

Theperitrophic  membrane 112 

d.  The  hind-intestine 112 

The  layers  of  the  hind-intestine 112 

The  regions  of  the  hind-intestine lip, 

The  Malpighian  vessels 113 

The  Malpighian  vessels  as  silk-glands 113 

The  caecum 113 

The  anus '. 113 

4.      THE  RESPIRATORY  SYSTEM 1 13 

a.  The  open  or  holopneustic  type  of  respiratory  organs 114 

1.  The  spiracles 114 

The  position  of  the  spiracles 114 

The  number  of  spiracles 114 

Terms  indicating  the  distribution  of  the  spiracles 115 

The  structure  of  spiracles 116 

The  closing  apparatus  of  the  tracheae 116 

2.  The  trachecB 116 

The  structure  of  the  tracheae 117 

J.     The  tracheoles 118 

4.     The  air-sacs 118 

5.     Modifications  of  the  open  type  of  respiratory  organs 119 

b.  The  closed  or  apneustic  type  of  respiratory  organs 119 

I.     The  Tracheal  gills 119 

2.     Respiration  of  parasites 120 

J.     The  blood-gills 120 


TABLE   OF   CONTENTS  xv 

5.      THE  CIRCULATORY  SYSTEM 121 

The  general  features  of  the  circulatory  system 121 

The  heart 121 

The  pulsations  of  the  heart 122 

The  aorta 122 

The  circulation  of  the  blood 122 

Accessory  circulatory  organs 122 

6.      THE  BLOOD 122 

7.      THE  ADIPOSE  TISSUE I23 

8.      THE  NERVOUS  SYSTEM I23 

a.  The  central  nervous  system 123 

b.  The  oesophageal  sympathetic  nervous  system 125 

c.  The  ventral  sympathetic  nervous  system 127 

d.  The  peripheral  sensory  nervous  system 128 

9.      GENERALIZATIONS  REGARDING  THE  SENSE-ORGANS  OF  INSECTS.  .  129 

A  classification  of  the  sense-organs 129 

The  caticular  part  of  the  sense-organs 130 

10.   THE  ORGANS  OF  TOUCH I3I 

II.   THE  ORGANS  OF  TASTE  AND  SMELL I32 

12.   THE  ORGANS  OF  SIGHT I34 

o.     The  general  features 134 

The  two  types  of  eyes 134 

The  distinction  between  ocelli  and  compound  eyes 134 

The  absence  of  compound  eyes  in  most  of  the  Apterygota 135 

The  absence  of  compound  eyes  in  larvae 135 

b.  The  ocelli 135 

The  primary  ocelli 135 

The  adaptive  ocelli 136 

The  structure  of  a  visual  cell 137 

The  structure  of  a  primary  ocellus 137 

Ocelli  of  Ephemerida 139 

c.  The  compound  eyes 139 

The  physiology  of  compound  eyes   141 

The  theory  of  mosaic  vision 141 

Day-eyes    142- 

Night-eyes  143- 

Eyes  with  double  function I43. 

Divided  eyes 144- 

The  tapetum 144- 


TABLE   OF   CONTENTS 

13.      THE  Or^CANS  01"  IIEARI.NG I_|^- 

a.     The  general  features j  ,- 

The  tympana i  , - 

The chordotonal organs i  ,- 

The  scolopale  and  the  scolopophore j  ,5 

The  integumental  and  the  subintegumental  scolopophores 146 

The  structure  of  a  scolopophore j_,5 

The  structure  of  a  scolopale i ,  y 

The  simpler  forms  of  chordotonal  organs 14-- 

The  chordotonal  ligament i  ly 

i.     The  chordotonal  organs  of  larvs , 148 

c.  The  chordotonal  organs  of  the  Looustidas 148 

d.  The  chordotonal  organs  of  the  Tettigoniidee  and  of  the  Gryllidae. .  149 

The  trachea  of  the  leg 1 50 

The  spaces  of  the  leg 151 

The  supra-tympanal  or  subgenual  organ 151 

The  intermediate  organ 1 52 

Siebold's  organ  or  the  crista  acustica 1 52 

e.  Johnston's  organ 152 


14.       SENSE-OKGANS  OF  UNKNOWN  FUNCTIONS 

The  sense-domes  or  the  olfactory  pores 154 

15.      THE  REPRODUCTIVE  ORGANS 

The  general  features 156 

Secondary  sexual  characters 157 

The  reproductive  organs  of  the  female 157 

The  general  features  of  the  ovary 157 

The  wall  of  an  ovarian  tube 158 

The  zones  of  an  ovarian  tube 158 

The  contents  of  an  ovarian  tube 158 

The  egg-follicles 158 

The  functions  of  the  follicular  epithelium 1 59 

The  ligament  of  the  ovary 1 59 

The  oviduct 159 

The   egg-calyx 1 59 

The  vagina 1 59 

The  spermatheca , .  1 59 

The  bursa  copulatrix i59 

The  coUeterial  glands 160 

The  reproductive  organs  of  the  male 160 

The  general  features  of  the  testes 160 

The  structure  of  a  testicular  follicle 161 

The  spermatophores 162 

Other  structures 162 


TABLE   OF   CONTENTS  xvii 

l6.      THE  SUSPENSORIA  OF  THE  VISCERA 

The  dorsal  diaphragm 162 

The  ventral  diaphragm 163 

The  thread-like  suspensoria  of  the  viscera 163 

17.      SUPPLEMENTARY  DEFINITIONS 

The  oenocytes 163 

The  pericardial  cells 164 

The  phagocytic  organs 164 

The  light-organs 165 

CHAPTER  IV 

The  Metamorphosis  of  Insects 166 

i.    the  external  characteristics  of  the  metamorphosis  of  insects 

c.     The  egg 166 

The  shape  of  the  egg 167 

The  sculpture  of  the  shell 167 

The  microphyle 167 

The  number  of  eggs  produced  by  insects 168 

Modes  of  laying  eggs 168 

Duration  of  the  egg-state 170 

b.  The  hatching  of  young  insects 171 

The  hatching  spines 171 

c.  The  molting  of  insects 171 

General  features  of  the  molting  of  insects 171 

The  molting  fluid 172 

The  number  of  postembryonic  molts 172 

Stadia 172 

Instars 172 

Head  measurements  of  larvae 173 

The  reproduction  of  lost  limbs 173 

d.  Development  without  metamorphosis 174 

The  Ametabola 174 

e.  Gradual  metamorphosis 175 

The  Paurometabola 176 

The  term  nymph 176 

Deviations  fi  om  the  usual  type 176 

The  Saltitorial  Orthoptera 177 

The  Cicadas • 177 

The  Coccidge , 177 

The  Aleyrodidae 177 

The  Aphididae 177 

The  Thysanoptera 177 

f.  Incomplete  metamorphosis 178 

The  Hemimetabola 179 

The  term  naiad 179 

Deviations  from  the  usual  type 1 80 

The  Odonata 180 

The  Ephemerida 180 


i  TABLE   OF  CONTENTS 

g.     Complete  metamorphosis i8o 

The  Holometabola l8o 

The  term  larva i8o 

Theadapth'e  characteristics  of  larvae iSi 

The  different  types  of  larvae 183 

The  prepupa 185 

The  pupa 186 

The  chrysalis 186 

Active  pupae 187 

The  cremaster 187 

The  cocoon 188 

Modes  of  escape  from  the  cocoon , .  188 

The  puparium 190 

Modes  of  escape  from  the  puparium   190 

The  different  types  of  pups 190 

The  imago 191 

h.    Hyper  metamorphosis 191 

i.     Viviparous  insects 191 

\^iviparity  with  parthenogenetic  reproduction 192 

Viviparity  with  sexual  reproduction 193 

j.     Neoteinia I94 

2.      THE  DEVELOPMENT  OF  APPENDAGES I94 

a.  The  development  of  wings I95 

Thedevelopmentof  the  wings  of  nymphs  and  naiads 195 

The  development  of  the  wings  in  insects  with  a  complete  meta- 
morphosis    195 

b.  The  development  of  legs I97 

The  development  of  the  legs  of  nymphs  and  naiads 198 

The  development  of  the  legs  in  insects  with  a  complete  meta- 
morphosis    198 

c.  The  development  of  antennae I99 

d.  The  development  of  mouth-parts 200 

e.  The  development  of  the  gential  appendages 201 

3.  the  development  of  the  head  in  the  muscid^ 202 

4.  the  transformation  of  the  internal  organs 2o4 

Bibliography ' 206 

Index 213 


TABLE  OF  CONTENTS 


PART  II.    THE  CLASSIFICATION  AND  THE 
LIFE-HISTORIES  OF  INSECTS 

Chapter  V. — The  sub-classes  and  the  orders  of  the  class  Hexapoda  .  2og 

Chapter  VI. — Order  Thysanura 2  20 

Chapter  VII.— Order  Collembola 225 

Chapter         VIII. — Order  Orthoptera 230 

Chapter  IX. — Order  Zoraptera 270 

Chapter  X. — Order  Isoptera 273 

Chapter  XL — Order  Neuroptera 281 

Chapter  XII. — Order  Ephemerida 308 

Chapter        XIII. — Order  Odonata 314 

Chapter         XIV. — Order  Plecoptera 325 

Chapter  XV. — Order  Corrodentia 331 

Chapter         XVI.— Order  Mallophaga   335 

Chapter       XVII. — Order  Embiidina 338 

Chapter      XVIII. — Order  Thysanoptera    341 

Chapter        XIX. — Order  Anoplura 347 

Chapter  XX. — Order  Hemiptera 350 

Chapter         XXI. — Order  Homoptera 394 

Chapter       XXII. — Order  Dermaptera 460 

Chapter     XXIII. — Order  Coleoptera 464 

Chapter      XXIV. — Order  Strepsiptera 546 

Chapter       XXV. — Order  Mecoptera 550 

Chapter      XXVI. — Order  Trichoptera 555- 

Chapter   XXVII. — Order  Lepidoptera 571 

Chapter  XXVIIL— Order  Diptera 773 

Chapter     XXIX. — Order  Siphonaptera 877 

Chapter       XXX. — Order  Hymenoptera S84 

BibHography 991 


PART  I 

THE  STRUCTURE  AND  METAMORPHOSIS 
OF  INSECTS 


CHAPTER   I 


THE    CHARACTERISTICS  OF  INSECTS  AND   OF  THEIR 
NEAR  RELATIVES 

Phylum  ARTHROPODA 
The  Arthropods 

If  an  insect,  a  scorpion,  a  centipede,  or  a  lobster  be  examined, 
the  body  will  be  found  to  be  composed  of  a  series  of  more  or  less 
similar  rings  or  segments  joined  together;    and  some  of  these  seg- 
ments will  be  found  to  bear  jointed  legs  (Fig.  i ) .     All  animals  possess- 
ing these  characteristics  are  classed  together 
as  the  Arthropoda,  one  of  the  chief  divisions  or 
phyla  of  the  animal  kingdom. 

A  similar  segmented  form  of  body  is  found 
among  worms;  but  these  are  distinguished 
from  the  Arthropoda  by  the  absence  of  legs. 
It  should  be  remembered  that  many  animals 
commonly  called  worms,  as  the  tomato-worm, 
the  cabbage-worm,  and  others,  are  not  true 
1'  ^r^  I  worms,  but  are  the  larvae  of  insects  (Fig.  2). 

■f      ^^/  '^^^  angle-worm  is  the  most  familiar  example 

of  a.  true  worm. 

In  the  case  of  certain  arthropods  the  dis- 
tinctive characteristics  of  the  phylum  are 
not  evident  from  a  cursory  examination. 
This  may  be  due  to  a  very  generalized  condi- 
tion, as  perhaps  is  true  of  Peripatns;  but  in 
Fig.  I. — An  arthropod,  most  instances  it  is  due  to  a  secondary  modifi- 
cation of  forni,  the  result  of  adaptation  to 
Thus  the  segmentation  of  the  body  may  be 


special  modes  of  life. 


2. — A  larva  of  an  insect. 
(1) 


AN  INTRODUCTION  TO  ENTOMOLOGY 


% 


Fig. 


obscured,  as  in  spiders  and  in  mites  (Fig.  3);  or  the  jointed  append- 
ages may  be  absent,  as  in  the  larvae  of  flies  (Fig.  4),  of  bees,  and  of 
many  other  insects.     In  all  of  these  cases,  however,  a  careful  study 
of  the  structure  of  the  animal,  or 
of  its  complete  life-history,  or  of 
other  animals  that  are  evidently 
closely  allied  to  it  removes  any 
doubt    regarding    its    being    an 
arthropod. 
\  ^;|'  The  phylum    i^ithropoda    is 

the  largest  of  the  phyla  of  the  WT^^ 
animal  kingdom,  including  many 
more  known  species  than  all  the 
other  phyla  taken  together.  This 
vast  assemblage  of  animals  in- 
cludes forms  differing  widely  in 
structure,  all  agreeing,  however, 
in  the  possession  of  the  essential 
characteristics  of  the  Arthropoda. 
Several  distinct  types  of  arthropods  are  recognized; 
and  those  of  each  type  are  grouped  together  as  a  class. 
The  number  of  distinct  classes  that  should  be  recog- 
nized, and  the  relation  of  these  classes  to  each  other  are 
matters  regarding  which  there  are  still  differences  of 
opinion;  we  must  have  much  more  knowledge  than  we 
now  possess  before  we  can  speak  with  any  degree  of 
certainty  regarding  them. 

Each  of  the  classes  envmerated  below  is  regarded  by 
all  as  a  distinct  group  of  animals ;  but  in  some  cases  there 
may  be  a  question  whether  the  group  should  be  given    ^^^^^^^'^• 
the  rank  of  a  distinct  class  or  not.     The  order  in  which  the  classes 
are  discussed  in  this  chapter  is  indicated  in  the  following  list. 


3. — A  mite,  an 
arthropod  in  which  the 
segmentation  of  the 
body  is  obscured.  The 
southern  cattle-tick, 
Boophilus  anntdatiis. 


LIST      OF      THE      CLASSES      OF      THE      ARTHROPODA 


THE  MOST  PRIMITIVE  ARTHROPODS 

Class  Onychophora,  page  4 

THE  AQUATIC  SERIES 

Class  Crustacea,  page  6 
Class  Palffiostracha,  page  8 

AN     OFFSHOOT     OF     THE    AQUATIC    SERIES, 

Class  Arachnida,  page  9 


SECONDARILY    AERIAL 


CHARACTERISTICS   OF  INSECTS  AND    THEIR   RELATIVES      3 

IV.  DEGENERATE   ARTHROPODS   OF   DOUBTFUL   POSITION 

Class  Pychnogonida,  page  lo 
Class  Tardigrada,  page  1 2 
Class  Pentastomida,  page  14 

V,  THE    PRIMARILY   AERIAL  SERIES 

Class  Onychophora  (See  above) 
Class  Diplopoda,  page  1 5 
Class  Pauropoda,  page  18 
Class  Chilopoda,  page  20 
Class  Symphyla,  page  23 
Class  Myrientomata,  page  24 
Class  Hexapoda,  page  26 

TABLE    OF    CLASSES    OF   THE   ARTHROPODA 

A.        Worm-like  animals,  with  an  unsegmented  body,  but  with  many, 

unjointedlegs Onychophora 

A  A.     Body  more  or  less  distinctly  segmented  except  in  a  few  degen- 
erate forms. 
B.     With  two  pairs  of  antennse  and  at  least  five  pairs  of  legs; 

respiration  aquatic Crustacea 

BB.     Without  or  apparently  without  antennae. 

C.     With  well-developed  aquatic  respiratory  organs. 

Pal^ostracha 
CC.     With  well-developed  aerial  respiratory  organs  or  with- 
out distinct  respiratory  organs. 
D.     With  well-developed  aerial  respiratory  organs. 
E.     Body  not  resembling  that  of  the  Thysanura  in  form. 

Arachnida 
EE.     Body  resembling  that  of  the  Thysanura  in  form 

(Family  Eosentomidae) Myrientomata 

DD.     Without  distinct  respiratory  organs. 
E.     With   distinctly   segmented   legs. 
F.    Body  resembling  that  of  the  Thysanura  in  form,  but 
without  antennae,  and  with  three  pairs  of  thoracic 
legs  and  three  pairs  of  vestigial  abdominal  legs 

(Family   Acerentomidas) Myrientomata 

FF.     With  four    or  five  pairs   of   ambulatory   legs; 

abdomen  vestigial Pychnogonida 

EE.     Legs  not  distinctly  segmented. 

F.     With  four  pairs  of  legs  in  the  adult  instar. 

Tardigrada 


4  AN   INTRODUCTION   TO  ENTOMOLOGY 

FF.     Lar\'a  with  two  pairs  of  legs,  adult  without 

legs Pentastomida 

BBB.     With  one    pair,    and  only    one,  of   feeler-like  antennae. 
Respiration  aerial. 
C.     With  more  than  three  pairs  of  legs,  and  without  wings. 
D.     With  two  pairs  of  legs  on  some  of  the  body-segments. 

DiPLOPODA 

DD .     With  only  one  pair  of  legs  on  each  segment  of  the  body. 

E.     Antennae  branched Pauropoda 

EE.     Antennse  not  branched. 

F.  Head  without  a  Y-shaped  epicranial  suture. 
Tarsi  of  legs  with  a  single  claw  each.  Opening  of 
the  reproductive  organs  near  the  caudal  end  of 

the  bod}^ Chilopoda 

FF.  Head  with  a  Y-shaped  epicranial  suture,  as  in 
insects.  Tarsi  of  legs  with  two  claws  each. 
Opening  of  the  reproductive  organs  near  the  head. 

Symphyla 

CC.     With  only  three  pairs  of  legs,  and  usually  with  wings  in 
the  adult  state Hexapoda 

Class  ONYCHOPHORA 

The  fienus  Peripatus  oj  authors 
The  members  of  this  class  are  air-breathing  animals,  with  a  nearly 
cylindrical,  unsegmented  body,  which  is  furnished  with  many  pairs  of 
unjointed  legs.  The  reproductive  organs  open  near  the  hind  end  of  the  body. 
The  class  Onychophora  occupies  the  position  of  a  CDnnecting  link 
between  the  Arthropoda  and  the  phylum  Annulata  or  worms ;  and  is 
therefore  of  the  highest  interest  to  students  of  systematic  zoolog}'. 
All  known  members  of  this  class  have  been  included  until  recently  in  a 
single  genus  Peripatus;  but  now  the  fifty  or  more  known  species  are 
distributed  among  nearly  a  dozen  genera. 

The    body 
(Fig.  5)  is  nearly 

cylindrical,    cat- 

fff^^T^^^^^^lS^^'^^Ty^:^  in 

^-     €  .„-J2'^'^^''^^  form,  but  is  un- 
^    %     ^  Y     segmented    ex- 

ternally.      It   is 
r'ig-  5-—Peripatoides  novcB-zealandica.  furnished     With 

many  pairs  cf  legs,  the  number  of  which  varies  in  different  species. 
The  legs  have  a  ringed  appearance,  but  are  not  distinctly  jointed. 


CHARACTERISTICS   OF  INSECTS  AND    THEIR   RELATIVES      5 

The  head  bears  a  pair  of  ringed  antennae  (Fig.  6) ;  behind  thes3  on 
the  sides  of  the  head,  there  is  a  pair  of  short  appendages  teTnsd  oral 
papillse.  The  mouth  opening  is  surrounded  by  a  row  of  lobes  which 
constitute  the  Hps,  and  between  these  in  the  anterior  part  of  the 
mouth-cavity  there  is  an  obtuse  pro- 
jection, which  bears  a  row  of  chitinous 
points.  Within  the  mouth  cavity  there 
are  two  pairs  of  hooked  plates,  which 
have  been  termed  the  mandibles,  the 
two  plates  of  each  side  being  regarded 
as  a  single  mandible. 

Although  the  body  is  unsegmented 
externally,  internally  there  are  evi- 
dences of  a  metameric  arrangement  of 
parts.  The  ventral  nerve  cords,  which 
at  first  sight  appear  to  be  without 
ganglia,  are  enlarged  opposite  each 
pair  of  legs,  and  these  enlargments 
are  regarded  as  rudimentary  ganglia,  pig.  6.— Ventral  view  of  the  head 
We  can,  therefore  speak  of  each  sec-  and  first  pair  of  legs  of  Peri- 
,.  p         1      1  1-  ,  paloides;    a,  antenna;    o,  oral 

tion  of  a  body    correspondmg    to  a       papilla. 

pair  of  appendages  as  a  segment.     The 

metameric  condition  is  farther  indicated  by  the  fact  that  most  of 
these  segments  contain  each  a  pair  of  nephridia;  each  nephridium 
opening  at  the  base  of  a  leg. 

The  respiratory  organs  are  short  tracheae,  which  are  rareiy 
b"anched,  and  in  which  the  tasnidia  appear  to  be  rudimentary.*  In 
some  species,  the  spiracles  are  distributed  irregularly;  in  others,  they 
are  in  longitudinal  rows. 

The  sexes  are  distinct.  The  reproductive  organs  open  near  the 
hind  end  of  the  body,  either  between  the  last  or  the  next  to  the  last 
pair  of  legs. 

The  various  species  are  found  in  damp  situations,  under  the  bark 
of  rotten  stumps,  under  stones  or  other  objects  on  the  ground.  They 
have  been  found  in  Africa,  in  Australia,  in  South  America,  and  in  the 
West  Indies. 

Their  relationship  to  the  Arthropoda  is  shown  by  the  presence  of 
paired  appendages,  one,  or  perhaps  two,  pairs  of  which  are  modified  as 
jaws;   the  presence  of  tracheae  which  are  found  nowhere  else  except 

*IL  is  quite  possible  that  the  "short  tracheae"  described  by  writers  on  the 
structure  of  these  animals  are  tracheoles.  See  the  account  of  the  distinguishing 
features  of  trache;E  and  tracheoles  m  Chapter  III. 


AN  INTRODUCTION   TO  ENTOMOLOGY 


■in  the  Arthropoda;  the  presence  of  paired  ostia  in  the  wall  of  the 
heart;  and  the  presence  of  a  vascular  body  cavity  and  pericardium. 

They  resemble  the  Annulata  in  having  a  pair  of  nephridia  in  most 
of  the  segments  of  the  body  corresponding  to  the  pairs  of  legs,  and  in 
having  ciha  in  the  generative  tracts. 

An  extended  monograph  of  the  Onychophora  v/as  published  by 
Bouvier  {'o$-o-j). 

Class  CRUSTACEA 
The  Crustaceans 

The  members  of  this  class  are 
aquatic  arthropods,  which  breathe 
by  true  gills.  They  have  two 
pairs  of  antennoe  and  at  least  five 
pairs  of  legs.  The  position  of  the 
openings  of  the  reproductive  organs 
varies  greatly;  but  as  a  rule  they 
are  situated  far  forward. 

The  most  familiar  examples 
of  the  Crustacea  are  the  cray- 
fishes, the  lobsters,  the  shrimps, 
and  the  crabs.  Cray-fishes  (Fig. 
7)  abound  in  our  brooks,  and  are 
often  improperly  called  crabs. 
The  lobsters,  the  shrimps,  and 
the  true  crabs  live  in  salt 
water. 
Excepting  Lhnulus,  the  sole  hving  representative  of  the  class 
described  next,  the  Crus- 
tacea are  distinguished 
from  all  other  arthro- 
pods by  their  mode  of 
respiration,  being  the 
only  ones  that  breathe 
by  true  gills.  Many  in- 
sects live  in  water  and 
are  furnished  with  gill- 
like organs;  but  these 
are  either  tracheal  gills  or 
blood-gills,  organs  which 

differ  essentially  in  struc-     ^.     ^     ■,.,.     ^ 

Fig.  8. — Minute  crustaceans 
ture  from  true  gills,  as  Cypridopsis,   c,  Cyclops. 


Fig.  7. — A  cray-fish. 


Daphnia; 


CHARACTERISTICS   OF  INSECTS  AND    THEIR   RELATIVES      V 


described  later.  The  Crustacea  also  differ  from  other  Arthropoda 
in  having  two  pairs  of  antennae.  Rudiments  of  two  pairs  of  antennge 
have  been  observed  in  the  embryos  of  many  other  arthropods ;  but 
in  these  cases  one  or  the  other  of  the  two  pairs  of  antennae  fail 
to  develop. 

The  examples  of  crustaceans  named  above  are  the  more  con- 
spicuous members  of  the  class;  but  many  other  smaller  forms  abound 
both  in  the  sea  and  in  fresh  water.  Some  of  the  more  minute  fresh- 
water forms  are  almost  sure  to  occur  in  any  fresh-water  aquarium. 

In  Figure  8  are  repre- 
sented three  of  these 
greatly  enlarged.  The 
minute  crustaceans  form 
an  important  element  in 
the  food  of  fishes. 

Some  crustaceans  live 
in  damp  places  on  land, 
and  are  often  found  by 
collectors  of  insects; 
those  most  often  ob- 
served are  the  sow-bugs 
(Oniscoida),  which  fre- 
quently occur  about 
water-soaked  wood. 
Figure  9  represents  one 
of  these. 
As  there  are  several,  most  excellent  text  books  devoted  to  the 
Crustacea,  it  is  unnecessary  to  discuss  farther  this  class  in  this  place. 


Fig.  9. — A  sow-bug,  Cylisticus  convexus  (From 
Richardson  after  Sars). 


AN  INTRODUCTION   TO   ENTOMOLOGY 


Class  PALiEOSTRACHA 

The  King-crabs  or  Horseshoe-crabs 

The  members  of  this  class 
are  aquatic  arthropods,  which 
resemble  the  Crustacea  in  that 
they  breathe  by  true  gills,  but 
in  other  respects  are  closely 
allied  to  the  Arachnida.  They 
are  apparently  without 
antenncB,  the  appendages  hom- 
ologous to  antenncB  being  not 
feeler-like.  The  reproductive 
organs  open  near  the  base  of 
the  abdomen. 

The  class  Palseostracha 
is  composed  almost  entirely 
of  extinct  f  orm.s,  there  being 
living  representatives  of  only 
a  single  order,  the  Xiphosura, 
and  this  order  is  nearly 
extinct;  for  of  it  there  re- 
mains only  the  genus 
Ltmrdus,  represented  by 
only  five  known  species. 

I  The  members  of  this 
genus  are  known  as  king- 
crabs  or  horseshoe-crabs ; 
the  former  name  is  sug- 
gested by  the  great  size  of  some  of  the  species;  the  latter,  by 
shape  of  the  cephalothorax  (Fig.   lo). 

The  king-crabs  are  marine;  they  are  found  on  our  Atlantic  Coast 
from  Maine  to  Florida,  in  the  West  Indies,  and  on  the  eastern  shores 
of  Asia.  They  are  found  in  from  two  to  six  fathoms  of  water  on 
sandy  and  muddy  shores ;  they  burrow  a  short  distance  in  the  sand 
or  mud  and  feed  chiefly  on  worms.  The  single  species  of  our  coast  is 
Lmtulus  polyphemiis. 


Fig.  10. — A  horseshoe 
Packard) . 


cralj,  Limulus  (After 


the 


CHARACTERISTICS  OF  INSECTS  AND    THEIR   RELATIVES      9 

Class  ARACHNIDA 

Scorpions,  Harvestmen,  Spiders,  Mites,  and  others 

The  members  of  this  class  are  air-breathing  arthropods,  in  which  the 
head  and  thorax  are  usually  grown  together,  forming  a  cephalothorax, 
which  have  four  pairs  of  legs,  and  which  apparently  have  no  antenncB. 
The  reproductive  organs  open  near  the  base  of  the  abdomen. 


Fig.  II  b 

Fig.  II. — Arachnids:  a,  a  scorpion;  h,  a  harvestman. 
c,  a  spider;  d,  an  itch-mite,  from  below  and  from 
above. 


The  Arachnida  abound  wherever  insects  occur,  and  are  often 
mistaken  for  insects.  But  they  can  be  easily  distinguished  by  the 
characters  given  above,  even  in  those  cases  where  an  exception  occurs 
to  some  one  of  them.  The  more  important  of  the  exceptions  are  the 
following :     in  one  order,  the  Solpugida,  the  head  is  distinct  from  the 


10  AN  INTRODUCTION   TO  ENTOMOLOGY 

thorax ;  as  a  rule  the  young  of  mites  have  only  six  legs,  but  a  fourth 
pair  is  added  during  growth ;  and  in  the  gall-mites  there  are  only  four 
legs. 

The  Arachnida  are  air-breathing;  but  it  is  believed  that  they 
have  been  evc'lved  from  aquatic  progenitors.  Two  forms  of  respira- 
tory organs  exist  in  this  class :  first,  book-lungs ;  and  second,  tubular 
trachea.  Some  members  of  it  possess  only  one  of  these  types;  but 
the  greater  number  of  spiders  possess  both. 

A  striking  characteristic  of  the  Arachnida,  which,  however,  is  also 
possessed  by  the  Palaeostracha,  is  the  absence  of  true  jaws.  In  other 
arthropods  one  or  more  pairs  of  appendages  are  jaw-like  in  form  and 
are  used  exclusively  as  jaws;  but  in  the  Arachnida  the  prey  is  crushed 
either  by  the  modified  antennas  alone  or  by  these  organs  and  other 
more  or  less  leg-like  appendages.  The  arachnids  suck  the  blood  of 
their  victims  by  means  of  a  sucking  stomach;  they  crush  their  prey, 
but  do  not  masticate  it  so  as  to  swallow  the  solid  parts. 

In  the  Arachnida  there  exist  only  simple  eyes. 

The  reproductive  organs  open  near  the  base  of  the  abdomen  on  the 
ventral  side.  In  this  respect  the  Arachnida  resemble  Limulus,  the 
millipedes,  and  the  Crustacea,  and  differ  from  the  centipedes  and 
insects. 

Among  the  more  familiar  representatives  of  this  class  are  the 
scorpions  (Fig.  ii,  a),  the  harvestmen  (Fig.  ii,  h),  the  spiders  (Fig. 
II,  c),  and  the  mites  (Fig.  ii,  d). 

As  the  writer  has  devoted  a  separate  volume  (Comstock,  '12)  to 
the  Arachnida,  it  will  not  be  discussed  farther  in  this  place. 


Class  PYCNOGONIDA 

The  Pycnogonids 

The  members  oj  this  class  are  marine  arachnid-like  arthropods,  in 
which  the  cephalothorax  bears  typically  seven  pairs  of  jointed  appen- 
dages, but  in  a  few  fcrms  there  are  eight  pairs,  and  in  some  the  anterior 
two  or  three  pairs  are  absent;  and  in  which  the  abdomen  is  reduced  to  a 
legless,  unsegmented  condition.  They  possess  a  circulatory  system,  but 
no  evident  respiratory  organs.  The  reproductive  organs  open  through 
the  second  segment  of  the  legs;  the  number  of  legs  bearing  these  opening 
varies  from  one  to  five  pairs. 

The  Pycnogonida  or  pycnogonids  are  marine  animals,  which  bear 
a  superficial  resemblance  to  spiders  (Fig.  12).  Some  of  them  are 
found  under  stones,  near  the  low  water  line,  on  sea  shores;   but  they 


CHARACTERISTICS   OF  INSECTS  AND    THEIR   RELATIVES    11 

are  more  abundant  in  deep  water.     Some  are  found  attached  to  sea- 
anemones,  upon  which  they  probably  prey;  others  are  found  climbing 


Fig.  12. — A  pycnogonid,  Nymphon  hispidum:  r,  chelophore;  p, 
palpus;  0,  ovigerous  legs;  /,  /,  I,  I,  ambulatory  legs;  ab,  abdo- 
men (After  Hoeck). 

over  sea-weeds  and  Hydroids;  and  sometim.es  they  are  dredged  in 
great  numibers  from  deep  water. 

They  possess  a  suctorial  proboscis.  In  none  of  the  appendages  are 
the  basal  segments  modified  into  organs  for  crushing  the  prey. 

The  cephalothorax  comprises  almost  the  entire  body ;  the  abdomen 
being  reduced  to  a  mere  vestige,  without  appendages,  and  with  no 
external  indication  of  segmentation.  But  the  presence  of  two  pairs 
of  abdominal  ganglia  indicates  that  originally  the  abdomen  consisted 
of  more  than  one  segment. 

There  are  typically  seven  pairs  of  appendages;  but  a  few  forms 
possess  eight  pairs ;  and  in  some  the  first  two  or  three  pairs  are  absent. 
The  appendages,  when  all  are  present,  consist  of  a  pair  of  chelophores, 
each  of  which  when  well-developed  consists  of  one  or  two  basal  seg- 
ments and  a  chelate  "hand;"  the  palpi,  which  are  supposed  to  be 
tactile,  and  which  have  from  five  to  ten  joints  when  well-developed; 
the  ovigerous  legs,  which  are  so-called  because  in  the  males  they  are 
used  for  holding  the  mass  of  eggs  beneath  the  body;  and  the  ambula- 
tory legs,  of  which  there  are  usually  four  pairs,  but  a  few  forms  possess 
a  fifth  pair.  The  ambulatory  legs  consist  each  of  eight  segments  and 
a  terminal  claw. 

The  only  organs  of  special  sense  that  have  been  found  in  these 
animals  are  the  eyes.     These  are  absent  or  at  least  very  poorly 


12  AN  INTRODUCTION   TO  ENTOMOLOGY 

developed  in  some  forms,  especially  those  that  are  found  in  very  deep 
water,  i.  e.  below  four  or  five  hundred  fathoms.  When  well-developed 
they  are  simple,  and  consist  of  two  pairs,  situated  on  a  tubercle,  on 
the  head  or  the  first  compound  segment  of  the  body,  the  segment  that 
bears  the  first  four  pairs  of  appendages. 

The  reproductive  organs  open  in  the  second  segment  of  the  legs. 
In  some  these  openings  occur  only  in  the  last  pair  of  legs ;  in  others,  in 
all  of  the  ambulatory  legs. 

Very  little  is  known  regarding  the  habits  of  these  animals.  The 
most  interesting  features  that  have  been  observed  is  perhaps  the  fact 
that  the  males  carry  the  eggs  in  a  mass,  held  beneath  the  body  by  the 
third  pair  of  appendages,  the  ovigerous  legs,  and  also  carrv^  the  young 
for  a  time. 

As  to  the  systematic  position  of  the  class  Pycnogonida,  very  little 
can  be  said.  These  animals  are  doubtless  arthropods,  and  they  are 
commonly  placed  near  the  Arachnida. 


Class  TARDIGRADA 
The  Tardigrades  cr  Bear  Animalcules 

The  members  oj  this  class  are  very  minute  segmented  animals,  with 
four  pairs  of  legs,  but  without  antennce  or  mouth-appendages,  and  without 
special  circulatory  or  respiratory  organs;  the  reproductive  organs  open 
into  the  intestine. 

The  Tardigrada  or  tardigrades  are  microscopic  animals,  measuring 
from  one  seventy-fifth  to  one  twenty-fifth  of  an  inch  in  length.  They 
are  somewhat  mite-like  in  appearance;  but  are  very  different  from 
mites  in  structure  (Fig.  13  and  14). 

The  head  bears  neither  antennae  nor  mouth-appendages.  The 
four  pairs  of  legs  are  short,  un jointed,  and  are  distributed  along  the 

entire  length  of  the  body,  the 
fourth  pair  being  at  the  cau- 
dal end.  Each  leg  is  termin- 
ated by  claws,  which  differ  in 
number  and  form  in  different 
genera. 

The  more  striking  features 

of   the   internal    structure  of 
Fig,  13. — A  tardigrade  (After  Doyere).       ^,  ■       ^    ■     ^^        -u  c 

^    ^  fa        V  J     ^       these  animals  is  the  absence  of 

special  circulatory  and  respiratory  organs;  the  presence  of  a  pair  of 

chitinous  teeth,  either  in  the  oral  cavity  or  a  short  distance  back  of 


CHARACTERISTICS   OF  INSECTS  AND    THEIR   RELATIVES    13 

it ;  the  presence  of  Malpighian  tubules ;  the  unpaired  condition  of 
the  reproductive  organs  of  both  sexes ;  and  the  fact  that  these  organs 
open  into  the  intestine.  The  central  nervous  system  consists  of  a 
brain,  a  suboesophageal  ganglion,  and  a  ventral  chain  of  four  ganglia, 
connected  by  widely  separated  connectives. 

The  tardigrades  are  very  abundant,  and  are  very  widely  dis- 
tributed. Some  live  in  fresh  water,  a  few  are  marine,  but  m^st  of 
them  live  in  damp  places,  and  especially  on  the  roots  of  moss,  gro  ,ving 
in  gutters,  on  roofs  or  trees,  or  in  ditches. 
Bvit  although  they  are  common,  their 
minute  size  and  retiring  habits  result  in 
their  being  rarely  seen  except  by  those 
who  are  seeking  them. 

Many   of  them  have   the   power   of 

withstanding  desiccation  for  a  long  period. 

This  has  been  demonstrated  artificially  by 

placing  them  on  a  microscopic  slide  and 

allowing     the     mositure     to     evaporate 

slowly.     The    body     shrinks,     its     skin 

becomes  wrinkled,  and  finally  it  assumes 

the  appearance  of  a  grain  of  sand  in 

which  no  parts  can  be  distinguished.     In 

this  state  they  can  remain,  it  is  said,  for 

years;    after  which,  if  water  be  added, 

the  body  swells,  assumes  its  normal  form, 

and  after  a  time,  the  creatures  resume 

their  activities. 

T-,  J.        ,1  ,  ^.  ..  .  Fi.s;.  14.— A  tardigrade  (After 

Kegardmg  the  systematic  position  of      Dovere). 

this  class  of  animals  nothing  definite  can 

be  stated  beyond  the  fact  that  they  are  doubtless  arthropods.     Their 

relationship  to  the  other  classes  of  arthropods  has  been  masked  by 

degenerative  modifications.     They  are  placed  here  near  the  e'.id  of 

the  series  of  classes  of  arthropods,  merely  as  a  matter  of  convenience, 

in  what  may  be  termed,  an  appendix  to  the  arthropod  series,  which 

includes  animals  of  doubtful  relationships. 


14 


AN  INTRODUCTION   TO  ENTOMOLOGY 


Class  PENTASTOMIDA 
The  Pentastomids  or  Linguatulids 
The  members  of  this  class  are  degenerate,  worm-like,  parasitic 
arthropods,  which  in  the  adult  state  have  no  appendages,  except  two  pairs 
of  hooks  near  the  mouth;  the  larvce  have  two  pairs  of  short  legs.  These 
animals  possess  neither  circulatory  nor  respiratory  organs.  The 
reproductive  organs  of  the  male  open  a  short  distance  behind  the  mouth; 
those  of  the  female  near  the  caudal  end  of  the  body. 

The  Pentastomida  or  pentastomids  are  worm-like  creatures,  whose 
form  has  been  greatly  modified  by  their  parasitic  life.  The  adults 
bear  little  resemblance  to  any  other  arthropods.  Representatives  of 
three  genera  are  known.  These  are  Lingudtula  in  which  the  body  is 
fluke-like  in  form  (Fig.  15)  and  superficially  annulated;  Porocephahts, 
in  which  the  body  is  cylindrical  (Fig.  16)  and  ringed;  and  Re ighdrdia, 
which  is  devoid  of  annulations,  and  with  poorly  developed  hooks  and 
a  mouth-armature. 

The  arthropodan  nature  of  these  animals  is 
indicated  by  the  form  of  the  larvae,  which  although 
greatly  degenerate,  are  less  so  than  the  adults, 
having  two  pairs  of  legs  (Fig.  17). 


Fig.  15. — A  pentasto- 
mici,  Linguatula 
tccnioides,  female  at 
the  time  of  copula- 
tion: h,  hooks;  oe, 
oesophagus,  rs,  re- 
ceplaaila  seminis, 
one  of  which  is  still 
empty;  i,  intestine; 
07',  ovary;  fa,  vagina 
(From  Lang  after 
Leuckart). 


Fig.  16. — A  pentastomid, 
Porocephalus  annulatus; 
a,  ventral  view  of  head, 
greatly  enlarged;  h, 
ventral  view  of  animal, 
slightly  enlarged  (After 
Shipley). 


Fig.  17  — A  pentastomid,  larva  of 
Porocephalus  proboscideus,  seen 
from  below,  highly  magnified:  i, 
boring  anterior  end;  2,  first  pair 
of  chitinous  procespes  seen  be- 
tween the  forks  of  the  second  pair; 
3,  ventral  nerve  ganglion;  4,  ali- 
mentary canal;  5,  mouth;  6  and 
7,  gland  cells  (From  Shipley  after 
Stiles). 


CHARACTERISTICS   OF  INSECTS  AND    THEIR   RELATIVES    15 

Like  many  of  the  parasitic  worms,  these  animals,  in  some  cases  at 
least,  pass  their  larval  life  in  one  host,  and  complete  their  development 
in  another  of  a  different  species ;  some  larvae  being  found  in  the  bodies 
of  herbivorous  animals  and  the  adults  in  predacious  animals  that  feed 
on  these  herbivorous  hosts. 

The  systematic  position  of  the  pentastomids  is  very  uncertain. 
They  have  been  considered  by  some  writers  to  be  allied  to  the  mites. 
But  it  seems  better  to  merely  place  them  in  this  appendix  to  the 
arthropod  series  until  more  is  known  of  their  relationships. 

Class  DIPLOPODA 
The  Millipedes  or  Diplopods 

The  members  of  this  class  are  air-breathing  arthropods  in  which  the 
head  is  distinct,  and  the  remaining  segments  oj  the  body  form  a  continuous 
region.  The  greater  number  of  the  body-segments  are  so  grouped  that 
each  apparent  segment  bears  two  pairs  of  legs.  The  antennce  are  short 
and  very  similar  to  the  legs.  The  openings  of  the  reproductive  organs  are 
paired,  and  situated  behind  the  second  pair  of  legs. 


Vig.  1 8. — A  millipede,  Spiroholus  marginalus. 

The  Diplopoda  and  the  three  following  classes  were  formerly 
grouped  together  as  a  single  class,  the  Myridpoda.  But  this  grouping 
has  been  abandoned,  because  it  has  been  found  that  the  Chilopoda  are 
more  closely  allied  to  the  insects  than  they  are  to  the  Diplopoda;  and 
the  Pauropoda  and  Symphyla  are  both  very  distinct  from  the  Diplo- 
poda on  the  one  hand  and  the  Chilopoda  on  the  other.  Owing  to  the 
very  general  and  long  continued  use  of  the  term  Myriapoda,  the 
student  who  wishes  to  look  up  the  literature  on  these  four  classes 
should  consult  the  references  under  this  older  name. 

The  most  distinctive  feature  of  the  millipedes  is  that  which  sug- 
gested the  name  Diplopoda  for  the  class,  the  fact  that  throughout  the 
greater  part  of  the  length  of  the  body  there  appears  to  be  two  pairs  of 
legs  borne  by  each  segment  (Fig   i8). 

This  apparent  doubling  of  the  appendages  is  due  to  a  grouping  of 
the  segments  in  pairs  and  either  a  consolidation  of  the  two  terga  of 


16 


AN  INTRODUCTION   TO  ENTOMOLOGY 


each  pair  or  the  non-development  of  one  of  them;    which  of  these 
alternatives  is  the  case  has  not  been  definitely  determined. 

It  is  clear,  however,  that  there  has  been  a  grouping  of  the  seg- 
ments in  pairs  in  the  region  where  the  appendages  are  doubled,  for 
corresponding  with  each  tergum  there  are  two  sterna  and  two  pairs  of 
spiracles. 

A  few  of  the  anterior  body  segments,  usually  three  or  four  in 
number,  and  sometimes  one  or  two  of  the  caudal  segments  remain 
single.  Frequently  one  of  the  anterior  single  segments  is  legless,  but 
the  particular  segment  that  lacks  legs  differs  in  the  different  families. 

The  head,  which  is  as  distinct  as  is  the  head  of  insects,  bears  the 
antennae,  the  eyes,  and  the  mouth -parts.     The  antennse  are  short, 
and  usually  consist  each  of  seven  segments.     The  eyes  are  usually 
represented  by  a  group  of  ocelli  on  each  side  of  the 
head;  but  the  ocelli  vary  greatly  in  number,  and  are 
sometimes  absent.     The  mouth-parts  consist  of  an  P 
upper  lip  or  lahrum;  a  pair  of  mandibles;  and  a  pair 
of  jaws,  which  are  united  at  the  base,  forming  a  large 
plate,  which  is  known  as  the  gnathochildrium.     In 
the  genus  Polyxenus  there  is  a  pair  of  lobes  between    t 
the  mandibles  and  the  gnathochilarium,  which  have 
been  named  the  maxUlulcB.     (paragnatha?). 

The  labrum  is  merely  the  anterior  part  of  the 
upper  wall  of  the  head  and,  as  in  insects,  is  not  an 
appendage.  The  mandibles,  in  the  forms  in  which 
they  are  best  developed,  are  fitted  for  biting,  and 
consist  of  several  parts  (Fig.  19) ;  but  in  some  forms 
they  are  vestigial.  The  gnathochilarium  (Fig.  20)  is 
ccm-plicated  in  structure,  the  details  of  which  vary  greatly  in  different 
genera. 


¥\g,.  19. — A  mandi- 
ble of  Jidi'.s;  c, 
cardo;  d,d,teeth\ 
m,  muscle;  ma, 
mala;  p,  pecti- 
nate plate;  s, 
stipes  (After 
Latzel) . 


Fig.  20. — The  gnathochilarium.  or  second  jaws  of  three  diplopods;  A,  Spirostrep- 
ttis;  B,Julus;  C,  Glomeris:  r,  cardo;  A.hypostoma;  /g,  lingua;  m,  menttun* 
pm,  promentum;   st,  stipes  (After  Silvestri). 


CHARACTERISTICS   OF  INSECTS  AND    THEIR   RELATIVES    17 


In  one  subdivision  of  the  class  Diplopoda,  which  is  represented 
by  the  gentis  Polyxemis  and  a  few  others,  the  mandibles  are  one- 
jointed;     and    be- 
«.*■/  tween   the   mandi- 

^^■lo  .  blesandthe 

gnathochilarium 
there  is  a  pair   of 
one-jointed  lobes, 
which  have  not 
been   fovmd   in 
other  diplopods; 
these  are  the  "max- 
illute"     (Fig.     2i). 
The  correspondence 
of  the  parts  of  the 
gnathochilarium  of 
Polyxenus   and  its 
allies  with  the  parts 
of    the    gnathocil- 
larium  of  other  di- 
plopods    has     not 
been    satisfactorily 
determined. 
Most  of  our  more  common  millipedes  possess  stink-glands,  which 
open  by  pores  on  a  greater  or  less  number  of  the  body  segments. 
These  glands  are  the  only  means  of  defence  possessed  by  millipedes, 
except  the  hard  cuticula  protecting  the  body. 

The  millipedes  as  a  rule  are  harmless,  living  in  damp  places  and 
feeding  on  decaying  vegetable  matter;  but  there  are  a  few  species 
that  occasionally  feed  upon  growing  plants. 

For  a  more  detailed  account  of  the  Diplopoda  see  Pocock  ('ii). 


Fig.  21. — The  second  pair  of  jaws,  maxillulse,  and  the 
third  pair  of  jaws,  maxillae  or  gnathochilarium,  of 
Polyxenus;  the  parts  of  the  maxillae  or  gnathochila- 
rium are  stippled  and  some  are  omitted  on  the  right 
side  of  the  figure:  vib,  basal  membrane  of  the  labium; 
la,  "labium"  of  Carpenter,  perhaps  the  mentum  and 
promentum  of  the  gnathochilarium;  mx,  basal  seg- 
ment of  the  maxilla,  perhaps  the  stipes  of  the 
gnathochilarium;  wx. /o,  lobe  of  the  maxilla;  mx.p, 
maxihary  palpus;  /z,  tongue  or  hypopharynx;  mxl, 
maxillula;    fl.  flagellate  process     (After  Carpenter). 


18 


AN  INTRODUCTION   TO  ENTOMOLOGY 


Class  PAUROPODA 
The  Panropods 

The  members  of  this  class  are  small  arthropods  in  which  the  head  is 
distinct,  and  the  segments  of  the  body  form  a  single  continuous  region. 
Most  of  the  body-segments  bear  each  a  single  pair  of  legs.  Although 
most  of  the  terga  of  the  body-segments  are  usually  fused  in  couples,  the 
legs  are  not  grouped  in  double  pairs  as  in  the  Diplopoda.  The  antennce. 
are  branched.  The  reproductive  organs  open  in  the  third  segment  back 
of  the  head. 

The  Pauropoda  or  pauropods  are  minute  creatures,  the  described 
species  measuring  only  about  one  twenty-fifth  inch  in  length,  more 
or  less.  They  resemble  centipedes  in  the  elongated  form  of  the  body 
and  in  the  fact  that  the  legs  are  not  grouped  in  double  pairs  as  in  the 
Diplopoda,  although  the  terga  of  the  body-region  are  usually  fused  in 
couples.  These  characteris- 
tics are  well-shown  by  the 
dorsal  and  ventral  views  of 
Pauropus  (Fig.  22  and  23). 
Although  the  pauropods 
resemble  the  chilopods  in 
the  distribution  of  their  legs, 
they  differ  widely  in  the 
position  of  the  openings  of 
the  reproductive  organs. 
These  open  in  the  third  seg- 
ment back  of  the  head;  that 
of  the  female  is  single,  those 
of  the  male  are  double. 

The  head  is  distinct  from 
the  body-region.  It  bears 
one  pair  of  antenna  and  two 
pairs  of  jaws;  the  eyes  are 
absent  but  there  is  an  eye- 
like spot  on  each  side  of  the 
head  (Fig.  24).  The  first 
pair  of  jaws  are  large,  one- 
jointed  mandibles;  the 
second  pair  are  short  pear-shaped  organs.     Between  these  two  pairs 


Fig.  22. — A  pauropod, 
Pauropus  huxleyi,  dor- 
sal aspect  (After  Ken- 
yon). 


Pig.  23. — Pauropus 
huxleyi,  ventral  as- 
pect (After  Lub- 
bock). 


CHARACTERISTICS   OF  INSECTS  AND    THEIR   RELATIVES    19 


Fig.  24  — Eurypatiropus  spina- 
sus;  face  showing  the  base  of 
the  antennse,  the  mandibles, 
and  the  eye-like  spots  (After 
Kenyon). 


of  jaws,  there  is  a  horny  framework  forming  a  kind  of  lower  lip  to  the 
mouth  (Fig.  25).  The  homologies  of  the  mouth-parts  with  those  of 
the  alHed  classes  of  arthropods  have  not 
been  determined. 

The  body-region  consists  of  twelve 
segments.  This  is  most  clearly  seen  by 
an  examination  of  the  ventral  aspect  of 
the  body.  When  the  body  is  viewed  from 
above  the  number  of  segments  appears  to 
be  less,  owing  to  the  fact  that  the  terga  of 
the  first  ten  segments  are  fused  in 
couples.  Nine  of  the  body-segments  bear 
well-developed  legs.  The  appendages  of 
the  first  segment  are  vestigial,  and  the 
last  two  segments  bear  no  appendages. 
The  most  distinctive  feature  of  mem- 
bers of  this  class  is  the  form  of  the 
antennae,  which  differ  from  tliose  of  all 
other  arthropods  in  structure.  Each 
antenna  (Fig.  26)  consists  of  four  short 
Dasal  segments  and  a  pair  of  one-jointed 
branches  borne  by  the  fourth  segment. 
One  of  these  branches  bears  a  long,  many- 
ringed  filament  with  a  rounded  apical 
knob;  and  the  other  branch  bears  two 
such  filaments  with  a  globular  or  pear- 
shaped  body  between  them.  This  is  prob- 
ably an  organ  of  special  sense. 

The  pauropods  live  under  leaves  and 

stones    and    in    other    damp    situations. 

Representatives   of  two  quite  distinct  families  are  found  in  this 

country  and  in  various  other  parts  of  the  world.     In  addition  to  these 

a  third   family,  the 

BrachypauropodidcE, 

is  found  in  Europe. 

In  this    family    the 

pairs  of  terga  consist 

each  of  two  distinct 

plates.     Our  two 

„.       ^      A   ^  c  v      ^       J,        ^-  famiUes  are  the  fol- 

rig.   26. — Antenna  of  Eurypatiropus  sptnosus 

(A  f ter  Kenyon) .  lowmg : 


Fig.  25. — Mouth-parts  of  Eury- 
pauropus  ornatus;  nid,  man- 
dible; mx,  second  iaws;  /, 
lower  lip  (After  Latzel). 


20  AN  INTRODUCTION   TO   ENTOMOLOGY 

Family  Pauropodidce. — In  members  of  this  family  the  head  is 
not  covered  by  the  first  tergal  plate  and  the  anal  segment  is  not 
covered  by  the  sixth  tergal  plate. 

The  best  known  representatives  of  this 
family  belong  to  the  genus  Pauropus  (Fig. 
22).  This  genus  is  widely  distributed,  represen- 
tatives having  been  found  in  Europe  and  in  both- 
North  and  South  America.  They  are  active, 
measure  about  one  twenty-fifth  inch  in  length, 
and  are  white. 


%.r 


Family    Eiirypauropida. — The     members     of 

this  family  are  characterized  by  the  wide  form 

of  the  body,  which  bears  some  resemblance  to 

^  that  of  a  sow-bug.     The  head  is  concealed  by  the 

first  tergum  of  the  body-region;    and  the  anal 

-.^  segment,  by  the  penultimate  tergum.     Our  most 


I  ^  ^ 


famihar  representative  is  Eurypanropus  spinosus 


T\g.  27.— Lnrypauro-    rpia.  27).     This,  unlike  Pauropus,  is  slow  m  its 
pus  spinosus  {Aitev 
Kenyon).  movements. 


Class  CHILOPODA 
The  Centipedes  or  Chilopods 

The  members  of  this  class  are  air-breathing  arthropods  in  which  the 
head  is  distinct,  and  the  remaining  segments  of  the  body  form  a  continuous 
region.  The  numerous  pairs  of  legs  are  not  grouped  in  double  pairs,  as 
in  the  Diplopoda.  The  antennce  are  long  and  many-jointed.  The 
appendages  of  the  first  body-segment  are  jaw-like  and  f  miction  as  organs 
of  offense,  the  poison-jaws.  The  opening  of  the  reproductive  organs  is 
in  the  next  to  the  last  segment  of  the  body. 

The  animals  constituting  the  class  Chilopoda  or  chilopods  are 
commonly  known  as  centipedes.  They  vary  to  a  considerable  degree 
in  the  form  of  the  body,  but  in  all  except  perhaps  the  sub-class 
Notostigma  the  body-segments  are  distinct,  not  grouped  in  couples 
as  in  the  diplopods  (Fig.  28).  They  are  sharply  distinguished  from 
the  three  preceding  classes  in  the  possession  of  poison-jaws  and  in 
having  the  opening  of  the  reproductive  organs  at  the  caudal  end  of 
the  body 

The  antennae  are  large,  flexible,  and  consist  of  fourteen  or  more 
segments.     There   are   four   pairs   of   jaws   including   the   jaw-like 


CHARACTERISTICS   OF  INSECTS  AND    THEIR   RELATIVES    21 


appendages  of  the  first  body-segment.  These  are  the  mandibles 
(Fig.  29,  A),  which  are  stout  and  consist  each  of  two  segments;  the 
maxillcB  (Fig.  29,  B,  a),  which  are  foHaceous, 
and  usually  regarded  as  biramous ;  the  second 
maxillcB  or  palpognaths,  which  are  leg-like  in 
form,  consisting  of  five  or  six  segments,  and 
usually  have  the  coxas  united  on  the  middle 
line  of  the  body  (Fig.  29,  B,  6),  and  the  poison- 
claws  or  toxicognaths,  which  are  the  appendages 
of  the  first  body-segment  (Fig.  29,  C). 

The  poison-claws  consist  each  of  six  seg- 
ments, of  which  the  basal  one,  or  coxa  is  usually 
fused  with  its  fellow,  the  two  forming  a  large 
coxal  plate,  and  the  distal  one  is  a  strong  pierc- 
ing fang  in  which  there  is  the  opening  of  the 
duct  leading  from  a  poison  gland,  which  is  in 
the  appendage. 

The  legs  consist  typically  of  six  segments, 
of  which  the  last,  the  tarsus,  is  armed  with  a 
single  terminal  claw.  The  last  pair  of  legs  are 
directed  backwards,  and  are  often  greatly 
modified  in  form. 
The  class  Chilopoda  includes  two  quite  distinct  groups  of  animals 

which  are  regarded  by    Pocock   ('u)   as  sub-classes,   the  Pleuro- 

stigma  and  theNoto- 

stigma.    The  names  A'^/M     W^W  \  ^ 

of     the     sub-classes 

refer  to  the  position      ^       a 

of  the  spiracles. 

Sub-Class 
PLEUROSTIGMA 

The  typical  Centipedes 

In  the  typical  cen- 
tipedes, the  sub-class 
Pleurostigma,  the 
spiracles  are  paired 
and  are  situated  in  the  sides  of  the  segments  that  bear  them.  Each 
leg-bearing  segment  contains  a  distinct  tergum  and  sternum,  the 
number  of  sterna  never   exceeding   that   of   the  terga.     The  eyes 


Fig.  28. — A  centipede 
Bothropolys   miilti- 
dentatus. 


Fig.  29. — Mouth-parts  of  a  centipede,  Geophilus  flavi- 
dus.  A,  right  mandible,  greatly  enlarged.  B,  the 
two  pairs  of  maxillae,  less  enlarged;  a,  the  united 
coxae  of  the  maxillae;  b,  the  united  coxae  of  the 
second  maxillae  or  palpognaths.  C,  the  poison  claws 
or  toxicognaths  (After  Latzel) 


22 


AN  INTRODUCTION   TO   ENTOMOLOGY 


when  present  are  simple  ocelli;    but  there  may  be  a  group  of  ocelli 
on  each  side  of  the  head.      Figure  28  represents  a  typical  centipede. 

Sub-Class  NOTOSTIGMA. 

Sctitigera  and  its  Allies 

In  the  genus  Scutlgera  and  its  allies, 
which  constitute  the  sub-class  Notostigma, 
there  is  a  very  distinctive  type  of  respiratory 
organs.  There  is  a  single  spiracle  in  each 
of  the  spiracle-bearing  segments,  which  are 
seven  in  number.  These  spiracles  open  in 
the  middle  line  of  the  back,  each  in  the  hind 
margin  of  one  of  the  seven  prominent  terga 
of  the  body-region.  Each  spiracle  leads  into 
a  short  sac  from  which  the  tracheal  tubes 
extend  into  the  pericardial  blood-sinus. 

There  are  fifteen  leg-bearing  segments  in~ 
the  body  region;  but  the  terga  of  these 
segments  are  reduced  to  seven  by  fusion  and 
suppression. 

The  eyes  differ  from  those  of  all  other 
members  of  the  old  group  Myriapoda  in 
being  compound,  the  ommatidia  resembling 
in  structure  the  ommatidia  of  the  compound 
eyes  of  insects. 

The  following  species  is  the  most  familiar 
representative  of  the  Notostigma. 

The  house  centipede,  Scuttgera  forceps. — 
This  centipede  attracts  attention  on  account 
of  the  great  length  of  its  appendages 
(Fig.  30),  and  the  fact  that  it  is  often  seen, 
in  the  regions  where  it  is  common,  running  on  the  walls  of  rooms  in 
dwelling  houses,  where  it  hunts  for  flies  and  other  insects.  It  prefers 
damp  situations;  in  houses  it  is  most  frequently  found  in  cellars, 
bathrooms,  and  closets.  Sometimes  it  becomes  very  abundant  in 
conservatories,  living  among  the  stored  pots  and  about  the  heating 
pipes.      It  is  much  more  common  in  the  South  than  in  the  North. 


Fig-  30. — SaUigcra  forceps. 


CHARACTERISTICS  OF  INSECTS  AND    THEIR   RELATIVES   23 


The  body  of  the  adult  measures  an  inch  or  a  Httle  more  in 
length.  It  is  difficult  to  obtain  perfect  specimens,  as  they  shed 
their  legs  when  seized. 

Class  SYMPHYLA 

The  Symphylids 

The  members  of  this  class  are  small 
arthropods  in  which  the  head  is  distinct,  and 
the  segments  of  the  body  form  a  single  con- 
tinuous region.  Most  of  the  body-segments 
bear  a  single  pair  of  legs.  The  antenncB  are 
very  long  and  many-jointed.  The  head  bears 
a  Y-shaped  epicranial  suture,  as  in  insects. 
The  opening  of  the  reproductive  organs  is  in 
the  third  segment  behind  the  head. 

The  class  Symphyla  includes  a  small 
number  of  many-legged  arthropods  which 
exhibit  striking  affinities  with  insects,  and 
especially  with  the  Thysanura.  The  body 
is  centipede-like  in  form  (Fig  31).  The 
head  is  distinct,  and  is  not    bent    dow!? 

as  it   is    in    the   diplopods  and  pauro- 

pods ;  it  is  shaped  as  in  Thysanura  and 

bears  a  Y-shaped  epicranial  suture.     The 

body-region  bears  fifteen  terga,  which  are 

distinct,  not  grouped  in  couples  as  in  the 

two    preceding   classes;    and    there  are 

eleven  or  twelve  pairs  of  legs. 

The  antennae  are  long  and  vary  greatly 

in  the  number  of  the  segments.    There  are 

noeyes.    The  mandibles,  the  "maxillui^" 

(paragnatha).  the  maxillae,  and  the  sec- 
ond maxillae  or  labium  are  present. 


Fig.     3 1 . — ScolopendreUa 
(After  Latzel). 


ig.  32.—  Mouth-parts  of 
ScolopendreUa  seen  from 
below:  wi,  mandible;  inx, 
maxillse;  s,  stipes;  p,  pal- 
pus; /,  second  maxillas  or 
labium.  The  mandible  on 
the  right  side  of  the  figur '. 
is  omitted  (After  Hansen). 


The  mandibles  (Fig.  32,  md)  are  two- 
jointed;  the  maxillulcB  (Fig.  33,  m)  are 
small,  not  segmented,  and  are  attached  to  a  median  lobe  o.' 
hypopharynx  (Fig.  33,  h);  they  are  hidden  when  the  mouth-part-,' 
are  viewed  from  below  as  represented  in  Figure  32 ;    the  maxillcB  (Fig, 


24  AN  INTRODUCTION   TO  ENTOMOLOGY 

2,2,  mx)  resemble  in  a  striking  degree  the  maxillas  of  insects,  consisting 
of  a  long  stipes,  (s),  which  bears  a  minute  palpus,  {p),  and  an  outer 
and  inner  lobe;  th.e  second  maxillcB  or  labium  (Fig. 
32,/)  also  resembles  the  corresponding  part  of  the 
more  generalized  insects,  being  composed  of  a  pair 
of  united  gnathites. 

The  legs  of  the  first  pair  are  reduced  in  size  and 
in  the  number  of  their  segments.  The  other  legs  ^popharynx  ^  (h) 
consist  each  of  five  segments;  the  last  segment  aridmaxillulae(m) 
bears  a  pair  of  claws.  Excepting  the  first  two  ?After^  Hansen f 
pairs  of  legs,  each  leg  bears  on  its  proximal  seg- 
ment a  slender  cylindrical  process,  the  parapodium  (Fig.  34,  p). 
These  parapodia  appear  to  correspond  with  the  styli  of  the 
Thysanura. 

At  the  caudal  end  of  the  body  there  is  a  pair  of 
appendages,  which  are  believed  to  be  homologous 
with  the  cerci  of  insects  (Fig.  35,  c). 

A  striking  peculiarity  of  the  symphylids  is  that 
Fig.  34-— A  leg  of  i]yQy  possess  only   a   single  pair  of  tracheal  tubes, 
p,  parapodium.  which  open  by  a  pair  01  spiracles,  situated  m  the 
head  beneath  the  insertion  of  the  antennse. 
The  members  of  this  class  are  of  small  size,  the 
larger  ones  measuring  about  one-fourth  inch  in 
length.   They  live  in  earth  under  stones  and  decay- 
ing wood,  and  in  other  damp  situations.     Imma- 
ture individuals    possess    fewer    body-segments 
and  legs  than  do  adults. 

Less  than  thirty  species  have  been  described; 
but  doubtless  many  more  remain  to  be  discovered. 

The  known  species  are  classed  in  two  genera:   pig.  35.— The  caudal 

Scolopendre'.la  and  Scutigerella.     In  the  former  the     ^nd  of  the  body  of 

J  J  J  ScolopendreUa;  I, 
posterior  angles  01  the  terga  are  produced  and  leg;  c,  cercus  (After 
angular;  while  in  the  latter  they  are  rounded.  Latzel). 

A  monograph  of  the  Symphyla  has  been  published  by  Hansen  ('03) . 

Class  MYRIENTOMATA 

The  Myrientoniatids 

The  members  of  this  class  are  small  arthropods  in  which  the  body  ia 
elongate,  as  in  the  Thysamira,  fttsiform,  pointed  behind,  and  depressed; 
it  may  be  greatly  extended  and  retracted.     The  antennas  and  cerci  are 


CHARACTERISTICS  OF  INSECTS  AND   THEIR  RELATIVES     25 


absent.  The  oral  apparatus  is  suctoral,  and  consists  of  three  pairs  of 
gnathites.  There  are  three  pairs  oj  thoracic  legs,  and  three  pairs  of 
vestigial  abdominal  legs.  The  abdomen  is  composed  of  eleven  segments 
and  a  telson.  The  opening  of  the  reproductive  organs  is  unpaired,  and 
near  the  hind  end  of  the  body.  The  head  bears  a  pair  of  organs,  termed 
pseudoculi,  the  nature  of  which  has  not  been  definitely  determined. 

The  known  members  of  this 
class  are  very  small  arthropods, 
the  body  measuring  from  one- 
fiftieth  to  three-fiftieths  of  an 
inch  in  length.  The  form  of  the 
body  is  shown  by  Figure  36. 

These  exceedingly  interesting 
creatures  are  found  in  damp 
situations,  as  in  the  humus  of 
gardens;  as  yet  very  little  is 
known  of  their  geographical  dis- 
tribution, as  almost  all  of  the 
studies  of  them  have  been  made 
by  two  Italian  naturalists. 

The  first  discovered  species 
was  described  in  1907  by  Pro- 
fessor F.  Silvestri  of  Portici,  who 
regarded  it  as  the  type  of  a 
distinct  order  of  insects,  for  which 
he  propo  ed  the  name  Protura. 
Later  Professor  Antonio  Berlese 
of  Florence  described  several 
additional  species,  and  published 
an  extended  monograph  of  the 
order  (Berlese  '09  b). 

Professor  Berlese  concluded 
that  these  arthropods  are  more 
closely  allied  to  the  "Myriapoda" 
and  especially  to  the  Pauropoda 
than  they  are  to  the  insects,  and  changed  the  name  of  the  order,  in 
an  arbitrary  manner,  to  Myrientomata. 

It  seems  clear  to  me  that  in  either  case  whether  the  order  is 
classed  among  the  insects  or  assigned  to  some  other  position  it  should 
be  known  by  the  name  first  given  to  it,  that  is,  the  Protura 


Fig.  36. — Acerentomon  doderoi:  A,  dor- 
sal aspect;  B,  ventral  aspect;  1,1,1, 
vestigial  abdominal  legs  (After 
Berlese). 


26  AN  INTRODUCTION  TO  ENTOMOLOGY 

In  the  present  state  of  our  knowledge  of  the  affinities  of  the  classes 
of  arthropods,  it  seems  best  to  regard  the  Protura  as  representing  a 
separate  class,  of  rank  equal  to  that  of  the  Paiiropoda,  Sjnnphyla,  etc. ; 
and  for  this  class  I  have  adopted  the  name  proposed  for  the  group  by 
Berlese,  that  is  the  Myrientomata. 

The  class  Myrientomata  includes  a  single  order. 

Order  PROTURA 

As  this  is  the  only  order  of  the  class  Myrientomata  now  known  it 
must  be  distinguished  by  the  characteristics  of  the  class  given  above. 

Two  families  have  been  established :  the  Acerentomidas,  charac- 
terized by  the  absence  of  spiracles  and  tracheae ;  and  the  Eosentomidse 
the  members  of  which  possess  two  pairs  of  thoracic  spiracles  and 
simple  trachea. 

That  the  Protura  are  widely  distributed  is  evident  from  the  fact 
that  in  addition  to  those  found  in  Italy,  representatives  of  the  order 
have  been  found  in  peat  in  Hampshire,  England,  and  others  have  been 
taken  near  New  York  City,  and  near  Washington,  D.  C. 

Class  HEXAPODA 
The  Insects 

The  members  of  this  class  are  air-breathing  arthropods,  with  distinct 
head,  thorax,  and  abdomen.  They  have  one  pair  oj  antennce,  three  pairs 
of  legs,  and  Msually  one  or  two  pairs  of  wings  in  the  adult  state.  The 
opening  of  the  reproductive  organs  is  near  the  caudal  end  of  the  body. 

We  have  now  reached  in  our  hasty  review  of  the  classes  of  arthro- 
pods the  class  of  animals  to  which  this  book  is  chiefly  devoted,  the 
Hexapoda,*  or  Insects,  the  study  of  which  is  termed  entomology. 

Insects  are  essentia  Ty  terrestrial ;  and  in  the  struggle  for  existence 
they  are  the  most  successful  of  all  terrestrial  animals,  outnumbering 
both  in  species  and  individuals  all  others  together.  On  the  land  they 
abound  under  the  greatest  variety  of  conditions,  special  forms  having 
been  evolved  fitted  to  live  in  each  of  the  various  situations  where 
other  animals  and  plants  can  live;  but  insects  are  not  restricted  to 
dry  land,  for  many  aquatic  forms  have  been  developed. 

The  aquatic  insects  are  almost  entirely  restricted  to  small  bodies 
of  fresh  water,  as  streams  and  ponds,  where,  they  exist  in  great  num- 
bers. Larger  bodies  of  fresh  water  and  the  seas  are  nearly  destitute 
of  them  except  at  the  shores. 

*Hexapoda:     hex  (^^),  six;   pons  (iroiJs),  afoot. 


and    the    destruction    of    many    flowering 
^   ^^^^^     .^        plants  that   depend   upon   insects   for   the 


m 


CHARACTERISTICS  OF  INSECTS  AND   THEIR  RELATIVES     27 

As  might  be  inferred  from  a  consideration  of  the  immense  number 
of  insects,  the  part  they  play  in  the  economy  of  nature  is  an  exceed- 
ingly important  one.  Whether  this  part  is  to  be  considered  a  bene- 
ficial or  an  injurious  one  when  judged  from  the  human  standpoint 
would  be  an  exceedingly  difficult  question  to  determine.  For  if 
insects  were  to  be  removed  from  the  earth  the  whole  face  of  nature 
would  be  changed. 

While  the  removal  of  insects  from  the  earth  would  eliminate  many 

pests  that  prey  on  vegetation,  would  relieve  many  animals  of  annoying 

parasites,  and  would  remove  some  of  the  most  terrible  diseases  to 

which  our  race  is  subject,  it  would  result  in  the  destruction  of  many 

groups    of    animals    that    depend,     either 

,*:p=^^  ^  z-.^^^^"*^  directlv  or  indirectly,  upon  insects  for  food, 

Aa'  //  fertilization  of  their  blossoms.     Truly  this 

^^-'^  world  would  speedily  become  a  very  differ- 

ent one  if  insects  were  exterminated. 

It  may  seem  idle  to  consider  what 
would  be  the  result  of  the  total  destruction 
of  insects;  but  it  is  not  wholly  so.  A  care- 
ful study  of  this  question  will  do  much 
to  open  our  eyes  to  an  appreciation  of  the 
wonderful  "web  of  life"  of  which  we  are  a 
Fig- 37- — Wasp  with  head,  part. 
thorax,   and   abdomen  Most   adult   insects   can   be  readily   dis- 

tinguished from  other  arthropods  by  the 
form  of  the  body,  the  segments  being  grouped  into  three  distinct 
regions,  head,  thorax,  and  abdomen  (Fig.  37),  by  the  possession  of 
only  three  pairs  of  legs,  and  in  most  cases  by  the  presence  of  wings 

The  head  bears  a  single  pair  of 
antennae,  the  organs  of  sight,  and  the 
mouth-parts.  To  the  thorax,  are 
articulated  the  organs  of  locomotion, 
the  legs  and  the  wings  when  they  are 
present.     The    abdomen    is    usually 

without    organs    of    locomotion    but        ^.       „     ,,       ,      ,    , 

r  XI     1  .1  ■,  Fig.  38.— Nymph  of  the  red- 

trequently  bears  other  appendages  at  legged  locust. 

the  caudal  end. 

These  characteristics  are  also  possessed  by  the  immature  forms 

of  several  of  the  orders  of  insects;  although  with  these  the  wings  are 


^^^^ 


28 


AN  INTRODUCTION   TO  ENTOMOLOGY 


rudimentary  (Fig.  38).  But  in  other  orders  of  insects  the  immature 
forms  have  been  greatly  modified  to  adapt  them  to  special  modes  of 
life,  with  the  result  that  they  depart  widely  from  the  insect  type.  For 
example,  the  lar\^se  of  bees,  wasps,  flies,  ^nd  many  beetles  are  legless 
and  more  or  less  worm-like  in  form  (Fig.  4) ;  while  the  larv^se  of  butter- 
flies and  moths  possess  abdominal  as  well  as  thoracic  legs  (Fig.  39). 


Fig.  39. — A  larva  of  a  handmaid  moth,  Datana. 


Although  the  presence  of  wings  in  the  adult  state  is  characteristic 
of  most  insects,  there  are  two  orders  of  insects,  the  Thysanura  and 
the  Collembola,  in  which  wings  are  absent.  These  orders  represent 
a  branch  of  the  insect  series  that  separated  from  the  main  stem  before 
the  evolution  of  wings  took  place;  their  wing- 
less condition  is,  therefore,  a  primitive  one. 
There  are  also  certain  other  insects,  as  the  lice 
and  bird-lice,  that  are  wingless.  But  it  is 
^.  believed  that  these  have  descended  from 
/  winged  insects,  and  have  been  degraded  by 
their  parasitic  life ;  in  these  cases  the  wingless 
condition  is  an  acquired  one.  Beside  these 
there  are  many  species  belonging  to  orders  in 
w'hich  most  of  the  species  are  winged  that 
have  acquired  a  wingless  condition  in  one  or 
both  sexes.  Familiar  examples  of  these  are  the 
females  of  the  Coccidas  (Fig.  40),  and  the 
females  of  the  canker-worm  moths.  In  fact, 
wingless  forms  occur  m  most  of  the  orders  of 
winged  insects. 
As  the  structure  and  transformations  of  insects  are  described  in 
detail  in  the  following  chapters,  it  is  unnecessary  to  dwell  farther  on 
the  characteristics  of  the  Hexapoda  in  this  place. 


Fig.  40. — A  mealy-bug, 
Dactylopius. 


CHAPTER   II. 
THE  EXTERNAL  ANATOMY  OF  INSECTS 

I.     THE   STRUCTURE   OF  THE   BODY-WALL 


a.      THE   THREE    LAYERS    OF   THE    BODY-WALL 

Three,  more  or  less  distinct,  layers  can  be  recognized  in  the  body- 
wall  of  an  insect:  first,  the  outer,  protecting  layer,  the  cuticula; 
second,  an  intermediate,  cellular  layer,  the  hypodermis;  and  third,  an 
inner,  delicate,  membranous  layer,  the  basement  membrane.     These 

layers  can  be  distinguished 
only  by  a  study  of  carefully 
prepared,  microscopic  sec- 
tions of  the  body-wall. 
Figure  41  represents  the  ap- 
pearance of  such  a  section. 
As  the  outer  and  inner  layers 
are  derived  from  the  hypo- 
derm  s,  this  layer  will  be 
described  first. 

The  hypodermis. — The  ac- 
tive living  part  of  the  body- 
wall  consists  of  a  layer  of  cells, 
which  is  termed  the  hypo- 
dennis  (Fig.  4^,  h). 

The  hypodermis  is  a  portion  of  one  of  the  germ-layers,  the  ectoderm.  In 
other  words,  that  portion  of  the  ectoderm  which  in  the  course  of  the  development 
of  the  insect  comes  to  form  a  part  of  the  body- wall  is  termed  the  hypodermis; 
while  to  invaginated  portions  of  the  ectoderm  other  terms  are  applied,  as  the 
epithelial  layer  of  the  trachea?,  the  epithelial  layer  of  the  fore-intestine,  and  the 
epithelial  layer  of  the  hind-intestine. 

The  cells  of  which  the  hypodermis  is  composed  vary  in  shape;  but 
they  are  usually  columnar  in  form,  constituting  what  is  known  to 
histologists  as  a  columnar  epitheliimi.  Sometimes  the  cells  are  so 
flattened  that  they  form  a  simple  pavement  epithelium.  I  know  of 
no  case  in  which  the  hypodermis  consists  of  more  than  a  single  layer 
of  cells;  although  in  wing-buds  and  buds  of  other  appendages,  where 
the  cells  are  fusiform,  and  are  much  crowded,  it  appears  to  be  irregu- 

(29) 


Fig.  41. — A  section  of  the  body-wall  of 
an  insect:  c,  cuticula;^,  hypodermis; 
bm,  basement  membrane;  e,  epidermis, 
d,  dermis;  tr,  trichogen;  s,  seta. 


30  AN  INTRODUCTION   TO  ENTOMOLOGY 

larly  stratified.     This  is  due  to  the  fact  that  the  nuclei  of  different 
cells  are  in  different  levels. 

The  trichogens. — Certain  of  the  hypodermal  cells  become  highly- 
specialized  and  produce  hollow,  hair-like  organs,  the  setas,  with  which 
they  remain  connected  through  pores  in  the  cuticula.  Such  a  hair- 
forming  cell  is  termed  a  Mchogen  (Fig.  41,  tr);  and  the  pore  in  the 
cuticula  is  termed  a  tnchopore. 

The  cuticula. — Outside  of  the  hypodermis  there  is  a  firm  layer, 
which  protects  the  body  and  serves  as  a  support  for  the  internal 
organs;  this  is  the  cuticula  (Fig.  41,  c).  The  cuticula  is  produced  by 
the  hypodermis;  the  method  of  its  production  is  discussed  in  a  later 
chapter  where  the  molting  of  insects  is  treated.  The  cuticula  is  not 
destroyed  by  caustic  potash ;  it  is  easy,  therefore,  to  separate  it  from 
the  tissues  of  the  body  by  boihng  or  soaking  it  in  an  aqueous  solution 
of  this  substance. 

Chitin. — The  well-known  firmness  of  the  larger  part  of  the  cuticula 
of  adult  insects  is  due  to  the  presence  in  it  of  a  substance  which  is 
termed  chitin.  This  substance  bears  some  resemblance  in  its  physical 
properties  to  horn ;  but  is  very  different  from  horn  in  chemical  com- 
position. In  thin  sheets  it  is  yellowish  in  color;  thicker  layers  of  it 
are  black.  It  is  stained  yellow  by  picric  acid  and  pink  by  safranin. 
Chitinized  and  non-chitinized  cuticula. — When  freshly  formed,  the 
cuticula  is  flexible  and  elastic,  and  certain  portions  of  it,  as  at  the 
nodes  of  the  body  and  of  the  appendages,  remain  so.  But  the  greater 
part  of  the  cuticula,  especially  of  adult  insects,  usually  becomes  firm 
and  inelastic;  this  is  probably  due  to  a  che  mical  change  resulting  in 
the  production  of  chitin.  What  the  natureof  this  change  is  or  how  it 
is  produced  is  not  yet  known,  but  it  is  evident  that  a  change  occurs ; 
we  may  speak,  therefore,  of  chitinized  cuticula  and  non-chitinized 
cuticula.  This  difference  is  well-shown  in  sections  of  the  cuticula 
stained  by  picro-carmine,  which  colors  the  chitinized  portions  yellow 
and  the  non-chitinized  parts  pink;  it  can  be  shown  also  by  other 
double  stains,  as  eosin-methylene-blue. 

Chitinized  cuticula  is  inelastic,  while  non-chitinized  cuticula  is 
elastic.  The  elasticity  of  non-chitinized  cuticula  is  well-shown  by  the 
stretching  of  the  body-wa'l  after  a  molt  and  before  the  hardening  of 
the  cuticula.  It  is  also  shown  by  the  expanding  of  the  abdomen  of 
females  to  accommodate  the  growing  eggs,  the  stretching  of  the  body- 
wall  taking  place  in  the  non-ch'.tinized  portions  between  the  segments. 
An  extreme  case  of  this  is  shown  by  the  queens  of  Termites. 


THE  EXTERNAL  ANATOMY  OF  INSECTS  31 

The  formation  of  chitinisnot  restricted  to  the  hypodermis,  but  is 
a  property  of  the  invaginated  portions  of  the  ectoderm:  the  fore- 
intestine,  the  hind-intestine,  and  the  tracheae  are  all  lined  with  a 
cuticular  layer,  which  is  continuous  with  the  cuticula  of  the  body -wall 
and  is  chitinized.  The  most  marked  case  of  internal  formation  of 
chitin  is  the  development  of  large  and  powerful  teeth  in  the  proven- 
triculus  of  many  insects. 

The  epidermis  and  the  dermis. — Two  quite  distinct  parts  of  the 
cuticula  are  recognized  by  recent  writers;  these  are  distinguished  as 
the  epidermis  and  the  dermis  respectively. 

The  epidermis  is  the  external  portion ;  in  it  are  located  all  of  the 
cuticular  pigments;  and  from  it  are  formed  all  scales,  hairs,  and  other 
surface  structures.  It  is  designated  by  some  writers  as  the  primary 
aiticida,  (Fig.  41,  e). 

The  dermis  is  situated  beneath  the  epidermis.  It  is  formed  in 
layers,  which  give  sections  of  the  cuticula  the  well-known  laminate 
appearance.     It  is  sometimes  termed  the  secondary  cuticula  (Fig.  41,  d) 

The  basement  membrane. — The  inner  ends  of  the  hy  podermal  cells 
are  bounded  by  a  more  or  less  distinct  membrane;  this  is  termed  the 
basement  membrane  (Fig.  41,  bm).  The  basement  membrane  is  most 
easily  seen  in  those  places  where  the  inner  ends  of  the  hypodermal  cells 
are  much  smaller  than  the  outer  ends;  here  it  is  a  continuous  sheet 
connecting  the  tips  of  the  hypodermal  cells. 

b.       THE    EXTERNAL    APOPHYSES    OF    THE    CUTICULA 

The  outer  surface  of  the  cuticula  bears  a  wonderful  variety  of  pro- 
jections. These,  however,  can  be  grouped  under  two  heads :  first, 
those  that  form  an  integral  part  of  the  cuticula;  and  second,  those 
that  are  connected  with  the  cuticula  by  a  joint.  Those  that  form  an 
integral  part  of  the  cuticula  are  termed  apophyses;  those  that  are  con- 
nected by  a  joint  are  termed  appendages  of  the  cuticula. 

The  cuticular  nodules. — The  most  frequently  occurring  out- 
growths of  the  cuticula  are  small,  more  or  less  conical  nodules. 
These  vary  greatly  in  size,  form,  and  distribution  over  the  surface  of 
the  body  in  diifersnt  species  cf  insects,  and  are  frequently  of 
taxGv.omic  value. 

The  fixed  hairs. — On  the  wings  of  some  insects,  as  the  Trichoptera 
and  certain  of  the  Lepidoptera,  there  are  in  addition  to  the  more 
obvious  setae  and  scales  many  very  small,  hair-like  structures,  which 


32 


AN  INTRODUCTION   TO  ENTOMOLOGY 


differ  from  setae  in  being  directly  continuous  with  the  cuticula,  and 
not  connected  with  it  by  a  joint;  these  are  termed  the  fixed  hairs,  or 
aculeae.  The  mode  of  origin  and  development  of  the  fixed  hairs  has  not 
been  studied. 

The  spines. — The  term  spine  has  been  used  loosely  by  writers  on 
entomology.  Frequently  large  setae  are  termed  spines.  In  this  work 
such  setae  are  called  spine-like  setae;  and  the  term  spine  is  applied 
only  to  outgrowths  of  the  cuticula  that  are  not  separated  from  it  by  a 
joint.  Spines  differ  also  from  spine-like  setae  in  being  produced  by 
undifferentiated  hypodermal  cells  and  are  usually  if  not  always  of 
multicellular  origin,  while  each  seta  is  produced  by  a  single  trichogen 
cell.     The  accompanying  diagram  (Fig.  42)  illustrates  this  difference. 


C.      THE   APPENDAGES    OF    THE    CUTICULA 

Under  this  head  are  included  those  outgrowths  of  the  cuticula  that 
are  connected  with  it  by  a  joint.  Of  these  there  are  two  quite  dis- 
tinct types  represented  by  the  spurs  and  the  setae  respectively. 

The  spurs. — There  exist  upon  the  legs  of  many  insects  appendages 
which  on  account  of  their  form  and  position  have  been  termed  spurs. 
Spurs  resemble  the  true  spines  described  above  and  differ  from  setae 
in  being  of  multicellular  origin;    they  differ  from  spines  in  being 

appendages,  that  is,  in 
being  connected  with  the 
body-wall  by  a  joint. 

The  setae. — The  setas 
are  what  are  commonly 
called  the  hairs  of  in- 
sects. Each  seta  (Fig. 
42,  5)  is  an  appendage  of 
the  body-wall,  which 
arises  from  a  cup-like 
cavity  in  the  cuticula, 
the  alveolus,  situated  at 
the  outer  end  of  a  per- 
foration of  the  cuticula, 
the  tnchopore;  and  each 
seta  is  united  at  its  base  with  the  wall  of  the  trichopore  by  a  ring  of 
thin  membrane,  the  articular  membrane  of  the  seta. 

The  setffi  are  hollow;  each  is  the  product  of  a  single  hypodermal 
cell,  a  trichogen  (Fig.  42),  and  is  an  extension  of  the  epidermal 
layer  of  the  cuticiila. 


Fig.  42. — Diagram  illustrating  the  difference  be- 
tween a  spine  (sp)  and  a  seta  (s). 


THE  EXTERNAL  ANATOMY  OF  INSECTS  33 

In  addition  to  the  trichogen  there  may  be  a  gland-cell  Opening  into 
the  seta,  thus  forming  a  glandular  hair,  or  a  nerve  may  extend  to  the 
seta,  forming  a  sense-hair;  each  of  these  types  is  discussed  later. 

The  most  common  type  of  seta  is  bristle-like  in  form;  familiar 
examples  of  this  type  are  the  hairs  of  many  larvae.  But  numerous 
modifications  of  this  form  exist.  Frequently  the  setae  are  stout  and 
firm,  such  are  the  spine-like  setce;  others  are  Jurnished  with  lateral 
prolongations,  these  are  the  plumose  hairs;  and  still  others  are  flat, 
wide,  and  comparatively  short,  examples  of  this  form  are  the  scales 
of  the  Lepidoptera  and  of  many  other  insects. 

The  taxonomic  value  of  setcB. — In  many  cases  the  form  of  the  setae 
and  in  others  their  "arrangement  on  the  cuticula  afford  useful  charac- 
teristics for  the  classification  of  insects.  Thus  the  scale-like  form  of 
the  setae  on  the  wing-veins  of  mosquitoes  serves  to  distinguish  these 
insects  from  closely  allied  midges;  and  the  clothing  of  scales  is  one 
of  the  most  striking  of  the  characteristics  of  the  Lepidoptera. 

The  arrangement  of  the  setae  upon  the  cuticula,  in  some  cases  at 
least,  is  a  very  definite  one.  Thus  Dyar  ('94)  was  able  to  work  out  a 
classification  of  lepidopterous  larvae  by  a  study  of  the  setae  v..ith 
which  the  body  is  clothed. 

A  classification  oj  setce. — If  only  their  function  be  considered  the 
hairs  or  setae  of  insects  can  be  grouped  in  the  three  following  classes : 

(i)  The  clothing  hairs. — Under  this  head  are  grouped  those  hairs 
and  scales  whose  primary  function  appears  to  be  merely  the  protection 
of  the  body  or  of  its  appendages.  So  far  as  is  known,  such  hairs  con- 
tain only  a  prolongation  of  the  trichogen  cell  that  produced  them.  It 
should  be  stated,  however,  that  this  group  is  merely  a  provisional  one; 
for  as  yet  comparatively  little  is  known  regarding  the  relation  of  these 
hairs  to  the  activities  of  the  insects  possessing  them. 

In  some  cases  the  clothing  hairs  have  a  secondary  function.  Thus 
the  highly  specialized  overlapping  scales  of  the  wings  of  Lepidoptera, 
which  are  modified  setae,  may  serve  to  strengthen  the  wings;  and  the 
markings  of  insects  are  due  almost  entirely  to  hairs  and  scales.  The 
fringes  on  the  wmgs  of  many  insects  doubtless  aid  in  flight,  and  the 
fringes  on  the  legs  of  certain  aquatic  insects  also  aid  in  locomotion. 

(2)  The  glandular  hairs. — Under  this  head  are  grouped  those  hairs 
that  serve  as  the  outlets  of  gland  cells.  They  are  discussed  in  the  next 
chapter,  under  the  head  of  hypodermal  glands. 

(3)  The  sense-hairs — In  many  case  a  seta,  more  or  less  modified 
in  form,  constitutes  a  part  of  a  sense-organ,  either  of  touch,  taste,  or 
smell ;   examples  of  these  are  discussed  in  the  next  chapter. 


34  AN  INTRODUCTION   TO  ENTOMOLOGY 

d.       THE    SEGMENTATION    OF    THE    BODY 

The  cuticular  layer  of  the  body-wall,  being  more  or  less  rigid, 
forms  an  external  skeleton;  but  this  skeleton  is  flexible  along  certain 
transverse  lines,  thus  admitting  of  the  movements  of  the  body,  and 
producing  the  jointed  appearance  characteristic  of  insects  and  of 
other  arthropods. 

An  examination  of  a  longitudinal  section  of  the  body-wall  shows 
that  it  is  a  continuous  layer  and  that  the  apparent  segmentation  is  due 
to  infoldings  of  it  (Fig.  43). 

The  body-seg- 
ments, somites,  or 
metameres.^ — Each 

section  of  the  body      .^.  _.  ^     .      .^  j-    1       ^-       t  ^i. 

Fig.  43. — Diagram  of  a  longitudinal  section  of  the 
between  two  of  the  body- wall  of  an  insect. 

infoldings  described 

above  is  termed  a  body-segment,  or  somite,  or  metamere. 

The  transverse  conjunctivae. — The  infolded  portion  of  the  body- 
wall  connecting  two  segments  is  term^ed  a  conjunctiva.  These  con- 
junctivae may  be  distinguished  from  others  described  later  as  the 
transverse  conjunctivce. 

The  conjunctivee  are  less  densely  chitinized  than  the  other  portions 
of  the  cuticula;  their  flexibility  is  due  to  this  fact,  rather  than  to  a 
comparative  thinness  as  has  been  commonly  described. 

e.       THE    SEGMENTATION    OF    THE    APPENDAGES 

The  segmentation  of  the  legs  and  of  certain  other  appendages  is 
produced  in  the  same  way  as  that  of  the  body.  At  each  node  of  an 
appendage  there  is  an  infolded,  flexible  portion  of  the  wall  of  the 
appendage,  a  conjunctiva,  which  renders  possible  the  movements  of 
the  appendage. 

/.       THE    DIVISIONS    OF    A    BODY-SEGMENT 

In  many  larvae,  the  cuticula  of  a  large  part  of  the  body-wall  is  of 
the  non-chitinized  type ;  in  this  case  the  wall  of  a  segment  may  form 
a  ring  which  is  not  divided  into  parts.  But  in  most  nymphs,  naiads, 
and  adult  insects,  there  are  several  densely  chitinized  parts  in  the  wall 
of  each  segment;  this  enables  us  to  separate  it  into  well-defined 
portions. 

The  tergum,  the  pleura,  and  the  sternum. — The  larger  divisions  of 
a  segment  that  are  commonly  recognized  are  a  dorsal  division,  the 


THE  EXTERNAL  ANATOMY  OF  INSECTS  35 

tergiim;  two  lateral  divisions,  one  on  each  side  of  the  body,  the  pleura; 
and  a  ventral  division,  the  sternum. 

Each  of  these  divisions  may  include  several  definite  areas  of 
chitinization.  In  this  case  the  sclerites  of  the  tergum  are  referred  to 
collectively  as  the  tergites,  those  of  each  pleurum,  as  the  pleurites,  and 
those  constituting  the  sternum,  as  the  siernites. 

The  division  of  a  segment  into  a  tergum,  two  pleura,  and  a  sternum 
are  most  easily  seen  in  the  wing-bearing  segments,  but  it  can  be 
recognized  also  in  the  prothorax  of  certain  generalized  insects.  This 
is  especially  the  case  in  many  Orthoptera,  as  cockroaches  and  walking- 
sticks,  where  the  pleura  of  the  prothorax  are  distinct  from  the  tergum 
and  the  sternum.  In  the  abdomen  it  is  evident  that  correlated  with 
the  loss  of  the  abdominal  appendages  a  reduction  of  the  pleura  has 
taken  place. 

The  lateral  conjunctivae. — On  each  side  of  each  abdominal  segment 
of  adults  the  tergum  and  the  sternum  are  united  by  a  strip  of  non- 
chitinized  cuticula;  these  are  the  lateral  conjunctivas.  Like  the 
transverse  conjunctivse,  the  lateral  ones  are  more  or  less  infolded. 

The  sclerites. — Each  definite  area  of  chitinization  of  the  cuticula 
is  termed  a  sclerite. 

The  sutures. — The  lines  of  separation  between  the  sclerites  are 
termed  sutures.  Sutures  vary  greatly  in  form ;  they  may  be  infolded 
conjunctivae ;  or  they  may  be  mere  lines  indicating  the  place  of  union 
between  two  sclerites.  Frequently  adjacent  sclerites  grow  together 
so  completely  that  there  is  no  indication  of  the  suture ;  in  such  cases 
the  suture  is  said  to  be  obsolete. 

The  median  sutures. — On  the  middle  line  of  the  tergites  and  also  of 
the  sternites  there  frequently  exist  longitudinal  sutures.  These  are 
termed  the  median  sutures.  They  represent  the  lines  of  the  closure 
of  the  embryo,  and  are  not  taken  into  account  in  determining  the 
number  of  the  sclerites. 

The  dorsal  median  suture  has  been  well-preserved  in  the  head  and 
thorax,  as  it  is  the  chief  line  of  rupture  of  the  cuticula  at  the  time  of 
molting. 

The  piliferous  tubercles  of  larvae. — The  setae  of  larvae  are  usually 
borne  on  slightly  elevated  annular  sclerites ;  these  are  termed  pilif- 
erous tubercles. 

The  homologizing  of  the  sclerites. — ^While  it  is  probable  that  the 
more  important  sclerites  of  the  body  in  winged  insects  have  been 
derived  from  a  common  winged  ancestor  and,  therefore,  can  be 
homologized,  many  secondary  sclerites  occiu:  which  can  not  be  thu«, 
homoiogized. 


36  AN  INTRODUCTION   TO   ENTOMOLOGY 

g.      THE    REGIONS    OF    THE    BODY 

The  segments  of  the  body  in  an  adult  insect  are  grouped  into  three, 
more  or  less  well-marked  regions:  the  head,  the  thorax,  and  the 
abdomen.  Each  of  these  regions  consists  of  several  segments  more  or 
less  closely  united 

The  head  is  the  first  of  these  regions;  it  bears  the  mouth-parts, 
the  eyes,  and  the  antennae.  The  thorax  is  the  second  region ;  it  bears 
the  legs  and  the  wings  if  they  are  present.  The  abdomen  is  the  third 
region;  it  may  bear  appendages  connected  with  the  organs  of  repro- 
duction. 

II.     THE  HEAD 

The  external  skeleton  of  the  head  of  an  insect  is  composed  of 
several  sclerites  more  or  less  closely  united,  forming  a  capsule,  which 
includes  a  portion  of  the  viscera,  and  to  which  are  articulated  certain 
appendages. 

a.      THE   CORNEAS    OF   THE    EYES 

The  external  layer  of  the  organs  of  vision,  the  corneas  of  the  eyes, 
is,  in  each  case,  a  translucent  portion  of  the  cuticula.  It  is  a  portion 
of  the  skeleton  of  the  head,  which  serves  not  merely  for  the  admission 
of  light  but  also  to  support  the  more  delicate  parts  of  the  visual 
apparatus. 

The  corneas  of  the  compound  eyes. — The  compound  eyes  are  the 
more  commonly  observ^ed  eyes  of  insects.  They  are  situated  one  on 
each  side  of  the  head,  and  are  usually  conspicuous.  Sometimes,  as  in 
dragon-flies,  they  occupy  the  larger  part  of  the  surface  of  the  head. 
The  compound  eyes  are  easily  recognized  as  eyes;  but  when  one 
of  them  is  examined  with  a  microscope  it  is  found  to  present  an 
appearance  very  different  from  that  of  the  eyes  of  higher  animals,  its 
surface  being  divided  into  a  large  number  of  six-sided  divisions  (Fig. 
44) ;   hence  the  term  compound  eyes  applied  to  them. 

A  study  of  the  internal  structure  of  this  organ 
has  shown  that  each  of  these  hexagonal  divisions 
is  the  outer  end  of  a  distinct  element  of  the  eye. 
Each  of  these  elements  is  termed  an  ommattdium. 
The  number  of  ommatidia  of  which  a  compound 
p.  ^  ^^  i-^f       ®^'®  ^^  composed  varies  greatly;  there  may  be  not 
cornea  of  a  com-    more  than  fifty,  as  in  certain  ants,  or  there  may 
pound  eye.  j^g  many  thousand,  as  in  a  butterfly  or  a  dragon-fly. 

As  a  rule,  the  immature  stages  of  insects  with  a  gradual  metamor- 
phosis and  also  those  of  insects  with  an  incomplete  metamorphosis. 


THE  EXTERNAL  ANATOMY  OF  INSECTS  37 

that  is  to  say  nymphs  and  naiads  possess  compound  eyes.  But  the 
larvae  of  insects  with  a  complete  metamorphosis,  do  not  possess  well- 
developed  compound  eyes;  although  there  are  frequently  a  few  sep- 
arate ommatidia  on  each  side  of  the  head.  These  are  usually  termed 
ocelli;  but  the  ocelli  of  larva>  should  not  be  confused  with  the  ocelli 
of  nymphs,  naiads,  and  adults. 

The  corneas  of  the  ocelli. — In  addition  to  the  compound  eyes  most 
nymphs,  naiads,  and  adult  insects  possess  other  eyes,  which  are 
termed  ocelli.  The  cornea  of  each  ocellus  is  usually  a  more  or  less 
nearly  circular,  convex  area,  which  is  not  divided  into  facets.  The 
typical  number  of  ocelli  is  four;  but  this  number  is  rarely  found. 
The  usual  number  is  three,  a  median  ocellus,  which  has  been  derived 
from  a  pair  of  ocelli  united,  and  a  distinct  pair  of  ocelli.  Frequently 
the  median  ocellus  is  lacking,  and  less  frequently,  all  of  the  ocelli 
have  been  lost.     The  position  of  the  ocelli  is  discussed  later. 

h.       THE  AREAS  OF  THE  SURFACE  OF  THE  HEAD 

In  descriptions  of  insects  it  is  frequently  necessary  to  refer  to  the 
different  regions  of  the  surface  of  the  head.  Most  of  these  regions 
were  named  by  the  early  insect  anatomists;  and  others  have  been 
described  by  more  recent  writers. 

This  terminology  is  really  of  comparatively  little  morphological  value;  for 
in  some  cases  a  named  area  includes  several  sclerites,  while  in  others  only  a  portion 
of  a  sclerite  is  included.  This  is  due  to  the  fact  that  but  few  of  the  primitive 
sclerites  of  the  head  have  remained  distinct,  and  some  of  them  greatly  over- 
shadow others  in  their  development.  The  terms  used,  however,  are  sufficiently 
accurate  to  meet  the  needs  of  describers  of  species,  and  will  doubtless  continue  in 
use.  It  is  necessary,  therefore,  that  students  of  entomology  become  familiar 
with  them. 

The  best  landmark  from  which  to  start  in  a  study  of  the  areas  of 
the  surface  of  the  head  is  the  epicranial  suture,  the  inverted  Y-shaped 
suture  on  the  dorsal  part  of  the  head,  in  the  more  generalized  insects 
(Fig.  45,  e.  su.).  Behind  the  arms  of  this 
suture  there  is  a  series  of  paired  sclerites,  which 
meet  on  the  dorsal  wall  of  the  head,  the  line  of 
union  being  the  stem  of  the  Y,  a  median  suture ; 
and  between  the  arms  of  the  Y  and  the  mouth 
there  are  typically  three  single  sclerites  (Fig.  45, 
F,  C,  L).  It  is  with  these  unpaired  sclerites 
that  we  will  begin  our  definitions  of  the  areas 
of  the  head.  Fig.  45   —Head  of  a 

The   front. — The    front    is    the   unpaired 
sclerite  between  the  arms  of  the  epicranial  suture  (Fig.  45,  F). 


38 


AN   INI  ROD  UCT ION    TO  ENTOMOLOGY 


Fig  46.  —  Head  of 
a  cockroach;  m, 
muscle  impres- 
sions. 


In  the  more  generalized  insects  at  least,  if  not  in  all,  the  front 

bears  the  median  ocellus ;  and  in  the  Plecoptera,  the  paired  ocelli  also. 

Frequently  the  suture  between  the  front  and  the  following  sclerite,  the 

clypeus,  is  obsolete;  but  as  it  ends  on  each  side  in  the  invagination 

which  forms  an  anterior  arm  of  the  tentorium  or 

endo-skeleton  (Fig.  46,  at),  its  former  position  can 

be    inferred,    at    least    in    the    more   generalized 

insects,  even  when  no  other  trace  of  it  remains. 

In  Figure  46  this  is  indicated  by  a  dotted  line. 

The  clypeus. — The  clypeus  is  the  intermediate 
of  the  three  unpaired  sclerites  between  the  epi- 
cranial suture  and  the  mouth  (fig.  46,  c).  To  this 
part  one  condyle  of  the  mandible  articulates. 

Although  the  clypeus  almost  always  appears 
to  be  a  single  sclerite,  except  when  divided  trans- 
versely as  indicated  below,  it  really  consists  of  a 
transverse  row  of  three  sclerites,  one  on  the  median  line,  and  one  on 
each  side  articulating  with  the  mandible.  The  median  sclerite  may 
be  designated  the  clypeus  proper,  and  each  lateral  sclerite,  the  ante- 
coxal  piece  of  the  mandible.  Usually  there  are  no  indications  of  the 
sutures  separating  the  clypeus  proper  from  the  antecoxal  pieces;  but 
in  some  insects  they  are  distinct.  In  the  larva  of  Corydalus,  the  ante- 
coxal pieces  are  not  only  distinct  but  are  quite  large  (Fig.  47,  ac,  ac). 
In  some  insects  the  clypeus  is  completely  or  partly  divided  by  a 
transverse  suture  into  two  parts  (Fig.  45).  These  may  be  designated 
as  the  first  clypeus  and  the  second  clypeus,  respectively;  the  first 
clypeus  being  the  part  next  the  front  (Fig. 
45,  Ci)  and  the  second  clypeus  being  that  next 
the  labrum  (Fig.  45,  C2). 

The  suture  between  the  clypeus  and  the 
epicranium  is  termed  the  clypeal  suture. 

The  labrum. — The  labrum  is  the  movable 
flap  which  constitutes  the  upper  lip  of  the 
mouth  (Fig.  45,  L).  The  labrum  is  the  last  of 
the  series  of  unpaired  sclerites  between  the 
epicranial  suture  and  the  mouth.  It  has  the 
appearance  of  an  appendage  but  is  really  a 
portion  of  one  of  the  head  segments. 

The    epicranium. — Under     the     term     epi- 
cranium are  included  all  of  the  paired  sclerites  of  the  skull,  and  some- 
times also  the  front.     The  paired  sclerites  constitute  the  sides  of 


Fig;.  4Z  ■ — Head  of  a 
larva  of  Corydahis, 
dorsal  aspect 


THE  EXTERNAL   ANATOMY  OF  INSECTS 


39 


the  head  and  that  portion  of  the  dorsal  surface  that  is  behind  the 

arms    of    the    epicranial   suture.     The    sclerites    constituting    this 

region  are  so  closely  united  that  they  were  regarded  as  a  single 

piece  by  Straus-Durckheim  (1828),  who  also  inc  uded  the  front  in 

this  region,  the  epicranial  suture  being  obsolete  in  the  May  beetle, 

which  he  used  as  a  type. 

The  vertex. — The  dorsal  portion  of  the  epicraniiim;    or,  more 

specifically,  that  portion  which  is  next  the  front  and  between  the 

compound  eyes  is  known  as  the  mrtex  (Fig.  45,  V,   V).     In  many 

insects  the  vertex  bears  the  paired  ocelli.     It  is  not  a  definite  sclerite; 

but  the  term  vertex  is  a  very  useful  one  and  will  doubtless  be  retained. 

The  occiput. — The  hind  part  of  the  dorsal  surface  of  the  head  is  the 

occiput.     When  a  distinct  sclerite,  it  is  formed 

from  the  tergal  portion  of  the  united  postgenas 

described  below  (Fig.  47,  0,  0). 

The  genae. — The  gencB  are  the  lateral  portions 
of  the  epicranium.  Each  gena,  in  the  sense  in 
which  the  word  was  used  by  the  older  writers, 
includes  a  portion  of  several  sclerites.  Like 
vertex,  however,  the  term  is  a  useful  one. 

The  postgenae. — In  many  insects  each  gena  is 
divided  by  a  well-marked  suture.  This  led  the 
writer,  in  an  earlier  work  ('95),  to  restrict  the 
term  gena  to  the  part  in  front  of  the  suture  (Fig. 
48,  G),  and  to  propose  the  term  postgena  for  the 
part  behind  the  suture  (Fig.  48,  Pg). 
The  gula. — The  gula  is  a  sclerite  forming  the  ventral  wall  of  the 

hind  part  of  the  head  in  certain  orders  of  insects, 

and  bearing  the  labium   or  second  maxillae  (Fig. 

49,  Gu).      In  'the  more   generalized  orders,  the 

sclerite  corresponding  to  the  gula  does  not  form 

a  part  of  the  skull.      The  sutures   forming  the 

lateral  boundaries   of   the   gula   are   termed  the 

gular  sutures. 

The  ocular  sclerites. — In  many  insects  each 

compound   eye    is  situated   in    the    axis    of   an 

annular    sclerite;     these    sclerites    bearing    the 

compound  eyes  are  the  ocular  sclerites  (Fig.  50,  os). 
The  antennal  sclerites. — In  some  insects  there 

is  at  the  base  of  each  antenna  an  annular  sclerite ; 

these  are  the  antennal  sclerites  (Fig.  50,  as).      The  antennal  sclerites 

are  most  distinct  in  the  Plecoptera. 


Fig.  48. — Hoad  and 
neck  of  a  cock- 
roach. 


-Head  of 
Corydiilus,  adult, 
ventral  aspect. 


40  AN  INTRODUCTION   TO  ENTOMOLOGY 

The  trochantin  of  the  mandible. — In  some  insects,  as  Orthoptera 
there  is  a  distinct  sclerite  between  each  mandible  and  the  gena; 
this  is  the  trochantin  of  the  mandible  (Fig.  45,  ir). 

The  maxillary  pleurites. — ^In  some  of  the  more  generalized  insects, 
as  certain  cockroaches  and  crickets,  it  can  be  seen  that  each  maxilla 
is  articulated  at  the  ventral  end  of  a  pair  of  sclerites,  between  which 
is  the  invagination  that  forms  the  posterior  arm  of  the  tentorium; 
these  are  the  maxillary  pleurites;  the  pos- 
terior member  of  this  pair  of  sclerites  can 
be  seen  in  the  lateral  view  of  the  head  of  a 
cockroach  (Fig.  48,  m.  em). 

The  cervical  sclerites. — The  cervical  scler- 
ites are  the  small  sclerites  found  in  the  neck  of 
many  insects.  Of  these  there  are  dorsal, 
lateral,  and  ventral  sclerites.  The  cervical 
sclerites  v/ere  so  named  by  Huxley  ('78); 

„.  TT     ,       f  recently  they  have  been  termed  the  ^"«/er5^g- 

cricket,    ental    surface     mental  plates  by  Crampton  ('17),  who  con- 
of  the  dorsal  wall.  g^^^^-g  ^j^g^^  ^^  ^^  homologous  with  sclerites 

found  in  the  intersegmental  regions  of  the 
thorax  of  some  generalized  insects. 

The  lateral  cervical  sclerites  have  long  been  known  as  the  jugular 
sclerites  {pieces  jugulaires,  Straus  Durckheim,  1828). 

C.       THE    APPENDAGES    OF    THE    HEAD 

Under  this  category'  are  classed  a  pair  of  jointed  appendages 
termed  the  antenncE,  and  the  organs  known  collectively  as  the  mouth- 
parts. 

The  antemiae. — The  antennce  are  a  pair  of  jointed  appendages 
articulated  with  the  head  in  front  of  the  eyes  or  between  them.  The 
antennae  vary  greatly  in  form;  in  some  insects  they  are  thread-like, 
consisting  of  a  series  of  similar  segments;  in  others  certain  segments 
are  greatly  modified.     The  thread-like  form  is  the  more  generalized. 

In  descriptive  works  names  have  been  given  to  particular  parts  of  the  antennae, 
as  follows  (Fig.  51): 

The  Scape. — The  first  or  proximal  segment  of  an  antenna  is  called  the  scape  (a). 
The  proximal  end  of  this  segment  is  often  subglobose,  appearing  like  a  distinct 
segment;  in  such  cases  it  is  called  the  bulb  (a'). 


THE   EXTERNAL   ANATOMY  OF  INSECTS 


41 


The  Pedicel. — The  pedicel  is  the    second    segment    of  an  antenna  {b).      In 
some  insects  it  differs  greatly  in  form  from  the  other  segments. 

The  Cldvola.— The  term  cla- 
vola  is  applied  to  that  part  of 
the  antenna  distad  of  the  pedi- 
cel (c);  in  other  words,  to  all 
of  the  antenna  except  the  first 
and  second  segments.  In  some 
insects  certaia  parts  of  the  cla- 
vola  are  specialized  and  have 
received  particular  names. 
These  are  the  ring-joints,  the 
funicle,  and  the  club. 

The  Ring-j oinis .~ln  certain 
Fig.  51.— Antennaofachalcis-fly.  -^g^^^g    (^_g_^    Chalcidids)    the 

proximal  segment  or  segments   of  the  clavola  are  much  shorter  than  the  suc- 
ceeding segments;   in  such  cases  they  have  received  the  name  of  ring-joints  (c*). 

The  Club. — In  many  insects  the  distal  seg- 
ments of  the  antennae  are  more  or  less  enlarged. 
In  such  cases  they  are  termed  the  club  (c^). 

The  Fiinicle. — The  funicle  (c^)  is  that  part 
of  the  clavola  between  the  club  and  the  ring- 
joints;  or,  when  the  latter  are  not  specialized, 
between  the  club  and  the  pedicel. 

The  various  forms  of  antennse  are  designated 
by  special  terms.  The  more  common  of  these 
forms  are  represented  in  Fig.  52.  They  are 
as  follows : 

1.  Setaceous  or  bristle-like,  in  which  the 
segments  are  successively  smaller  and  smaller, 
the  whole  organ  tapering  to  a  point. 

2.  Ftliform  or  thread-like,  in  which  the 
segments  are  of  nearly  uniform  thickness. 

3.  Momlijorm  or  necklace-form,  in  which 
the  segments  are  more  or  less  globose,  suggesting 
a  string  of  beads. 

4.  Serrate  or  saw-like,  in  which  the  segments 
are  triangular  and  project  like  the  teeth  of  a  saw. 

5.  Pectinate  or  comb-like,  in  which  the  seg- 
ments have  long  processes  on  one  side,  like  the 
teeth  of  a  comb. 

6.  Cldvate  or  club-shaped,  in  which  the  segments  become  gradually  broader, 
so  that  the  whole  organ  assumes  the  form  of  a  club. 

7.  Capitate  or  with  a  head,  in  which  the  terminal  segment  or  segments  form 
a  large  knob. 

8.  Lamellate  in  which  the  segments  that  compose  the  knob  are  extended  on 
one  side  into  broad  plates. 

When  an  antenna  is  bent  abruptly  at  an  angle  like  a  bent  knee  (Fig.  51)  it  is 
said  to  be  geniculate. 


Fig.  52. — Various  forms  of 
antennas. 


42 


AN  INTRODUCTION   TO  ENTOMOLOGY 


The  mouth-parts. — The  mouth-parts  consist  typically  of  an  upper 
lip,  labrum,  an  under  lip,  labium,  and  two  pairs  of  jaws  acting  hori- 
zontally between  them.     The  upper  jaws  are  called  the  mandibles; 

the  lower  pair,  the  maxilke. 
The  maxillae  and  labium  are 
each  furnished  with  a  pair  of 
feelers,  called  respectively 
the  maxillary  palpi,  and 
the  labial  palpi.  There 
may  be  also  within  the 
mouth  one  or  two  tongue- 
like organs,  the  epipharynx 
and  the  hypopharynx.  The 
mouth-par  s  of  a  locust  will 
serve  as  an  example  of  the 
typ  cal  form  of  the  mouth- 
parts  (Fig.  53). 

The  mouth-parts  enumer- 
ated in  the  preceding  paragraph 
are  those  commonly  recognized 
in  insects;  but  in  certain  insects 
there  exist  vestiges  of  a  pair  of 
lobes  between  the  mandibles  and 
the  maxillsp,  these  are  the  parag- 
natha. 

No  set  of  organs  in  the 
body  of  an  insect  vary  in 
form  to  a  greater  degree  than 
do  the  mouth-parts.  Thus 
with  some  the  mouth  ''s 
formed  for  chewing,  while  with  others  it  is  formed  for  sucking. 
Among  the  chewing  insects  some  are  predaceous,  and  have  jaws  fitted 
for  seizing  and  tearing  their  prey ;  others  feed  upon  vegetable  matter, 
and  have  jaws  for  chewing  this  kind  of  food.  Among  the  sucknig 
insects  the  butterfly  merely  sips  the  nectar  from  flowers,  while  the 
mosquito  needs  a  powerful  instrument  for  piercing  its  victim.  In 
this  chapter  the  typical  form  of  the  mouth-parts  as  illustrated  by  the 
biting  insects  is  described.  The  various  modifications  of  it  presented 
by  the  sucking  insects  are  described  later,  in  the  discussions  of  the 
characters  of  those  insect.^. 


Fig-  53- — Mouth-parts  of  a  locust:  la,  lab- 
rum  ;m£?,  mandible;  mx,  maxilla;  h,  hypo- 
pharynx;    /,  labium. 


THE  EXTERNAL   ANATOMY  OF  INSECTS 


43 


The  lab  rum. — The  Idhnmi  or  upper  lip  (Fig.  53),  is  a  more  or  less 
flap-like  organ  above  the  opening  of  the  mouth.  As  it  is  often  freely 
movable,  it  has  the  appearance  of  an  appendage  of  the  body;  but  it 
is  not  a  true  appendage,  being  a  part  of  one  of  the  body  segments  that 
enter  into  the  composition  of  the  head. 

The  mandibles. — The  mandibles  are  the  upper  pair  of  jaws  (Fig. 
53).  They  represent  the  appendages  of  one  of  the  segments  of  the 
head.  In  most  cases  they  are  reduced  to  a  single  segment;  but  in 
some  insects,  as  in  certain  beetles  of  the  family  Scarabasidae,  each 
mandible  consists  of  several  more  or  less  distinct  sclerites. 

The  paragnatha. — In  some  insects  there  is  between  the  mandibles 
and  the  maxillae  a  pair  of  more  or  less  appendage-like  organs  borne  by 
the  hypopharynx.  These  are 
the  "paragloss^"  of  writers  on 
the  Thysanura  and  Collemh  ola 
and  the  "superlinguae"  of  Fol- 
som  ('00).  They  were  termed 
the  maxillulae,  a  diminutive  of 
maxillae  by  Hansen  ('93),  who 
regards  them  as  homologous 
with  the  first  maxillae  of  the 
Crustacea.  But  it  has  been 
shown  by  Crampton  ('21)  that 
they  are  homologous  with  the  paragnatha  of  Crustacea.  In 
Figure  54,  A.  represents  a  ventral  view  of  the  hypopharynx,  parag- 
natha, and  mandibles  of  the  crustacean  Ligyda;  and  B.  the  same 
parts  of  a  naiad  of  a  May-fly,  Heptagenia.  Paragnatha  have  been 
found  in  the  Thysanura,  Dermoptera,  Orthoptera,  Carrodentia,  the 
naiads  of  Ephemerida,  and  the  larvae  of  Coleoptera. 

The  Maxilla;. — The  maxilla:  are  the  second  pair  of  jaws  of  insects. 
Like  the  mandibles  they  are  the  appendages  of  one  of  the  segments 
of  the  head. 

The  maxillag  are  much  more  complicated  than  the  mandibles,  each  maxilla 
consisting,  when  all  of  the  parts  are  present,  of  five  primary  parts  and  three 
appendages.  The  primary  parts  are  the  cardo  or  hinge,  the  stipes  or  foot.- 
stalk,  the  palpifer  or  palpus-bearer,  the  subgalea  or  helmet-bearer,  and  the 
lacinia  or  blade.     The  appendages  are  the  maxillary  palpus  or  feeler,  the  galea 


Fig.  54. — A.  Posterior  (ventral")  view  of 
mandibles  and  hypopharynx  of  the 
crustacean  Ligyda ;^  h,  hypopharynx; 
p,  paragnatha;  m,  mandibles:  B. 
.Same  of  a  nymph  of  the  Mayfly 
Heptagenia    (From  Crampton). 


44 


AN  INTRODUCTION   TO   ENTOMOLOGY 


or  superior  lobe,  and  the  digitus  or  finger.     The  maxilla  may  also  bear  claw-like 
or  tooth-like  projections,  spines,  bristles,  and  hairs. 

In  the  following  description  of  the  parts  of  the  maxillae,  only  very  general 
statements  can  be  made.  Not  only  is  there  an  infinite  variation  in  the  form  of 
these  parts,  but  the  same  part  may  have  a  very  different  outline  on  the  dorsal 
aspect  of  the  maxilla  from  what  it  has  on  the  ventral.  Compare  Fi;j.55  and  Fig. 
56,  which  represent  the  two  aspects  of  the  maxilla  of  Hydrophilus.  Excepting 
Fig.  56,  the  figures  of  maxilla;  represent  the  ventral  aspect  of  this  organ. 

The  cardo  or  hinge  (a)  is  the  first  or  proximal  part  of  the  maxilla.  It  is  usually 
more  or  less  triangular  in  outline,  and  is  the  part  upon  which  nearly  all  of  the 
motions  of  this  organ  depend  In  many  cases,  however,  it  is  not  the  only  part 
directly  joined  to  the  body;  for  frequently  muscles  extend  direct  to  the  L:iibgalea, 
without  passing  through  the  cardo. 

The  stipes  or  footstallc  ih)  is  the  part  next  in  order  proceeding  distad.  It  is 
usually  triangular,  and  articulates  with  the  cardo  by  its  base,  with  the  palpifer 
by  its  lateral  margin,  and  with  the  subgalea  by  its  mesal  side.  In  many  insects 
the  stipes  is  united  with  the  subgalea,  and  the  two  form  the  larger  portion  of  the 
body  of  the  maxilla  (Fig.  53).  The  stipes  has  no  appendages;  but  the  palipfer 
on  the  one  ide,  and  the  subgalea  on  the  other,  may  become  united  to  the  stipes 
without  anys  trace  of  suture  remaining,  and  their  appendages  will  then  appear 
to  be  borne  by  the  stipes.  Thus  in  Fig.  53  it  appears  to  be  the  stipes  that  bears 
the  galea,  and  that  receives  muscles  from  the  body. 

The  palpifer  or  palpus-bearer  (c)  is  situated  upon  the  lateral  (outer)  side 

of  the  stipes;  it  does  not, 
however,  extend  to  the  base 
of  this  organ,  and  frequently 
projects  distad  beyond  it. 
It  is  often  much  more 
developed  on  the  dorsal 
side  of  the  maxilla  than  on 
the  ventral  (Figs.  55  and  56). 
It  can  bereadily  distinguished 
when  it  is  distinct  by  the 
insertion  upon  it  of  the  ap- 
pendage which  gives  to  it 
its  name. 

The  maxillary  palpus  or 
feeler  (d)  is  the  most  conspicuous  of  the  appendages  of  the  maxilla.  It  is  an 
organ  composed  of  from  one  to  six  freely  movable  segments,  and  is  articulated 
to  the  palpifer  on  the  latero-distal  angle  of  the  body  of  the  maxilla. 

The  subgalea  or  heknet-bearer  (e)  when  developed  as  a  distinct  sclerite  is  most 
easily  distinguished  as  the  one  that  bears  the  galea.  It  bounds  the  stipes  more 
or  less  completely  on  its  mesal  (inner)  side,  and  is  often  directly  connected 
with  the  body  by  muscles.  In  many  Coleoptera  it  is  closely  united  to  the 
lacinia;  this  gives  the  lacinia  the  appearance  of  bearing  the  galea,  and  of  being 
connected  with  the  body  (Fig.  56).  In  several  orders  the  subgalea  is  united  to 
the  stipes;  consequently  in  these  orders  the  stipes  appears  to  bear  the  galea, 
and  to  be  joined  directly  to  the  body  if  any  part  besides  the  cardo  is  so 
connected. 


Fig.  55. — Ventral  as- 
pect of  a  maxilla  of 
Hydrophilus. 


Fig.  56. — Dorsal  as- 
pect of  a  maxilla  of 
Hydrophilus. 


THE   EXTERNAL   ANATOMY  OF  INSECTS 


45 


Fig'  57- — Maxilla  of  Cicindela. 


The  galea   or  helmet   (/)   is  the  second  in  prominence  of  the  appendages 

of  the  maxilla.      It  consists  of  one  or  two  segments,  and  is  joined  to  the  maxilla 

mesad  of  the  palpus.     The  galea  varies  greatly 

in  form:    it  is  often  more  or  less  flattened,  with 

the    distal    segment   concave,  and    overlapping 

the  lacinia  like  a  hood.     It  was  this  form  that 

suggested  the  name  galea  or  helmet.     In  other 

--^\\  'HI       A  1  r^   'i^'  ^         cases  the  galea  resembles  a  palpus  in  form  (Fig. 

Jx.^   X    \\  V>    \^I~^^     5"^-     "^^^^  galea  is  also  known  as  the  outer  lohe, 

^^  the  upper  lobe,  or  the  superior  lobe. 

The  lacinia  or  blade  (g)  is  borne  on  the  mesal 
(inner)  margin  of  the  subgalea.  It  is  the  cutting 
or  chewing  part  of  the  maxilla,  and  is  often 
furnished  with  teeth  and  spines.  The  lacinia  is 
also  known  as  the  inner  lobe,  or  the  inferior  lobe. 

The  digitus  or  finger  Qi)  is  a  small  appendage 
sometimes  borne  by  the  lacinia  at  its  distal  end. 
In  the  Cicindelidse  it  is  in  the  form  of  an  articu- 
lated claw  (Fig.  57);  but  in  certain  other  beetles 
it  is  more  obviously  one  of  the  segments  of  the 
maxilla  (Figs.  55  and  56). 

The  labium  or  second  maxillcs. — The  labium  or  under  lip  (Fig.  53), 
is  attached  to  the  cephalic  border  of  the  gula,  and  is  the  most  ventral 
of  the  mouth-parts.  It  appears  to  be  a  single  organ,  although  some- 
times cleft  at  its  distal  extremity;  it  is,  however,  composed  of  a  pair 
of  appendages  grown  together  on  the  middle  ine  of  the  body.  In  the 
Crustacea  the  parts  corresponding  to  the  labiimi  of  insects  consists  of 
two  distinct  organs, 
resembling  the 
maxillse;  and  in  the 
embryos  of  insects 

the  labium  arises  as     \    \  \V'-    "1    T  »  i-i/  d- 

a  pair    of  append- 
ages. 

In  naming  the  parts 
of  the  labium,  entomo- 
logists have  usually 
taken  some  form  of  it 
in  which  the  two  parts 
are  completely  grown 
together,  that  is,  one 
which  is  not  cleft  on 
the  middle   line    (Fig. 

58).     I  will  first   describe  such  a  labium,  and  later    one    in  which  the  division 
into  two  parts  is  carried  as  far  as  we  find  it  in  insects. 


Fig.  58. — Labium  of  Harpalus. 


46  AN    INTRODUCTION   TO  ENTOMOLOGY 

The  labium  is  usually  described  as  consisting  of  three  principal  parts  and  a 
pair  of  appendages.  The  principal  parts  are  the  submentum,  the  mentum,  and 
the  ligula;  the  appendages  are  the  labial  palpi. 

The  submentum.  The  basal  part  of  the  labium  consists  of  two  transverse 
sclerites;  the  proximal  one,  which  is  attached  to  the  cephaUc  border  of  the  gula, 
is  the  submentum  (a).  This  is  often  the  most  prominent  part  of  the  body  of 
the  labium. 

The  mentum  is  the  more  distal  of  the  two  primary  parts  of  the  labium  (b). 
It  is  articulated  to  the  cephaHc  border  of  the  submentum,  and  is  often  so 
slightly  developed  that  it  is  concealed  by  the  submentum. 

The  Itgula  includes  the  remaining  parts  of  the  labium  except  the  labial  palpi. 
It  is  a  compound  organ;  but  in  the  higher  insects  the  sutures  between  the 
different  sclerites  of  which  it  is  composed  are  usually  obsolete.  Three  parts, 
however,  are  commonly  distinguished  (Fig.  58),  a  central  part,  often  greatly 
prolonged,  the  glossa  (c^)  and  two  parts,  usually  small  membranous  projections, 
one  on  each  side  of  the  base  of  the  glossa,  the  paraglosscB  (c^) .  Sometimes,  how- 
ever, the  paraglossas  are  large,  exceeding  the  glossa  in  size. 

The  labial  palpi.  From  the  base  of  the  ligula  arise  a  pair  of  appendages,  the 
labial  palpi.  Each  labial  palpus  consists  of  from  one  to  four  freely  movable 
segments. 

In  the  forms  of  the  labium  just  described,  the  correspondence  of  its  parts  tc 
the  parts  of  the  maxillae  is  not  easily  seen;  but  this  is  much  more  evident  in  the 
labium  of  some  of  the  lower  insects,  as  for  example  a  cockroach  (Fig.  59).  Here 
the  organ  is  very  deeply  cleft;  only  the  submentum 
and  mentum  remain  united  on  the  median  line;  while 
the  ligula  consists  of  two  distinct  maxilla-like  parts. 
It  is  easy  in  this  case  to  trace  the  correspondence 
referred  to  above.  Each  lateral  half  of  the  submentum 
corresponds  to  the  cardo  of  a  maxilla;  each  half  of  the 
mentum,  to  the  stipes;  while  the  remaining  parts  of  a 
maxilla  are  represented  by  each  half  of  the  ligula,  as 
follows:  near  th-  base  of  the  ligula  there  is  a  part  (c') 
which  bears  the  labial  palpus;  this  appears  in  the 
figure  like  a  basal  segment  of  the  palpus;  but  in  many 
insects  it  is  easily  seen  that  it  is  undoubtedly  one  of 
the  primary  parts  of  the  organ;    it  has  been  named 

pig_  CQ_ Labium  of  a      ^^^^  palpiger,  and  is  the  homologue  of  the  palpifer  of 

cockroach.  a  maxilla.     The  trunk  of  each   half  of  the  ligula  is 

formed  by  a  large  sclerite  (c*) ;  this  evidently  corres- 
ponds to  the  subgalea.  At  the  distal  extremity  of  this  subgalea  of  the  labium 
there  are  two  appendages.  The  lateral  one  of  these  (f^)  is  the  paraglossa, 
and  obviously  corresponds  to  the  galea.  The  mesal  one  (<,-)  corresponds  to  the 
lacinia  or  inner  lobe.  This  part  is  probably  wanting  in  those  insects  in  which 
the  glossa  consists  of  an  undividei:  part;  and  in  this  case  the  glossa  probably 
represents  the  united  and  more  or  less  elongated  subgalese. 

The  epipharynx. — In  some  insects  there  is  borne  on  the  ental  stir- 
face  of  the  labium,  within  the  cavity  of  the  mouth,  an  unpaired  fold, 
which  is  membranous  and  more  or  less  chitinized;  this  is  the  epi- 
ph&rynx. 


THE   EXTERNAL   ANATOMY  OF  INSECTS  47 

The  hypopharynx. — The  hypophdrynx  is  usually  a  tongue-like 
organ  borne  on  the  floor  of  the  mouth  cavity.  This  more  simple  form 
of  it  is  well-shown  in  the  Orthoptera  (Fig.  53).  To  the  hypopharnyx 
are  articulated  the  ])aragnatha  when  they  are  present.  The  hypo- 
pharynx  is  termed  the  lingua  by  some  writers. 

d.       THE    SEGMENTS    OF    THE    HEAD 

The  determination  of  the  number  of  segments  in  the  head  of  an  insect  is  a 
problem  that  has  been  much  discussed  since  the  early  days  of  entomology.  The 
first  important  step  towards  its  solution  was  made  by  Savigny  (1816),  who  sug- 
gested that  the  movable  appendages  of  the  head  were  homodyanmous  with  legs. 
This  conclusion  has  been  accepted  by  all;  and  as  each  segment  in  the  body  of  an 
insect  bears  only  a  single  pair  of  appendages,  there  are  at  least  four  segments 
in  the  head;  i.e.,  the  antennal,  the  mandibular,  the  maxillary,  and  the  second 
maxillary  or  labial. 

In  more  recent  times  workers  on  the  embryology  of  insects  have  demonstrated 
the  presence  of  'wo  additional  segments.  First,  there  has  been  found  in  the 
embryos  of  many  insects  a  pair  of  evanescent  appendages  situated  between  the 
antennae  and  the  mandibles.  These  evidently  correspond  to  the  second  antennae 
of  Crustacea,  and  indicate  the  presence  of  a  second  antennal  segment  in  the  head 
of  an  insect.  This  conclusion  is  confirmed  by  a  study  of  the  development  of  the 
nervous  system.  And  in  the  Thysanura  and  Collembola  vestigs-s  of  the  second 
antennas  persist  in  the  adults  of  certain  members  of  these  orders. 

Second,  as  the  compound  eyes  are  borne  on  movable  stalks  in  certain  Crusta- 
cea, it  was  held  by  Milne-Edwards  that  they  represent  another  pair  of  appendages; 
but  this  view  has  not  been  generally  accepted.  It  is  not  necessary,  however,  to 
discuss  whether  the  eyes  represent  appendages  or  not;  the  existence  of  an  ocjlar 
segment  has  been  demonstrated  by  a  study  of  the  development  of  the  nervous 
system. 

It  has  been  shown  that  the  brain  of  an  insect  is  formed  from  three  pairs  of 
primary  ganglia,  which  correspond  to  the  three  principal  divisions  of  the  brain, 
the  protecerebrum,  the  deutocerehrum,  and  the  triiocerebrum.  And  it  has  also  been 
shown  that  the  protocerebrum  innervates  the  compound  eyes  and  ocelli;  the 
deutocerehrum,  the  antennae;  and  the  tritocerebrum,  the  labrum.  This  demon- 
strates the  existence  of  three  premandibular  segments:  an  ocular  segment  or 
protocerebral  segment,  without  appendages,  unless  the  compound  eyes  repre- 
sent them;  an  antennal  or  deutocerebral  segment,  bearing  antennae;  and  a 
second  antennal  or  tritocerebral  segment,  of  which  the  labrum  is  a  part,  and  to 
which  the  evanescent  appendages  between  the  antennae  and  the  mandibles  doubt- 
less belong.  As  Viallanes  has  shown  that  the  tritocerebrum  of  Crustacea  inner- 
vates the  second  antennae,  we  are  warranted  in  considering  the  tritocerebral 
segment  of  insects  to  be  the  second  antennal  segment. 

l^olsom  ('00)  in  his  work  on  the  development  of  the  mouth-parts  of  Annrida 
described  a  pair  of  primary  ganglia  which  he  believed  indicated  the  presence  of  a 
segment  between  the  mandibular  and  maxillary  segments.  He  named  the  ap- 
pendages of  this  segment  the  superlinguce;  they  are  the  paragnatha  described 
above. 

The  existence  of  the  supposed  ganglia  indicating  the  presence  of  a  super- 
lingual  segment  has  not  been  confirmed  by  other  investigators  and  is  no  longer 
maintained  by  Folsom. 


48 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  suboesophageal  ganglion  is  formed  by  the  union  of  three  pairs  of  primitive 
ganglia,  pertaining  respectively  to  the  mandibular,  the  maxillary,  and  the  labial 
segments  of  the  embryo. 

LIST  OF  THE  SEGMENTS  OF  THE  HEAD 

First,  ocular,  or  protocerebral. 

Second,  antennal,  or  deutocerebral. 

Third,  second  antennal,  or  tritocerebral. 

Fourth,  mandibular. 

Fifth,  maxillary. 

Sixth,  labial,  or  second  maxillary. 


III.     THE   THORAX 

a.       THE   SEGMENTS  OF  THE  THORAX 

The  prothorax,  the  meso'ihorax,  and  the  metathorax. — The  thorax 
is  the  second  or  intermediate  region  of  the  body;  it  is  the  region  that 
in  nymphs,  naiads,  and  adults  bears  the  organs  of  locomotion,  the  legs, 
and  the  wings  when  they  are  present.  This  region  is  composed  of 
three  of  the  body-segments  more  or  less  firmly  joined  together;  the 
segments  are  most  readily  distinguished  by  the 
fact  that  each  bears  a  pair  of  legs.  In  winged 
insects,  the  wings  are  borne  by  the  second  and 
third  segments.  The  first  segment  of  the  thorax, 
the  one  next  the  head,  is  named  the  prothorax; 
the  second  thoracic  segment  is  the  mesothorax; 
and  the  third,  the  metathorax. 

The  simplest  form  of  the  thorax  in  adult 
insects  occurs  in  the  Apterygota  (the  Thysanura 
and  the  Collembola)  where  although  the  seg- 
ments differ  in  size  and  proportions,  they  are 
distinct  and  quite  similar  (Fig.  60). 

In    the    Pterygota,    or    winged   insects,  the 
prothorax  is  either  free  or  closely  united  to  the 
mesothorax ;  in  many  cases  it  is  greatly  reduced  in 
size;  it  bears  the  first  pair  of  legs.     The  meso- 
thorax and  the  metathorax  are  more  or  less  closely 
united,  forming  a  box,  which  bears  the  wings  and 
the  second  and  third  pairs  of  legs.     This  union  of 
these  two  segments  is  often  so  close  that  it  is  ver\^  difficult  to  distin- 
guish their  limits.     Sometimes  the  matter  is  farther  complicated  by 
a  union  with  the  thorax   of  a   part   or   of   the   whole   of   the   first 


Fig.  60. — Lepisma 
saccharina  (After 
Lubbock) . 


THE   EXTERNAL   ANATOMY  OF  INSECTS  49 

abdominal  segment.  In  the  Acridiid^,  for  example,  the  sternum  of 
the  first  abdominal  segment  forms  a  part  of  the  intermediate  region 
of  the  body,  and  in  the  Hymenoptera  the  entire  first  abdominal 
segment  pertains  to  this  region. 

The  alitrunk. — ^When,  as  in  the  Hymenoptera,  the  intermediate 
region  of  the  body  includes  more  than  the  three  true  thoracic  seg- 
ments it  is  designated  the  alitrunk. 

The  propodeum  or  the  median  segment. — ^When  the  alitrunk  con- 
sists of  four  segments  the  abdominal  segment  that  forms  a  part  of  it  is 
termed  the  -propodeum  or  the  median  segment.  In  such  cases  the  true 
second  abdominal  segment  is  termed  the  first. 

h.       THE    SCLERITES    OF    A   THORACIC    SEGMENT 

The  parts  of  the  thorax  most  generally  recognized  by  entomologists 
were  described  nearly  a  century  ago  by  Audouin  (1824) ;  some  addi- 
tional parts  not  observed  by  Audouin  have  been  described  in  recent 
times,  by  the  writer  ('02),  Verhoeff  ('03),  Crampton  ('09),  and 
Snodgrass  ('09,  '10  a,  and  '10  6).  The  following  account  is  based  on 
all  of  these  works. 

In  designating  the  parts  of  the  thorax  the  prefixes  pro,  meso,  and 
meta  are  used  for  designating  the  three  thoracic  segments  or  corres- 
ponding parts  of  them;  and  the  prefixes  pre  and  post  are  used  to 
designate  parts  of  any  one  of  the  segments.  Thus  the  scutum  of  ths 
prothorax  is  designated  the  proscutum;  while  the  term  prescutum  is 
applied  to  the  sclerite  immediately  in  front  of  the  scutum  in  each  of 
the  thoracic  segments.  This  system  leads  to  the  use  of  a  number  of 
hybrid  combinations  of  Latin  and  Greek  terms,  but  it  is  so  firmly 
established  that  it  would  not  be  wise  to  attempt  to  change  it  on  this 
account. 

Reference  has  already  been  made  to  the  division  of  a  body-segment 
into  a  tergum,  two  pleura,  and  a  sternum ;  each  of  these  divisions  will 
be  considered  separately;  and  as  the  maximum  number  of  parts  are 
found  in  the  wing-bearing  segments,  one  of  these  will  be  taken  as  an 
illustration. 

The  sclerites  of  a  tergum. — In  this  discussion  of  the  external  ana- 
tomy of  the  thorax  reference  is  made  only  to  those  parts  that  form 
the  external  covering  of  this  region  of  the  body.  The  infoldings  of 
the  body-wall  that  constitute  the  internal  skeleton  are  discussed  in  the 
next  chapter. 

The  notum. — In  nymphs  and  in  the  adults  of  certain  generalized 
insects  the  tergum  of  each  wing-bearing  segment  contains  a  single 


50 


AN  INTRODUCTION   TO   ENTOMOLOGY 


chitinized  plate;  this  sclerite  is  designated  the  notuni.  The  term 
notum  is  also  applied  to  the  tergal  plate  of  the  prothorax  and  to  that 
of  each  abdominal  segment.  The  three  thoracic  nota  are  designated 
as  the  pronotum,  the  mesonotum,  and  the  metanotum  respectively. 

The  notum  of  a  wing-bearing  segment  is  the  part  that  bears  the 
wings  of  that  segment,  even  when  the  tergum  contains  more  than  one 
sclerite.  Each  wing  is  attached  to  two  processes  of  the  notum,  the 
anterior  notal  process  (Fig.  61,  a  n  p)  and  the  posterior  notal  process 
(Fig.  61,  p  n  p);  and  the  posterior  angles  of  the  notum  are  produced 
into  the  axillary  cords,  which  form  the  posterior  margins  of  the  basal 
membranes  of  the  wings 

The  postnotum  or  postscuteUum. — In  the  wing-bearing  segments  of 
most  adult  insects  the  tergum  consists  of  two  principal  sclerites;  the 
notum  already  described,  and  behind  this  a  narrower,  transverse 
sclerite  which  is  commonly  known  as  the  postscuteUum,  and  to  which 
Snodgrass  has  applied  the  term  postnotum  (Fig.  61,  P  N). 

The  divisions  of  the  notum. — In  most  specialized  insects  the  notum 
of  each  wing-bearing  segment  is  more  or  less  distinctly  divided  by 
transverse  lines  or  sutures  into  three  parts;  these  are  known  as  the 
prescUtum  (Fig.  61,  Psc),  the  scutum  (Fig.  61,  Set),  and  the  scutellum 
(Fig.  61,  Scl). 

It  has  been  commonly  held,  since  the 
days  of  Audouin,  that  the  tergum  of  each 
thoracic  segment  is  composed  typically  of  four 
sclerites,  the  prescutum,  scutum,  scutellum, 
and  postscuteUum.  But  the  investigations  of 
Snodgrass  indicate  that  in  its  more  genera- 
lized form  the  tergum  contains  a  single  y^j,.^ 
sclerite,  the  notum;  that  the  postscuteUum  Tg-- 
or  postnotum  is  a  secondary  tergal  chitini-  ^^ 
zation  in  the  dorsal  membrane  behind  the 
notum,  in  more  specialized  insects;  and  that 
the  separation  of  the  notum  into  tliree  parts, 
the  prescutum,  scutum,  and  scutellum,  is  a 
still  later  specialization  that  has  arisen 
independently  in  diflerent  orders,  and  does 
not  indicate  a  division  into  homologous 
parts  in  all  orders  where  it  exists. 

The  patagia. — In  many  of  the  more 
speciaHzed  Lepidoptera  the  pronotum  Fig.61.— Diagram  of  a  generalized 
is   produced  on  each  side  into  a  fiat        thoracic  segment   (From  Snod- 
lobe,  which  in  some  cases  is  even  con-      S^^^^'- 

stricted  at  the  base  so  as  to  become  a  stalked  plate,  these  lobes  are 
the  patagia. 


THE  EXTERNAL  ANATOMY  OF  INSECTS 


51 


The  parapsides. — In  some  Hymenoptera  the  scutum  of  the  meso- 
thorax  is  divided  into  two  parts  by  the  prescutum;  these  separated 
halves  of  the  scutum  are  called  the  parapsides  (see  Fig.  1130A). 

The  sclerites  of  the  pleura. — ^In  the  accompanying  figure  (Fig.  61) 
the  sclerites  of  the  left  pleurum  of  a  wing-bearing  segment  are  repre- 
sented diagrammatically;   these  sclerites  are  the  following: 

The  episternum. — Each  pleurum  is  composed  chiefly  of  two 
sclerites,  which  typically  occupy  a  nearly  vertical  position,  but 
usually  are  more  or  less  oblique.  In  most  insects  the  dorsal  end  of 
these  sclerites  extends  farther  forward  than  the  ventral  end,  but  in 
the  Odonata  the  reverse  may  be  true.  The  more  anterior  in  position 
of  these  two  sclerites  is  the  episternum  (Fig.  61,  Eps). 

In  several  of  the  orders  of  insects  one  or  more  01  the  epistema  are 
divided  by  a  distinct  suture  into  an  upper  and  a  lower  part.  These 
two  parts  have  been  designated  by  Crampton  ('09)  as  the  anepistSr- 
num  and  the  katepisternum  respectively  (Fig.  62). 

The  epimerum. — The  epimerum  is  the  more  posterior  of  the  two 
principal  sclerites  of  a  pleurum  (Fig.  61).  It  is  separated  from  the 
episternum  by  the  pleural  suture  (Fig.  61 ,  PS)  which  extends  from  the 
pleural  wing  process  above  (Fig.  61,  Wp)  to  the  pleural  coxal  process 
below  (Fig.  61,  CxP). 

In  some  of  the  orders  of  insects  one  or  more  of  the  epimera  are 
divided  by  a  distinct  suture  into  an  upper  and  a 
lower  part.  These  two  parts  have  been  desig- 
nated by  Crampton  ('og)  as  the  anepimerum 
and  the  katepimerum  respectively  (Fig.  62). 

The  preepisternum. — In  some  of  the  more 
generalized  insects  there  is  a  sclerite  situated 
in  front  of  the  episternum;  this  is  the  pre- 
episternum..' 

The  paraptera. — i'n  many  insects  there  is  on 
each  side  a  small  sclerite  between  the  upper 
end  of  the  episternum  and  the  base  of  the  wing ; 
these  have  long  been  known  as  the  paraptera. 

^^-  ^^■—^^^^''^^^^^V^^^  Snodgrass  (10  a)  has  shown  that  there  are  in 
of  the  meso-  and  meta-  ..... 

thorax     of     Maniispa  some  msects  two  sclerites  in  this  region,  which , 

rugicolHs;    i    i   anepis-  ^g    designates    the    episternal    paraptera    or 
ternum;  2,2,katcpister-  '^  -^  r        r 

num;    j,   ?,  anepimer-  preparaptera  (Fig.  61,    iP  and  2P);    and  that 
um;  <^,  4,  katepimerum;  ^^^  ^j.  occasionally  two  are  similarly  situated 
between  the  epimerun  and  the  base  of  the  wing, 
the  epimeral  paraptera  or  postparaptera  (Fig.  61,  3F). 


52  AN  INTRODUCTION   TO  ENTOMOLOGY 

The  spiracles. — The  external  openings  of  the  respiratory  system 
are  termed  spiracles.  Of  these  there  are  two  pairs  in  the  thorax. 
The  first  pair  of  thoracic  spiracles  open,  typically,  one  on  each  side  in 
the  transverse  conjunctiva  between  the  prothorax  and  the  meso- 
thorax ;  the  second  pair  open  in  similar  positions  between  the  meso- 
thorax  and  the  me  athorax.  In  some  cases  the  spiracles  have 
migrated  either  forward  or  backward  upon  the  adjacent  segment. 
For  a  discussion  of  the  number  and  distribution  of  the  spiracles,  see 
the  next  chapter. 

The  periiremes. — In  many  cases  a  spiracle  is  surrounded  by  a  cir- 
cular sclerite;   such  a  sclerite  is  termed  a  peritreme. 

The  acetabula  or  coxal  cavities. — In  some  of  the  more  specialized 
insects,  as  many  beetles  for  example,  the  basal  segment  of  the  legs  is 
inserted  in  a  distinct  cavity ;  such  a  cavity  is  termed  an  acetabulum  or 
coxal  caz'ity.  When  the  epimera  of  the  prothorax  extend  behind  the 
coxse  and  reach  the  prostemum,  the  coxal  cavities  are  said  to  be 
closed  (Fig.  63) ;  when  the  epimera  do  not  extend  behind  the  coxa; 
to  the  prosterum,  the  coxal  cavities  are  described  as  open  (Fig.  64) . 

The  sclerites  of  a  sternum. — In  the  more  generalized  insects  the 
sterniim  of  a  wing-bearing  segment  may  consist  of  three  or  four 
sclerites.     These  have  been  designated,  beginning  with  the  anterior 
one,  the  presternum  (Fig.                                      ,      ^<K^^~ 
61,  Ps),  the  sternum  or                                     xP^^^M-MyT^ 
eusternum   (Fig.   61,   5),  ^^^^:^^7>v 

the  sternellum   (Fig.  61,  ^^^c\ 

Sl),a.ndt\-\epoststernellum  >^  /-\       ^\\ 

(Fig.  61,  Psl).  /  /V ^       '^^^^J^^^^^^^ 

In  the  more  special-        /   /       \  '       ^     ^     'Xl^         / 

ized  insects  only  one  of  /     /  \^^^]     \/~yv^  /     ^y\ 

these,   the  sternum,   re-  /      I  ^^K|  ^  \C  X—-^^^!       \ 

mains  distinctly  visible.  \  ^^^m--   A  '^/      ^^   /  ' 

It  is  an  inteTes!:ing  fact  I  \v.//'""'^l-J_J^^^^^\   y^  I 

that  while  in  the  speciali-  \  |  \  '^       I 

zation     of    the     tergum  | y  v. j 

there    is    an    increase    in    ^-^^  63.-Prothorax  of  Harpalus,  ventral  aspect; 
the  ntimber  of  the  scleri-        c,   coxa;     em,    epimerum;     es,    episternum;    /, 
tes  in  this  division  of  a        ^^"^^=   "'  P^o^o^um;   .,  .,  .,  prostemum. 
segment,  in  the  specialization  of  the  sternum  there  is  a  reduction. 

It  is  a  somewhat  unfortunate  fact  that  the  term  sterntmi  has  been 
used  in  two  senses :  first,  it  is  applied  to  the  entire  ventral  division  of 
a  segment ;  and  second,  it  is  applied  to  one  of  the  sclerites  entering 


THE   EXTERNAL   ANATOMY  OF  INSECTS 


53 


Fig.  64. — ^Prothorax  of  Penlhe;   c,  coxa;    cc,  coxal 
cavity ;/,  femur ;   5,  prosternum;  ir,  trochanter. 


into  the  composition  of  this  division  when  it  consists  of  more  than 
a  single  sclerite.      To  meet  this  difhctilty  Snodgrass  has  proposed 

that  the  term  eusternum 
be  apphed  to  the  sclerite 
that  has  been  known  as 
the  sternum;  and  that 
the  word  sternum  be 
used  only  to  designate 
the  entire  ventral  divi- 
sion of  a  segment. 

C.       THE    ARTICULAR 

SCLERITES  OF  THE 

APPENDAGES 

At  the  base  of  each  leg 
and  of  each  wing  there 
are  typically  several 
sclerites  between  the  appendage  proper  and  the  sclerites  of  the  trunk 
of  the  segment ;  these  sclerites,  which  occupy  an  intermediate  position 
between  the  body  and  its  appendage,  are  termed  the  articular  sclerites. 

Frequently  one  or  more  of  the  articular  sclerites  become  consoli- 
dated wdth  sclerites  of  the  trunk  so  as  to  appear  to  form  a  part  of  its 
wall;   this  is  especially  true  of  those  at  the  base  of  the  legs. 

The  articularscleritesof  thelegs. — ^The  proximal  segment  of  the  leg, 
the  coxa,  articulates  with  the  body  by  means  of  two  distinct  articula- 
tions, which  may  be  termed  the  pleural  articulation  of  the  coxa  and  the 
ventral  articulation  of  ike  coxa  respectively.  The  pleural  articulation 
is  with  the  ventral  end  of  the  foot  of  the  lateral  apodeme  of  the  seg- 
ment, i.  e.  with  the  pleural  coxal  process,  which  is  at 
the  ventral  end  of  the  suture  between  the  epistemum 
and  the  epimerun  (Fig.  61,  CxP).  The  ventral  arti- 
culation is  with  a  sclerite  situated  between  the  coxa 
and  the  epistemum;  this  sclerite  and  others  asso- 
ciated with  it  may  be  termed  the  articular  sclerites 
of  the  legs.  The  articular  sclerites  of  the  legs  to 
which  distinctive  names  have  been  applied  are  the 
following : 

The  irochantin. — The  maximtmi  number  of 
articular  sclerites  of  the  legs  are  found  in  the  more 
generalized  insects;  in  the  more  specialized  insects 
the  number  is  reduced  by  a  consolidation  of  some  of  them  with 


Fig.  65.— The 
base  of  a  leg 
of  a  cock- 
roach. 


54  ,  AN  INTRODUCTION   TO  ENTOMOLOGY 

adjacent  parts.  The  condition  found  in  a  cockroach  may  be  taken 
as  typical.  In  this  insect  the  trcchantin  (Fig.  65,  t)  is  a  triangular 
sclerite,  the  apex  of  which  points  towards  the  middle  line  of  the  body, 
and  is  near  the  ventral  articulation  of  the  coxa  (Fig.  65,3/).  In  most 
specialized  insects  the  trochantin  is  consolidated  with  the  antecoxal 
piece,  and  the  combined  sclerites,  which  appear  as  one,  are  termed 
the  trochantin. 

The  antecoxal  piece. — Between  the  trochantin  and  the  epistemum 
there  are,  in  the  cockroach  studied,  two  sclerites;  the  one  next  the 
trochantin  is  the  antecoxal  -piece.  This  is  the  articular  sclerite  that 
articulates  directly  with  the  coxa  (Fig.  65,  ac).  As  stated  above,  the 
antecoxal  piece  is  usually  consolidated  with  the  trochantin,  and  the 
term  trochantin  is  applied  to  the  combined  sclerites.  Using  the  term 
trochantin  in  this  sense,  the  statement  commonly  made  that  the 
ventral  articulation  of  the  coxa  is  with  the  trochantin  is  true. 

The  second  antecoxal  piece. — The  sclerite  situated  between  the 
antecoxal  piece  and  the  episternum  is  the  second  antecoxal  piece  (Fig. 
65,  n^ac).  This  is  quite  distinct  in  certain  generalized  insects;  but  it 
is  usually  lacking  as  a  distinct  sclerite. 

The  articular  sclerites  of  the  wings.- — In  the  Ephemerida  and  Odo- 
nata  the  chitinous  wing-base  is  directly  continuous  with  the  walls  of 
the  thorax.  In  all  other  orders  there  are  at  the  base  of  each  wing 
several  sclerites  which  enter  into  the  composition  of  the  joint  by  which 
the  wing  is  articulated  to  the  thorax ;  these  may  be  termed  collectively 
the  articular  sclerites  of  the  wings.  Beginning  with  the  front  edge 
of  this  joint  and  passing  backward  these  sclerites  are  as  follows: 

The  tegula. — In  several  orders  of  insects  there  is  at  the  base  of  the 
costal  vein  a  small,  hairy,  sHghtly  chitinized  pad;  this  is  the  tegula 
(Fig.  66,  Tg) .  In  the  more  highly  specialized  orders,  the  Lepidoptera, 
the  Hymenoptera,  and  the  Diptera,  the  tegula  is  largely  developed 
so  as  to  form  a  scale-like  plate  overlapping  the  base  of  the  wing. 

The  tegulas  of  the  front  wings  of  Lepidoptera  are  specially  large 
and  are  carried  by  special  tegular  plates  of  the  notum.  These,  in  turn, 
are  supported  by  special  internal  tegular  arms  from  the  bases  of  the 
pleural  wing-processes  (Snodgrass,  '09) 

The  axillaries. — Excepting  the  tegula,  which  is  at  the  front  edg3 
of  the  wing-joint,  the  articular  sclerites  of  the  wings  have  been  termed 
collectively  the  axillaries.  Much  has  been  written  about  these 
sclerites,  and  many  names  have  been  applied  to  them.  The  simplest 
terminology  is  that  of  Snodgrass  ('09  and  '10  a)  which  I  here  adopt. 


THE  EXTERNAL   ANATOMY  OF  INSECTS 


55 


The  first  axillary. — This  sclerite  (Fig.  66,  i  Ax)  articulates  with 
the  anterior  notal  wing -process  and  is  specially  connected  with  the 
base  of  the  subcostal  vein  of  the  wing.  In  rare  cases  it  is  divided 
into  two. 

The  second  axillary. — The  second  axillary  (Fig.  66,  2  Ax)  articulates 
with  the  first  axillary  proximally  and  usually  with  the  base  of  the 
radius  distally ;  it  also  articulates  below  with  the  wing-process  of  the 
pleurum,  constituting  thus  a  sort  of  pivotal  element. 

The  third  axillary. — The  third  axillary  (Fig.  66,  3  Ax)  is  interposed 
between  the  bases  of  the  anal  veins  and  the  fourth  axillary  when  this 
sclerite  is  present.     When  the  fourth  axillary  is    absent,  as  it  is  in 


Fig.  66. — Diagram  of  a  generalized  wing  and  its  articular  sclerites  (From 
Snodgrass) . 


nearly  all  insects  except  Orthoptera  and  Hymenoptera,  the  third 
axillary  articulates  directly  with  the  posterior  notal  wing-process. 

The  fourth  axillary. — When  this  sclerite  is  present  it  articulates 
with  the  posterior  notal  wing-process  proximally  and  with  the  third 
axillary  distally  (Fig.  66,  4  Ax).  Usually  this  sclerite  is  absent;  it 
occurs  principally  in  Orthoptera  and  Hymenoptera. 

The  median  plates. — The  median  plates  of  the  wing-joint  are  not 
of  constant  shape  and  occurrence;  when  present,  these  plates  are 
associated  with  the  bases  of  the  media,  the  cubitus,  and  the  first  anal 
vein  when  the  latter  is  separated  from  the  other  anals.  Often  one  of 
them  is  fused  with  the  third  axillary  and  sometimes  none  of  them  are 
present. 

d.       THE  APPENDAGES  OF  THE  THORAX 

The  appendages  of  the  thorax  are  the  organs  of  locomotion. 
They  consist  of  the  legs  and  the  vcings.     Of  the  former  there  are  three 


56 


AN  INTRODUCTION   TO   ENTOMOLOGY 


pairs,  a  pair  borne  by  each  of  the  three  thoracic  segments;  of  the 
latter  there  are  never  more  than  two  pairs,  a  pair  borne  by  the  meso- 
thorax  and  a  pair  borne  by  the  metathorax.  One  or  both  pairs  of 
wings  may  be  wanting. 

The  legs. — Each  leg  consists  of  the  following  named  parts  and 
their  appendages:     coxa,  trochanter,  femur,  tibia,  and  tarsus. 

The  coxa. — The  coxa  is  the  proximal  segment  of  the  leg ;  it  is  the 
one  by  which  the  leg  is  articulated  to  the  body  (Fig.  67).  The  coxa 
varies  much  in  form,  but  it  is  usually  a  truncated  cone  or  nearly 
globular.  In  some  insects  the  coxse  of  the  third  pair  of  legs  are  more 
or  less  flattened  and  immovably  attached  to  the  metastemtmi;  this 
is  the  case  in  beetles  of  the  family  Carabidae  for  example.  In  such 
cases  the  coxae  really  form  a  part  of  the  body-wall,  and  are  liable  to  be 
mistaken  for  primary  parts  of  the  metathorax  instead  of  the  proximal 
segments  of  appendages. 

In  several  of  the  orders  of  injects  the  coxa  is  apparently  composed 

of  two,  more 
or  less  dis- 
tinct, parallel 
parts;  this  is 
the  case,  for 
example,  in  in- 
sects of  the 
trichopterous 
genus  Neuro- 
ma (Fig.  68, 
Cx  and  epm). 
But  it  has 
been  shown 
by  Snodgrass 
('09)  that  the 
posterior  part 
of  the  sup- 
posed double 
coxa,  the 
"rreron"  (Fig. 
68,  epm)  is  a 
detached  por- 
tion of  the 
epimej-um. 
The  siyli — In  certain  generalised  insects,  as  Machilis  of  the  order 


B  C 

!Fig.  67. — Legs  of  insects:  A,  wasp;  B,  ichneumon-fiy;  C, 
bee;  c,  coxa;  tr,  trochanter;  /,  femur;  //,  tibia;  k,. 
tarsus;    m,  metatarsus. 


THE  EXTERNAL   ANATOMY  OF  INSECTS 


57 


Thysanura,  the  coxa  of  each  middle  and  hind  leg  bears  a  small 
appendage,  the  stylus  (Fig.  69).  The  styli  are  of  great  interest  as 
they  are  believed  to  correspond  to  one  of  the  two  branches  of  the  legs 
of  Crustacea;  thus  indicating  that  insects  have  descended  from 
forms  in  which  the  legs  were  biramous. 

In  several  genera  of  the  Thysanura  one  or  more  of  the  abdominal 
segments  bear  each  a  pair  of  styli ;  in  Machilis  they  are  found  on  the 
second  to  the  ninth  abdominal  segments.  These  styli  are  regarded  as 
vestiges  of  abdominal  legs. 

The  trochanter. — The  trochanter  is  the  second  part  of  the  leg.  It 
consists  usually  of  a  very  short,  triangular  or  quadrangular  segment, 
between  the  coxa  and  the  femur.  Sometimes  the  femur  appears  to 
articulate  directly  with  the  coxa ;  and  the  trochanter  to  be  merely  an 
appendage  of  the  prox'mal  end  of  the  femur  {e.  g.  Carabidae) .  But 
the  fact  is  that  in  these  insects,  although  the  femur  may  touch  the 
coxa,  it  does  not  articulate  with  it;  and  the 
organs  that  pass  from  the  cavity  of  the  coxa 
to  that  of  the  femur  must  pass  through  the ' 
trochanter.  In  some  Hymenoptera  the  tro- 
chanter consists  of  two  segments  (67,  B). 

The  femur. — The  femur  is  the  third  part  of 
the  leg;  and  is  usually  the  largest  part.  It 
consists  of  a  single  segment. 

The  tibia. — The  tibia  is  the  fourth  part  of 
the  leg.  It  consists  of  a  single  segment;  and 
Fig.  68.— Lateral  aspect  ^^  usually  a  little  more  slender  than  the  femur, 
of  the  mesothorax  of  although  it  often  equals  or  exceeds  it  in  length. 
In  such  species  as  burrow  in  the  ground,  the 
distal  extremity  is  greatly  broadened  and 
shaped  more  or  less  like  a  hand.  Near  the  distal  end  of  the  tibia 
there  are  in  most  insects  one  or  more  spurs,  which  are  much  larger 
than  the  hairs  and  spines  which  arm  the 
leg;  these  are  called  the  tibial  spurs,  and 
are  much  used  in  classification. 

The  tarsus. — The  tarsus  is  the  fifth  and 
most  distal  part  of  the  leg,  that  which  is 
popularly  called  the  foot.  It  consists  of  a 
series  of  segments,  varying  in  number 
from  one  to  six.  The  most  common  ntmi- 
ber  of  segments  in  the  tarsus  is  five. 

In  many  insects,  the  first  segment  of  the  tarsus  is  much  longer, 


Neuronia  (From  Snod- 
grass). 


Fig.  69.— A 
s,  stylus. 


of  Machilis; 


58  AN  INTRODUCTION   TO  ENTOMOLOGY 

and  sometimes  much  broader,  than  the  other  segments.  In  such 
cases  this  segment  is  frequently  designated  as  the  metatarsus  (Fig. 
67,  C,  m). 

In  some  insects  the  claws  borne  by  the  distal  end  of  the  tarsus  are 
outgrowths  of  a  small  terminal  portion  of  the  leg,  the  sixth  segment 
of  the  tarsus  of  some  authors.  This  terminal  part  with  its  appendages 
has  received  the  name  pr(starsus  (De  Meijere  '01).  As  a  rule  the 
prajtarsus  is  withdrawn  into  the  fifth  segment  of  the  tarsus  or  is  not 
present  as  a  distinct  segment. 

On  the  ventral  surface  of  the  segments  of  the  tarsus  in  many 
insects  are  cushion-like  structures;  these  are  called  puMlU.  The 
cuticula  of  the  pulvilli  is  traversed  by  ntimerous  pores  which  open 
either  at  the  surface  of  the  cuticula  or  through  hollow  hairs,  the 
tenent-hairs,  and  from  which  exudes  an  adhesive  fluid  that  enables  the 
insect  to  walk  on  the  lower  surface  of  objects. 

With  many  insects  (e.  g.  most  Diptera)  the  distal  segment  of  the 
tarsus  bears  a  pair  of  pulvilli,  one  beneath  each  claw.  In  such  cases 
there  is  frequently  between  these  pulvilli  a  third  single  appendage  of 
similar  structure ;  this  is  called  the  empodium;  writers  on  the  Orthop- 
tera  commonly  called  the  appendage  between  the  claws  the  arolium. 
In  other  insects  the  empodium  is  bristle-like  or  altogether  wanting. 

In  many  insects  the  pul villus  of  the  distal  segment  of  the  tarsus 
is  a  circular  pad  projecting  between  the  tarsal  claws.  In  many 
descriptive  works  this  is  referred  to  as  the  pulvillus ,  even  though  the 
other  pulvilli  are  well-developed.  The  pulvilH  are  called  the  onychii 
by  some  writers. 

The  claws  borne  at  the  tip  of  the  tarsus  are  termed  the  tarsal  claws 
or  ungues;  they  vary  much  in  form;  they  are  usually  two  in  number, 
but  sometimes  there  is  only  one  on  each  tarsus. 

The  wings. — The  wings  of  insects  are  typically  two  pairs  of  mem- 
branous appendages,  one  pair  borne  by  the  mesothorax  and  one  pair 
by  the  metathorax;  pro  thoracic  wings  are  unknown  in  living  insects 
but  they  existed  in  certain  paleozoic  forms. 

Excepting  in  the  subclass  Apterygota  which  includes  the 
orders  Thysanura  and  CoUembola,  wings  are  usually  present  in  adult 
insects.  Their  absence  in  the  Apterygota  is  due  to  the  fact  that 
they  have  not  been  evolved  in  this  division  of  the  class  Hexapoda; 
but  when  they  are  absent  in  adult  members  of  the  subclass  Pterygo- 
ta,  which  includes  the  other  orders  of  insects,  their  absence  is  due 
to  a  degradation,  which  has  resulted  in  their  loss. 


THE   EXTERNAL   ANATOMY  OF  INSECTS  59 

The  loss  of  wings  is  often  confined  to  one  sex  of  a  species;  thus 
with  the  canker-worm  moths,  for  example,  the  females  are  wingless, 
while  the  males  have  well-developed  wings;  on  the  other  hand,  with 
the  fig-insects,  Blastophaga,  the  female  is  winged  and  the  male 
wingless. 

Studies  of  the  development  of  wings  have  shown  that  each  wing  is 
a  Saclike  fold  of  the  body-wall;  but  in  the  fully  developed  wing,  its 
saclike  nature  is  not  obvious;  the  upper  and  lower  walls  become 
closely  applied  throughout  the  greater  part  of  their  extent ;  and  since 
they  become  very  thin,  they  present  the  appearance  of  a  single  delicate 
membrane.  Along  certain  lines,  however,  the  walls  remain  separate, 
and  are  thickened,  forming  the  firmer  framework  of  the  wing.  These 
thickened  and  hollow  lines  are  termed  the  veins  of  the  wing;  and  their 
arrangement  is  described  as  the  venation  of  the  wing. 

The  thin  spaces  of  the  wings  which  are  bounded  by  veins  are 
called  cells.  When  a  cell  is  completely  surrounded  by  veins  it  is  said 
to  be  closed;  and  when  it  extends  to  the  margin  of  the  wing  it  is  said 
to  be  open. 

The  (liferent  types  of  insect  wings. — What  may  be  regarded  as  the 
typical  form  of  insect  wing  is  a  nearly  flat,  dehcate,  membranous 
appendage  of  the  body,  which  is  stiffened  by  the  so-called  wing- veins ; 
but  striking  modifications  of  this  form  exist;  and  to  certain  of  them 
distinctive  names  have  been  applied,  as  follows : 

In  the  Coleoptera  and  in  the  Dermaptera,  the  front  wings  are 

thickened  and  serve  chiefly  to  protect  the  dorsal  wall  of  the  body  and 

the  membranous  hind  wings,  which  are  folded  beneath  them  when 

not  in  use.     Front  wings  of  this  type  are  termed  wing-covers  or  elytra. 

The  front  wings  of  the  Heteroptera,  which  are  thickened  at  the 

base  like  elytra,  are  often  desig- 
nated the  hemelytra. 

The  thickened  fore  wings  of 
Orthoptera  are  termed  iegmina  by 
many  writers. 

The  hind  wings  of  Diptera, 
which  are  knobbed,  thread-like 
organs,  are  termed  halteres.  The 
hind  wings  of  the  males  of  the 
family  Coccid^  are  also  thread- 
Fig.  70.— Diagram  of  a  wing  showing  ijj^g 
margins  and  angles.  _ 

I  he  reduced  front  wmgs  of  the 

Strepsiptera  are  known  as  the  pseudo-halteres. 


60 


AN  INTRODUCTION   TO   ENTOMOLOGY 


The  margins  of  wings. — Most  insect  wings  are  more  or  less 
triangular  in  outline;  they,  therefore,  present  three  margins:  the 
costal  margin  or  costa  (Fig.  70,  a-b);  the  outer  margin  (Fig.  70, 
b-c);   and  the  inner  margin  (Fig.  70,  c-d). 

The  angles  of  wings. — The  angle  at  the  base  of  the  costal  margin 
of  a  wing  is  the  humeral  angle  (Fig.  70,  a);  that  between  the  costal 
margin  and  the  outer  margin  is  the  apex  of  the  wing  (Fig.  70.  6); 


Fig.  71. — Wing  of  Conops;  ae,  a  ciliary  excision;   /,  posterior  lobe. 

and  that  between  the  outer  margin  and  the  inner  margin  is  the  anal 
angle  (Fig.  70,  c). 

The  axillary  cord. — The  posterior  margin  of  the  membrane  at  the 
base  of  the  wing  is  usually  thickened  and  corrugated;  this  cord-like 
structure  is  termed  the  axillary  cord.  The  axillary  cord  normally 
arises,  on  each  side,  from  the  posterior  lateral  angle  of  the  notum,  and 
thus  serves  as  a  mark  for  determining  the  posterior  limits  of  the 

notum. 

The  axillary  membrane. — The 
membrane  of  the  wing  base  is 
termed  the  axillary  membrane; 
it  extends  from  the  tegula  at  the 
base  of  the  costal  margin  to  the 
axillary  cord ;  in  it  are  found  the 
axillary  sclerites. 

The  alula.— In  certain  families 
of  the  Diptera  and  of  the  Coleop- 
tera  the  axillary  membrane  is 
expanded  so  as  to  form  a  lobe  or 
lobes  which  fold  beneath  the  base  of  the  wing  when  the  wings  are 
closed;  this  part  of  the  wing  is  the  alula  or  alulet.  The  aivlse  are 
termed  the  squamce  by  some  writers,  and  the  calypteres  by  others. 


Fie 


72. — ^Wings    of    the    honeybee; 
hamuli. 


THE   EXTERNAL   ANATOMY  OF  INSECTS 


61 


The  axillary  excision. — In  the  wings  of  most  Diptera  and  in  the 
wings  of  many  other  insects  there  is  a  notch  in  the  inner  margin  of 
the  wing  near  its  base  (Fig.  71,  ae),  this  is  the  axillary  excision. 

The  posterior  lobe  of  the  wing. — That  part  of  the  wing  lying  between 
the  axillary  excision  when  it  exists,  and  the  axillary  membrane  is  the 
posterior  lobe  of  the  wing.  The  posterior  lobe  of  the  wing  and  an  alula 
are  easily  differentiated  as  the  alula  is  margined  by  the  axillary  cord. 

The  methods  of  uniting  the  two  wings  of  each  side. — It  is  obvious 
that  a  provision  for  ensuring  the  synchronous  action  of  the  fore  and 
hind  wings  adds  to  their  efficiency;  it  is  as  important  that  the  two 
pairs  of  wings  should  act  as  a  unit  as  it  is  that  the  members  of  a  boat's 
crew  should  pull  together.  In  many  insects  the  synchronous  action 
of  the  wings  is  ensured  by  the  fore  wing  overlapping  the  hind  wing. 
But  in  other  insects  special  structures  have  been  developed  which 
fasten  together  the  two  wings  of  each  side.  The  different  types  of 
these  structures  have  received  special  names  as  follows: 

The  hamuli. — With  certain  insects  the  costal  margin  of  the  hind 
wings  bears  a  row  of  hooks,  which  fasten  into  a  fold  on  the  inner 
margin  of  the  fore  wings  (Fig.  7  2) ;  these  hooks  are  named  the  hdmtdi. 

The  frenulum  and  the  frenulum  hook. — In  most  moths  there  is  a 
strong  spine-like  organ  or  a 
bunch  of  bristles  borne  by  the 
hind  wing  at  the  htuneral 
angle  (Fig.  73,/);  this  is  the 
frenulum  or  little  bridle.  As  a 
rule  the  frenulum  of  the  female 
consists  of  several  bristles ;  that 
of  the  male,  of  a  single,  strong, 
spine-like  organ.  In  the  males 
of  certain  moths,  where  the 
frenulum  is  highly  developed, 
there  is  a  membranous  fold  on 
the  fore  wing  for  receiving  the 
end  of  the  frenulum,  this  is  the 
frenulum  hook  (Fig.  7s,fh). 

The  jugum. — In  one  family 
of  moths,  the  HepiaHdae,  the 
posterior  lobe  of  the  fore  wing 
is  a  slender,  finger-like  organ 
which  is  stiffened  by  a  branch 
of  the  third  anal  vein,  and  which  projects  beneath  the  costal  margin 
of  the  hind  wing.     As  the  greater  part  of  the  inner  margin  of  the  fore 


Fig- 73. — Wings  of  Thyridopteryx  ephemerce- 
formds;  f,  frenulum;  fh,  frenulum  hook. 


62 


AN  INTRODUCTION   TO  ENTOMOLOGY 


wing  overlaps  the  hind  wing,  the  hind  wing  is  held  between  the  two 
(Fig.  74).  This  type  of  the  posterior  lobe  of  the  fore  wing  is  termed 
the  jugum  or  yoke.  The  structure  of  the  jugum  is  shown  in  Figure  75. 
The  fibula. — In  several  groups  of  insects  an  organ  has  been 
developed  that  serves  to  unite  the  fore  and  hind  wings,  but  which 
functions  in  a  way  quite  different  from  that  of  the  jugum.  Like  the 
jugum  it  is  found  at  the  base  of  the  fore  wing ;  but  unlike  the  jugum 
it  extends  back  above  the  base  of  the  hind  wing  and  is  clasped  over  an 
elevated  part  of  the  hind  wing;  this  organ  is  the  fibula  or  clasp. 
In  some  insects,  as  in  the  Trichoptera,  the  fibula  consists  only  of 
a  specialized  posterior  lobe  of  the  fore  wing;  in  others,  as  in  the 
genus  Corydalus  of  the  order  Neuroptera,  the  proximal  part  of  the 
fibula  is  margined  by  the  axillary  cord,  showing  that  the  axillary 
membrane  enters  into  the  composition  of  this  organ  (Fig.  76). 

The  hypothetical  type  of  the  primitive  wing-venation. — A  careful 
study  of  the  wings  of  many  insects  has  shown  that  the  fundamental 
type  of  venation  is  the  same  in  all  of  the  orders  of  winged  insects. 
But  this  fact  is  evident  only  when  the  more  primitive  or  generalized 
members  of  different  orders  are  compared  with  each  other.  In  most 
of  the  orders  of  insects  the  greater  nrmiber  of  species  have  become  so 

modified  or  specialized  as 
regards  the  structure  of 
their  wings  that  it  is  diffi- 
cult at  first  to  trace  out  the 
primitive  type. 

This  agreement  in  the 
important  features  of  the 
venation  of  the  wings  of 
the  generalized  members  of 
the  different  orders  of  insects 
is  still  more  evident  when 
the  wings  of  nymphs,  naiads, 
and  pupae  are  studied.  It 
has  been  demonstrated  that 
in  the  development  of  wings 
of  generalized  insects  the 
longitudinal  wing-veins  are 
formed  about  preexisting 
trachese.  In  the  develop- 
ment of  the  wing,  these 
tracheae  grow  out  into  the 
wing-bud,  and  later  the  wing-veins  are  formed  about  them. 


Fig.  74.- 
below; 


-Wings  of  a  hepialid,  seen  from 
c,  accessory  vein. 


THE   EXTERNAL   ANATOMY  OF  INSECTS 


6;: 


The  wings  of  nymphs,  naiads,  and  pupag  are  broad  at  the  base, 
and  consequently  the  tracheae  that  precede  the  wing-veins  are  not 
crowded  together  as  are  the  wing-veins  at  the  base  of  the  wings  of 


Fig.  75. — Jugum  of  a  hepialid. 


Fig.  76. — Fibula  of  Corydalus. 


adults.  For  this  reason  the  identity  of  the  wing-veins  can  be  deter- 
mined more  surely  in  the  wings  of  immature  insects  than  they  can  be 
in  the  wings  of  adults.  This  is  especially  true  where  two  or  more 
veins  coalesce  in  the  adult  wing  while  the  tracheae  that  precede  these 
veins  are  distinctly  separate  in  the  immature  wing. 

A  study  was  made  of  the  tracheation  of  the  wings  of  immature 
insects  of  representatives  of  most  of  the  orders  of  insects,  and,  assum- 
ing that  those  features  that  are  possessed  by  all  of  them  must  have 
been  inherited  from  a  common  ancestor,  a  diagram  was  made  repre- 
senting the  hypothetical  tracheation  of  a  nymph  of  the  primitive 
winged  insect  (Fig.  77).     In  this  diagram  the  trachese  are  lettered 


Fig-  77- — Hypothetical  tracheation  of  a  wing  of  the  primitive  nymph. 

with  the  abbreviations  used  in  designating  the  veins  that  are  formed 
about  them  in  the  course  of  the  development  of  the  wing.  The  dia- 
gram will  serve,  therefore,  to  indicate  the  typical  venation  of  an  insect 


64  AN  INTRODUCTION   TO  ENTOMOLOGY 

wing,  except  that  the  tracheae  are  not  crowded  together  at  the  base  of 
the  wing  as  are  the  veins  in  the  wings  of  adults.* 

Longitudinal  veins  and  cross-veins. — The  veins  of  the  wing  can  be 
grouped  under  two  heads:  first,  longitudinal  veins,  those  that 
normally  extend  lengthwise  the  wing;  and  second,  cross-veins,  those 
that  normally  extend  in  a  transverse  direction. 

The  insertion  of  the  word  normally  in  the  above  definitions  is 
important;  for  it  is  only  in  comparatively  generalized  wings  that  the 
direction  of  a  vein  can  be  depended  upon  for  determining  to  which  of 
these  two  classes  it  belongs. 

The  principal  wing-veins. — The  longitudinalwing- veins  constitute 
the  principal  framework  of  the  wings.  In  the  diagram  representing 
the  typical  venation  of  an  insect  wing  (Fig.  77),  only  longitudinal 
veins  are  indicated ;  this  is  due  to  the  fact  that  the  diagram  was  based 
on  a  study  of  the  tracheation  of  wings,  and  in  the  more  generalized 
wings  the  cross-veins  are  not  preceded  by  tracheae;  moreover  in  the 
wings  of  more  generalized  paleozoic  insects  there  were  no  definite 
cross-veins,  but  merely  an  irregular  network  of  thickened  lines 
between  the  longitudinal  veins. 

There  are  eight  principal  veins;  and  of  these  the  second,  third, 
fourth,  and  fifth  are  branched.  The  names  of  these  veins  and  the 
abbreviations  by  which  they  are  known  are  as  follows,  beginning  with 
the  on3  nsarest  the  costal  margin  of  the  wing: 

Nam3s  of  vsins  Ahhrcjiitions 

Costa C 

Subcosta Sc 

Radius R 

Media M 

Cubitus    Cu 

First  Anal ist  A 

Second  Anal 2dA 

ThirdAnal 3dA 

The  chief  branches  of  the  wing-veins. — The  chief  branches  of  the 
principal  veins  are  numbered,  beginning  with  the  branch  nearest  to 
the  costal  margin  of  the  wing.  The  term  used  to  designate  a  branch 
of  a  vein  is  formed  by  compounding  the  name  of  the  vein  with  a 

*For  many  details  regarding  the  development  of  the  wings  of  insects,  their 
structure,  and  the  terminology  of  the  wing-veins,  that  can  not  be  included  in 
this  work,  see  a  volume  by  the  writer  entitled  The  Wings  of  Insects.  This  is 
published  by  The  Comstock  Publishing  Company,  Ithaca,  N.  Y. 


THE   EXTERNAL   ANATOMY  OF  INSECTS  65 

numeral  indicating  the  number  of  the  branch ;  thus,  for  example,  the 
first  branch  of  the  radius  is  radius-one  or  vein  Ri. 

In  the  case  of  radius  and  media,  each  of  which  has  more  than  two 
branches,  each  division  of  the  vein  that  bears  two  or  more  branches 
has  received  a  special  name.  Thus  after  the  separation  of  radius-one 
from  the  main  stem  of  radius  there  remains  a  division  which  is  typi- 
cally four-branched;  this  division  is  termed  the  radial  sector,  or 
vein  Rsi  the  first  division  of  the  radial  sector,  which  later  separates 
into  radius-two  and  radius-three,  is  designated  as  radius-two-plus- 
three  or  vein  R2+3;  and  the  second  division  is  termed  radius-four- 
plus-five  or  vein  R4+5.  Media  is  typically  separated  into  two  divi- 
sions, each  of  which  is  two-branched ;  the  first  division  is  media-one- 
pl'us  two  or  vein  Mi +2,  the  second  is  media-three-plus-four  or  vein 
M3+4. 

The  veins  of  the  anal  area. — -The  three  anal  veins  exhibit  a  wide 
range  of  variation  both  as  to  their  persistence  and  to  their  form  when 


^/?..» 


Sc        _ 

/?, 

/?.., 

^ 

'^  f^r 

^^-w 

/?5 

iJ.A 
Fig.  78. — A  wing  of  Rhyphus. 

present.  In  those  cases  where  the  anal  veins  are  branched  there  is 
no  indication  that  the  branching  has  been  derived  from  a  uniform 
primitive  type  of  branching.  For  this  reason  in  describing  a  branched 
anal  vein  merely  the  number  of  branches  is  indicated. 

In  some  cases,  as  in  the  Odonata,  there  is  a  single  anal  vein  the 
identity  of  which  can  not  be  determined.  In  such  cases  this  vein  is 
designated  merely  as  the  anal  vein  or  vein  A,  and  its  branches  as  Ai, 
Ai,  Az,  etc. 

The  reduction  of  the  number  of  wing-veins. — In  many  wings  the 
number  of  the  veins  is  less  than  it  is  in  the  hypothetical  type.  In 
some  cases  this  is  due  to  the  fact  that  one  or  more  veins  have  faded 
out  in  the  course  of  the  evolution  of  the  insects  showing  this  deficiency; 
frequently  in  such  wings  vestiges  of  the  lacking  veins  remain,  either 
as  faint  lines  in  the  positions  formerly  occupied  by  the  veins  or  as 


66 


AN  INTRODUCTION   TO  ENTOMOLOGY 


short  fragments  of  the  veins.  A  much  more  common  way  in  which 
the  niimber  of  veins  has  been  reduced  is  by  the  coalescence  of  adja- 
cent veins.  In  many  wings  the  basal  parts  of  two  or  more  principal 
veins  are  united  so  as  to  appear  as  a  single  vein ;  and  the  number  of 
the  branches  of  a  vein  has  been  reduced  in  very  many  cases  by  two  or 
more  branches  becoming  united  throughout  their  entire  length. 

When  a  vein  consists  of  two  or  more  of  the  primitive  veins  united, 
the  name  applied  to  the  compound  vein  should  indicate  this  fact.  In 
the  wing  of  Rhyphus  (Fig.  78),  for  example,  radius  is  only  three- 
branched;  but  it  would  be  misleading  to  designate  these  branches  as 
Ri,  R2,  and  R3,  for  this  would  indicate  that  veins  R4  and  R5  are  lacking. 
The  first  branch  is  evidently  Ri ;  the  second  branch  is  composed  of  the 


Fig.  79. — A  wing  of  Tabanus. 


coalesced  R2  and  R3,  it  is,  therefore,  designated  as  R2+3;  and  the 
third  branch,  which  consists  of  the  coalesced  R4  and  R5,  is  designated 
as  R4+5. 

A  second  method  of  coalescence  of  veins  is  illustrated  by  a  wing  of 
Tabanus  (Fig.  79).  In  this  wing  the  tips  of  cubitus-two  and  the 
second  anal  vein  are  united ;  here  the  coalescence  began  at  the  margin 
of  the  wing  and  is  progressing  towards  the  base.  The  united  portions 
of  the  two  veins  are  designated  as  2d  A+Cu2. 

When  it  is  desired  to  indicate  the  composition  of  a  compound 
vein  it  can  be  readily  done  by  combining  the  terms  indicating  its 
elements.  But  in  descriptions  of  hymenopterous  wings  where  a 
compound  vein  may  be  formed  by  the  coalescence  of  several  veins  the 
logical  carrying  out  of  this  plan  would  result  in  a  very  cumbersome 
terminology,  one  that  it  is  impracticable  to  use  in  ordinary  descrip- 
tions. In  such  cases  the  compound  vein  is  designated  by  the  term 
indicating  its  most  obvious  element.     Thus,  for  example,  in  the  fore 


THE   EXTERNAL   ANATOMY  OF  INSECTS 


67 


wing  of  Pampkilius,  where  veins  M4,  Cui,  and  Cu2  coalesce  with  the 
first  anal  vein,  the  united  tips  of  these  veins  is  designated  as  vein  ist  A, 
the  first  anal  vein  being  its  most  obvious  element  (Fig.  80),  although 
it  is  really  vein  M4+Cui+Cu2  +  ist  A. 

Serial  veins. — In  the  wings  of  some  insects,  where  the  wing-vena 
tion  has  been  greatly  modified,  as  in  certain  Hymenoptera,  there  exist 
what  appears  to  be  simple  veins  that  in  reality  are  compound  veins 
composed  of  sections  of  two  or  more  veins  joined  end  to  end  with  no 
indication  of  the  point  of  union.     Compound  veins  formed  in  this 


Fig.  80. — Wings  of  Pampkilius. 


manner  are  termed  serial  veins.  Examples  of  wings  in  which  there  ar  e 
serial  veins  are  figured  in  the  chapter  treating  of  the  Hymenoptera. 

In  designating  serial  veins  either  the  sign  &  or  a  dash  is  used 
between  the  terms  indicating  the  elements  of  the  vein,  instead  of  the 
sign  +  as  the  latter  is  used  in  designating  compound  veins  formed  by 
the  coalescence  of  veins  side  by  side.  If  the  serial  vein  consists  of 
only  two  elements  the  sign  &  is  used;  thus  the  serial  vein  in  the  wings 
of  braconids,  which  consists  of  the  medial  cross-vein  and  vein  M2,  is 
designated  as  w  &  M2. 

In  those  cases  where  sections  of  several  veins  enter  into  the  com- 
position of  a  serial  vein,  the  serial  vein  is  designated  by  the  abbrevia- 
tion of  the  name  of  the  basal  element  connected  by  a  dash  with  the 


AN  INTRODUCTION   TO  ENTOMOLOGY 


abbreviation  of  the  name  of  the  terminal  element.  Thus  a  serial 
vein,  the  basal  element  of  which  is  the  cubitus  and  the  terminal  ele- 
ment vein  Ml,  is  designated  as  vein  Cu — Mi.  A  serial  vein  thus 
formed  exists  in  the  hind  wings  of  certain  ichneumon  flies. 

The  increase  of  the  number  of  wing-veins.  In  the  wings  of  many- 
insects  the  number  of  veins  is  greater  than  it  is  in  the  hypothetical 
type.     This  multiplication  of  veins  is  due  either  to  an  in^reisi  in  the 


Fig.  8i. — Wings  of  Osmylns  hyalinatus. 

number  of  the  branches  of  the  principal  veins  by  the  addition  of 
secondary  branches,  termed  accessory  veins,  or  to  the  development  of 
secondary  longitudinal  veins  between  these  branches,  termed  inter- 
calary veins.  In  no  case  is  there  an  increase  in  the  number  of  principal 
veins. 

The  accessory  veins. — The  wings  of  Osmylus  (Fig.  8i)  are  an  exam- 
ple of  wings  in  which  accessory  veins  have  been  developed ;  here  the 
radial  sector  bears  many  more  branches  than  the  typical  niimber; 
those  branches  that  are  regarded  as  the  primitive  branches  are 
lettered  Ri,  Ro,  R3,  R4,  and  R5  respectively  (Fig.  82);    the  other 


THE   EXTERNAL   ANATOMY  OF  INSECTS 


6y 


branches  are  the  secondarily  developed  accessory  veins.  Two  types 
of  accessory  veins  are  recognized  the  marginal  accessory  veins  and 
the  definitive  accessory  veins. 

The  marginal  accessory  veins  are  twig-like  branches  that  are  the 
result  of  bifurcations  of  veins  that  have  not  extended  far  back  from 
the  margin  of  the  wing;  many  such  short  branches  of  veins  exist  in 
the  vvings  of  Osmylus  (Fig.  8i).  The  number  and  position  of  the 
marginal  accessory  veins  are  not  constant,  differing  in  the  wings  of 
the  two  sides  of  the  same  individual. 

The  definitive  accessory  veins  differ  from  the  marginal  accessory 


Fig.  82. — Base  of  fore  wing  shown  in  Figure  81. 


veins  in  having  attained  a  position  that  is  comparable  in  stability  to 
that  of  the  primitive  branches  of  the  principal  veins. 

In  those  cases  where  the  accessory  veins  are  believed  to  have  been 
developed  in  regular  order  they  are  designated  by  the  addition  of  a 
letter  to  the  abbreviation  of  the  name  of  the  vein  that  bears  them; 
thus  if  vein  R2  bears  three  accessory  veins  they  are  designated  as 
veins  R2a,  R2b,  and  R2C,  respectively. 

The  intercalary  veins. — The  intercalary  veins  are  secondarily 
developed  longitudinal  veins  that  did  not  arise  as  branches  of  the 
primitive  veins,  but  were  developed  in  each  case  as  a  thickened  fold  in 
a  corrugated  wing,  more  or  less  nearly  midway  between  two  pre- 
existing veins,  with  which  primarily  it  was  connected  only  by  cross- 
veins.    Excellent  examples  of  unmodified  intercalary  veins  are  com- 


'0 


^.V   INTRODUCTION    TO   ENTOMOLOGY 


Fig.  83. — Wing  of  a  May-fly  (After  Morgan). 


mon  in  the  Ephemerida,  where  most  of  the  intercalary  veins  remain 
distinct  from  the  veins  between  which  they  were  developed,  being 

connected  with 
them  only  by 
cross-veins,  the 
proximal  end  of 
the  intercalary 
vein  being  free 
(Fig.  83). 

When  it  is 
desirable  to  re- 
fer to  a  parti- 
cular interca- 
lary vein  it  can 
be  done  by  combining  the  initial  /,  indicating  intercalary,  with  the 
designation  of  the  area  of  the  wing  in  which  the  intercalary  vein  occurs. 
For  example,  in  the  wings  of  most  May-flies  there  is  an  intercalary 
vein  between  veins  Cui  and  Cu2,  i  e.  in  the  area  Cui ;  this  intercalary 
vein  is  desig- 
nated as  ICui. 
The  adven- 
titious veins. — 
In  certain  in- 
sects there  are 
secon  dary 
veins  that  are 
neither  acces- 
sory veins  nor 
intercalary 
veins  as  de- 
fined above; 
these  are 
termed  adven- 
titious veins. 
Examples  of 
these  are  the 
supplements  of 
the   wings   of 


Fig.  84.- 


-Wings  of  Prionoxystus. 


certain  Odonata  and  the  spurious  vein  of  the  Syrphids. 

The  anastomosis  of  veins. — The  typical  arrangement  of  wing-veins 
is  often  modified  by  an  anastomosis  of  adjacent  veins;   that  is,  two 


THE   EXTERNAL    ANATOMY    OF    INSECTS 


71 


veins  will  come  together  at  some  point  more  or  less  remote  from  their 
extremities  and  merge  into  one  for  a  greater  or  less  distance,  while 
their  extremities  remain  separate.  In  the  fore  wing  of  Prionoxystus 
(Fig.  84),  for  example,  there  is  an  anastomosis  of  veins  R3  and  R4+5. 
The  named  cross-veins. — In  the  wings  of  certain  insects,  as  the 
dragon-fiies,  May-flies,  and  others,  there  are  many  cross-veins;  it  is 
impracticable  in  cases  of  this  kind  to  name  them.  But  in  several  of 
the  orders  of  insects  there  are  only  a  few  cross-veins,  and  these  have 
been  named.     Figure  85  represents  the  hypothetical  primitive  type 


3dA 


2d  A 


Fig.  85.— The  hypothetical  primitive  type  of  wing-venation  with  the  named 
cross-veins  added. 

of  wing-venation  with  the  named  cross-veins  added  in  the  positions  in 
which  they  normally  occur ;    these  are  the  following : 

The  humeral  cross-vein  (h)  extends  from  the  subcosta  to  costa  near 
the  humeral  angle  of  the  wing. 

The  radial  cross-vein  (r)  extends  between  the  two  principal  divi- 
sions of  radius,  i.  e.  from  vein  Ri  to  vein  Rg. 

The  sectorial  cross-vein  {s)  extends  between  the  principal  divisions 
of  the  radial  sector —  i.  e.,  from  vein  R2+3  to  vein  R4+5  or  from  vein 
R3  to  vein  R4. 

The  radio-medial  cross-vein  (r—m)  extends  from  radius  to  media, 
usually  near  the  center  of  the  wing.  When  in  its  typical  position 
this  cross- vein  extends  from  vein  R4-1.5  to  vein  Mi +2. 

The  medial  cross-vein  (m)  extends  from  vein  M2  to  vein  M3.  This 
cross-vein  divides  cell  M2  into  cells,  ist  Mo  and  2d  M2;  see  Figure  87 
where  the  cells  are  lettered. 

The  medio-cubital  cross-vein  {m — cu)  extends  from  media  to 
cubitus. 


72 


AN  INTRODUCTION   TO   ENTOMOLOGY 


R^AU 


Cu 


^/.+.+ 


The  arculus. — In  many  insects  there  is  what  appears  to  be  a  cross- 
vein  extending  from  the  radius  to  the  cubitus  near  the  base  of  the 
wing;  this  is  the  arculus.  The  arculus  is  designated  in  figures  of 
wings  by  the  abbreviation  ar.  Usually  when  the  arculus  is  present 
the  media  appears  to  arise  from  it;  the  fact  is,  the  arculus  is  com- 
pound,  being  composed  of  a  section  of  media  and  a  cross-vein. 

Figure  86  is  a  dia- 
gram representing 
the  typical  struc- 
ture of  the  arculus. 
That  part  of  the 
arculus  which  is  a 
section  of  media  is 
designated  as  the 
anterior  arculus  (aa) 
and  that  part  formed  by  a  cross-vein,  the  posterior  arculus  (pa) . 

The  terminology  of  the  cells  of  the  wing. — Each  cell  of  the  wing  is 
designated  by  the  name  of  the  vein  that  normally  forms  its  front 
margin  when  the  wings  are  spread.  See  Figure  87  where  both  the 
veins  and  the  cells  of  the  wing  are  lettered. 

The  cells  of  the  wing  fall  naturally  into  two  groups:  first,  those 
on  the  basal  part  of  the  wing;  and  second,  those  nearer  the  distal  end 
of  the  wing.  The  former  are  bounded  by  the  stems  of  the  principal 
veins,  the  latter,  by  the  branches  of  these  veins;  a  corresponding 
distinction  is  made  in  designating  the  cells.  Thus  a  cell  lying  behind 
the  main  stem  of  radius  and  in  the  basal  part  of  the  wing  is  designated 
as  cell  R;  while  a  cell  lying  behind  radius-one  is  designated  as  cell  Ri. 


Fig.  86. — Diagram  of  an  arculus  of  a  dragon-fly. 


/?,        /?.  +  3 


Fig,  87. — A  wing  of  Rhyphus. 

It  should  be  remembered  that  the  coalescence  of  two  veins  results 
in  the  obliteration  of  the  cell  that  was  between  them.     Thus  when 


THE   EXTERNAL   ANATOMY   OF  INSECTS  73 

veins  R2  and  Rz  coalesce,  as  in  the  wings  of  Rhyphus  (Fig.  87),  the  cell 
lying  behind  vein  i?2+3  is  cell  Rz,  and  not  cell  R^+z,  cell  R2  having  been 
obliterated. 

When  one  of  the  principal  cells  is  divided  into  two  or  more  parts  by 
one  or  more  cross- veins,  the  parts  may  be  numbered,  beginning  v\'-ith 
the  proximal  one.  Thus  in  Rhyphus  (Fig.  87),  cell  M2  is  divided  by 
the  medial  cross-vein  into  cell  istMi  and  cell  2dMi. 

When  two  or  more  cells  are  united  by  the  atrophy  of  the  vein  or 
veins  separating  them,  the  compound  cell  thus  formed  is  designated 
by  a  combination  of  the  terms  applied  to  the  elements  of  the  com- 
pound cell.  When,  for  example,  the  stem  of  media  is  atrophied,  the 
cell  resulting  from  the  combination  of  cells  R  and  M  is  designated  as 
cell  R+M. 

The  application  of  this  system  of  naming  the  cells  of  the  wing  is  an 
easy  matter  in  those  orders  where  there  are  but  few  cross-veins ;  but 
in  those  orders  where  there  are  many  cross-veins  it  is  not  practicable 
to  apply  it.  In  the  latter  case  we  have  to  do  with  areas  of  the  wing 
rather  than  with  separate  cells.  These  areas  are  designated  as  are  the 
cells  of  the  few- veined  wings  with  which  they  correspond;  thus  the 
area  immediately  behind  vein  R2  is  area  R2. 

The  corrugations  of  the  wings. — The  wings  of  comparatively  few 
insects  present  a  flat  surface ;  in  most  cases  the  membrane  is  thrown 
into  a  series  of  folds  or  corrugations.  This  corrugating  of  the  wing  in 
some  cases  adds  greatly  to  its  strength,  as  in  the  wings  of  dragon-flies; 
in  other  cases  the  corrugations  are  the  result  of  a  folding  of  the  wing 
when  not  in  use,  as  in  the  anal  area  when  this  part  is  broadly  ex- 
panded. 

It  rarely  happens  that  there  is  occasion  to  refer  to  individual 
members  of  either  of  these  classes  of  folds,  except  perhaps  the  one 
between  the  costa  and  the  radius,  which  is  the  subcostal  fold  and  that 
which  is  normally  between  the  cubitus  and  the  first  anal  vein,  the 
cubito-a  lal  fold. 

Convex  a)id  concave  veins. — When  the  wings  are  corrugated,  the 
wing-veins  that  follow  the  crests  of  ridges  are  termed  convex  veins; 
and  those  that  follow  the  furrows,  concave  veins. 

The  furrows  of  the  wing. — There  are  found  in  the  wings  of  many 
insects  one  or  more  suture-like  grooves  in  the  membrane  of  the  wing; 
these  are  termed  the  furrows  of  the  wing.  The  more  important  of 
these  furrows  are  the  four  following: 

The  anal  furrow  when  present  is  usually  developed  in  the  cubito 
anal  fold;   but  in  the  Heteroptera  it  is  found  in  front  of  the  cubitus. 


74  AN  INTRODUCTION   TO  ENTOMOLOGY 

The  median  furrow  is  usually  between  radius  and  media. 

The  nodal  furrow  is  a  transverse  suture  beginning  at  a  point  in  the 
costal  margin  of  the  wing  corresponding  to  the  nodus  of  the  Odonata 
and  extending  towards  the  inner  margin  of  the  wing  across  a  varying 
ntunber  of  veins  in  the  different  orders  of  insects. 

The  axillary  furrow  is  a  line  that  serves  as  a  hinge  which  faciHtates 

the  folding  of  the  posterior  lobe  of  the  wing  of  many  insects  under  that 

^^  part  of  the  wing 

w^^^^^^^^^^^^^T'^^Ciilr^       ^-llr^ — '"^'^  ^^   veins   of  the 

\  \    ^ — ~— I^r~~~~~"^  wing  where  they 

\J   \.___     ><^  ^^s/**'^'^-^,.^^  ^^~-~-- y  are    crossed    by 

^^""'■~~~~~-----_l____^i^--"^'^  furrows.     The 

^.     „„     _.         ,  ,,  bullae  are  usually 

Fig.  88. — Wmgs  of  Myrmecia;    b,  b,  b,  bullae.  ,         .  , 

paler  m  color 

than  the  other  portions  of  the  wing ;    they  are  common  in  the  wings 

of  the  Hymenoptera  (Fig.  88),  and  of  some  other  insects. 

The  ambient  vein. — Sometimes  the  entire  margin  of  the  wing  is 
stiffened  by  a  vein-like  structure;  this  is  known  as  the  ambient  vein. 

The  humeral  veins. — In  certain  Lepidoptera  and  especially  in  the 
Lasiocampidas,  the  hiimeral  area  of  the  hind  wings  is  greatly  expanded 
and  in  many  cases  is  strengthened  by  the  development  of  secondary 
veins.     These  are  termed  the  humeral  veins. 

The  pterostigma  or  stigma. — A  thickened,  opaque  spot  which 
exists  near  the  costal  margin  of  the  outer  part  of  the  wing  in  many 
insects  is  known  as  the  pterostigma  or  stigma. 

The  epipleurcB. — A  part  of  the  outer  margin  of  the  elytra  of  beetles 
when  turned  down  on  the  side  of  the  thorax  is  termed  the  epipleura. 

The  discal  cell  and  the  discal  vein. — The  term  discal  cell  is  applied 
to  a  large  cell  which  is  situated  near  the  center  of  the  wing;  and  the 
term  discal  vein,  to  the  vein  or  series  of  veins  that  limits  the  outer  end 
of  the  discal  cell.  These  terms  are  not  a  part  of  the  uniform  terminol- 
ogy used  in  this  book,  and  can  not  be  made  so,  being  applied  to 
different  parts  of  the  wing  by  writers  on  different  orders  of  insects. 
They  are  included  here  as  they  are  frequently  used,  as  a  matter  of 
convenience,  by  those  who  have  adopted  the  uniform  terminology. 
The  discal  cell  of  the  Lepidoptera  is  cell  R+M  +  lstM2;  that  of  the 
Dipcera  is  cell  ist  M2;  and  that  of  the  Trichoptera  is  cell  R2+3. 


THE   EXTERNAL   ANATOMY  OF  INSECTS  75 

The  anal  area  and  the  preanal  area  of  the  wing. — In  descriptions  of 
wings  it  is  frequently  necessary  to  refer  to  that  part  of  the  wing 
supported  by  the  anal  veins ;  this  is  designated  as  the  anal  area  of  the 
wing;  and  that  part  lying  in  front  of  the  anal  area,  including  all  of 
the  wing  except  the  anal  area,  is  termed  the  preanal  area. 

IV.     THE  ABDOMEN 

a.       THE  SEGMENTS  OF  THE  ABDOMEN 

The  third  and  terminal  region  of  the  body,  the  abdomen,  consists 
of  a  series  of  approximately  similar  segments,  which  as  a  rule  are 
without  appendages  excepting  certain  segments  near  the  caudal  end 
of  the  body. 

The  body-wall  of  an  abdominal  segment  is  usually  comparatively 
simple,  consisting  in  adults  of  a  tergum  and  a  sternum,  united  by 
lateral  conjunctivce.  Sometimes  there  are  one  or  two  small  sclerites 
on  each  lateral  aspect  of  a  segment;  these  are  probably  reduced 
pleura. 

The  number  of  segments  of  which  the  abdomen  appears  to  be 
composed  varies  greatly  in  different  insects.  In  the  cuckoo-flies 
(Chrysididae)  there  are  usually  only  three  or  four  visible;  while  in 
many  insects  ten  or  eleven  can  be  distinguished.  All  intergrades 
between  these  extremes  occur. 

The  apparent  variation  in  the  number  of  abdominal  segments  is 
due  to  two  causes:  in  some  cases,  some  of  the  segments  are  tele- 
scoped ;  and  in  others,  adjacent  segments  coalesce,  so  that  two  or  more 
segments  appear  as  one. 

A  study  of  embryos  of  insects  has  shown  that  the  abdomen  con- 
sists typically  of  eleven  segments;  although  this  number  may  be 
reduced  during  the  development  of  the  insect  by  the  coalescence  of 
adjacent  segments. 

In  some  insects  there  is  what  appears  to  be  a  segment  caudad  of 
the  eleventh  segment;  this  is  termed  the  telson.  The  telson  differs 
from  the  segments  preceding  it  in  that  it  never  bears  appendages. 

Special  terms  have  been  applied,  especially  by  writers  on  the 
Coleoptera,  to  the  caudal  segments  of  the  abdomen.  Thus  the 
terminal  segment  of  a  beetle's  abdomen  when  exposed  beyond  the 
elytra  is  termed  the  pygldmm;  the  tergite  cephalad  of  the  pygidium, 
especially  in  beetles  with  short  elytra,  the  propygtdium;  and  the  last 
abdominal  stemite,  the  hypopygium.  The  term  hypopygium  is  also 
applied  to  the  genitalia  of  male  Diptera  by  writers  on  that  order  of 
insects. 


76 


AN  INTRODUCTION   TO  ENTOMOLOGY 


b.       THE   APPENDAGES    OF    THE   ABDOMEN 

In  the  early  embryonic  stages  of  insects,  each  segment  of  the 
abdomen,  except  the  telson,  bears  a  pair  of  appendages  (Fig.  89) .  This 
indicates  that  the  primitive  ancestor  of  insects  possessed  many  legs, 
like  a  centipede.  But  the  appendages  of  the  first 
seven  abdominal  segments  are  usually  lost  during 
embryonic  life,  these  segments  being  without  appen- 
dages in  postembryonic  stages,  except  in  certain 
Thysanura  and  CoUembola,  and  in  some  larvse. 

Reference  is  made  here  merely  to  the  primary 
appendages  of  the  segments,  those  that  are  homodyna- 
mous  with  the  thoracic  legs;  secondarily  developed 
appendages,  as  for  example,  the  tracheal  gills,  are 
present  in  the  immature  instars  of  many  insects. 
The  styli  or  vestigial  legs  of  certain  Thysanura. — In 
certain  Thysanura  the  coxa  of  each  middle  and  hind 
thoracic  leg  bears  a  small  appendage,  the  stylus  (Fig.  90) ; 
and  on  from  one  to  nine  abdominal  segments  there  is 
a  pair  of  similar  styli.  These  abdominal  styli  are 
believed  to  be  homodynamous  with  those  of  the  thoracic 
legs,  and  must,  therefore,  be  regarded  as  vestiges  of 
abdominal  legs. 

The  collophore  of  the  Collembola. — Although  in  the 
postembryonic  stages  of  Collembola  the  collophore  is 
an  unpaired  organ  on  the  middle  line  of  the  ventral  aspect  of  the  first 
abdominal  segment,  the  fact  that  it  arises  in  the  embryo  as  a  pair  of 
appendages  comparable  in  position  to  the  thoracic  legs,  has  led  to  the 
belief  that  it  represents  the  legs  of  this  segment.  The  structure  of 
the  collophore  is  described  more  fully  later  in  the  chapter  treating  of 
the  Collembola. 

The  spring  of  the  CoUembola. — The  spring  of  the  Collembola, 
like  the  collophore,  is  believed  to  represent  a  pair  of  primary  append- 
ages. This  organ  is  discussed  in  the  chapter  treating  of  the  Col- 
lembola. 

The  genitalia. — ^In  most  insects  there  are  more  or  less  prominent 
appendages  connected  with  the  reproductive  organs.  These  append- 
ages constitute  in  males  the  genital  daspers  and  in  females  the  ovi- 
positor; to  them  have  been  applied  the  general  term  genitalia,  they 
are  also  known  as  the  gonapophyses. 

The  genitaha,  when  all  are  developed  consist  of  three  pairs  of 
appendages.    Writers  vary  greatly  in  their  views  regarding  the  seg- 


Fig.  Sg.-Em- 
bryo  of  7^3'- 
drop  kilns 
showing  ab- 
dominal ap- 
pendages. 


THE   EXTERNAL   ANATOMY  OF  INSECTS 


77 


ments  of  the  abdomen  to  which  these  appendages  belong.  One  cause 
of  difference  is  that  some  writers  regard  the  last  segment  of  the  abdo- 
men as  the  tenth  abdominal 
segment  while  others  believe  it 
to  be  the  eleventh,  which  is 
the  view  adopted  in  this  work, 
this  segment  bears  the  cerci 
when  they  are  present.  The 
three  pairs  of  appendages  that 
constitute  the  genitalia  are 
borne  by  the  eighth  and  ninth 
segments,  two  pairs  being 
borne  by  the  ninth  segment. 
The  outer  pair  of  the  ninth 
segment  constitute  the  sheath 
of  the  ovipositor.  See  ac- 
count of  the  genitalia  of  the 
Orthoptera  in  Chapter  eight. 

The  genitalia  of  many  in- 
sects have  been  carefully  fig- 
ured and  described  and  special 
terms  have  been  applied  to 
each  of  the  parts.  But  as  most 
of  these  descriptions  have  been 
based  upon  studies  of  repre- 
sentatives of  a  single  order  of 
insects  or  even  of  some  smaller 
group,  there  is  a  great  lack 
of  uniformity  in  the  terms 
applied  to  homologous  parts 
in  the  different  orders  of  in- 
sects; such  of  these  tenns  as 
are  commonly  used  are  defined 

later  in  the  characterizations  of  the  several  orders  of  insects. 

The  cerci. — In  many  insects  there  is  a  pair  of  caudal  appendages 

which  are  known  as  the  cerci;    these  are  the  appendages  of  the 

eleventh  abdominal  segment,  the  last  segment  of  the  body  except  in 

the  few  cases  where  a  telson  is  present. 

The  cerci  vary  greatly  in  form;    in  some  insects,  as  in  most  Thy- 

sanura,  in  the  Plecoptera,  and  in  the  Ephermerida,  they  are  long  and 


Fig.  90. — Ventral  aspect  of  MachiHs;  c,  cer- 
cus;  Z/>,  labial  palpus;  mf,  median  caudal 
filament;  mp,  maxillary  palpus;  o,  oviposi- 
tor; s,  s,  styli.  That  part  of  the  figure 
representing  the  abdomen  is  after  Ou  de- 
mans. 


78  AN  INTRODUCTION   TO  ENTOMOLOGY 

many  jointed;    while  in  others  they  are  short  and  not  segmented. 
The  function  of  the  cerci  is  different  in  different  insects ;    they  are 

\  believed  to  be  tactile  in  some,  olfactory  in  others, 

/  and  in  some  males  they  aid  in  holding  the  female 
/      during  copulation. 

The  median  caudal  filament. — ^In  many  of  the 
Ephemerida  and  in  some  of  the  Thysanura,  the  last 
abdominal  segment  bears  a  long,  median  filament, 
which  resembles  the  many-jointed  cerci  of  these 
insects  (Fig.  91);  this  filament  is  believed  to  be  a 
prolongation  of  the  tergum  of  this  segment  and  not  a 
true  appendage  like  the  cerci. 

The  prolegs  of  larvae. — The  question  whether  the 
prolegs  of  larv^as  represent  true  appendages  or  are 
merely  hypodermal  outgrowths  has  been  much  dis- 
cussed. Several  embryologists  have  shown  that  in 
embryos  of  Lepidoptera  and  of  saw-flies  limb-rudi- 
^nia^sacchanna.  ments  appear  on  all  or  most  of  the  abdominal  seg- 
ments; and  that  they  very  soon  disappear  on  those 
segments  which  in  the  larva  have  no  legs  while  on  other  segments 
they  are  transferred  into  functional  prolegs.  If  this  view  is  estab- 
lished we  must  regard  such  prolegs  as  representing  primitive  abdo- 
minal appendages,  that  is  as  true  abdominal  legs. 

V.     THE  MUSIC  AND  THE  MUSICAL  ORGANS 
OF  INSECTS 

Much  has  been  written  about  music ;  but  the  greater  part  of  this 
literature  refers  to  music  made  by  man  for  human  ears.  Man,  how- 
ever, is  only  one  of  many  musical  animals;  and,  although  he  excels 
all  others  in  musical  accompHshments,  a  study  of  what  is  done  by  our 
hiunbler  relatives  is  not  without  interest. 

The  songs  of  birds  command  the  attention  of  all  observers.  But 
there  is  a  great  orchestra  which  is  performing  constantly  through  the 
warmer  portions  of  the  year,  which  is  almost  unnoticed  by  man. 
Occasionally  there  is  a  performer  that  cannot  be  ignored,  as:— 

"The  shy  Cicada,  whose  noon- voice  rings 
So  piercing  shrill  that  it  almost  stings 
The  sense  of  hearing."     (Elizabeth  Akers.) 

But  the  great  majority  fiddle  or  drum  away  unnoticed  by  human  ears. 


THE   EXTERNAL   ANATOMY  OF  INSECTS  79 

Musical  sounds  are  produced  by  many  different  insects,  and  in 
various  ways.  These  sounds  are  commonly  referred  to  as  the  songs  of 
insects;  but  properly  speaking  few  if  any  insects  sing;  for,  with  some 
possible  exceptions,  the  note  of  an  insect  is  always  at  one  pitch,  lacking 
musical  modulations  like  those  of  the  songs  of  man  and  of  birds. 

The  sound  produced  by  an  insect  may  be  a  prolonged  note,  or  it 
may  consist  of  a  series  of  short  notes  of  varying  length,  with  intervals 
of  rest  of  varying  lengths.  These  variations  with  differences  in  pitch 
give  the  wide  range  of  insect  calls  that  exists. 

In  some  cicadas  where  the  chambers  containing  the  musical  organs 
are  covered  by  opercula,  the  insect  can  give  its  call  a  rhythmic 
increase  and  decrease  of  loudness,  by  opening  and  closing  these 
chambers. 

As  most  insect  calls  are  strident,  organs  specialized  for  the  pro- 
duction of  these  calls  are  commonly  known  as  stridulating  organs. 
But  many  sounds  of  insects  are  produced  without  the  aid  of  organs 
specialized  for  the  production  of  sound.  The  various  ways  in  which 
insects  produce  sounds  can  be  grouped  under  the  following  heads : 

First. — By  striking  blows  with  some  part  of  the  body  upon  sur- 
rounding objects. 

Second. — By  rapid  movements  of  the  wings.  In  this  way  is 
produced  what  may  be  termed  the  music  of  flight. 

Third. — By  rasping  one  hard  part  of  the  body  upon  another. 
Under  this  head  fall  the  greater  number  of  stridulating  organs. 

Fourth. — By  the  rapid  vibration  of  a  membrane  moved  by  a  muscle 
attached  to  it.     This  is  the  type  found  in  the  cicadas. 

Fifth. — By  the  vibration  of  membranes  set  in  motion  by  th':j  rush 
of  air  through  spiracles.  The  reality  of  this  method  has  been  ques- 
tioned. 

Sixth. — By  rapid  changes  of  the  outline  of  the  thorax  due  to  the 
action  of  the  wing  muscles. 

a.       SOUNDS     PRODUCED     BY     STRIKING     OBJECTS     OUTSIDE     THE     BODY 

Although  the  sounds  produced  by  insects  by  striking  blows  with 
some  part  of  the  body  upon  surrounding  objects  are  not  rapid  enough 
to  give  a  musical  note,  they  are  referred  to  here  for  the  sake  of 
completeness. 

The  most  familiar  sounds  of  this  kind  are  those  produced  by  the 
insects  known  as  the  death-watch.  These  are  small  beetles  of  the 
family  Ptinidse,  and  especially  those  of  the  genus  Anohium.  These 
are  wood-boring  insects,  frequently  found  in  the  woodwork  of  old 


80  AN  INTRODUCTION   TO  ENTOMOLOGY 

houses  and  in  furniture,  where  they  make  a  ticking  sound  by  striking 
their  heads  against  the  walls  of  their  burrows.  The  sound  consists  of 
several,  sharp,  distinct  ticks,  followed  by  an  interval  of  silence,  and  is 
believed  to  be  a  sexual  call. 

The  name  death-watch  was  applied  to  these  insects  by  supersti- 
tious people  who  believed  that  it  presaged  the  death  of  some  person 
in  the  house  where  it  is  heard.  This  belief  probably  arose  from  the 
fact  that  the  sound  is  most  likely  to  be  heard  in  the  quiet  of  the  night, 
and  would  consequently  be  observed  by  watchers  by  sick-beds. 

The  name  death-watch  has  also  been  applied  to  some  species  of  the 
Psocidas,  Clothtlla  pulsatoria  and  Atropos  divinatoria,  which  have  been 
believed  to  make  a  ticking  sound.  This,  however,  is  doubted  by 
some  writers,  who  urge  that  it  is  difficult  to  believe  that  such  minute 
and  soft  insects  can  produce  sounds  audible  to  himian  ears. 

The  death-watches  produce  their  sounds  individually;  but  an 
interesting  example  of  an  insect  chorus  is  cited  by  Sharp  ('99,  p.  156), 
who,  quoting  a  Mr.  Peal,  states  that  an  ant,  presumably  an  Assamese 
species,  "makes  a  concerted  noise  loud  enough  to  be  heard  by  a  human 
being  at  twenty  or  thirty  feet  distance,  the  sound  being  produced  by 
each  ant  scraping  the  horny  apex  of  the  abdomen  three  times  in  rapid 
succession  on  the  dry,  crisp  leaves  of  which  the  nest  is  usually  com- 
posed." 

h.      THE    MUSIC    OF   FLIGHT 

The  most  obvious  method  by  which  insects  produce  sounds  is  by 
beating  the  air  with  their  wings  during  flight.  It  can  be  readily  seen 
that  if  the  wing-strokes  are  sufficiently  rapid  and  are  uniform,  they 
will  produce,  like  the  flapping  reeds  of  a  mouth  organ,  a  musical  note. 

When,  however,  we  take  into  account  the  fact  that  to  produce  the 
lowest  note  regularly  employed  in  music,  the  C  of  the  lowest  octave, 
requires  32  vibrations  a  second,  i.  e.,  nearly  2,000  vibrations  per 
minute,  it  will  seem  marvellous  that  muscular  action  can  be  rapid 
enough  to  produce  musical  notes.  Nevertheless,  it  is  a  fact  that 
many  insects  sing  in  this  way ;  and  too  their  notes  are  not  confined  to 
the  lower  octaves.  For  example,  the  common  house  fly  hums  F  of 
the  middle  octave,  to  produce  which,  it  must  vibrate  its  wings  345 
times  per  second  or  20,700  times  per  minute. 

As  a  rule,  the  note  produced  by  the  wings  is  constant  in  each 
species  of  insect.  Still  with  insects,  as  with  us,  the  physical  condition 
of  the  singer  has  its  influence.  The  vigorous  honey-bee  makes  the  A 
of  435  vibrations,  while  the  tired  one  hums  on  the  E  of  326  vibrations. 


THE   EXTERNAL   ANATOMY  OF  INSECTS  81 

While  it  is  only  necessary  to  determine  the  note  produced  by 
vibrating  wings  to  ascertain  the  rate  of  vibration,  a  graphical  demon- 
stration  of  the  rate  is  more  convincing.  Such  a  demonstration  has 
been  made  by  Marey  ('69)  who  fixed  a  fly  so  that  the  tip  of  the  wing 
just  touched  the  smoked  surface  of  a  revolving  cylinder,  and  thus 
obtained  a  wavy  line,  showing  that  there  were  actually  320  strokes  in 
a  second.  This  agrees  almost  exactly  with  the  nimiber  inferred  from 
the  note  prodviced. 

The  music  of  flight  may  be,  in  many  cases,  a  mere  accidental  result 
of  the  rapid  movement,  and  in  no  sense  the  object  of  that  movement, 
like  the  hum  of  a  trolley  car ;  but  there  are  cases  where  the  song  seems 
to  be  the  object  of  the  movement.  The  honeybee  produces  different 
sounds,  which  can  be  understood  by  man,  and  probably  by  bees,  as 
indicating  different  conditions.  The  contented  hum  of  the  worker 
collecting  nectar  may  be  a  song,  like  the  well-known  song  of  a  hen 
wandering  about  on  a  pleasant  day,  or  may  be  an  accidental  sound. 
But  the  honeybee  produces  other  sounds  that  communicate  ideas. 
The  swarming  sound,  the  hum  of  the  queenless  colony,  and  the  note 
of  anger  of  a  belligerent  bee  can  be  easily  distinguished  by  the  experi- 
enced beekeeper,  and  doubtless  also  by  the  bee  colony.  It  seems 
probable,  therefore,  that  in  each  of  these  cases  the  rate  of  vibration  of 
the  wings  is  adjusted  so  as  to  produce  a  desired  note.  This  is  also 
probably  true  of  the  song  of  the  female  mosquito,  which  is  pitched  so 
as  to  set  the  antennal  hairs  of  the  male  in  vibration. 

While  the  music  of  flight  is  a  common  phenomenon,  many  insects 
have  a  silent  flight  on  account  of  the  slowness  of  the  wing-movement. 

C.       STRIDULATING    ORGANS    OF    THE    RASPING    TYPE 

The  greater  number  of  the  insect  sounds  that  attract  our  attention 
are  produced  by  the  friction  of  hard  parts  of  the  cuticula  by  which  a 
vibrating  surface  is  set  in  motion.  In  some  cases,  as  in  many  of  the 
Orthoptera,  the  vibrating  surface  is  apart  of  the  wings  that  is  special- 
ized for  this  purpose;  but  in  other  cases,  a  specialized  vibrating  sur- 
face has  not  been  obser\^ed. 

Stridulating  organs  of  the  rasping  type  are  possessed  by  represen- 
tatives of  several  of  the  orders  of  insects ;  but  they  are.  most  common 
in  the  order  Orthoptera,  and  especially  in  the  families  Acridiidse, 
Locustidas,  and  Gryllidae,  where  the  males  of  very  many  species 
possess  them.  Very  few  other  Orthoptera  stridulate;  and  with  few 
exceptions  it  is  only  the  males  that  sing. 


82 


AN  INTRODUCTION  TO  ENTOMOLOGY 


In  each  of  these  families  the  vibrating  element  of  the  stridulating 
organ  is  a  portion  of  one  or  of  both  of  the  fore  wings ;  but  this  is  set  in 
motion  in  several  different  ways.  In  some  exotic  Acridiid^  abdominal 
stridulating  organs  exist. 

The  stridulating  organs  of  the  Locustidae. — With  many  species 
of  the  Locustidae  we  find  the  males  furnished  with  stridulating  organs ; 
but  these  are  comparatively  simple,  and  are  used  only  in  the  day  time. 

Two  methods  of  stridulation  are  used  by  members  of  this  family. 
The  simpler  of  these  two  methods  is  employed  by  several  common 
species  belonging  to  the  (Edipodinas;  one  of  which  is  the  Carolina 
locust,  Dissosteira  Carolina,  whose  crackling  flight  is  a  common  feature 
of  country  roadsides.  These  locusts,  as  they  fly,  rub  the  upper  sur- 
face of  the  costal  margin  of  the  hind  wings  upon  the  lower  surface  of 
the  thickened  veins  of  the  fore  wings,  and  thus  produce  a  loud  but  not 
musical  sound. 

The  second  method  of  stridulation  practiced  by  locusts  consists 
in  rubbing  the  inner  surface  of  the  hind  femora,  upon  each  of  which 
there  is  a  series  of  bead-like  prominences  (Fig.  92),  against  the  outer 

surface    of    the    fore    wings 


With  these  insects,  there  is  a 
thickening  of  the  radius  in  the 
basal  third  of  each  fore  wing, 
and  a  widening  of  the  two 
areas  between  this  vein  and 
the  costal  margin  of  the  wing, 
which  serves  as  a  sounding 
board  (Fig.  93).  The  two 
wings  and  femora  constitute  a 
pair  of  vioHn-like  organs;  the  thickened  radius  in  each  case  cor- 
responding to  the  strings;  the  membrane  of  the  wing,  to  the  body 
of  the  instrument ;  and  the  file  of  the  femur,  to  the  bow.  These  two 
organs  are  used  simultaneously.     When  about  to  stridulate,  the  insect 


B— 


Fig.  92. — A,  hind  femora  of  Slenobolhrus; 
B,  file  greatly  enlarged. 


Fig-  93- — Fore  wing  of  a  male  of  Stenobothrus. 
C,  costa. 


R,  radius;    Sc,  subcosta; 


THE   EXTERNAL   ANATOMY   OF  INSECTS 


83 


B 


i^^^.'fi^ 


places  itself  in  a  nearly  horizontal  position,  and  raising  both  hind  legs 
at  once  rasps  the  femora  against  the  outer  surface  of  the  wings.  The 
most  common  representatives  of  insects  that 
stridulate  in  this  way  belong  to  the  genus  Steno- 
bothrns. 

The  stridulating  organs  of  the  Gryllidae  and 
the  Tettigoniidae. — The  stridulating  organs  of 
the  Gryl-lid^  and  the  Tettigoniidae  are  of  the  same 
type,  and  are  the  most  highly  specialized  found  in 
the  Orthoptera.  They  consist  of  modified  portions 
of  the  fore  wings ;  both  the  vibrating  and  the  rasp- 
ing elements  of  the  organs  pertaining  to  the  wings. 

It  is  by  rubbing  the  two  fore  wings  together 
that  sound  is  produced. 

In  what  is  probably  the  more  generalized  con- 
dition of  the  organs,  as  seen  in  Gryllus,  each 
fore  wing  bears  a  rasping  organ,  the  file  (Fig. 
94,  /)  a  hardened  area,  the  scraper  (Fig.  94,  s), 
,  against  which  the  file  of  the  other  wing  acts,  and 
•I  I;  t;  Eli  If  If  11 )  vibrating  areas,  the  tympana  (Fig.  94,  t,  t).  As 
the  file  of  either  wing  can  be  used  to  set  the 
tympana  of  the  wings  in  vibration,  we  may  say 

Fig- 94- — Fore  wing  of  that  Gryllus  is  ambidextrous. 
Grvllus;    A,  as  seen 
from    above,    that         When  the  cricket  wishes  to  make  his  call,  he 

part  of  the  wing  elevates  his  fore  wings  so  that  they  make  an  angle 
which  IS  bent  down      .     ,  .  „        ^  .  ,    V,       ,      .  , 

on  the  side  of  the  of  about  forty-five  degrees  with  the  body;    then 

abdomen  is  not  holding  them  in  such  a  position  that  the  scraper 
shown;   5,  scraper;^,  ^  ,       _,        f^  ,  ,  ,  , 

.'.tympana.  B,base  of  one  rests  on  the  file  of  the  other,  he  moves  the 
of  wing  seen  from  ^i^gs  back  and  forth  laterally,  so  that  the  file  and 
below;     s,    scraper;  °  ,         ,  rr^i  •       , 

f,  file.  C,  file  great-  scraper  rasp  upon  each  other.  This  throws  the 
ly  enlarged.  wings  into  vibration  and  produces  the  call. 

It  is  easy  to  observe  the  chirping  of  crickets.  If  one  will  move 
slowly  towards  a  cricket  that  is  making  his  call,  and  stop  when  the 
cricket  stops  chirping  until  he  gains  confidence  and  begins  again, 
one  can  get  sufficiently  near  to  see  the  operation  clearly.  This  can 
be  done  either  in  the  day  time  or  at  night  with  the  aid  of  a  light. 

The  songs  of  the  different  genera  of  crickets  can  be  easily  dis- 
tinguished, and  that  of  each  species,  with  more  care.  Writers  on  the 
Orthoptera  have  carefully  described  the  songs  of  our  more  common 
crickets,  andespeciallythoseof  the  tree  crickets.     The  rate  of  chirping 


84 


^iV  INTRODUCTION   TO  ENTOMOLOGY 


is  often  influenced  by  temperature,  being  slower  in  cool  nights  than 
in  warm  ones;  and  becoming  slower  towards  morning  if  the  tem- 
perature falls. 

In  certain  genera  of  crickets  as  Nemohius  and  CEcanthus,  while 
each  fore  wing  is  furnished  with  a  file  and  tympana,  the  scraper  of  the 
right  wing  is  poorly  formed  and  evidently  not  functional.  As  these 
insects  use  only  the  file  of  the  right  wing  to  set  the  tympana  of  the 
wings  in  vibration,  they  may  be  said  to  be  right-handed. 


Fig-  95- — Wings  of  a  female  nymph  of  CEcanthus  ("From  Comstock  and 
Needham). 

In  the  Locustidag  a  similar  modification  of  the  function  of  the 
stridulating  organs  has  taken  place.  In  all  of  our  common  represen- 
tatives of  the  family,  at  least,  only  one  of  the  files  is  used.  But  in 
these  cases  it  is  the  file  of  the  left  wing  that  is  functional ;  we  may  say, 
therefore,  that  so  far  as  observed  the  Locustidae  are  left-handed. 
Different  genera  exhibit  great  differences  as  to  the  extent  of  the  reduc- 
tion of  the  unused  parts  of  the  stridulating  organs.  The  file  is 
present  in  both  wings  of  all  of  the  forms  that  I  have  studied ;  but  the 
imused  file  is  sometimes  in  a  vestigial  condition.  The  scraper  is  less 
persistent,  being  frequently  entirely  lacking  in  one  of  the  wings.  In 
some  cases,  the  tympana  of  one  wing  have  been  lost;  but  in  others 
the  tympana  of  both  wings  are  well  preserved,  although  only  one  file 


THE   EXTERNAL   ANATOMY   OF  INSECTS 


85 


is  used.  In  these  cases  it  is  probable  that  the  tympana  of  both  wings 
are  set  in  vibration  by  the  action  of  the  single  functional  file. 

The  determination  of  the  homologies  of  the  parts  of  the  wing  that 
enter  into  the  composition  of  the  stridulating  organs  was  accomplished 
by  a  study  of  the  tracheation  of  the  wings  of  n3nnphs  (Comstock  and 
Needham,  'qS-'qq).  The  results  obtained  by  a  study  of  the  wings  of 
CEcauthus  will  serve  as  an  illustration. 

Figure  95  represents  the  wings  of  a  female  n}Tnph  of  this  genus, 
with  the  tracheae  lettered.  The  only  parts  to  which  we  need  to  give 
attention  in  this  discussion  are  the  cubital  and  anal  areas  of  the  fore 
wing;  for  it  is  this  part  of  the  wing  that  is  modified  in  the  male  to 
form  the  musical  organ.  Both  branches  of  cubitus  are  present,  and 
Cui  bears  three  accessory  branches.  The  three  anal  tracheae  are 
present  and  are  quite  simple. 


Fig.  96. — Fore  wine 

Needham). 


of  a  male  nymph  of  CEranthus  (From  Comstock  and 


The  homologies  of  the  trachea  of  the  fore  wing  of  a  male  nymph, 
Figure  96,  were  easily  determined  by  a  comparison  with  the  tracheae 
of  the  female.  The  most  striking  difference  between  the  two  sexes 
is  a  great  expanding  of  the  area  between  the  two  branches  of  cubitus 
in  the  male,  brought  about  by  the  bending  back  of  the  basal  part 
of  Cuo. 

The  next  step  in  this  study  was  to  compare  the  wing  of  an  adult 
male.  Figure  97,  with  that  of  the  nymph  of  the  same  sex;  and  the 
solution  of  the  problem  was  soon  reached.  It  can  be  easily  seen  that 
the  file  is  on  that  part  of  Cu2  that  is  bent  back  toward  the  inner  mar- 
gin of  the  wing  (Fig.  97,  /);  the  tympana  are  formed  between  the 
branches  of  cubitus  (Fig.  97,  /,  t);  and  the  scraper  is  formed  at  the 
outer  end  of  the  anal  area  (Fig.  97,5). 


AN  INTRODUCTION   TO  ENTOMOLOGY 


A  similar  study  was  made  of  the  wings  of  Conocephalus.  as  an 
example  of  the  Tettigoniidae,  Figure  98  represents  the  wings  of  a  male 

nymph;  and 
Figure  99  the 
fore  wing  of 
an  adult.  The 
most  striking 
feature,  and 
one  character- 
istic of  the 
family,  is  that 
the  musical 
organ  occupies 
an  area  near 
the  base  of 
the  wing  which 

Fig-  97- — Fors  v/ing  of  an  adult  male  of  (Ecanlhus;  f,  vein        jg  gj^a.11   com- 
bearing  the  file;   5,  scraper;   /,/,  tympana.  ,  .     , 

pared     with 

the  area  occupied  by  the  musical   organs  of  the   Gryllidae.        But 
here,  as  in  the  Gryllidee,  the  file  is  borne  by  the  basal  part  of  Cu2,  the 


Fig.  98. — Wings  of  a  male  nymph  of  Conocephalus,  (From  Comstock  and 
Needham). 


tympana  are  formed  between  the  br-anches  of  cubitus,  and  the  scraper 
is  formed  at  the  outer  end  of  the  anal  area. 


THE   EXTERNAL    ANATOMY   OF   INSECTS 


87 


Rasping  organs  of  other  than  orthopterous  insects. — Rasping 
organs  are  found  in  many  other  than  orthopterous  insects  and  vary 

M 


Fig.  99. — Right  fore  wing  of  an  adult  male  of  Conocephalus,  seen 
from  below;  /,  file;   s,  scraper. 

greatly  in  foiTn  and  in  their  location  on  the  body.  Lack  of  space  for- 
bids any  attempt  to  enumerate  these  variations  here ;  but  examples  of 
various  types  of  stridulating  organs  will  be  described  in  later  chapters 
when  treating  of  the  insects  that  possess  them.  As  in  the  Orthoptera, 
they  consist  of  a  rasp  and  a  scraper.  The  rasp  is  a  file-like  area  of  the 
surface  of  a  segment  of  the  body  or  of  an  appendage;  and  the  scraper 
is  a  hard  ridge  or  point  so  situated  that  it  can  be  drawn  across  the  rasp 

by  movements 
of  the  body  or 
of  an  append- 
age. In  some 
cases  the  ap- 
paratus con- 
sists of  two 
rasps  so  situ- 
ated that  they 
can  be  rubbed 
together. 

With  many 
beetles  one  of 


Fig.  100. — Stridulating  organ  of  an  ant,  Myrmica  rubra 
(From  Sharp  after  Janet) ;    J,  scraper;    f,'file. 


the  two  parts  of  the  stridulating  organ  is  situated  upon  the  elytra ; 
and  it  is  quite  probable  that  in  these  cases  the  elytra  acts  as  vibrating 
surfaces,  as  do  the  wings  of  locusts  and  crickets.  But  in  many 
cases  as  where  a  part  of  a  leg  is  rubbed  against  a  portion  of  a 
thoracic  segment,  there  appears  to  be  no  vibrating  surface  unless  it  is 
the  wall  of  the  body  or  of  the  appendage  that  acts  as  a  sounding 
board.  In  the  stridulating  organ  of  Myrmica  rubra,  var.  IcBvinodis, 
figured  by  Janet  (Fig.  100),  the  scraper  is  the  posterior  border  of 
one  abdominal  segment,  and  the  file  is  situated  on  the  dorsum  of 
the  following   segment.       It  is  quite  conceivable  that   in  this  case 


S8  AN  INTRODUCTION   TO   ENTOMOLOGY 

the  dorsal  wall  of  the  segment  bearing  the  file  is  made  to  vibrate 
by  the  successive  impacts  of  the  scraper  upon  the  ridges  of  the 
file.  In  fact  this  seems  to  me  more  probable  than  that  the 
sound  produced  is  merely  that  of  the  scraper  striking  against  the 
successive  ridges  of  the  file.  There  is  at  least  one  recorded  case 
where  the  body  wall  is  specialized  to  act  as  a  sounding  board. 
According  to  Sharp  ('95,  p.  200),  in  the  males  of  the  Pneumorides, 
a  tribe  of  South  African  Acridiidse,  where  the  phonetic  organ  is 
situated  on  the  abdomen,  this  part  is  inflated  and  tense,  no 
doubt  with  the  result  of  increasing  the  volume  and  quality  of  the 
sound. 

Ordinarily  the  stridulating  organs  of  insects  are  fitted  to  produce 
notes  of  a  single  degree  of  pitch;  but  Gahan  ('00)  figures  those  of 
some  beetles  that  are  evidently  fitted  to  produce  sounds  of  more  than 
one  degree  of  pitch ;  the  file  of  Hispopria  foveicollis,  consists  of  three 
parts,  one  very  finely  striated,  followed  by  one  in  which  the  striae  are 
much  coarser,  and  this  in  turn  followed  by  one  in  which  the  striation 
is  intermediate  in  character  between  the  other  two. 

While  the  stridulating  organs  of  the  Orthoptera  are  possessed 
almost  exclusively  by  the  males,  in  the  Coleoptera,  very  many  species 
of  which  stridulate,  the  phonetic  organs  are  very  commonly  possessed 
by  both  sexes,  and  serve  as  a  mutual  call.  In  one  genus  of  beetles, 
Phoftapate,  stridulating  organs  have  been  found  only  in  the  females 
(Gahan,  '00). 

It  seems  evident  that  in  the  great  majority  of  cases  the  sounds 
produced  by  insects  are  sexual  calls;  but  this  is  not  always  so.  It 
was  pointed  out  long  ago  by  Charles  Darwin  that  "beetles  stridulate 
under  various  emotions,  in  the  same  manner  as  birds  use  their  voices 
for  many  purposes  besides  singing  to  their  mates.  The  great  Chiasog- 
nathus  stridulates  in  anger  or  defiance ;  many  species  do  the  same  from 
distress  or  fear,  if  held  so  that  they  cannot  escape;  by  striking  the 
hollow  stems  of  trees  in  the  Canary  Islands,  Messrs.  Wollaston  and 
Crotch  were  able  to  discover  the  presence  of  beetles  belonging  to  the 
genus  Acalles  by  their  stridulation.  Lastly  the  male  Ateuchus 
stridulates  to  encourage  the  female  in  her  work  and  from  distress 
when  she  is  removed"  {The  Descent  of  Man). 

The  most  remarkable  case  where  stridulating  organs  have  been 
developed  for  other  than  sexual  pusposes  is  that  of  the  larvae  of  certain 
Lucanidas  and  Scarabaeidae  described  by  Schiodte  ('74)-  In  these 
larvae  there  is  a  file  on  the  coxa  of  each  middle  leg,  and  the  hind  legs 
are  shortened  and  modified  so  as  to  act  as  scrapers.     The  most  highly 


THE   EXTERNAL   ANATOMY   OF  INSECTS 


89 


specialized  example  of  this  type  of  stridulatinj^  organ  is  possessed  by 
the  larvce  of  Passalus,  in  which  the  legs  of  the  third  pair  are  so  much 

shortened  that  the 
larv£e  appear  to 
have  only  four  legs ; 
each  hind  leg  is  a 
paw-like  structure 
fitted  for  rasping 
the  file  (Fig.   loi). 

These  insects 
are  social,  a  pair  of 
beetles  and  their 
progeny  living  to- 
gether in  decaying 
wood.  The  adults 
prepare  food  for  the 
larvce;  and  the  col- 
ony is  able  to  keep 
together  by  stridu- 
latory  signals. 

a.  THE     MUSICAL 

ORGANS  OF  A  CICADA 

With  the  cica- 
das there  exists  a 
type  of  stridulating 
organ  peculiar  to 
them,  and  one  that  is  the  most  complicated  organ  of  sound 
found  in  the  animal  kingdom.  Yet,  while  the  cicadas  are  the 
most  noisy  of  the  insect  world,  the  results  obtained  by  their  com- 
plicated musical  apparatus  are  not  comparable  with  those  pro- 
duced by  the  comparatively  simple  vocal  organs  of  birds  and  of 
man. 

It  is  said  that  in  some  species  of  Cicada  both  sexes  stridulate ;  but 
as  a  rule  the  females  are  mute,  possessing  only  vestiges  of  the  musical 
apparatus. 

The  structure  of  the  stridulating  organs  varies  somewhat  in 
details  in  different  species  of  Cicada;  but  those  of  Cicada  plebeia, 
which  were  described  and  figured  by  Carlet  ('77),  may  be  taken  as  an 
example  of  the  more  perfect  form.  In  the  male  of  this  species  there  is 
a  pair  of  large  plates,  on  the  ventral  side  of  the  body,  that  extend  back 


Fig.  1 01. — Stridulating  organ  of  a  larva  of  Passalus; 
a,  b,  portions  of  the  metathorax;  c,  coxa  of  the 
second  leg;  d,  file;  e,  basal  part  of  femur  of  middle 
leg;  /,  hairs  with  chitinous  process  at  base  of  each; 
g,  the  diminutive  third  leg  modified  for  scratching 
the  file  (From  Sharp). 


90 


AN  INTRODUCTION   TO  ENTOMOLOGY 


Fig.  I02. — The  musical  apparatus  of  a  cicada;  fm, 
folded  membrane;  /,  base  of  leg;  Ic,  lateral  cavity; 
m,  mirror;  o,  operculum,  that  of  the  opposite 
side  removed;  5/>,  spiracle;  /,  timbal;  ir,  ventral 
cavity  (After  Car  let). 


from  the  hind  border  of  the  thorax  and  overlap  the  basal  part  of  the 
abdomen;  these  are  the  opercula  (Fig.  102,  0).  The  opercula  are 
expansions  of  the  ster- 

nellimi   of  the  meta-  ^  r^^ 

thorax,  and  each 
serves  as  a  lid  covering 
a  pair  of  cavities,  con- 
taining the  external 
parts  of  the  musical 
apparatus  ot  one  side 
of  the  body. 

The  two  cavities 
covered  by  a  single 
operculum  may  be  de- 
signated as  the  ventral 
cavity  (Fig.  102,  v.  c.) 
and  the  lateral  cavity 
(Fig.  102, 1.  c.)  respec- 
tively.    Each  cavity  is  formed  by  an  infolding  of  the  body- wall. 

In  the  walls  of  these  cavities  are  three  membranous  areas;  these 
are  known  as  the  timbal,  the  folded  membrane,  and  the  mirror. 

The  timbal  is  in  the  lateral  cavity  on  the  lateral  wall  of  the  parti- 
tion separating  the  two  cavities  (Fig.  102,  t);  the  other  two  mem- 
branes are  in  the  ventral  cavity.  The  folded  membrane  is  in  the 
anterior  wall  of  the  ventral  cavity  (Fig.  10  2,  /.  m.);  and  the  mirror 
is  in  the  posterior  wall  of  the  same  cavity  (Fig.  102,  m).  Within  the 
body,  there  is  in  the  region  of  the  musical  apparatus  a  large  thoraco- 
abdomnal  air  chamber,  which  co,mmunicates  with  the  exterior 
througih  a  pair  of  spiracles  (Fig.  102  sp);  and  a  large  muscle,  which 
extends  from  the  furca  of  the  second  abdominal  segment  to  the  inner 
face  of  the  timbal. 

By  the  contraction  of  this  muscle  the  timbal  is  pulled  towards  the 
center  of  the  body;  and  when  the  muscle  is  relaxed,  the  elasticity  of 
the  chitinous  ring  supporting  the  timbal  causes  it  to  regain  its  form  er 
position.  By  a  very  rapid  repetition  of  these  movements  of  the  timbal 
the  sound  is  produced. 

It  is  probable  that  the  vibrations  of  the  timbal  are  transmitted  to 
the  folded  membrane  and  to  the  mirror  by  the  air  contained  in  the 
large  air  chamber  mentioned  above;  as  the  strings  of  a  piano  are 
made  to  vibrate  by  the  notes  of  a  near-by  violin.  The  sound,  how- 
ever, is  produced  primarily  by  the  timbal,  the  destruction  of  which 


THE   EXTERNAL   ANATOMY  OF  INSECTS  91 

renders  the  insect  a  mute;   while  the  destruction  of  the  other  mem- 
branes, the  timbal  remaining  intact,  simply  reduces  the  sound. 

The  chief  function  of  the  opercula  is  doubtless  the  protecting  of 
the  deHcate  parts  of  the  musical  organ;  but  as  they  can  be  lifted 
slightly  and  as  the  abdomen  can  be  moved  away  from  them  to  some 
extent,  the  chambers  containing  the  vibrating  parts  of  the  organ  can 
be  opened  and  closed,  thus  giving  a  rhythmic  increase  and  decrease  of 
the  loudness  of  the  call. 

e.       THE    SPIRACULAR   MUSICAL   ORGANS 

There  has  been  much  discussion  of  the  question  whether  insects, 
and  especially  Diptera  and  Hymenoptera,  possess  a  sound -producing 
organ  connected  with  the  spiracles  or  not.  Landois  ('67)  believed 
that  he  found  such  an  organ  and  figures  and  describes  it  in  several 
insects.  It  varies  greatly  in  form  in  different  insects.  In  the  Diptera 
it  consists  of  a  series  of  leaf-like  folds  of  the  intima  of  the  trachea; 
these  are  held  against  each  other  by  a  special  humming  ring,  which 
lies  close  under  the  opening  of  the  spiracle;  and  is  found  within  t^^'o 
or  all  four  of  the  thoracic  spiracles.  These  membranous  folds  of  the 
intima  are  set  in  vibration  by  the  rush  of  air  through  the  spiracles. 

In  the  May-beetle,  according  to  Landois,  a  buzzing  organ  is  foimd 
near  each  of  the  fourteen  abdominal  spiracles.  It  is  a  tongue-like 
fold  projecting  into  the  lumen  of  the  trachea  under  the  base  of  the 
closing  apparatus.  On  its  upper  surface  it  is  marked  with  very  fine 
arched  furrows.  He  concludes  that  this  tongue  is  put  in  vibration  by 
the  breathing  of  the  insect,  and  hence  the  buzzing  of  the  flying  beetle. 

If  insects  produce  sounds  in  the  way  described  by  Landois.  they 
have  a  voice  quite  analogous  to  our  own.  But  the  validity  of  the 
conclusions  of  Landois  has  been  seriously  questioned;  the  subject, 
therefore,  demands  further  investigation.     See  also  Duncan  ('24). 

/.       THE    ACUTE    BUZZING    OF    FLIES    AND    BEES 

Many  observers  have  found  that  when  the  wings  of  a  fly  or  of  a  bee 
are  removed  or  held  so  that  they  can  not  vibrate  the  insect  can  still 
produce  a  sound.  The  sound  produced  under  these  circumstances  is 
higher,  usually  an  octave  higher,  than  that  produced  by  the  wings. 
It  is  evident,  therefore,  that  these  insects  can  produce  sounds  in  two 
ways;  and  an  extended  search  has  been  made  for  the  organ  or  organj 
producing  the  higher  note. 


92  AN  INTRODUCTION   TO   ENTOMOLOGY 

Landois  believed  that  the  spiracular  organs  referred  to  above  were 
the  source  of  ttie  acute  sound.  But  more  recently  Perez  ('78)  and 
Bellesme  ('78)  have  shown  that  when  the  spiracles  are  closed  artifi- 
cially the  insect  can  still  produce  the  high  tone.  Perez  attributes  the 
sound  to  the  vibrations  of  the  stumps  of  the  wings  against  the  solid 
parts  which  surround  them  or  of  the  sclerites  of  the  base  of  the  wing 
against  each  other.  But  Bellesme  maintains  that  the  sound  is  pro- 
duced by  changes  in  the  form  of  the  thorax  due  to  the  action  of  the 
wing-muscles.*  When  the  wing-muscles  are  at  rest  the  section  of  this 
region,  according  to  this  writer,  represent  an  elhpse  elongated  ver- 
tically; the  contraction  of  the  muscles  transforms  it  to  an  elHpse 
elongated  laterally;  the  thorax,  therefore,  constitutes  a  vibrating 
body  which  moves  the  air  like  a  tine  of  a  tuning  fork.  Bellesme 
states  that  by  fastening  a  style  to  the  dorsal  wall  of  the  thorax  he 
obtained  a  record  of  the  rate  of  its  vibrations,  the  num.ber  of  which 
corresponded  exactly  to  that  required  to  produce  the  acute  sound 
which  the  ear  perceives. 

The  fact  that  the  note  produced  when  the  wings  are  rem.oved  is 
higher  than  that  produced  by  the  wings  is  supposed  by  Bellesme  to  be 
due  to  the  absence  of  the  resistance  of  air  against  the  wings,  which 
admits  of  the  maximum  rate  of  contraction  of  the  wing-muscles. 


g.      MUSICAL   NOTATION   OF   THE    SONGS    OF   INSECTS 

Mr.  S.  H.  Scudder  ('93)  devised  a  musical  notation  by  which  the 
songs  of  stridulating  insects  can  be  recorded.  As  the  notes  are  always 
at  one  pitch  the  staff  in  this  notation  consists  of  a  single  horizontal 
line,  the  pitch  being  indicated  by  a  separate  statement.  Each  bar 
represents  a  second  of  time,  and  is  occupied  by  the  equivalent  of  a 
semibreve ;  consequently  a  quarter  note  1  ,  or  a  quarter  rest  1,  repre- 
sents a  quarter  of  a  second ;  a  sixteenth  note  t,  or  a  sixteenth  rest  ~1 
a  sixteenth  of  a  second  and  so  on.  For  convenience's  sake  he  intro- 
duced a  new  form  of  rest,  shown  in  the  second  example  given  below, 
which  indicates  silence  through  the  remainder  of  a  measure;  this 
differs  from  the  whole  rest  commonly  employed  in  musical  notation 
by  being  cut  oft"  obliquely  at  one  end. 

*This  view  was  maintained  by  Siebold  at  a  much  earlier  date  in  his  Anatomy 
of  the  Invertebrates. 


THE   EXTERNAL    ANATOMY  OF  INSECTS  93 

The  following  examples  taken  from  his  paper  on  "The  Songs  of 
our  Grasshoppers  and  Crickets"  will  serve  to  illustrate  this  method 
of  notation. 

The  chirp  of  Gryllotalpa  horealis  (Fig.  103)  "is  a  guttural  sort  of 
sound,  like  grii  or  greeu,  repeated  in  a  trill  indefinitely,  but  seldom 

grii          gru  gru          gru  grfl  grfl  g^a  grn  grii        ^gra^ 

Fig.  103. — The  chirp  of  Gryllotalpa  borealis  (From  Scudder). 

for  more  than  two  or  three  minutes,  and  often  for  less  time.     It  is 
pitched  at  two  octaves  above  middle  C." 

XT!  xr!  xr!.  ct!  xt! 

Fig.  104. — The  chirp  of  the  katydid  (From  Scudder). 

The  note  of  the  true  katydid,  Cyrtophyllus  concavus,  (Fig.  104) 
"which  sounds  like  xr,  has  a  shocking  lack  of  melody;  the  poets  who 
have  sung  its  praises  must  have  heard  it  at  a  distance  that  lends 
enchantment."  "They  ordinarily  call  'Katy'  or  say  'She  did'  rather 
than  'Katy  did' ;  that  is  they  rasp  their  fore  wings  twice  more  fre- 
quently than  thrice."  Mr.  Scudder  in  his  account  of  this  song  fails 
to  indicate  its  pitch. 

h.      INSECT   CHORUSES 

Most  insect  singers  are  soloists,  singing  without  reference  to  other 
singers  or  in  rivalry  with  them.  But  there  are  a  few  species  the 
members  of  which  sing  in  unison  with  others  of  their  kind  that  are 
near  them.  The  most  familiar  sound  of  autimin  evenings  in  rural 
places  in  this  country  is  a  chorus  of  the  snowy  tree  cricket,  CEcanthus 
niveus.  Very  many  individuals  of  this  species,  in  fact  all  that  are 
chirping  in  any  locality,  chirp  in  unison.  Early  in  the  evening,  when 
the  chirping  first  begins,  there  may  be  a  lack  of  unanimity  in  keeping 
time;  but  this  lasts  only  for  a  short  period,  soon  all  chirp  in  unison, 
and  the  monotonous  beat  of  their  call  is  kept  up  uninterrupted 
throughout  the  night.  Individual  singers  will  stop  to  rest,  but  when 
they  start  again  they  keep  time  with  those  that  have  continued  the 
chorus. 

Other  instances  of  insect  choruses  have  been  recorded.  Sharp 
('99,  156)  quotes  accounts  of  two  produced  by  ants;  one  of  these  is 
given  on  an  earlier  page  (p.  80). 


CHAPTER   HI 
THE  INTERNAL   ANATOMY  OF  INSECTS 

Before  making  a  more  detailed  study  of  the  internal  anatomy  of 
insects,  it  is  well  to  take  a  glance  at  the  relative  positions  of  the  differ- 
ent systems  of  organs  within  the  body  of  insects  and  other  arthropods. 

One  of  the  most  striking  features  in  the  structure  of  these  animals 
is  that  the  body-wall  serves  as  a  skeleton,  being  hard,  and  giving  sup- 
port to  the  other  organs  of  the  body.  This  skeleton  may  be  repre- 
sented, therefore,  as  a  hollow  cylinder.  We  have  now  to  consider  the 
arrangement  and  the  general  form  of  the  organs  contained  in  this 
cylinder. 

The  accompanying  diagram  (Fig.  105),  which  represents  a  vertical, 
longitudinal  section  of  the  body,  will  enable  the  student  to  gain  an 


Fig.  105. — Diagram  showing  the  relations  of  the  internal  organs; 
a ,  alimentary  c anal ;  A,  heart;  ot,  muscle;  w,  nervous  system; 
r,  reproductive  organs. 

idea  of  the  relative  positions  of  some  of  the  more  important  organs. 
The  parts  shown  in  the  diagram  are  as  follows:  The  body-wall,  or 
skeleton;  this  is  made  up  of  a  series  of  overlapping  segments;  that 
part  of  it  between  the  segments  is  not  hardened  with  chitine,  thus 
remaining  flexible  and  allowing  for  the  movements  of  the  body.  Just 
within  the  body-wall,  and  attached  to  it,  are  represented  a  few  of  the 
muscles  {m) ;  it  will  be  seen  that  these  muscles  are  so  arranged  that  the 
contraction  of  those  on  the  lower  side  of  the  body  would  bend  it  down, 
while  the  contraction  of  those  on  the  opposite  side  would  act  in  the 
opposite  direction,  other  muscles  not  shown  in  the  figure  provide 
for  movements  in  other  directions.  The  alimentary  canal  (a)  occupies 
the  centre  of  the  body,  and  extends  from  one  end  to  the  other.  The 
heart  (/i)  is  a  tube  open  at  both  ends,  and  lying  between  the  alimentary 
canal  and  the  muscles  of  the  back.  The  central  part  of  the  nervous 
system  {n)  is  a  series  of  small  masses  of  nervous  matter  connected  by 

(94) 


THE   INTERNAL   ANATOMY  OF  INSECTS  95 

two  longitudinal  cords:  one  of  these  masses,  the  brain,  lies  in  the 
head  above  the  alimentary  canal ;  the  others  are  situated,  one  in  each 
segment,  between  the  alimentary  canal  and  the  layer  of  muscles  of  the 
ventral  side  of  the  body;  the  two  cords  connecting  these  masses,  or 
ganglia,  pass  one  on  each  side  of  the  oesophagus  to  the  brain.  The 
reproductive  organs  (r)  lie  in  the  cavity  of  the  abdomen  and  open  near 
the  caudal  end  of  the  body.  The  respiratory  organs  are  omitted  from 
this  diagram  for  the  sake  of  simplicity.  We  will  now  pass  to  a  more 
detailed  study  of  the  different  systems  of  organs. 

I.     THE  HYPODERMAL*  STRUCTURES 

The  active  living  part  of  the  body-wall  is  the  hypodermis,  already 
described  in  the  discussion  of  the  external  anatomy  of  insects.  In 
addition  to  the  external  skeleton,  there  are  derived  from  the  hypo- 
dermis an  internal  skeleton  and  several  types  of  glands. 

a,  THE    INTERNAL    SKELETON 

Although  the  skeleton  of  an  insect  is  chiefly  an  external  one,  there 
are  prolongations  of  it  extending  into  the  body-cavity.  These 
inwardly  directed  processes,  which  serve  for  the  attachment  of 
muscles  and  for  the  support  of  other  viscera  are  termed  collectively 
the  internal  skeleton  or  endo-skeleton.  The  internal  skeleton  is  much 
more  highly  developed  in  adult  insects  than  it  is  in  the  immature 
instars. 

Sources  of  the  internal  skeleton. — The  parts  of  the  internal  skele- 
ton are  formed  in  two  ways :  first  by  the  chitinization  of  tendons  of 
muscles;    and  second,  by  invaginations  of  the  body-wall. 

Chitinized  tendons. — Chitinized  tendons  of  the  muscles  that  move 
the  mouth-parts,  of  muscles  that  move  the  legs,  and  of  other  muscles 
are  of  frequent  occurrence.  As  these  chitinized  tendons  help  support 
the  internal  organs  they  are  considered  as  a  part  of  the  internal 
skeleton. 

Invaginations  of  the  body-wall  or  apodemes. — The  second  and  more 
important  source  of  the  parts  of  the  internal  skeleton  consists  of 
invaginations  of  the  body- wall.  Such  an  invagination  is  termed  an 
dpodeme.  The  more  important  apodemes,  if  not  all,  arise  as  invagina- 
tions of  the  body-wall  between  sclerites  or  at  the  edge  of  a  sclerite  on 
the  margin  of  a  body-segment;  although  by  the  fusion  of  sclerites 
about  an  apodeme,  it  may  appear  to  arise  from  the  disc  of  a  sclerite. 


96 


AN  INTRODUCTION   TO   ENTOMOLOGY 


Frequently,  in  the  more  generalized  insects,  the  mouth  of  an  apodeme 
remains  open  in  the  adult  insects.  In  Figure  io6  are  represented  two 
apodemes  that  exist  in  the  thorax  of  a 
locust,  Melanophis.  Each  of  these  {ap 
and  ap)  is  an  invagination  of  the  body- 
wall,  between  the  epistemum  and  the 
epimeron  of  a  segment,  immediately 
above  the  base  of  a  leg.  These  are  known 
as  the  lateral  apodemes  of  the  thorax  and 

serve  as  points  of  attachment  of  muscles. 

rrvi  1  r  J  i  Fig.     io6. — Ental    su-face    of 

The  number  of  apodemes  may  be  very      \^^  pkurites  of  the  meso- 


and  metathorax  of  Melano- 
plus,  showing  the  lateral 
apodemes,  ap,  ap. 


large,  and  it  varies  greatly  in  different 
insects.  Among  the  more  important  apo- 
demes are  the  following: — 

The  tentorium. — The  chief  part  of  the  internal  skeleton  of  the 
head  is  termed  the  tentorium.  This  was  studied  by  Comstock 
and  Kochi  ('02).  We  found  that  in  the  generalized  insects  studied 
by  us  it  is  composed  of  two  or  three  pairs  of  apodemes  that,  extend- 
ing far  into  the  head,  meet  and  coalesce.  The  three  pairs  of 
apodemes  that  may  enter  into  the  formation  of  the  tentorium 
were  termed  the  anterior,  the  posterior,  and  the  dorsal  arms  of  the 
tentorium,  respectively.  The  coalesced  and  more  or  less  expanded 
tips  of  these  apodemes  constitute  the  body  of  the  tentorium.  From 
the  body  of  the  tentoritim  there  extend  a  variable  number  of  processes 
or  chitinized  tendons. 

The  posterior  arms  of  the  tentorium.— The  posterior  arms  of  the 
tentorium  (Fig.  107,  109,  no,  pt)  are  the  lateral  apodemes  of  the 


Fig.  107. —  Tentorium 
of  a  cockroach,  dor- 
sal aspect. 


Fig.  108.— Part  of  the 
tentorium  of  a  cric- 
ket, ventral   aspect. 


maxillary  segment.     In  many  Orthoptera  the  open  mouth  of  the 
apodeme  can  be  seen  on  the  lateral  aspect  of  the  head,  just  above  the 


THE   INTERNAL   ANATOMY  OF  INSECTS  97 

articulation  of  the  maxilla  (Fig.  48).  In  the  Acridiidae  (Fig.  109) 
these  apodemes  bear  a  striking  resemblance  to  the  lateral  apodemes 
of  the  thorax  (Fig.  106),  except  that  the  ventral  process  of  the  maxil- 
lary apodeme  is  much  more  prominent,  and  the  two  frorri  the  opposite 
sides  of  the  head  meet  and  coalesce,  thus  forming 
the  caudal  part  of  the  body  of  the  tentorium. 

The  anterior  arms  of  the  tentorium. — Each  anterior 
arm  of  the  tentorium  (Fig.  107,  108,  no,  at)  is  an 
invagination  of  the  body-wall  which  opens  on  the 
margin  of  the  antecoxal  piece  of  the  mandible 
when  it  is  distinct ;  if  this  part  is  not  distinct  the 
apodeme  opens  between  the  clypeus  and  the  front 
Fie.io9.-Headof  (Fig- 46,  a/). 
Melano plus, can-  The  dorsal  arms  of  the  tentorium. — Each  dorsal 

a  aspec  .  ^^,^  ^^  ^-^^  tentorium  arises  from  the  side  of  the 

body  of  the  tentorium  between  the  anterior  and  posterior  arms 
and  extends  either  to  the  front  or  to  the  margin  of  the  antennal 
sclerite  (Fig.  107,  108,  no,  dt). 

The  frontal  plate  of  the  tentorium. — In  the  cockroaches  the  anterior 
arms  of  the  tentoriimi  meet  and  fuse,  forming  a  broad  plate  situated 
between  the  crura  cerebri  and  the  mouth ;  this  plate  was  termed  by 
us  the  frontal  plate  of  the  tentorium  (Fig.  107,  fp).  On  each  side,  an 
extension  of  this  plate  connects  it  with  the  body  of  the  tentoriiun; 
these  enclose  a  circular  opening  through  which  pass 
the  crura  cerebri. 

Other  cervical  apodemes  and  some  chitinized 
tendons  are  described  in  the  paper  cited  above. 

The  endothorax. — The  internal  skeleton  of  the 
thorax  is  commonly  termed  the  endothorax;  under 
this  head  are  not  included  the  internal  processes  of 
the  appendages. 

The  endothorax  is  composed  of  invaginations  of 
each  of  the  sections  of  a  thoracic  ring.  Those  por-  torium  of  Mela- 
tions  that  are  derived  from  tergites  are  termed  aspect'. Thedistal 
phragmas;  those  derived  from  the  pleurites,  lateral  end  of  the  dorsal 
apodemes;   and  those,  from  the  sternites,  furcce.  ^^"^^ 

The  phragmas. — A  phragma  is  a  transverse  partition  extending 
entad  from  the  front  or  the  hind  margin  of  a  tergite;  three  of  them 
are  commonly  recognized;  these  were  designated  by  Kirby  and 
Spence  (1826)  the  prophragma,  the  mesophragma,  and  the  nieta- 
phragma;    but,  as  they  do  not  arise  one  from  each  segment  of  the 


98 


AN  INTRODUCTION   TO  ENTOMOLOGY  ' 


thorax,  and  arise  differently  in  different  insects,  these  terms  are  mis- 
leading. No  phragma  is  borne  by  the  prothorax;  the  mesothorax 
may  bear  two  and  the  metathorax  one,  or  the  mesothorax  one  and  the 

metathorax  two.  A  more  definite 
terminology  is  that  used  by  Snod- 
grass  ('09)  by  which  the  anterior 
phragma  of  any  segment  is  termed 
the  prephragma  of  that  segment, 
and  the  posterior  phragma  of  any 
segment  is  termed  the  postphragma 
of  that  segment. 

The  lateral  apodemes. — Each  lat- 
eral apodeme  is  an  invagination  of 
the  body-wall  between  the  epister- 
num  and  the  epimeron.  The  lateral  apodemes  are  referred  to  above 
(Fig.  106). 

ThefurccB. — Each  furca  is  an  invagination  of  the  body-wall  arising 
between  the  sternum  and  the  sternellum  (Fig.  in);  when  the  sternel- 
lum  is  obsolete,  as  it  is  in  most  insects,  the  furca  arises  at  the  caudal 
margin  of  the  segment  (Fig.  112). 


Fig.  Ill . — Ventral  aspect  of  the 
metathorax  of  Stenopelmatus. 
The  position  of  the  furca 
within  the  body  is  represented 
by  a  dotted  line. 


b.       THE    HYPODERMAL   GLANDS 

A  gland  is  an  organ  that  possesses  the  function  of  either  trans- 
forming nutritive  substances,  which  it  derives  from  the  blood,  into 
some  useful  substance,  as  mucus,  wax,  or  venom,  or  of  assimilating 
and  removing  from  the  body  waste 
material. 

The  different  glands  vary  greatly  in 
structure;     many    are    unicellular,    the 
gland  consisting  of  a  single  cell,  which 
differs  from  the  other  cells  of  the  epithe- 
litmi  of  which  it  is  a  part  in  being  larger 
and  in  possessing  the  secreting  and  ex- 
creting functions;    others  are  multicel- 
lular, consisting  of  more  than  one  cell.  Fig.  112.— Ventralaspectof  the 
usually  of  many  cells.     In  these  cases       'Si^^IsTL'^^^l^oat 
the    glandular    area    usually    becomes       furcae  within  the  body  are 
invaginated,    and    provided     with    an        indicated  by  dotted  lines. 
efferent  duct ;    and  often  the  invagination  is  much  branched. 

The  glands  found  in  the  body  of  an  insect  can  be  grouped  under 
three  heads;    the  hypodermal  glands,  the  glands  of  the  alimentary 


THE   INTERNAL   ANATOMY   OF  INSECTS 


99 


canal,   and  the  glands  of  the  reproductive  organs.     In  this  place 
reference  is  made  only  to  the  hypodermal  glands,  those  developed 

from  the  hypodermis. 

The  Molting-fluid  glands. — Under  this 
head  are  classed  those  unicellular,  hypo- 
dermal  glands  that  secrete  a  fluid  that 
facilitates  the  process  of  molting,  as  des- 
cribed in  the  next  chapter  (Fig.  113). 

While  molting-fluid  glands  are  very 
numerous  and  conspicuous  in  certain 
insects,  those  living  freely  exposed  where 
there  exists  the  greatest  liability  to  rapid 
desiccation,  Tower  ('06)  states  that  he 
has  never  found  these  glands  in  larvae 


Fig.  1 13. — Molting-fluid  glands 
of  the  last  larval  instar  of 
Leptinotarsa  decimlineata,  just 


epidermis;  Id,  larval  dermis; 
mf,  molting  fluid;  pe,  forming 
pupal  epidermis;  h,  hypoder- 
mis; g,  molting  fluid,  gland 
(After  Tower). 


before  pupation;  le,  larval  that  live  in  burrows,  or  in  the  soil,  or  in 
cells;  in  these  cases  the  molting  fluid  is 
apparently  secreted  by  the  entire  hypo- 
dermal  layer. 

Glands  connected  with  setae. — There 

are  in  insects  several  kinds  of  glands  in  which  the  outlet  of  the  gland 

is  through  the  Itimen  of  a  seta.     The  function  of  the  excretions  of 

these  glands  is  various  as  indicated 

below.      There  are  also  differences  in 

the  manner  of  issuance  of  the  excre- 
tion from  the  seta.     In  some  cases,  as 

in  the  tenent  hairs  on  the  feet  of  certain 

insects,  the  excretion  can  be  seen  to 

issue  through  a  pore  at  the  tip  of  the 

seta.     In  some  kinds  of  venomous  setae 

the  tip  of  the  seta  breaks  off  in  the 

wound  made  by  it  and  thus  sets  free 

the  venom.      But  in  most  cases  the 

manner  of  issuance  has  not  been  deter- 
mined, although  it  is  commonly  believed 

to  be  by  means  of  a  minute  pore  or 

pores  in  the  seta,  the  thickness  of  the 

wall  of  the  seta  making  it  improbable 

that  the  excretion  passes  from  the  seta 

by  osmosis. 

The  structure  of  a  glandular  seta 

is    illustrated    by    Figure     114;    the 

essential  difference  between  such  a  seta  and  an  ordinary  one,  that  is  a 


Fig.  1 14. — Glandular  s  ;ta;  j,  seta; 
c,  cuticula;  h,  hypodermis;  bm, 
basement  membrane;  tr,  tricho- 
gen;  g,  gland  (After  Holmgren). 


100 


AN  INTRODUCTION   TO  ENTOMOLOGY 


clothing  hair,  is  that  there  is  connected  with  it,  in  addition  to  the 
trichogen  cell  which  produced  it,  the  gland  cell  which  opens  through  it. 
In  most  of  the  published  figures  of  glandular  set®  there  is  no  indi- 
cation that  these  organs  are  supplied  with  nerves ;  but  in  some  cases 
a  nerve  extending  to  the  gland  cell  is  clearly  shown.  This  condition 
may  be  found  to  be  general  when  more  extended  investigations  of 
glandular  cells  have  been  made.  The  best  known  kinds  of  glandular 
set£e  are  the  following : 

Venomous  setcE  and  spines. — These  are  best  known  in  larvas  of 
Lepidoptera,  several  common  species  of  which  possess  stinging  hairs; 
among  these  are  Lagoa  crtspata,  Sihine  stimulea,  Automeris  io,  and 
the  brown-tail  moth,  Euproctis  chrysorrhcsa. 

Androconia. — The  term  androconia*  is  applied  to  some  peculiarly 
modified  scales  on  the  wings  of  certain  male  butterflies.  These  are 
the  outlets  of  glands,  which  secrete  a  fluid  with  an  agreeable  odor; 
the  supposed  function  of  which  is  to  attract  the  opposite  sex,  like  the 
beautiful  plumage  and  songs  of  male  birds.  The  androconia  differ 
marvelously  from  ordinary  scales  in  the 
variety  of  their  forms  (Fig.  115).  They 
usually  occur  in  patches  on  the  upper  sur- 
face of  the  fore  wings;  and  are  usually 
concealed  by  other  scales;  but  they  are 
scattered  in  some  butterflies.  The  most 
familiar  examples  of  grouped  androconia 
are  those  that  occur  in  the  discal  stigma  of 
the  hair-streaks,  in  the  brand  of  certain 
skippers  and  in  the  costal  fold  of  others, 
and  in  the  scent-pouch  of  the  male  of  the 
monarch  butterfly 

The  specific  scent-glands  of  females. — 
The  well-known  fact  that  if  an  unfertilized 
female  moth  be  confined  in  a  cage  or 
otherwise  in  the  open  many  males  of  the 

Fig.  115.— Androconia  from  the  same  Species  as  the  female  will  be  attracted 
wmgs  of  male  butterflies  (After        .  .  .,        ,     . 

Kellogg).  to  it,  and sometmies  evidently  from  a  great 

distance,  leads  to  the  conclusion  that  there 

must  emanate  from  the  female  a  specific  odor.     The  special  glands 

producing  this  odor  have  not  been  recognized. 

Tenent  hairs. — In  many  insects  the  pulvilli  or  the  empodia  are 

clothed  with  numerous  hairs  that  are  the  outlets  of  glands  which 


"Androconia:   andro- {a.vfjp^avbpbs),rr.a\e\  conia  {kovIo) ,  6\\si. 


THE    INTERNAL    ANATOMY   OF  INSECTS 


101 


secrete  an  adhesive  fluid;   this  enables  the  insect  to  walk  on  the  lower 
surface  of  objects  (Fig.  ii6). 


Fig.  Ii6. — A,  terminal  part  of  a  tenent  hair  from  Eiipokis,  showing  canal  in  the 
hair  and  opening  near  the  tip;  B,  cross-section  through  a  tarsal  segment  of 
Telephorus;  c,  cuticula;  g,  gland  of  tenent  hair;  h,  h,  tactile  hairs;  hy,  hypo- 
dermis;  n,  nerve;  s,  sense-cell  of  tactile  hair;  t,  t,  tenent  hairs  (After  Dewitz). 

The  osmeteria. — In  many  insects  there  are  hypodermal  glands  that 
o^en  into  sac-like  invaginations  of  the  body-wall  which  can  be 
evaginated  when  the  insect  wishes  to  make  use  of  the  secretion  pro- 
duced by  these  glands ;  svLch  an  organ  i^  termed  an  osmeterium.  The 
invagination  of  the  osmeteriimi  admits  of  an  accumulation  of  the 
products  of  the  gland  within  the  cavity  of  the  sac  thus  formed;  when 
the  osmeteriunj  is  evaginated  the  secretion  becomes  exposed  to  the  air, 
being  then  on,  the  outside  of  the  osmeterium,  and  rapid  diffusion,  of 
the  secretion  results. 

The  most  familiar  examples  of  osmeteria  are  those  of  the  larvee 
of  the  swallow-tailed  butterflies,  which  are  forked,  and  are  thrust  out 
from  the  upper  part  of  the  prothorax  when  the  caterpillar  is  disturbed, 

and  which 
diffuse  a  dis- 
agreeable odor 
(Fig.  117). 
They  are  ob- 
viously organs 
of  defense. 
Osmeteria 

are  present  in  the  larvae  of  certain  blue  butterflies,  Lycasnidae.  These 
are  in  the  seventh  and  eighth  abdominal  segments,  and  secrete  a 
honey-dew,  which  attracts  ants  that  attend  and  probably  protect 
the  larvse.  The  osmeteria  of  many  other  caterpillars  have  been 
described. 


Fig.  117  — Larva  of  Papilio  thoas;  0,  osmeterium  expanded. 


102 


AN   INTRODUCTION    TO   ENTOMOLOGY 


Fig.   1 1 8. — Wax-plates  of  the  honej-bee 
(After  Cheshire). 


Glands  opening  on  the  surface  of  the  body. — There  are  several 
kinds  of  hypodermal  glands,  differing  widely  in  function,  that  open 
on  the  surface  of  the  body;  among  the  best  known  of  these  are  the 
following: 

Wax-glands. — The  worker  honeybee  has  four  pairs  of  wax-glands; 
these  are  situated  on  the  ventral  wall  of  the  second,  third,  fourth,  and 
fifth  abdominal  segments,  and  on  that  part  of  the  segment  which  is 
overlapped  by  the  preceding  segment;  each  gland  is  simply  a  disc- 
like area  of  the  hypodermis 
(Fig.  1 1 8).  The  cuticle 
covering  each  gland  is 
smooth  and  delicate,  and  is 
known  as  a  wax  plate. 
The  wax  exudes  through 
these  plates  and  accumu- 
lates, forming  little  scales, 
which  are  used  in  making 
the  honey- comb. 

Wax -glands  exist  in 
many  of  the  Homoptera.  In  some  of  these  the  unicellular  wax- 
glands  are  distributed  nearly  all  o\'er  the  body;  and  the  product 
of  these  glands  forms,  in  some,  a  po.wdery  covering;  in  others, 
a  clothing  of  threads;  and  in  still  others  a  series  of  plates  (Fig.  119). 
Certain  coccids  excrete  wax  in  con- 
siderable quantities.  China  wax,  which 
was  formerly  an  article  of  commerce, 
is  the  excretion  of  a  coccid  known  as 
Pe-la  (Ericerus  Pe-la). 

Froth-glands  of  spittle-insects. — In 
the  spittle-insects  (Cercopidse)  there 
are  large  hypodermal  glands  in  the 
pleural  regions  of  the  seventh  and  eighth 
abdominal  segments,  which  open 
through  numerous  minute  pores  in  the 
cuticula.  These  glands  secrete  a  muci- 
laginous substance,  which  is  mixed  with 
a  fluid  excreted  from  the  anus,  and  thus 
fits  it  for  the  retention  of  bubbles  of  air 
included  in  it  by  means  of  abdominal  appendages  (Guilbeau  '08). 

Stink-glands. — Glands  that  secrete  a  liquid  having  a  fetid  odor  and 
that  are  doubtless  defensive  exist  in  many  insects.     In  the  stink-bugs 


Fig.  119. — Orthesia,  greatly  en- 
larged. 


THE    INTERNAL   ANATOMY   OF  INSECTS 


103 


(Pentatomidas)  the  fluid  is  excreted  through  two  openings,  one  on  each 
side  of  the  lower  side  of  the  body  near  the  middle  coxae;  in  the  bed- 
bug {Cimex) ,  the  stink-glands  open  in  the  dorsal  wall  of  the  first  three 
abdominal  segments ;  in  Dytiscus,  the  glands  open  on  the  prothorax; 
and  in  certain  Coleoptera  they  open  near  the  caudal  end  of  the  body. 
These  are  merely  a  few  examples  of  the  many  glands  of  this  type  that 
are  known. 

The  cephalic  silk-glands. — In  the  Lepidoptera,  Trichoptera,  and 
Hymenoptera,  there  is  a  pair  of  glands  that  secrete  silk,  and  which 
open  through  the  lower  lip.  These  glands  are  designated  as  the 
cephalic  silk-glands  to  distinguish  them  from  the  silk-glands  of  certain 
Neuroptera  and  Coleoptera  in  which  the  sillc  is  produced  by  modified 
Malpighian  vessels  and  is  spun  from  the  anus. 

The  cephalic  silk-glands  are  elongate  and  coiled;  they  often 
extend  nearly  the  whole  length  of  the  body ;  the  two  ducts  unite  and 
the  single  terminal  duct  opens  through  the  low^er  lip,  and  is  not 
connected    with  the  mouth   cavity.      These  glands  are  a  pair  of 

salivary  glands  which  have 
been  transformed  into  silk 
organs.     According  to  Carriere 


Fig.  1 20. — ^The  salivary  glands 
of  the  honeybee  (After 
Cheshire). 


Fig.  121. — The  man- 
dibular gland  of  a 
honeybee. 


and  Burger  ('97),  who  studied  their  development  in  the  embryo 
of  a  bee,  they  are  developed  from  the  rudiments  of  the  spiracles 
of  the  first  thoracic  segment.     In  the  later  development  they  move 


104  AN  INTRODUCTION    TO   ENTOMOLOGY 

cephalad  and  the  paired  openings  become  a  single  one.     This  is  the 
reason  that  in  the  adult  there  are  no  spiracles  in  the  prothorax. 

The  Salivary  glands. — The  term  salivary  glands  is  a  general  one, 
applied  to  various  glands  opening  in  the  vicinity  of  the  mouth.  The 
number  of  these  varies  greatly  in  different  insects;  the  maximum 
number  is  found  in  the  Hymenoptera.  In  the  adult  worker  honey- 
bee, for  example,  there  are  four  pairs  of  glands  opening  into  the 
mouth;  three  of  these  are  represented  in  Figure  120  and  the  fourth 
in  Figure  121.  These  are  designated  as  the  supracerebral  glands 
(Fig.  120,  i),  the  postcersbral  glands  (Fig.  120.  2),  the  thoracic 
glands  (Fig.  120,  j),  and  the  mandibulary  glands  (Fig.  121), 
respectively. 

II.     THE   MUSCLES 

There  exist  in  insects  a  wonderfully  large  number  of  muscles ; 
some  of  these  move  the  segments  of  the  body,  others  move  the  appen- 
dages of  the  body,  and  still  others  are  found  in  the  viscera.  Those 
of  the  viscera  are  described  later  in  the  accounts  of  the  organs  in 
which  they  occur. 

The  muscles  that  move  the  segments  of  the  body  form  several 
layers  just  within  the  body-wall,  to  which  they  are  attached.  The 
inner  layer  of  these  is  well  shown  in  Figure  122,  which  is  a  copy  of 
one  of  the  plates  in  the  great  work  by  Lyonet  (1762)  on  the  anatomy 
of  a  caterpillar,  Cossus  Ugniperda.  The  two  figures  on  this  plate 
represent  two  larvae  which  have  been  split  open  lengthwise,  one  on  the 
middle  line  of  the  back  (Fig.  5),  and  one  on  the  middle  line  of  the 
ventral  surface  (Fig.  4) ;  in  each  case  the  alimentary  canal  has  been 
removed,  so  that  only  those  organs  that  are  attached  quite  closely  to 
the  body-wall  are  left.  The  bands  of  parallel  fibers  are  the  muscles 
that  move  the  segments.  It  should  be  borne  in  mind,  however,  that 
only  a  single  layer  of  muscles  is  represented  in  these  figures,  the  layer 
that  would  be  seen  if  a  caterpillar  were  opened  in  the  way  indicated. 
When  these  muscles  are  cut  away  many  other  muscles  are  found 
extending  obliquely  in  various  directions  between  these  muscles  and 
the  body-wall. 

In  the  head  and  thorax  of  adult  insects  the  arrangement  of  the 
muscles  is  even  more  complicated ;  for  here  the  muscles  that  move  the 
appendages  add  to  the  complexity  of  the  muscular  system. 

As  a  rule,  the  muscles  of  insects  are  composed  of  many  distinct 
fibers,  which  are  not  enclosed  in  tendinous  sheaths  as  with  Verte- 


THE   INTERNAL   ANATOMY  OF  INSECTS 


105 


Fig.  122. — Internal  anatomy  of  a  caterpillar,  Cossus  ligniperda;  i,  principal 
longitudinal  trachse;  2,  central  nervous  system;  j,  aorta;  4,  longitudinal 
dorsal  muscles;  5,  longtiudinal  ventral  muscles;  6,  wings  of  the  heart ;_  7, 
tracheal  trunks  arising  near  the  spiracles;  8,  reproductive  organs;  9,  vertical 
muscles;    10,  last  abdominal  ganglion  (From  Lyonet). 


106  AN  INTRODUCTION   TO  ENTOMOLOGY 

brates.  But  the  muscles  that  move  the  appendages  of  the  body- 
are    furnished  with    a    tendon   at  the  end  farthest  from  the  body 

(Fig.  123). 

The    muscles    of    in- 
sects appear  very  differ- 
ently from  those  of  Ver- 
tebrates.    In  insects,  the 
Fig.  123.— A  leg  of  a  May-beetle  (After  Straus-    muscles  are    either  color- 
Durckheim).  ,  , 

less  and   transparent,  or 

yellowish  white;  and  they  are  soft,  almost  of  a  gelatinous  consistency; 
notwithstanding  this  they  are  very  efficient.  The  fibers  of  insect 
muscles  are  usually,  if  not  always,  of  the  striated  type. 

Much  has  been  written  regarding  the  muscular  power  of  insects, 
which  has  been  supposed  to  be  extraordinarily  great;  the  power  of 
leaping  possessed  by  many  and  the  great  loads,  compared  to  the 
weight  of  the  body  of  the  insect,  that  insects  have  drawn  when 
harnessed  to  them  by  experimenters,  have  been  cited  as  illustrating 
this.  But  it  has  been  pointed  out  that  these  conclusions  are  not 
warranted;  that  the  comparative  contractile  force  of  muscles  of  the 
same  kind  depends  on  the  ntmiber  and  thickness  of  the  fibers,  that  is, 
on  the  comparative  areas  of  the  cross-sections  of  the  muscles  com- 
pared ;  that  this  sectional  area  increases  as  the  square  of  any  linear 
dimension,  while  the  weight  of  similar  bodies  increases  as  the  cube  of 
any  linear  dimension;  and  consequently,  that  the  muscles  of  the  legs 
of  an  insect  one  fourth  inch  long  and  supporting  a  load  399  times  its 
own  weight,  would  be  subjected  to  the  same  stress,  per  square  inch  of 
cross-section,  as  they  would  be  in  an  insect  100  inches  long  of  precisely 
similar  shape,  that  carried  only  its  own  weight.  We  thus  see  that  it  is 
the  small  size  of  insects  rather  than  an  unusual  strength  of  their 
muscles,  that  makes  possible  the  apparently  marvelous  exhibitions  of 
muscular  power. 

Detailed  accounts  of  the  arrangement  of  the  muscles  in  particular 
insects  have  been  published  by  various  writers;  among  the  more 
important  of  these  monographs  are  the  following:  Lyonet  (1762), 
on  the  larva  of  a  cossid  moth;  Straus-Diu-ckheim  (1828),  on  a  May- 
beetle;  Newport  (1839),  on  the  larva  of  a  Sphinx  moth;  Lubbock 
(1858),  on  the  larva  Fygcsra  bucephala;  Berlese  ('09a),  on  several 
insects;  and  Forbes  ('14)  on  caterpillars. 


THE   INTERNAL   ANATOMY   OF  INSECTS  107 

III.     THE  ALIMENTARY  CANAL  AND  ITS  APPENDAGES 

a.       THE  MORE  GENERAL  FEATURES 

The  alimentary  canal  is  a  tube  extending  from  one  end  of  the  body 
to  the  other.  In  some  larvae,  its  length  is  about  the  same  as  that  of 
the  body;  in  this  case  it  extends  in  a  nearly  straight  line,  occupying 


u^ 


Fig.  124." — Internal  anatomy  of  a  cockroach,  Periplaneta  orientalis;  a,  antennas: 
bi,  62,  63,  first,  second,  and  third  legs;  c,  cerci :  d,  ventricular  ganglion:  e, 
salivary  duct;  /,  salivary  bladder,  g,  gizzard  or  proventriculus;  h,  hepatic 
coeca;  i,  mid-intestme;  j,  Malpighian  vessels;  k,  small  mtestine;  /,  large 
intestine:  m,  rectum;  n,  first  abdominal  ganglion;  o,  ovary;  p,  sebaceous 
glands  (From   Rolleston). 


108  AN  INTRODUCTION   TO  ENTOMOLOGY 

the  longitudinal  axis  of  the  body,  as  is  represented  in  the  diagram 
given  above  (Fig.  105).  In  most  insects,  however,  it  is  longer  than 
the  body,  and  is  consequently  more  or  less  convoluted  (Fig.  124); 
great  variations  exist  in  the  length  of  the  alimentary  canal  as  com- 
pared to  the  length  of  the  body;  it  is  longer  in  herbivorous  insects 
than  it  is  in  those  that  are  carnivorous. 

The  principal  divisions. — Three  chief  divisions  of  the  alimentary 
canal  are  recognized;  these  are  termed  the  fore-intestme,  the  mid- 
intestine,  and  the  hind-intestine,  respectively.  In  the  embryological 
development  of  the  alimentary  canal,  the  fore-intestine  and  the  hind- 
intestine  each  arises  as  an  invagination  of  the  ectoderm,  the  germ 
layer  from  which  the  hypodermis  of  the  body-wall  is  derived  (p.  29). 
The  invagination  at  the  anterior  end  of  the  body,  which  develops 
into  the  fore-intestine,  is  termed  the  stomodceum;  that  at  the  posterior 
end,  which  develops  into  the  hind-intestine,  the  proctodcBum.  Between 
these  two  deep  invaginations  of  the  outer  germ  layer  of  the  embryo, 
the  stomodasum  and  the  proctodaeum,  and  ultimately  connecting 
them,  there  is  developed  an  entodermal  tube,  the  mesenteron,  which 
becomes  the  mid-intestine. 

These  embryological  facts  are  briefly  stated  here  merely  to 
elucidate  two  important  features  of  the  alimentary  canal:  first,  the 
fore-intestine  and  the  hind-intestine  are  invaginations  of  the  body 
wall  and  consequently  resemble  it  in  structure,  the  chitinous  lining  of 
these  two  parts  of  the  alimentary  canal  is  directly  continuous  with 
the  cuticula  of  the  body  wall,  and  the  epithelium  of  these  two  parts 
and  the  hypodermis  are  also  directly  continuous;  and  second,  the 
striking  differences,  pointed  out  later,  in  the  structure  of  the  mid- 
intestine  from  that  of  the  fore-  and  hind-intestines  are  not  surprising 
when  the  differences  in  origin  are  considered. 

Imperforate  intestines  in  the  larvae  of  certain  insects. — In  the  larvae 
of  certain  insects  the  Itrmen  of  the  alimentary  canal  is  not  a  continuous 
passage;  in  these  larvas,  while  food  passes  freely  from  the  fore- 
intestine  to  the  mid-intestine,  there  is  no  passage  of  the  waste  from 
the  mid-intestine  to  the  hind-intestine ;  there  being  a  constr  iction  at 
the  point  where  the  mid-intestine  and  hind-intestine  join,  which 
closes  the  passage  during  a  part  or  the  whole  of  the  larval  life.  This 
condition  has  been  observed  in  the  following  families: — 

(a)  Hymenoptera. — Proctotrypidas  (in  the  first  larval  instar), 
Ichneumonids,  Formicidae,  Vespidse,  and  Apidae. 

(6)     Diptera. — Hippoboscidae. 


THE  INTERNAL  ANATOMY  OF  INSECTS 


109 


(c)  Neiiroptera. — Myrmeleonidce,  Osmylidas,  Sisyridae,  and 
Chrysopidas.     In  these  families  the  lan^se  spin  silk  from  the  anus. 

(d)  Coleoptera. — In  the  Campodeiform  larvse  of  Stylopidse  and 
Meloidae. 

b.       THE    FORE-INTESTINE 

The  layers  of  the  fore-intestine. — The  following  layers  have  been 
recognized  in  the  fore-intestine : 

The  intima. — This  is  a  chitinous  layer  which  lines  the  cavity  of 
the  fore-intestine;  it  is  directly  continuous  with  the  cuticula  of  the 
body- wall;   and  is  molted  with  the  cuticula  when  this  is  molted. 

The  epithelium. — This  is  a  cell  layer  which  is  continuous  with  the 
hypodermis;  it  is  sometimes  quite  delicate  so  that  it  is  difficult  to 
demonstrate  it. 

The  basement  membrane. — Like  the  hypodermis  the  epithelium  is 
bounded  on  one  side  by  a  chitinous  layer  and  on  the  other  by  a  base- 
ment membrane. 

The  longitudinal  muscles. — Next  to  the  basement  membrane  there 

is  a  layer  of  longitudinal  muscles. 
The  circular  muscles. — Out- 
side of  the  longitudinal  muscles 
there  is  a  layer  of  circular 
muscles. 

The  peritoneal  membrane. — 
Surrounding  the  alimentary 
canal  there  is  a  coat  of  con- 
nective tissue,  which  is  termed 
the  peritoneal  membrane.  This 
is  one  of  a  few  places  in  which 
connective  tissue,  so  abundant 
in  Vertebrates,  is  found  in  in- 
sects. 

The  regions  of  the  fore- 
intestine. — Several  distinct  reg- 
ions of  the  fore-intestine  are 
recognized;  but  the  extent  of 
these  regions  differ  greatly  in 
different  insects. 

The  pharynx. — The  pharynx 
is  not  a  well-defined  region  of  the 
intestine ;  the  term  pharynx  is  commonly  applied  to  a  region  between 
the  mouth  and  the  oesophagus;    in  mandibulate  insects  the  pharynx 


Fig.  125. — Longitudinal  section  through 
the  head  of  Anosa  plexippus,  showing 
the  interior  of  the  left  half;  mx,  left 
maxilla,  the  canal  of  which  leads  into  the 
pharynx;  ph,  pharynx;  0,  oesophagus; 
m,  ni,  muscles  of  the  pharynx;  sd, 
salivary  duct  (After  Burges). 


no 


AN  INTRODUCTION   TO  ENTOMOLOGY 


is  not  distinct  from  the  mouth-cavity;  but  in  sucking  insects  the 
pharynx  is  a  highly  specialized  organ,  being  greatly  enlarged,  muscu- 
lar, and  attached  to  the  wall  of  the  head  by  muscles.  It  is  the  pump- 
ing organ  by  which  the  liquid  food  is  drawn  into  the  alimentary  canal. 
The  pharnyx  of  the  milkweed  butterfly  (Fig.  125)  is  a  good  example 
of  this  type  of  pharynx. 

The  oesophagus. — The  oeso- 
phagus is  a  simple  tube  which 
traverses  the  caudal  part  of  the 
head  and  the  cephalic  part  of  the 
thorax.  There  are  variations  in 
the  application  of  the  term 
oesophagus  depending  on  the 
presence  or  absence  of  a  crop 
and  of  a  proventriculus,  which 
are  modified  portions  of  the 
oesophagus;  when  either  or  both 
of  these  are  present,  the  term 
oesophagus  is  commonly  restricted 
to  the  unmodified  part  of  the 
fore-intestine. 

The  crop. — In  many  insects  a 
portion  of  the  oesophagus  is  dilated 
and  serves  as  a  reservoir  of  food ; 
this  expanded  part,  when  present, 
is  termed  the  crop.  In  the  cock- 
roach (Fig.  124)  it  is  very  large, 
comprising  the  greater  part  of  the 
fore-intestine ;  in  the  ground-beetle 
Carahus  (Fig.  126,  c),  it  is  much 
more  restricted;  this  is  the  case 
also  in  the  honeybee,  where  it  is 
a  nearly  spherical  sac  in  which 
the  nectar  is  stored  as  it  is  col- 
lected from  flowers  and  carried  to 
the  hive.  In  some  insects  the 
crop  is  a  lateral  dilatation  of  the 
oesophagus,  and  in  some  of  these 
it  is  stalked. 

The  proventriculus. — In  certain 
stances,  the   terminal   portion   of 


Fig.  126. — Alimentary  canal  of  Carabus 
auratus;  h,  head;  or,,  oesophagus;  c, 
crop;  pv,  proventriculus;  mi,  mid- 
intestine  covered  with  villiform  gastric 
coeca;  mv,  Malpighian  vessels;  hi,  part 
of  hind-intestine;  r,  rectum;  ag,  anal 
glands ;  mr,  muscular  reservoir  (After 
Dufour). 

insects  that  feed  on  hard  sub- 
the   fore-intestine,  that   part  im- 


THE   INTERNAL   ANATOMY  OF  INSECTS 


111 


Fig.  127.— Cross-section  of  the 
proventriculus  of  a  larva  of 
Corydahis. 


mediately  in  front  of  the  mid-intestine  or  ventriculus,  is  a  highly 
speciahzed  organ  in  which  the  food  is  prepared  for  entrance  into 
the  more  delicate  ventriculus;  such  an 
organ  is  teiTned  the  proveninculus  (Fig. 
126,  pv).  The  characteristic  features 
of  a  proventriculus  are  a  remarkable 
development  of  the  chitinous  intima 
into  folds  and  teeth  and  a  great  in- 
crease in  the  size  of  the  muscles  of  this 
region.  The  details  of  the  structure 
of  this  organ  vary  greatly  in  different 
insects;  a  cross-section  of  the  proven- 
triculus of  the  larva  of  Corydalus  (Fig. 
127)  will  serve  to  illustrate  its  form. 
In  the  proventriculus,  the  food  is  both 
masticated  and  more  thoroughly 
mixed  with  the  digestive  fluids. 

The  cesophageal  valve. — When  the 
fore-intestine  projects  into  the  mid- 
intestine,  as  shown  in  Figure  128, 
the  folded  end  of  the  fore-intestine 
is  termed  the  cesophageal  valve. 


C.       THE    MID-INTESTINE 

The  mid-intestine  is  the  inter- 
mediate of  the  three  principal 
divisions  of  the  alimentary  canal, 
which  are  distinguished  by  differ- 
ences in  their  embr>'ological  origins, 
as  stated  above.  The  mid-intestine 
is  termed  by  different  writers  the 
niesenteron,  the  stcnnack,  the  chylific 
ventricle,  the  chylestomach,  and  the 
ventnciilns. 

The  layers  of  the  mid-intestine.— 
The  structure  of  the  mid-intestine 
differs  markedly  from  that  of  the 
fore-intestine.  In  the  mid-intestine 
there  is  no  chitinous  intima,  and  the 
relative  positions  of  the  circular  and 
longitudinal  muscles  are  reversed. 


Fig.  128. — The  oesophageal  valve  of  a 
larva  of  Simidium;  F,  fore-intestine: 
M,  mid-intestine;  u,  point  of  union 
of  fore-intestine  and  mid-intestine; 
/>,  peritoneal  membrane;  i, 
intima  of  fore-intestine;  e,  epithe- 
lium of  fore-intestine ;  pt,  peritrophic 
membrane;    m,  muscleb 


112 


AN  INTRODUCTION   TO  ENTOMOLOGY 


The  sequence  of  the  different  layers  is  as  follows :  a  lining  epithelium, 
which  is  supported  by  a  basement  membrane,  a  layer  of  circular 
muscles,  a  layer  of  longitudinal  muscles,  and  a  peritoneal  membrane. 

The  epithelium. — The  epitheliiim  of  the  mid-intestine  is  very  con- 
spicuous, being  composed  of  large  cells,  which  secrete  a  digestive  fluid. 
These  cells  break  when  they  discharge  their  secretion  and  are  replaced 
by  new  cells,  which  are  developed  in  centers  termed  nidi  (Fig.  129,  m). 
The  extent  of  the  digestive  epithelium  is  increased  in  many  insects 
by  the  development  of  pouch-like  diverticula  of  the  mid-intestine, 
these  are  the  gastric  cceca  (Fig.  124,  h).  These  differ  greatly  in  num- 
ber in  different  insects  and  are  wanting  in  some.  In  some  predaceous 
beetles  they  are  villiform  and  very  numerous  (Fig.  126,  mi). 

The  peritrophic  membrane. 
— In  many  insects  there  is  a 
membranous  tube  which  is  form- 
ed at  or  near  the  point  of  union  of 
the  fore-intestine  and  the  mid- 
intestine  and  which  incloses  the 
food  so  that  it  does  not  come  in 
contact  with  the  delicate  epithe- 
liimi  of  the  mid-intestine;  this  is 
known  as  the  peritrophic  mem- 
brane (Fig.  128,  pt).  As  a  rule 
this  membrane  is  found  in  insects 
that  eat  solid  food  and  is  lacking 
in  those  that  eat  liquid  food.  It 
is  obvious  that  the  digestive  fluid 
and  the  products  of  digestion 
pass  through  this  membrane.  It 
is  continuously  formed  at  its 
point  of  origin  and  passes  from 
the  body  inclosing  the  excrement. 

d.       THE    HIND-INTESTINE 

The  layers  of  the  hind-intes- 
tine.— The  layers  of  the  hind-in- 
testine are  the  same  as  those  of 
the  fore-intestine  described 
above,  except  that  a  greater  or 
less  number  of  circular  muscles  exist  between  the  basement  membrane 
of  the  epithelial  layer  and  the  layer  of  longitudinal  muscles.     The 


Fig.  129. — Resting  epithelium  of  mid- 
intestine  of  a  dragon-fly  naiad;  b, 
bases  of  large  cells  filled  with  digestive 
fluid;  cm,  space  filled  by  circular  mus- 
cles; /m,  longitudinal  muscles;  «,  nidus 
in  which  new  cells  are  developing  (From 
Needham). 


THE   INTERNAL   ANATOMY  OF  INSECTS  113 

sequence  of  the  layers  of  the  hind-intestine  is,  therefore,  as  follows: 
the  intinia,  the  epithelium,  the  basement  membrane,  the  ental  circular 
muscles,  the  longitudinal  muscles,  the  ectal  circular  muscles,  and  the 
peritoneal  membrane. 

The  regions  of  the  hind-intestine. — Three  distinct  regions  are 
commonly  recognized  in  the  hind-intestine,  these  are  the  small  intestine 
(Fig.  124,  k),  the  large  intestine  (Fig.  124,  /),  and  the  rectum  (Fig. 
124,  m). 

The  Malpighian  vessels. — There  open  into  the  beginning  of  the 
hind-intestine  two  or  more  simple  or  branched  tubes  (Fig.  124,  ;), 
these  are  the  Malpighian  vessels.  The  nimiber  of  these  vessels  varies 
in  different  insects  but  is  very  constant  within  groups;  there  are 
either  two,  four,  or  six  of  them;  but,  as  a  result  of  branching,  there 
may  appear  to  be  one  hundred  or  more.  The  function  of  the  Mal- 
pighian vessels  has  been  much  discussed ;  it  was  formerly  believed  to 
be  hepatic,  but  now  it  is  known  that  normally  it  is  urinary. 

The  Malpighian  vessels  as  silk-glands. — There  are  ceriain  larvse 
that  in  making  their  cocoons  spin  the  silk  used  from  the  anus.  These 
larvce  are  chiefly  found  among  those  in  which  the  passage  from  the 
mid-intestine  to  the  hind-intestine  is  closed.  The  silk  spun  from  the 
anus  is  secreted  by  the  Malpighian  vessels. 

Among  the  larvse  in  which  the  Malpighian  vessels  are  known  to 
secrete  silk  are  those  of  the  Myrmeleonidse,  Osmylus  (Hagen  1852), 
Sisyra  (Anthony  '02),  Lebia  scapularis  (Silvestri  '05),  and  the 
Coccidag  (Berlese  '96).  Berlese  states  that  the  Malpighian  vessels 
secrete  the  woof  of  the  scale  of  the  Coccidae. 

The  caecum. — In  some  insects  there  is  a  pouch-like  diverticulum 
of  the  rectum,  this  is  the  ccecum. 

The  anus. — The  posterior  opening  of  the  alimentary  canal,  the 
anus,  is  situated  at  the  caudal  end  of  the  abdomen. 

IV.     THE   RESPIRATORY  SYSTEM 

Insects  breathe  by  means  of  a  sj^stem  of  air-tubes,  which  ramify 
in  all  parts  of  the  body  and  its  appendages ;  these  air-tubes  are  of  two 
kinds,  which  are  termed  trachece  and  tracheoles,  respectively.  In 
adult  insxts  and  in  most  nymphs  and  larvae,  the  air  is  received 
through  openings  in  the  sides  of  the  segments  of  the  body,  which  are 
known  as  spiracles  or  stigmata. 

Many  insects  that  live  in  water  are  furnished  with  special  devices 
for  obtaining  air  from  above  the  water;    but  with  naiads  and  a  few 


114 


AN  INTRODUCTION  TO  ENTOMOLOGY 


aquatic  larvae  the  spiracles  are  closed;  in  these  insects  the  air  is 
purified  by  means  of  gill-like  organs,  termed  tracheal  gills.  A  few 
insects  have  blood-gills. 

Two  types  of  respiratory  systems,  therefore,  can  be  recognized: 
first,  the  open  type,  in  which  the  air  is  received  through  spiracles;  and 
second,  the  closed  type,  in  which  the  spiracles  are  not  functional. 

a.       THE    OPEN  OR  HOLOPNEUSTIC   TYPE   OR  RESPIRATORY  ORGANS 

That  form  of  respiratory  organs  in  which  the  trachese  communicate 
freely  with  the  air  outside  the  body  through  open  spiracles  is  termed 
the  open  or  holopneustic  type.* 

As  the  open  type  of  respiratory  organs  is  the  most  common  one, 
those  features  that  are  common  to  both  types  will  be  discussed  under 
this  head  as  well  as  those  that  are  peculiar  to  this  type.  Under  the 
head  of  closed  respiratory  organs  will  be  discussed  only  those  features 
distinctly  characteristic  of  that  type. 

I.     The  Spiracles 

The  position  of  the  spiracles. — The  spiracles  are  situated  one  on 
each  side  of  the  segments  that  bear  them  or  are  situated  on  the  lateral 
aspects  of  the  body  in  the  transverse  conjunctivse. 

The  question  of  the  position  of  the  spiracles  has  not  been  thor- 
oughly investigated;  but  I  believe  that  normally  the  tracheae,  of 


Fig.  130. — Lateral  view  of  a  silk  worm  thowing  the  spiracles 
(After  Verson) 


which  the  spiracles  are  the  mouths,  are  invaginations  of  the  transverse 
conjunctivas  between  segments.  From  this  normal  position  a  spiracle 
may  migrate  either  forward  or  backward  upon  an  adjacent  segment 
(Fig.  130). 

The  number  of  spiracles. — The  normal  number  of  spiracles  is  ten 
pairs;  when  in  their  normal  position,  there  is  a  pair  in  front  of  the 


*H61opneustic :   holo  (5Xoj),  whole;  pneiima  {nveufia),  breath. 


THE   INTERNAL   ANATOMY   OF  INSECTS  115 

second  and  third  thoracic  segments  and  the  first  to  the  eighth  abdom- 
inal segments,  respectively.  There  are  none  in  the  corresponding 
position  in  front  of  the  first  thoracic  segment.  See  account  of 
cephalic  silk-glands  p.   103. 

The  two  pairs  of  thoracic  spiracles  are  commonly  distinguished  as 
the  mesothoracic  and  the  metathoracic  spiracles ;  that  is  each  pair  of 
spiracles  is  attributed  to  the  segment  in  front  of  which  it  is  normally 
situated.  Following  this  terminology  there  are  no  prothoracic 
spiracles ;  although  sometimes  the  first  pair  of  spiracles  is  situated  in 
the  hind  margin  of  the  prothorax,  having  migrated  forward  from  its 
normal  position.  It  would  be  better  to  designate  the  thoracic 
spiracles  as  the  first  and  second  pairs  of  thoracic  spiracles,  respec- 
tively; in  this  way  the  same  term  would  be  applied  to  a  pair  of 
spiracles  w^hatever  its  position.  There  are  many  references  in 
entomological  works  to  "prothoracic  spiracles,"  but  these  refer  to  the 
pair  of  spiracles  that  are  more  commonly  designated  the  mesothoracic 
spiracles. 

In  many  cases  the  abdominal  spiracles  have  migrated  back  upon 
the  segment  in  front  of  which  they  are  normally  situated,  being  fre- 
quently situated  upon  the  middle  of  the  segment. 

The  statements  made  above  refer  to  the  normal  number  and  dis- 
tribution of  spiracles ;  but  a  very  wide  range  of  variations  from  this 
type  exists.  Perhaps  the  most  abnormal  condition  is  that  found  in 
the  genus  Smynthnrus  of  the  Collembola,  where  there  is  a  single  pair 
of  spiracles  which  is  borne  by  the  neck.  In  the  Poduridae,  also  of  the 
Collembola,  the  respiratory  system  has  been  lost,  there  being  neither 
tracheae  nor  spiracles. 

Terms  indicating  the  distribution  of  the  spiracles. — The  following 
terms  are  used  for  indicating  the  distribution  of  the  spiracles;  they 
have  been  used  most  frequently  in  descriptions  of  larvag  of  Diptera. 
These  terms  were  formed  by  combining  with  pneiistic  (from  pneo,  to 
breathe)  the  following  prefixes:  peri-,  around,  about;  pro-,  before; 
meta-  after;  and  amphi,  both. 

Peripneustic. — Having  spiracles  in  a  row  on  each  side  of  the  body, 
the  normal  t>^e. 

Propneustic. — With  only  the  first  pair  of  spiracles. 

Metapneustic. — With  only  the  last  pair  of  spiracles. 

Amphipneustic. — With  a  pair  of  spiracles  at  each  end  of  the  body. 


116 


AN  INTRODUCTION   TO   ENTOMOLOGY 


Fig.  131. — Spiracles;  a,  of  the  larva  of 
Corydalus;  b,  of  the  ]ar\^a  of  Droso- 
phila  amoena. 


The  structure  of  spiracles. — In  their  simplest  form  the  spiracles  or 
stigmata  are  small  round  or  oval  openings  in  the  body-wall.  In  many 
cases  they  are  provided  with  hairs  to  exclude  dust ;  in  some,  as  in  the 

larv^a  of  Corydalus,  each  spiracle  is 
furnished  with  a  lid  (Fig.  131,  a); 
in  fact,  very  many  forms  of 
spiracles  exist.  Usually  each  spir- 
acle opens  by  a  single  apertiu-e; 
but  in  some  larvae  and  pupas  of 
Diptera  they  have  several  openings 
(Fig.  131,  b). 

The  closing  apparatus  of  the 
tracheae. — Within  the  body,  a 
short  distance  back  of  the  spiracle, 
there  is  an  apparatus  consisting  of 
several  chitinous  parts,  surrounding  the  trachea,  and  moved  by  a 
muscle,  by  which  the  trachea  can  be  closed  by  compression  (Fig.  132). 
This  is  the  closing  apparatus  of  the  trachea.  The  closing  of  this  appara- 
tus and  the 
contraction  of 
the  body  by 
the  respiratory 
muscles  is  sup- 
posed to  force 
the  air  into 
thetracheoles, 
which  are  the 
essential  res- 
piratory or- 
gans. 


Fig.  11,2. — Diagrams  representing  the  closing  apparatus  of  the 
tracheae;  a,  b,c,  chitinous  parts  of  the  apparatus;  m,  muscle; 
A,  apparatus  open;  B,  apparatus  closed;  C,  spiracle  and 
trunk  of  trachea  showing  the  position  of  the  apparatus. 
(From  Judeich  and  Nitsche). 


2.      THE  TRACHEA 

Each  spiracle  is  the  opening  of  an  air-tube  or  trachea.  The  main 
tracheal  trunk  which  arises  from  the  spiracle  soon  divides  into  several 
branches,  these  in  turn  divide,  and  by  repeated  divisions  an  immense 
number  of  branches  are  formed.  Every  part  of  the  body  is  supplied 
with  tracheae. 

In  a  few  insects  the  group  of  tracheas  arising  from  a  spiracle  is  not 
connected  with  the  groups  arising  from  other  spiracles;  this  is  the 
case  in  Machilis  (Fig.  133).  In  most  insects,  however,  each  group  of 
trachccB  is  connected  with  the  corresponding  groups  in  adiacent  seg- 


THE   INTERNAL    ANATOMY    OF   INSECTS  117 

ments  by  one  or  more  longitudinal  tracheae,  and  is  also  connected 


The  tracheae  of  Machilis  (From  Oudemans). 

with  the  group  on  the  opposite  side  of  the  same  segment  by  one  or 
more  transverse  tracheas  (Fig.  134). 

The  structure  of  the  tracheae.— The  fact  that 
in  their  embryological  development  the  tracheee 
arise  as  invaginations  of  the  body- wall,  makes  it 
easy  to  understand  the  structure  of  the  trachcce. 
The  three  layers  of  the  body-wall  are  directly 
continuous  with  corresponding  layers  in  the  wall 
of  a  trachea  (Fig.  135).  These  layers  of  -a 
trachea  are  designated  as  the  intima,  the  epithe- 
Ihmi,  and  the  basement  membrane. 

The  mtinia  is  the  chitinous  inner  layer  of  the 
trachea.     It    is    directly   continuous    with    the 
cuticula  of  the  body- 
wall,    and    like    the 
cuticula  is  molted  at 
each  ecdysis. 

A  peculiar  feature 
of  the  intima  of 
tracheas  is  the  fact 
that  it  is  furnished 
with  thickenings 
which  extend  spirally. 
These  give  the 
Fig.    134. — Larva    of  tracheas  their  charac-  Fig.  135. 

Cantharis  vesicnloria,  ^^^■^^^:^^  transversely  and  ^  the  body- wall ;  c,  cuti- 
showmg  the  distnbu-         .  ^      cula;     h,    hypodermis;     bm, 

tion  of  tracheae  (From  striated  appearance,  basement  membrane;  sp, 
Henneguy  after  jf  ^  •  ^^  ^f  ^^^  ^f  spiral  thickening  of  the  ih- 
Beauregard).  ^  tima,  the  tasnidium. 

the  larger  tracheas  be 

pulled  apart  the  intima  will  tear  between  the  folds  of  the  spiral 
thickening,  and  the  latter  will  uncoil  from  within  the  trachea  like  a 


Section  of  a  trachea 


118  AN  INTRODUCTION   TO  ENTOMOLOGY 

thread  (Fig.  135).  The  spiral  thickening  of  the  intima  of  a  trachea  is 
termed  the  tcemdiunt.  In  some  insects  there  are  several  parallel 
tcenidia;  so  that  when  an  attempt  is  made  to  uncoil  the  thread  a 
ribbon-like  band  is  produced,  composed  of  several  parallel  threads. 
This  condition  exists  in  the  larger  tracheae  of  the  larva  Corydalus. 

The  epithelium  of  the  trachea  is  a  cellular  layer,  which  is  directly 
continuous  with  the  hypodermis  of  the  body -wall. 

The  basement  membrane  is  a  delicate  layer,  which  supports  the 
epithelium,  as  the  basement  membrane  of  the  body-wall  supports  the 
hypodermis. 

3.     The  Tracheoles 

The  tracheoles  are  minute  tubes  that  are  connected  with  the  tips 
of  tracheae  or  arise  from  their  sides,  but  which  differ  from  tracheae  in 
their  appearance,  structure,  and  mode  of  origin ;  they  ai'e  not  small 
tracheae,  but  structures  that  differ  both  histologically  and  in  their 
origin  from  tracheae. 

The  tracheoles  are  exceedingly  slender,  measuring  less  than  one 
micron  in  diameter;  ordinarily  they  do  not  taper  as  do  tracheae; 
they  contain  no  tasnidia;  and  they  rarely  branch,  but  often  anasto- 
mose which  gives  them  a  branched  appearance  (Fig.  136,  t  and 
138  B,  t). 

Each  tracheole  is  of  unicellular  origin,  and  is,  at  first,  intracellular 
in  position,  being  developed  coiled  within  a  single  cell  of  the  epithelium 
of  a  trachea.  In  this  stage  of  its  development  it  has  no  connection 
with  the  lumen  of  the  trachea  in  the  wall  of  which  it  is  developing, 
being  separated  from  it  by  the  intima  of  the  trachea.  A  subsequent 
molting  of  the  intima  of  the  trachea  opens  a  connection  between  the 
lumen  of  the  tracheole  and  the  trachea.  At  the  same  time  or  a  little 
later  the  tracheole  breaks  forth  from  its  mother  cell,  uncoils,  and 
extends  far  beyond  the  cell  in  which  it  was  developed. 

The  tracheoles  are  probably  the  essential  organs  of  respiration,  the 
tracheae  acting  merely  as  conduits  of  air  to  the  tracheoles. 

4.     The  Air-Sacs 

In  many  winged  insects  there  are  expansions  of  the  tracheee, 
which  are  termed  air-sacs.  These  vary  greatly  in  nimiber  and  size. 
In  the  honeybee  there  are  two  large  air-sacs  which  occupy  a  consider- 
able part  of  the  abdominal  cavity;  while  in  a  May-beetle  there  are 
hundreds  of  small  air-sacs.  The  air-sacs  differ  from  trachea  in 
lacking  tasnidia. 


THE   INTERNAL   ANATOMY  OF  INSECTS 


119 


As  the  air-sacs  lessen  the  specific  gravity  of  the  insect  they  proba- 
bly aid  in  flight ;  as  fiUing  the  lungs  with  air  makes  it  easier  for  a  man 
to  float  in  water;  in  each  case  there  is  a  greater  volimie  for  the  same 
weight. 

5.     Modifications  of  the  open  type  of  respiratory  organs  in 
aquatic  insects 

There  are  many  insects  in  which  the  spiracles  are  open  that  live  in 
water;  these  insects  breathe  air  obtained  from  above  the  surface  of 
the  water.     Some  of  these  insects  breathe  at  the  surface  of  the  water, 


Fig.  136.- 


-Part  of  a  tracheal  gill  of  the  larva  of  Corydalus;  T,  trachea;   t, 
tracheoles. 


as  the  larvce  and  pupse  of  mosquitoes,  the  larvas  of  Eristalis,  and  the 
Nepidas;  others  get  a  supply  of  air  and  carry  it  about  with  them 
beneath  the  surface  of  the  water,  as  the  Dytiscidse,  the  Notonectidae 
and  the  Corisidas.  The  methods  of  respiration  of  these  and  of  other 
aquatic  insects  with  open  spiracles  are  described  in  the  accounts  of 
these  insects  given  later. 


h.      THE  CLOSED  OR  APNEUSTIC  TYPE  OF  RESPIRATORY  ORGANS 

That  type  of  respiratory  organs  in  which  the  spiracles  do  not 

function  is  termed 
the  closed  or 
apneustic*  type;  it 
exists  in  naiads  and 
in  a  few  aquatic 
larv^ae. 


7.     The  Tracheal 

Gills 

In  the  immature 

insects     mentioned 

above,    the    air    in 

the   body  is  purified  by  means  of  organs  known  as  tracheal  gills. 


Fig-   137- — Part  of  a  tuft  of  tracheal  gills  of  a  larva  of 
Corydalus. 


*Apneustic:     apneiistos  {drrvevaTos),  without  breath. 


120 


AN   INTRODUCTION   TO  ENTOMOLOGY 


These  are  hair-like  or  more  or  less  plate-like  expansions  of  the  body- 
wall,  abundantly  supplied  with  trachece  and  tracheoles.  Figures  136 
and  137  represents  a  part  of  a  tuft  of  hair-like  tracheal  gills  of  a 
lar\'a  of  Corydalus  and  figiu-e  13  S  a  plate-like  tracheal  gill  of 
a  naiad  of  a  damsel -fly.  In  these  tracheal  gills  the  tracheoles 
are  separated   from  the    air    in    the    water   only    by  the  delicate 

wall  of  the  tracheal 
gill  which  admits  of 
the  transfer  of  gases 
between  the  air  in  the 
tracheoles  and  the  air 
in  the  ■^^iater. 

Tracheal  gills  are 
usually  borne  by  the 
abdomen,     sometimes 
by  the  thorax,  and  in 
case  of  one  genus  of 
stone-flies  by  the  head . 
They  pertain  almost 
exclusively  to  the  immature  stages  of  insects ;     but  stone- 
flies  of  the  genus  Pteronarcys  retain  them  throughout  their 
existence.     In  the  naiads  of  the  Odonata  the  rectum   is 
supplied  with  many  tracheae  and  functions  as  a  tracheal  gill. 


Fig.  138. — Tracheal  gill  of  a  damsel- 
fly:  A,  entire  gill  showing  the 
tracheae;  B,  part  of  gill  more 
magnified  showing. both  tracheae  (T) 
and  tracheoles  (t). 


2.     Respiration  of  Parasites 

It  is  believed  that  internal  parasitic  larvae  derive  their  air  from  air 
that  is  contained  in  the  blood  of  their  hosts,  and  that  this  is  done  by 
osmosis  through  the  cuticula  of  the  larva,  the  skin  of  the  larva  being 
furnished  with  a  network  of  fine  tracheae  (Seurat  '99). 


3.     The  blood-gills 

Certain  aquatic  lar\^ae  possess  thin  transparent  extensions  of  the 
body  wall,  which  are  filled  with  blood,  and  ser\^e  as  respiratory  organs. 
These  are  termed  blood-gills. 

Blood-gills  have  been  observed  in  comparatively  few  insects; 
among  them  are  certain  trichopterous  larv^ae;  the  larva  of  an  exotic 
beetle,  Pelobitis;  and  a  few  aquatic  dipterous  larvae,  Chironontus  and 
Simulium.  It  is  probable  that  the  ventral  sacs  of  the  Thysanura, 
described  in  the  account  of  that  order,  are  also  blood-gills. 


THE   INTERNAL   ANATOMY  OF  INSECTS 


121 


V.     THE   CIRCULATORY  SYSTEM 

The  general  features  of  the  circulatory  system. — In  insects  the  cir- 
culatory system  is  not  a  closed  one,  the  blood  flowing  in  vessels  during 
only  a  part  of  its  course.  The  greater  part  of  the  circulation  of  this 
fluid  takes  place  in  the  cavities  of  the  body  and  of  its  appendages, 
where  it  fills  the  space  not  occupied  by  the  internal  organs. 

Almost  the  only  blood-vessel  that  exists  in  insects  lies  just  beneath 
the  body-wall,  above  the  alimentary  canal  (Fig.  105,  h).  It  extends 
from  near  the  caudal  end  of  the  abdomen  through  the  thorax  into  the 
head.  That  part  of  it  that  lies  in  the  abdomen  is  the  heart;  the  more 
slender  portion,  which  traverses  the  thorax  and  extends  into  the  head 
is  the  aorta. 

On  each  side  of  the  heart,  there  is  a  series 
of  triangular  muscles  extending  from  the  heart 
1)    l^H  ^°  ^^^®  lateral  wall  of  the  body.      These  con- 

stitute the  dorsal  diaphragm  or  the  wings  of  the 
heart.  They  are  discussed  later  under  the 
head:     Suspensoria  of  the  Viscera. 


.^^J^ 


The  heart. — The  heart  is  a  tube,  which  is 
usually  closed  at  its  posterior  end;  at  its 
anterior  end  it  is  continuous  with  the  aorta. 
The  heart  is  divided  by  constrictions  into 
chambers  which  are  separated  by  valves  (Fig. 
139).  The  munber  of  these  chambers  varies 
greatly  in  different  insects;  in  some,  as  in 
Phasma  and  in  the  larva  of  Corethra,  there  is 
only  one,  in  others,  as  in  the  cockroach,  there 
are  as  many  as  thirteen,  but  usually  there  are 
not  more  than  eight.  The  blood  is  admitted  to 
the  heart  through  slit-like  openings,  the  ostia  of 
the  heart;  usually  there  is  a  pair  of  ostia  in  the 
lateral  walls  of  each  chamber.  Each  ostium  is 
furnished  with  a  valve  which  closes  it  when  the 
chamber  contracts. 

The  wall  of  the  heart  is  composed  of  two  dis- 
tinct layers:  aninner  muscular  layer;  and  an 
outer,  connective  tissue  or  peritoneal  layer. 
The  muscular  layer  consists  chiefly  of  annular 
but  longitudinal  fibers  have  also  been  observed. 


Fig.  139. — Heart  of  a 
May -beetle;  a,  lateral 
aspect  of  the  aorta;  b, 
interior  of  the  heart 
showing  valves;  c, 
ventral  aspect  of  the 
heart  and  wing-mus- 
cles, the  muscles  are 
represented  as  cut  away 
from  the  caudal  part  of 
the  heart;  d,  dorsal 
aspect  of  the  heart 
(After  Straus-Durck- 
heim). 


muscles ; 


122  AN  INTRODUCTION   TO  ENTOMOLOGY 

The  ptilsations  of  the  heart.— When  a  heart  consists  of  several 
chambers,  they  contract  one  after  another,  the  wave  of  contraction 
passing  from  the  caudal  end  of  the  heart  forwards.  As  the  valves 
between  the  chambers  permit  the  blood  to  move  forward  but  not 
in  the  opposite  direction,  the  successive  contraction  of  the  chambers 
causes  the  blood  received  through  the  ostia  to  flow  toward  the  head,  into 
the  aorta. 

The  aorta. — The  cephalic  prolongation  of   the  heart,   the  aorta- 
(Fig.  139,  a),  is  a  simple  tube,  which  extends  through  the  thorax  into 
the  head,  where  it  opens  in  the  vicinity  of  the  brain.     In  some  cases, 
at  least,  there  are  valves  in  the  aorta. 

The  circulation  of  the  blood. — The  circulation  of  the  blood  can  be 
observ^ed  in  certain  transparent  insects,  as  in  young  naiads,  in  larvae 
of  Trichoptera,  and  in  insects  that  have  just  molted.  The  blood  flows 
from  the  open,  cephalic  end  of  the  aorta  and  passes  in  quite  definite 
streams  to  the  various  parts  of  the  body-cavity  and  into  the  cavities 
of  the  appendages.  These  streams,  like  the  ocean  currents,  have  no 
walls  but  flow  in  the  spaces  between  the  internal  organs.  After 
bathing  these  organs,  the  blood  returns  to  the  sides  of  the  heart, 
which  it  enters  through  the  ostia. 

Accessory  circulatory  organs. — Accessory  pulsating  circulatory 
organs  have  been  described  in  several  insects.  These  are  sac-like 
structures  which  contract  independently  of  the  contractions  of  the 
heart.  They  have  been  found  in  the  head  in  several  Orthoptera ;  in 
the  legs  of  Hemiptera,  and  in  the  caudal  filaments  of  Ephemerida. 

VI.     THE  BLOOD 

The  blood  of  insects  is  a  fluid,  which  fills  the  perivisceral  cavity, 
bathing  all  of  the  internal  organs  of  the  body,  and  flowing  out  into  the 
cavities  of  the  appendages  of  the  body.  In  only  a  comparatively 
small  portion  of  its  cotirse,  is  the  blood  enclosed  in  definite  blood- 
vessels; these,  the  heart  and  the  aorta  are  described  above.  The 
blood  consists  of  two  elements,  a  fluid  plasma  and  cells  similar  to  the 
white  corpuscles  of  the  blood  of  vertebrates,  the  leucocytes. 

The  blood  of  insects  differs  greatly  in  appearance  from  the  blood 
of  vertebrates,  on  account  of  the  absence  of  red  blood-corpuscles.  In 
most  insects  the  blood  is  colorless ;  but  in  many  species  it  has  a  yellow- 
ish, greenish,  or  reddish  color.  In  the  latter  case,  however,  the  color 
is  not  due  to  corpuscles  of  the  type  which  gives  the  characteristic 
color  to  the  blood  of  vertebrates. 


THE   INTERNAL   ANATOMY   OF  INSECTS  123 

The  leucocytes  are  nucleated,  colorless,  amoeboid  cells  similar  to 
the  white  corpuscles  of  vertebrates,  in  appearance  and  function ;  they 
take  up  and  destroy  foreign  bodies  and  feed  upon  disintegrating  tissue. 
It  is  believed  that  the  products  of  digestion  of  disintegrating  tissue  by 
the  leucocytes  pass  into  the  blood  and  serve  to  nourish  new  tissue. 

The  blood  receives  the  products  of  digestion  of  food,  which  pass 
in  a  liquid  form,  by  osmosis,  through  the  walls  of  the  alimentary  canal. 
On  the  other  hand  it  gives  up  to  the  tissues  which  it  bathes  the 
materials  needed  for  their  growth.  In  insects  oxygen  is  supplied  to 
the  tissues  and  gaseous  wastes  are  removed  chiefly  by  the  respiratory 
system  and  not  by  means  of  the  blood  as  in  vertebrates. 

VII.     THE  ADIPOSE   TISSUE 

On  opening  the  body  of  an  insect,  especially  of  a  larva,  one  of  the 
most  conspicuous  things  to  be  seen  is  fatty  tissue,  in  large  masses. 
These  often  completely  surround  the  alimentary  canal,  and  are  held 
in  place  by  nimierous  branches  of  the  tracheae  with  which  they  are 
supplied.  Other  and  smaller  masses  of  this  tissue  adhere  to  the  inner 
surface  of  the  abdominal  wall,  in  the  vicinity  of  the  nervous  system, 
and  at  the  sides  of  the  body.  In  adult  insects  it  usually  exists  in 
much  less  quantity  than  in  larvse. 

The  chief  function  of  the  adipose  tissue  is  the  storage  of  nutriment ; 
but  it  is  believed  that  it  also  has  a  urinary  function,  as  concretions  of 
uric  acid  accumulate  in  it  during  the  life  of  the  insect. 

VIII.     THE   NERVOUS   SYSTEM 

a.       THE  CENTRAL  NERVOUS  SYSTEM 

The  more  obvious  parts  of  the  central  nervous  system  are  the 
following:  a  ganglion  in  the  head  above  the  oesophagus,  the  brain; 
a  ganglion  in  the  head  below  the  oesophagus,  the  suhoesophageal 
ganglion;  a  series  of  ganglia,  lying  on  the  floor  of  the  body  cavity  in 
the  thorax  and  in  the  abdomen,  the  thoracic  and  the  abdominal 
ganglia;  two  longitudinal  cords,  the  connectives,  uniting  all  of  these 
ganglia  in  a  series ;  and  many  nerves  radiating  from  the  ganglia  to  the 
various  parts  of  the  body. 

The  connectives  between  the  brain  and  the  suhoesophageal 
ganglion  pass  one  on  each  side  of  the  oesophagus ;  these  are  termed  the 
crura  cerebri,  or  the  legs  of  the  brain ;  in  the  remainder  of  their  course, 
the  two  connectives  are  quite  closely  parallel  (Fig.  124). 


124 


AN  INTRODUCTION   TO  ENTOMOLOGY 


The  series  of  ganglia  is  really  a  double  one,  there  being  typicall}^  a 
pair  of  ganglia  in  each  segment  of  the  body ;  but  each  pair  of  ganglia 
are  more  or  less  closely  united  on  the  middle  line  of  the  body,  and 
often  appear  to  be  a  single  ganglion. 

In  some  cases  the  ganglia  of  adjacent  segments  coalesce,  thus 
reducing  the  number  of  distinct  gangha  in  the  series.  It  has  been 
demonstrated  that  the  brain  is  composed  of  the  coalesced  ganglia  of 
three  of  the  head  segments,  and  the  suboesophageal  ganglion  of  the 
coalesced  ganglia  of  the  remaining  four  segments. 


Fig.  140.— Successive  stages  in  the  coalescence  of  thoracic  and  of  abdominal 
ganglia  m  Diptera;  A,  Chironomus;  B,  Empis;  C,  Tabanus;  D  Sar- 
cophaga  (From  Henneguy  after  Brandt). 

The  three  parts  of  the  brain,  each  of  which  is  composed  of  the  pair 
of  ganglia  of  a  head  segment,  are  designated  as  the  protocerebrum,  the 
deutocerebrum,  and  the  tritocerebrum,  respectively.  The  protocere- 
brum innervates  the  compound  eyes;  the  deutocerebrum,  the 
antennas;    and  the  tritocerebrum,  the  labrum. 

The  suboesophageal  ganglion  is  composed  of  four  pairs  of  primar}^ 
ganglia;  these  are  the  ganglia  of  the  segments  of  which  the  mandibles, 
the  maxillulae,  the  maxillas,  and  the  labium,  respectivelv,  are  the 
appendages. 

The  three  pairs  of  thoracic  ganglia  often  coalesce  so  as  to  form  a 
smgle  ganglionic  mass;  and  usually  in  adult  insects  the  number  of 
abdommal  ganglia  is  reduced  in  a  similar  way. 


THE   INTERNAL   ANATOMY   OF  INSECTS 


125 


Successive  stages  in  the  coalescence  of  the  thoracic  and  abdominal 
ganglia  can  be  seen  by  a  study  of  the  nervous  system  of  the  larva, 
pupa,  and  adult  of  the  same  species,  a  distinct  cephalization  of  the 
central  nervous  system  taking  place  during  the  development  of  the 
insect.  Varying  degrees  of  coalescence  of  the  thoracic  and  of  the 
abdominal  ganglia  can  be  seen  by  a  comparative  study  of  the  nervous 
systems  of  different  adult  insects  (Fig.  140). 

The  transverse  band  of  fibers  that  unite  the  two  members  of  a  pair 
of  ganglia  is  termed  a  commissure.  In  addition  to  the  commissures 
that  pass  directly  from  one  member  of  a  pair  of  ganglia  to  the  other, 

there  is  in  the  head  a  com- 
missure that  encircles  the 
oesophagus  in  its  passage 
from  one  side  of  the  brain 
to  the  other,  this  is  the  sub- 
osophageal  commissure  (Fig. 
141). 

The  nerves  that  extend 
Fig.  141.— Lateral  view  of  the  cesophagus  of  a   r  ^u      centra]    chain    of 

caterpillar,  showing  the  subcesophageal  com-  ^^om  me  central  cnam  ot 
missure;  b,  brain;  oe,  oesophagus;  sc,  sub-  ganglia  to  the  different 
oesophageal   commissure;    .g.suboesophageal         ^^       f  ^^    ^    .  ^ 

ganglion;  ^g,  paired  ganglion  (After  Lienard).    -^  j  j-/c^  o 

of  the  central  nervous  sys- 
tem ;  the  core  of  each  nerv^e  fiber  being  merely  a  process  of  a  ganglionic 
cell,  however  long  it  ^^ 

may  be.  „,,     .^    ^P      ^'     V        r    a^ 


b.     THE   CESOPHAGEAL 
SYMPATHETIC  NER- 
VOUS   SYSTEM 

In  addition  to  the 
central  nervous  sys- 
tem as  defined  above 
there  are  three  other 
nervous  complexes 
which  are  commonly 
described  as  separate 
systems  although 
they  are  connected 
to  the  central  nervous 
system  by  nerves. 
These  are  the  oeso- 
phageal sympathetic 


Fig.  142. — Lateral  view  of  the  nerves  of  the  head  in  the 
lar\'a  of  Corydalus;  a,  antennal  nerve;  ao,  aorta;  ar 
paired  nerves  connecting  the  frontal  ganglion  with  the 
brain;  &,  brain;  c/,  clypeo-labral  nerve;  cow,  connective; 
cr,  cnira  cerebri;  /g,  "frontal  ganglion;  /h ,  frontal  nerve ; 
i,  unpaired  nerve  connecting  the  frontal  ganglion  with 

.  the  brain;  /,  labial  nerve;  Ig,  the  paired  ganglia;  md, 
mandibular  nerve;  m,  p,  q,  s,  u,  z,  nerves  of  the  oesopha- 
geal sympathetic  system;  mx,  maxillary  nerve;  o,  optic 
nerves;  oes,  oesophagus;  ph,  pharynx;  pii,  pharyngeal 
nerve;  r,  recurrent  nerve;  sc,  subcesophageal  commis- 
sure; sg,  subcesophageal  ganglion;  st,  stomagastric 
nerve;  v,  ventricular  ganglion  (From  Hammar). 

nervous  system,  the  ventral  sympathetic  nervous 


126 


AN  INTRODUCTION   TO   ENTOMOLOGY 


system,  and  the  peripheral  sensory  nerv^ous  system.  The  first  of 
these  is  connected  with  the  brain;  the  other  two,  with  the  thoracic 
and  abdominal  ganglia  of  the  central  nerv^ous  system. 

The  oesophageal  sympathetic  ner\'ous  system  is  intimately 
associated  with  the  oesophagus  and,  as  just  stated,  is  connected  with 
the  brain.  It  is  described  by  different  writers  under  various  names; 
among  these  are  visceral,  vagus,  and  stomato gastric.  It  consists  of  two, 
more  or  less  distinct,  divisions,  an  unpaired  median  division  and  a 
paired  lateral  division. 

The  unpaired  division  of  the  oesophageal  s\Tnpathetic  nervous 
system  is  composed  of  the  following  parts,  which  are  represented  in 

Figures  141,  142,  143,  and 
144:  the  frontal  ganglion 
(Jg),  this  is  a  minute  gang- 
lion situated  abov^e  the 
oesophagus  a  short  distance 
in  front  of  the  brain;  the 
unpaired  nerve  connecting 
the  frontal  ganglion  with  the 
brain  (i),  this  is  a  small 
nerve  extending  from  the 
brain  to  the  frontal  gangHon; 
the  paired  nerves  connecting 
the  frontal  ganglion  with  the 
brain  (ar),  these  are  arching 
nerv^es,  one  on  each  side, 
extending  from  the  upper 
ends  of  the  crura  cerebri  to 
the  frontal  ganglion;  the 
frontal  nerve  (fn),  this  nerve 
arises  from  the  anterior  bor- 
der of  the  frontal  ganglion 
and  extends  cephalad  into 
the  clypeus,  where  it  bifur- 
cates; the  pharyngeal 
nerves  (pn),  these  extend, 
one  on  each  side,  from  the 
frontal  ganglion  to  the 
the  recurrent  nerve  (r),  this  is  a  single 
the  caudal  border  of  the  frontal 


Fig.  143. — Dorsal  view  of  the  nerves  of  the 
head  in  the  larv'a  of  Corydalus;  e,  ocelU; 
mnd.  mandible;  other  lettering  as  in 
Figvu-e  142    (From  Hammar). 


lower  portions  of  the  pharynx 

median  nerve,  which  arises  from 

ganglion,  and  extends  back,  passing  under  the  brain  and  between  the 


THE   INTERNAL   ANATOMY  OF  INSECTS 


127 


aorta  and  the  oesophagus,  to  terminate  in  the  ventricular  ganghon; 
the  ventricular  ganglion  (v),  this  is  a  minute  ganghon  on  the  middle 
line,  a  short  distance  caudal  of  the  brain,  and  between  the  aorta  and 
the  oesophagus;  and  the  stomogastric  nerves  (st),  these  are  two  nerves 
which  extend  back  from  the  caudal  border  of  the  ventricular  ganglion, 
they  are  parallel  for  a  short  distance,  then  they  separate  and  pass,  one 
on  each  side,  to  the  sides  of  the  alimentary  canal  which  they  follow 
to  the  pro ventri cuius. 

The  paired  division  of  the  oesophageal  sympathetic  nervous  system 
varies  greatly  in  form  in  different  insects.  In  the  larv^a  of  Corydalus, 
there  is  a  single  pair  of  ganglia  (Fig.  142  and  143,  Ig),  one  on  each 
side  of  the  oesophagus;  each  of  these  ganglia  is  connected  with  the 
brain  b}^  two  nerves  {m  and  u)  but  they  are  not  connected  with  each 

other  nor  with  the  unpaired  division 
of  this  system.  In  a  cockroach 
(Fig.  144),  there  are  two  pairs  of 
ganglia  (ag  and  pg);  the  two  ganglia 
of  each  side  are  connected  with  each 
'\  other  and  with  the  recurrent  nerve  of 
the  unpaired  division. 

As  yet  comparatively  little  is 
known  regarding  the  function  of  the 
oesophageal  sympathetic  nervous  sys- 
tem of  insects ;  nerves  extending  from 
it  have  been  traced  to  the  clypeus, 
the  muscles  of  the  pharynx,  the  oeso- 
phagus, the  mid-intestine,  the  sahvary 
glands,  the  aorta,  and  the  heart. 
Its  function  is  probably  analogous  to 
that  of  the  sympathetic  nervous  sys- 
tem of  Vertebrates. 


--sn 


Fig.  144. — The  a-sophageal  sympa- 
thetic nervous  system  of  Peri- 
planeta  orientalis;  the  outlines  of 
the  brain  {h)  and  the  roots  of  the 
antennal  nerve  which  cover  a  por- 
tion of  the  sympathetic  nervous 
system  are  given  in  dotted  lines; 
ag,  anterior  ganglion;  pg,  posterior 
ganglion;  /g,  frontal  ganglion;  sn, 
nerves  of  the  salivary  glands;  r, 
recurrent  nerve  (After  Hofer). 


THE  VENTRAL  SYMPATHETIC  NERV- 
OUS   SYSTEM 


The  ventral  sympathetic  nervous 
system  consists  of  a  series  of  more  or 
less  similar  elements,  each  connected 
with  a  ganglion  of  the  ventral  chain 
of  the  central  nervous  system.  Typi- 
cally there  is  an  element  of  this  system  arising  in  each  thoracic  and 


128 


AN  INTRODUCTION   TO  ENTOMOLOGY 


abdominal  ganglion;  and  each  element  consists  of  a  median  nerve 
extending  from  the  ganglion  of  its  origin  caudad  between  the  two 
connectives,  a  pair  of  lateral  branches  of  this  median  nerve,  and  one 
or  more  ganglionic  enlargements  of  each  lateral  branch.  Frequently 
the  median  ner\^e  extends  to  the  ganghon  of  the  following  segment. 
A  simple  form  of  this  system  exists  in  the  larva  ol 
Cossus  ligniperda  (Fig.  122);  and  a  more  compli- 
cated one,  in  Locusta  viridissima  (Fig.  145). 

From  each  lateral  branch  of  the  median  nerve  a 
slender  twig  extends  to  the  closing  apparatus  of  the 
tracheae. 

d.       THE     PERIPHER.\L     SENSORY    NERVOUS     SYSTEM 

Immediately  beneath  the  hypodermal  layer  of  the 
body- wall,  there  are  many  bipolar  and  multipolar 
nerve-cells  whose  prolongations  form  a  network  of 
ner\^es;  these  constitute  the  peripheral  sensory 
y.ervous  system  or  the  subhypodermal  nerve  plexus. 

The  fine  nerves  of  this  system  are  branches  of 
larger  nerves  which  arise  in  the  central  nervous  sys- 
tem; and  the  terminal  prolongations  of  the  bipolar 
nerve-cells  innervate  the  sense-hairs  of  the  body-wall. 

Figure  146  represents  a  surface  view  of  a  small 
part  of  the  peripheral  sensory  nervous  system  of  the 
silkworm,  Bmnbyx  mcri,  as  figured  by  Hilton  ('02); 
the  bases  of  several  sense  hairs  are  also  shown.    The 

tern;     gs    gang-   details  of  this  figure  are  as  follows:  h,  h,  h,  the  bases 
lion  of  the  svm-       r  ,     .  1  •      , 

pathetic  system  o*  sense-hairs;  s,  s,  s,  bipolar  nerve  cells;  m,  m,  m, 
(From  Berlese).  multipolar  cells;  n,  n,  n,  nerves.  All  of  these  struct- 
ures are  united,  forming  a  network.  Of  especial 
interest  is  the  fact  that  the  terminal  prolongation  of  each  bipolar 
nerve-cell  enters  the  cavity  of  a  sense-hair  and  that  the  other  pro- 
longation is  a  branch  of  a  larger  nerv-e  which  comes  from  the  central 
nerv^ous  system. 

The  peripheral  sensory  nervous  system  is  so  delicate  that  it  can 
not  be  seen  except  when  it  is  stained  by  some  dye  that  differentiates 
nervous  matter  from  other  tissues.  For  this  purpose  the  intra  vitam 
methylen  blue  method  of  staining  is  commonly  used. 


Fig.  145. — Part  of 
the  ventral  chain 
of  gangha  of  Lo- 
custa viridissima 
and  of  the  ven- 
tral sympathetic 
nervous  sys- 
tem; g,  ganglion 
of  the  central 
nervous  system ; 
M,  nerve;  c,  con- 
nective; m,  me- 
dian nerve  of  the 
sympathetic  sys- 


THE   INTERNAL   ANATOMY  OF  INSECTS 


129 


IX.     GENERALIZATIONS    REGARDING    THE    SENSE- 
ORGANS   OF   INSECTS 

The  sense-organs  of  insects  present  a  great  variety  of  forms,  some 
of  which  are  still  incompletely  understood,  in  spite  of  the  fact  that 
they  have  been  investigated  by  many  careful  observers.  In  the 
limited  space  that  can  be  devoted  to  these  organs  here  only  the  more 
general  features  of  them  can  be  described  and  some  of  the  disputed 
questions  regarding  them  briefly  indicated. 

A  classification  of  the  sense-organs. — The  different  kinds  of  sense- 
organs  are  distinguished  by  the  nature  of  the  stimulus  that  acts  on 


[46. — Surface  view  of  subhypodermal  nerves  and  nerve-cells  from 
the  silkworm  (From  Hilton) 

each.  This  stimulus  may  be  either  a  mechanical  stimulus,  a  chemical 
one,  or  light.  The  organs  of  touch  and  of  hearing  respond  to  mechani- 
cal stimuli;  the  former,  to  simple  contact  with  other  objects;  the 
latter,  to  vibratory  motion  caused  by  waves  of  sound.  The  organs  of 
taste  and  of  smell  are  influenced  only  by  soluble  substances  and  it 
seems  probable  that  chemical  changes  are  set  up  in  the  sense-cells  by 
these  substances ;  hence  these  organs  are  commonly  referred  to  as  the 
chemical  sense-organs ;  no  criterion  has  been  discovered  by  which  the 
organs  of  taste  and  of  smell  in  insects  can  be  distinguished.  The 
organs  of  sight  are  acted  upon  by  light ;  it  is  possible  that  the  action 
of  light  in  this  case  is  a  chemical  one,  as  it  is  on  a  photographic  plate, 


130 


AN  INTRODUCTION   TO  ENTOMOLOGY 


but  the  eyes  have  not  been  classed  among  the  chemical  sense-organs. 
For  these  reasons  the  following  groups  of  sense-organs  are  recognized: 
The  mechanical  sense-organs. — -The  organs  of  touch  and  of  hearing. 
The  chemical  sense-organs. — The  organs  of  taste  and  of  smell. 
The  organs  of  sight. — The  compound  eyes  and  the  ocelH. 
The  cuticular  part  of  the  sense-organs. — In  most  if  not  all  of  the 
sense-organs  of  insects  there  exists  one  or  more  parts  that  are  of  cuti- 
cular formation.     The  cuticular  parts  of  the  organs  of  sight  and  of 
hearing  are  described  later,  in  the  accounts  of  these  organs;   in  this 
place,  a  few  of  the  modifications  of  the  cuticula  found  in  other  sense- 
organs  are  described. 

Each  of  the  cuticular  formations  described  here  is  found  either 
within  or  at  the  outer  end  of  a  pore  in  the  cuticula ;  as  some  of  these 
formations  are  obviously  setae  and  others  are  regarded  as  modified 
setag,  this  pore  is  usually  termed  the  trichopore;  it  has  also  been 
termed  the  neuropore,  as  it  is  penetrated  by  a  nerve-ending. 

As  the  cuticular  part  of  this 
group  of  sense-organs,  those  other 
than  the  organs  of  hearing  and 
of  sight,  is  regarded  as  a  seta, 
more  or  less  modified,  these 
organs  are  often  referred  to  as 
the  setiferous  sense-organs;  they 
are  termed  the  Hautsinnesorgane 
by  German  writers. 

Special  terms  have  been 
applied  to  the  different  types  of 
setiferous  sense-organs,  based  on 
the  form  of  the  cuticular  part  of 
each;  but  these  types  cannot 
be  sharply  differentiated  as 
intergrades  exist  between  them. 
In  Figure  147  are  represented 
the  cuticular  parts  of  several  of 
these  different  types;  these  are 
designated  as  follows: 

The   thick-walled   sense-hair, 
sensillum    trichodeum. — In    this 
type  the  cuticular  part  is  a  seta, 
the  base  of  which  is  in  an  alveolus  at  the  end  of  a  trichopore  and  is 
connected  with  the  wall  of  the  trichopore  by  a  thin  articular  mem- 
brane (Fig.  147,  a.) 


Fig-  147-^Various  forms  of  the  cuticular 
portion  of  the  setiferous  sense-organs. 
The  lettering  is  explained  in  the  text. 


THE  INTERNAL  ANATOMY  OF  INSECTS  131 

If  the  sense-hair  is  short  and  stout,  it  is  termed  by  some  writers 
a  sense-bristle,  sensillum  chceticum;  but  there  is  Httle  use  for  this  dis- 
tinction. 

In  the  thick-walled  sense-hairs,  the  wall  of  the  seta  is  fitted  to 
receive  only  mechanical  stimuli,  being  relatively  thick,  and  as  these 
organs  lack  the  characteristic  features  of  the  organs  of  hearing,  they 
are  believed  to  be  organs  of  touch. 

The  sense-cones. — The  sense-cones  vary  greatly  in  form  and  in  their 
relation  to  the  cuticula  of  the  body-wall;  their  distinctive  feature  is 
that  they  are  thin-walled.  For  this  reason,  they  are  believed  to  be 
chemical  sense-organs,  the  thinness  of  the  wall  of  the  cone  permitting 
osmosis  to  take  place  through  it.  In  the  sense-cones,  too,  there  is  no 
joint  at  the  base,  as  in  the  sense-hairs,  the  articular  membrane  being 
of  the  same  thickness  as  the  wall  of  the  cone ;  there  is,  therefore,  no 
provision  for  movement  in  response  to  mechanical  stimuli. 

In  one  type  of  sense-cone,  the  sensillum  hasiconicuni,  the  base  of 
the  cone  is  at  the  surface  of  the  body -wall  (Fig.  147,  6).  In  another 
type,  sensillum  caloconicum,  the  cone  is  in  a  pit  in  the  cuticula  of  the 
body- wall  (Fig.  147,  c).  Two  forms  of  this  type  are  represented  in 
the  figure;  in  one,  the  sense-cone  is  conical;  in  the  other,  it  is  fungi- 
form. Intergrades  between  the  basiconicum  and  the  cceloconicum 
types  exist  (Fig.  147,  d). 

The  flask-like  sense-organ,  sensillum  ampullaceuni. — This  is  a 
modification  of  the  sense-cone  type,  the  characteristic  feature  of 
which  is  that  the  cone  is  at  the  bottom  of  an  invagination  of  the  articu- 
lar membrane;  in  some  cases  the  invagination  is  very  deep  so  that 
the  cone  is  far  within  the  body- wall  (Fig.  147,  ^) ;  intergrades  between 
this  foi-m  and  the  more  common  sensillum  cceloconicum  exist  (Fig. 

147,  /)• 

The  pore-plate,  sensillum  placodeum. — In  this  type  the  cuticular 
part  of  the  organ  is  a  plate  closing  the  opening  of  the  trichopore ;  in 
some  cases,  this  plate  is  of  considerable  thickness  with  a  thin  articular 
membrane  (Fig.  147,  g);  in  others  it  is  thin  throughout  (Fig.  147,  h). 

The  olfactory  pores. — This  type  of  sense-organ  is  described  later. 

X.     THE   ORGANS  OF  TOUCH 

The  organs  of  touch  are  the  simplest  of  the  organs  of  special  sense 
of  insects.  They  are  widely  distributed  over  the  surface  of  the  body 
and  of  its  appendages.  Each  consists  of  a  seta,  with  all  the  character- 
istics of  setse  already  described,  a  trichogen  cell,  which  excreted  the 


132  AN  INTRODUCTION   TO  ENTOMOLOGY 

seta,  and  a  bipolar  nen^e-cell.  These  organs  are  of  the  type  known  as 
sensillum  trichodeum  referred  to  in  the  preceding  section  of  this 
chapter. 

According  to  the  observ-ations  of  Hilton  ('02)  the  terminal  pro- 
longation of  the  ner\'e-cell  enters  the  hair  and  ends  on  one  side  of  it  at 
some  distance  from  its  base  (Fig.  148).  The  proximal  part  of  this 
nen-e-cell  is  connected  with  the  peripheral  sensory  ner\^ous  system,  as 
already  described  (page  128). 

The  presence  of  this  nerv-ous  connection  is  believed  to  distinguish 
tactile  hairs  from  those  termed  clothing  hairs,  and  from  the  scales 
that  are  modified  setas.  If  this  distinction  is  a  good  one,  it  is  quite 
probable  that  many  hairs  and  scales  that  are  now  regarded  as  merely 
clothing  will  be  found  to  be  sense-organs,  when  studied  by  improved 
histological  methods.  In  fact  Guenther  ('01)  and  others  have  shown 
that  some  of  the  scales  on  the  wings  of  Lepidoptera,  especially  those 
on  the  veins  of  the  wings,  are  supplied  with  nerves ;  but  the  function 
of  these  scales  is  unknown. 

Hilton  states  that  he  "fotmd  no  evidence  to  indicate  nerves  ending 
in  gland  cells  or  trichogen  cells  by  such  branches  as  have  been  described 
and  figured  by  Blanc  ('90),  but  in  every  case  the  very  fine  nerve 
termination  could  be  traced  up  past  the  hypodermal  cell  layer  with 
no  branches."  Many  figures  of  unbranched  nerve  fibers  ending  in 
sense-hairs  are  also  given  by  O.  vom  Rath  ('96). 

A  very  different  form  of  nerve-endings  in  sense-hairs  is  given  by 
Berlese  ('09,  a).  This  author  represents  the  nerve  extending  to  a 
sense-hair  as  dividing  into  many  bipolar  ner\-e-endings. 


XI.     THE  ORGANS  OF  TASTE  AND  OF  SMELL 

{The  chemical  sense-organs) 

It  is  necessary  to  discuss  together  the  organs  of  taste  and  of  smell, 
as  no  morphological  distinction  between  them  has  been  discovered. 
If  a  chemical  sense-organ  is  so  located  that  it  comes  in  contact  with 
the  food  of  the  insect,  it  is  commonly  regarded  as  an  organ  of  taste,  if 
not  so  situated,  it  is  thought  to  be  an  organ  of  smell.  In  the  present 
state  of  our  knowledge,  this  is  the  only  distinction  that  can  be  made 
between  these  two  kinds  of  organs. 

Many  experiments  have  been  made  to  determine  the  function  of 
the  various  chemical  sense-organs  but  the  results  are,  as  yet,  far  from 
conclusive.     The  problem  is  made  difficult  by  the  fact  that  these 


THE  INTERNAL  ANATOMY  OF  INSECTS 


133 


organs  are  widely  distributed  over  the  body  and  its  appendages,  and 
in  some  parts,  as  on  the  antennae  of  many  insects,  several  different 
types  of  sense-organs  are  closely  associated. 

Those  organs  that  are  characterized  by  the  presence  of  a  thin- 
walled  sense-cone  (Fig.  147,  h-j)  or  by  a  pore-plate  (Fig.  147,  g,  h)  are 
believed  to  be  chemical  sense-organs.  It  is  maintained  by  Berlese 
('09,  a)  that  an  essential  feature  of  these  chemical  sense-organs  is  the 
presence  of  a  gland -cell,  the  excretion  ofwhich,  passing  through  the  thin 
wall  of  the  cuticular  part,  keeps  the  outer  surface  of  this  part,  the 
sense-cone  or  pore-plate,  moist  and  thus  fitted  for  the  reception  of 
chemical  stimuli.  According  to  this  view  a  chemical  sense-organ 
consists  of  a  cuticular  part,  a  trichogen  cell  or  cells  which  produced 


Fig.  148. — Sections  through  the  body-wall  and  sense -hairs  of  the  silk- 
worm;   c,  cuticula;    h,  hair;    hy,  hypodermis;    n,  nerve;    s,  bipolar 
nerve-cell  (From  Hilton).     The  line  at  the  right  of  the  figure  indi- 
cates one  tenth  millimeter. 


this  part,  a  gland-cell  which  excretes  a  fluid  which  keeps  the  part 
moist,  and  a  nerve-ending. 

It  is  interesting  to  note  that  tactile  hairs  may  be  regarded  as 
specialized  clothing  hairs,  specialized  by  the  addition  of  a  nervous 
connection,  and  that  sense-cones  and  pore-plates  may  be  regarded  as 
specialized  glandular  hairs  with  a  nervous  connection;  in  the  latter 
case,  the  specialization  involves  a  thinning  of  the  wall  of  the  hair  so  as 
to  permit  of  osmosis  through  it. 

In  the  different  accounts  of  chemical  sense-organs  there  are 
marked  differences  as  regards  the  form  of  the  nerve-endings.  In 
many  of  the  descriptions  and  figures  of  these  organs  the  nerve-ending 
is  represented  as  extending  unbranched  to  the  chitinous  part  of  the 
organ,  resembling  in  this  respect  those  represented  in  Figure  148. 
In  other  accounts  the  gland-cell  is  surrounded  by  an  involucre  of 
nerve -cells  (Fig.  149). 


134 


AN  INTRODUCTION    TO  ENTOMOLOGY 


In    the    t3-pes    of    chemical    sense-organs 
action  of  the  chemical  stimuli  is  supposed  to 


■^'jM 


Fig.  149. — Section  of  the  external  layers  of  the  wall  of 
an  antenna  of  Acrida  turrita;  Ct,  cuticula;  Ip,  hypo- 
dermis;  A^,  nerve;  iVi",  involucre  of  nerve-cells  sur- 
rounding the  glandular  part  of  a  sense-organ;  Sbc, 
sensillumbasiconicum;  5ff ,  sensillum  coc-loconicum. 
Three  sense-organs  are  figured;  a  surface  view  of  the 
first  is  represented,  the  other  two  are  shown  in  section. 
(From  Berlese). 


described  above  the 
be  dependent  upon  os- 
mosis through  a  deli- 
cate cuticular  mem- 
brane. It  should  be 
noted,  however,  that 
several  writers  have  de- 
scribed sense-cones  in 
which  there  is  a  pore; 
but  the  accuracy  of 
these  observations  is 
doubted  by  other 
writers. 

A  very  different 
type  of  sense-organs 
which  has  been  termed 
olfactory  pores  is  de- 
scribed in  the  conclud- 
ing section  of  this 
Chapter. 


XII.     THE   ORGANS   OF   SIGHT 


a.       THE    GENERAL    FEATURES 

The  two  types  of  eyes  of  insects. — It  is  shown  in  the  preceding 
chapter  that  insects  possess  two  types  of  eyes,  the  ocelli  or  simple  eyes 
and  the  compound  or  facetted  eyes. 

Typically  both  types  of  eyes  are  present  in  the  same  insect,  but 
either  may  be  wanting.  Thus  many  adult  insects  lack  ocelli,  while 
the  larvffi  of  insects  with  a  complete  metamorphosis  lack  compound 
eyes. 

When  all  are  present  there  are  two  compound  eyes  and,  typically, 
two  pairs  of  ocelli ;  but  almost  invariably  the  members  of  one  pair  of 
ocelli  are  united  and  form  a  single  median  ocellus.  The  median  ocel- 
lus is  wanting  in  many  insects  that  possess  the  other  two  ocelli. 

The  distinction  between  ocelli  and  compound  eyes. — The  most 
obvious  distinction  between  ocelli  and  compound  eyes  is  the  fact  that 
in  an  ocellus  there  is  a  single  cornea  while  in  a  compound  eye  there  are 
many.  Other  features  of  compound  eyes  have  been  regarded  as  dis- 
tinctively characteristic  of  them;  but  in  the  case  of  each  of  these 
features  it  is  found  that  they  exist  in  some  ocelli. 


THE   INTERNAL   ANATOMY  OF  INSECTS  135 

Each  ommatidivim  of  a  compound  eye  has  been  considered  as  a 
separate  eye  because  its  nerve-endings  constituting  the  retinula  are 
isolated  from  the  retinulae  of  other  ommatidia  by  surrounding  acces- 
sory pigment  cells;  but  a  similar  isolation  of  retinulas  exist  in  some 
ocelli. 

It  has  also  been  held  that  in  compound  eyes  there  is  a  layer  of  cells 
between  the  corneal  hypodermis  and  the  retina,  the  crystalline-cone- 
cells,  which  is  absent  in  ocelli ;  but  in  the  ocelli  of  adult  Ephemerida 
there  is  a  layer  of  cells  between  the  lens  and  the  retina,  which,  at  least, 
is  in  a  position  analogous  to  that  of  the  crystalline-cone-cells;  the 
two  may  have  had  a  different  origin,  but  regarding  this,  we  have,  as 
yet,  no  conclusive  data. 

The  absence  of  compound  eyes  in  most  of  the  Apterygota. — 

Typically  insects  possess  both  ocelli  and  compound  eyes ;  when  either 
kind  of  eyes  is  wanting  it  is  evidently  due  to  a  loss  of  these  organs  and 
not  to  a  generalized  condition.  Although  compound  eyes  are  almost 
universally  absent  in  the  Apterygota  in  the  few  cases  where  they 
are  present  in  this  group  they  are  of  a  highly  developed  type  and  not 
rudimentary;  the  compound  eyes  of  Machilis,  for  example,  are  a^ 
perfect  as  those  of  winged  insects. 

The  absence  of  compound  eyes  in  larvae. — The  absence  of  com- 
pound eyes  in  larvse  is  evidently  a  secondary  adaptation  to  their 
particular  mode  of  life,  like  the  internal  development  of  wings  in  the 
same  forms.  In  the  case  of  the  compound  eyes  of  larvae,  the  develop- 
ment of  the  organs  is  retarded,  taking  place  in  the  pupal  stage  instead 
of  in  an  embryonic  stage,  as  is  the  case  m  ith  nymphs  and  naiads. 

While  the  development  of  the  compound  eyes  as  a  whole  is  retarded 
in  larvae,  a  few  ommatidia  may  be  developed  and  function  as  ocelli 
during  larval  life. 

b.       THE    OCELLI 

There  are  two  classes  of  ocelli  found  in  insects :  first,  the  ocelli  of 
adult  insects  and  of  nymphs  and  naiads,  which  may  be  termed  the 
primary  ocelli;  and  second,  the  ocelli  of  most  larvae  possessing  ocelli, 
which  may  be  termed  adaptive  ocelli. 

The  primary  ocelli. — The  ocelli  of  adult  insects  and  of  nymphs  and 
naiads  having  been  orig'nally  developed  as  ocelli  are  termed  the 
primary  ocelli.  Of  these  there  are  typically  two  pairs;  but  usually 
when  they  are  present  there  are  only  three  of  them,  and  in  many  cases 
only  a  single  pair. 


136 


AN  INTRODUCTION   TO  ENTOMOLOGY 


When  there  are  three  ocelh,  the  double  nature  of  the  median  ocel- 
lus is  shown  by  the  fact  that  the  root  of  the  ner\-e  is  double,  while  that 
of  each  of  the  other  two  is  single. 

In  certain  generalized  insects,  as  some  Plecoptera,  (Fig.  150)  all  of 
the  ocelli  are  situated  in  the  front;  but  in  most  insects,  the  paired 
ocelli  have  either  migrated  into  the  suture  between  the  front  and  the 
vertex  (Fig.  151),  or  have  proceeded  farther  and  are  situated  in  the 
vertex. 

The  structure  of  primary  ocelli  is  described  later. 
The  adaptive  ocelli. — Some  larva?,  as  those  of  the  Tenthredinida?, 
possess  a  single  pair  of  ocelli,  which  in  their  position  and  in  their 
structure  agree  with  the  ocelli  of  the  adult  insects ;  these  are  doubtless 
primary  ocelli.  But  most  larvas  have  lost  the  primary  ocelli;  and 
if  they  possess  ocelli  the  position  of  them  and  their  structure  differ 
greatly  from  the  positions  and  structure  of  primary  ocelli. 

Except  in  the  few  cases  where  primary  ocelli 
have  been  retained  by  larv^as,  the  ocelli  of 
larvas  are  situated  in  a  position  corresponding 
to  the  position  of  the  compound  eyes  of  the 
adult  (Fig.  152);  and  there  are  frequently 
several  of  these  ocelli  on  each  side  of  the  head. 
This  has  led  to  the  belief  that  they  represent 
a  few  degenerate  ommatidia,  which  have  been 
retained  by  the  lan^a,  while  the  development  of 
the  greater  niimber  of  ommatidia  has  been 
retarded.  For  this  reason  they  are  termed 
adaptive   ocelli. 

The  number  of  adaptive  ocelli  varies  greatly, 
and  sometimes  is  not  con- 
stant in  a  species;   thus 
in  the  larva  of  Corydalus, 
there  may  be  either  six  or  seven  ocelli  on  each 
side  of  the  head. 

There  are  also  great  variations  in  the  struct- 
ure of  adaptive  ocelli.  These  variations  pro- 
bably represent  different  degrees  of  degeneration 
or  of  retardation  of  development.  The  extreme 
of  simplicity  is  found  in  certain  dipterous  larvas ; 
according  to  Hesse  (01)  an  ocellus  of  Cerato- 
pogon  consists  of  only  two  sense-cells.  As  examples  of  com- 
plicated adaptive  ocelli,  those  of  lepidopterous  larvas  can  be  cited. 


Fig.  150. — Head  of  a 
naiad  of  Pteronacys; 
dt,  spots  in  the  cuti- 
cula  beneath  which 
the  dorsal  arms  of  the 
tentorium  are  at- 
tached; the  three 
ocelli  are  on  the  front 
(F),  between  these 
two  spots. 


Fig.  151. — Head  of  a 
cricket. 


THE   INTERNAL   ANATOMY   OF   INSECTS 


137 


Fig.  152. — Head  of  a 
larva  of  Corydalus, 
dorsal  aspect. 


The  ocellus  cf  Gastropacha  mbi,  which  is  described  and  figured  by 

Pankrath  ('90),  resembles  in  structure,  to  a  remarkable  degree,  an 
ommatidium,  and  the  same  is  true  of  the  ocellus 
of  the  larva  of  Arctia  caja  figured  by  Hesse  ('01). 
The  structure  of  a  visual  cell. — The  dis- 
tinctively characteristic  feature  of  eyes  is  the 
presence  of  what  is  termed  visual  cells.  In 
insects,  and  in  other  arthropods,  a  visual  cell 
is  a  nerve-end-cell,  which  contains  a  nucleus 
and  a  greater  or  less  amount  of  pigment, 
and  bears  a  characteristic  border,  termed  the 
rhabdomere;  this  is  so  called  because  it  forms 
a  part  of  a  rhab- 
dom. 

The    visual 

cells  are  grouped  in  such  a  way  that  the 

rhabdomeres  of  two  or  mere  of  them 

are  united  to  form  what  is  known  as  a 

rhabdcm  or  optic  rod.     A  group  of  two 

visual  cells  with  therhabdom  formed  by 

their  united  rhabdomeres  is  shown  in 

Figure  153,  A  and  B. 

The  form  of  the  rhabdomere  varies 

greatly  in  the  visual  cells  of  different 

insect  eyes;  and  the  number  of  rhab- 
domeres that  enter  into  the  composi- 
tion of  a  rhabdom  also  varies. 

Figure  153,  C  represents  in  a  dia- 
grammatic   manner  the    structure  of 

rhabdomere  a  s  described  by  Hesse  ('  o  i ) . 

The  rhabdomere  (r)  consists  of  many 

minute  rodlets  each  with  a  minute  knob 

at  its  base  and  connected  with  a  nerve 

fibril. 

The  structure  of  a  primary  ocellus. 

— The  primary  ocelli  vary  greatly  in 

the  details  of  the  form  of  their  parts, 

but  the  essential  features  of  their  structure  are 

accompanying  diagram  (Fig.   154). 

In  some  ocelli,   as  for  example  the  lateral  ocelli   of   scorpions, 

the  visual  cells  are  interpolated  among  ordinary  hypodermal  cells, 


Fig-  153- — Two  visual  cells  from 
an  ocellus  of  a  pupa  of  Apis 
mellifica.  A,  longitudinal  sec- 
tion ;  B,  transverse  section;  n, 
n,  nerves;  nu,  nucleus;  r, 
rhabdom;  p,  pigment  (After 
Redikorzew),  C,  diagram  il- 
lustrating the  structure  of  a 
rhabdomere;  r,  rhabdomere; 
c,  cell-body  (From  Berlese  after 
Hesse). 


illustrated  by  the 


138 


AN   INTRODUCTION    TO   ENTOMOLOGY 


Fig.  154. — A  diagram  illustrating  the  structure  of 
a  primary  ocellus;  c,  cornea;  c.  hy,  corneal 
hypodermis;  ret,  retina;  n,  ocellar  nerve;  p, 
accessory  pigment  cell;  r,  rhabdom. 


the    two    kinds    fonning     a    single    layer    of    cells    beneath    the 
cornea;    but  in  the  ocelli  of  insects,  the  sense-cells  form  a  distinct 

layer  beneath  the  hypo- 
dermal  cells.  In  this 
type  of  ocellus  the  fol- 
lowing parts  can  be  dis- 
tinguished : 

The  cornea . — T  h  e 
cornea  (Fig.  154,  c)  is  a 
transparent  portion  of 
the  cuticula  of  the  body- 
wall  ;  this  may  be  lenti- 
cular in  form  or  not. 

The  corneal  hypoder- 
mis.— The  hypodermis 
of  the  body-wall  is  con- 
tinued beneath  the 
cornea  (Fig.  154,  c.  hy.); 
this  part  of  the  hypo- 
dermis is  termed  by 
many  writers  the  vitreous 
layer  of  the  ocellus;  but  the  term  corneal  hypodermis,  being  a  self- 
explanatory  term,  is  preferable.  Other  terms  have  been  applied  to  it, 
as  the  lentigen  layer  and  the  corneagen,  both  referring  to  the  fact  that 
this  part  of  the  hypodermis  produces  the  cornea. 

The  retina. — Beneath  the  corneal  hypodermis  is  a  second  cellular 
layer,  which  is  termed  the  retina,  being  composed  chiefly  or  entirely  of 
visual  cells  (Fig.  154,  ret). 

The  visual  cells  of  the  retina  are  grouped,  as  described  above  (Fig. 
i53)>  so  that  the  rhabdomeres  of  several  of  them,  two,  three  or  four, 
unite  to  form  a  rhabdom;  such  a  group  of  retinal  cells  is  termed  a 
retinula. 

The  visual  cells  are  nerve-end-cells,  each  constituting  the  termina- 
tion of  a  fiber  of  the  ocellar  nerve,  and  are  thus  connected  with  the 
central  nervous  system. 

Accessory  pigment  cells. — In  some  ocelli  there  are  densely  pig- 
mented cells  between  the  retinulas,  which  serve  to  isolate  them  in  a 
similar  way  to  that  in  which  the  retinula  of  an  ommatidium  of  a  com- 
pound eye  is  isolated  (Fig.  154,  p).  Even  in  cases  where  accessory 
pigment  cells  are  wanting  a  degree  of  isolation  of  the  rhabdoms  of  the 
retinulas  of  an  ocellus  is  secured  by  pigment  within  the  visual  cells 
(Fig.   153.  P)- 


THE   INTERNAL  ANATOMY  OF  INSECTS 


139 


Ocelli  of  Ephemerida.— It  has  been  found  that  the  ocelli  of  certain 
adult  Ephemerida  differ  remarkably  from  the  more  common  type  of 
ocelli  described  above.  These  peculiar  ocelli  have  been  described  and 
figured  by  Hesse  (oi)  and  Seiler  (05).  In  them  the  cuticula  over  the 
ocellus,  the  cornea,  is  arched  but  not  thickened  and  the  corneal  hypo- 
dermis  is  a  thin  layer  of  cells  immediately  beneath  it.  Under  the 
hypodermis  there  is  a  lens-shaped  mass  of  large  polygonal  cells ;  and 
between  this  lens  and  the  retina  there  is  a  layer  of  closely  crowded 
columnar  cells. 

The  development  of  these  ocelli  has  not  been  studied;  hence  the 
origin  of  the  lens-shaped  mass  of  cells  and  of  the  layer  of  cells  between 
it  and  the  retina  is  not  known. 

C.       THE    COMPOUND    EYES 

A  compound  eye  consists  of  many 
quite  distinct  elements,  the  ommatidia, 
each  represented  externally  by  one  of 
the  many  facets  of  which  the  cuticular 
layer  of  the  eye  is  composed.  As  the 
ommatidia  of  a  given  eye  are  similar, 
a  description  of  the  stn.icture  of  one 
will  serve  to  illustrate  the  structure  of 
the  eye  as  a  whole. 

The  structure  of  an  ommatidium. — 
The  compound  eyes  of  different  insects 
vary  in  the  details  of  their  structure; 
but  these  variations  are  merely  modi- 
fications of  a  common  plan ;  this  plan  is 
well -illustrated  by  the  compound  eyes 
of  Machilis,  the  structure  of  which  was 
worked  out  by  Seaton  ('03).  Figure 
155  represents  a  longitudinal  section 
and  a  series  of  transverse  sections  of  an 
ommatidium  in  an  eye  of  this  insect, 
which  consists  of  the  following  parts. 

The  cornea. — The  cornea  is  a  hexa- 
gonal portion  of  the  cuticular  layer  of 
the  eye  and  is  biconvex  in  form  (Fig. 
155,  c). 

The  corneal  hypodermis. — Beneath 
each  facet  of  the  cuticular  layer  of  the  eye  are  two  hypodermal  cells 


Fig-  155- — -An  ommatidium  of 
Machilis.  The  lettering  is  ex- 
plained in  the  text. 


140  AN  INTRODUCTION   TO   ENTOMOLOGY 

which  constitute  the  corneal  hypodermis  of  the  ommatidium.  These 
cells  are  quite  distinct  in  Machilis  and  their  nuclei  are  prominent 
(Fig.  155,  hy);  but  in  many  insects  they  are  greatly  reduced,  and 
consequently  are  not  represented  in  many  of  the  published  figures 
of  compound  eyes. 

The  crystalline-cone-celis . — Next  to  the  corneal  hypodermis  there 
are  four  cells,  which  in  one  t3rpe  of  compound  eyes,  the  eucone  eyes, 
form  a  body  known  as  the  crystalline -cone,  for  this  reason  these 
cells  are  termed  the  crystalline-cone-cells  (Fig.  155,  cc).  Two  of 
these  cells  are  represented  in  the  figure  of  a  longitudinal  section 
and  all  four,  in  that  of  a  transverse  section.  In  each  cell  there  is  a 
prominent  nucleus  at  its  distal  end. 

The  iris -pigment-cells. — Surrounding  the  crystalline-cone-cells  and 
the  corneal  hypodermis,  there  is  a  curtain  of  densely  pigmented  cells, 
which  serves  to  exclude  from  the  cone  light  entering  other  ommatidia ; 
for  this  reason  these  cells  are  termed  the  iris -pigment  (Fig.  155,  i). 
They  are  also  known  as  the  distal  retinula  cells;  but  as  they  are  not  a 
part  of  the  retina  this  term  is  misleading. 

There  are  six  iris -pigment -cells  surrounding  each  crystalline -cone; 
but  as  each  of  these  cells  forms  a  part  of  the  iris  of  three  adjacent 
ommatidia,  there  are  only  twice  as  many  of  these  cells  as  there  are 
ommatidia.  This  is  indicated  in  the  diagram  of  a  transverse  section 
(Fig.  155,  i)- 

The  retinula. — At  the  base  of  each  ommatidium,  there  is  a  group 
of  visual  cells  forming  a  retinula  (Fig.  1 55,  r) ;  of  these  there  are  seven 
in  Machilis;  but  they  vary  in  number  in  the  eyes  of  different  insects. 
The  visual  cells  are  so  grouped  that  their  united  rhabdomeres  form  a 
rhabdom,  which  extends  along  the  longitudinal  axis  of  the  ommati- 
dium (Fig.  155,  rA).  The  distal  end  of  the  rhabdom  abuts  against  the 
proximal  end  of  the  crystalHne-cone ;  and  the  nerve-fibers  of  which  the 
visual  cells  are  the  endings  pass  through  the  basement  membrane 
(Fig.  155,  b)  to  the  optic  nerve. 

The  visual  cells  are  pigmented  and  thus  aid  in  the  isolation  of  the 
ommatidium. 

The  accessory  pigment -cells. — In  addition  to  the  two  kinds  of  pig- 
ment-cells described  above  there  is  a  variable  ntmiber  of  accessory 
pigment -cells  (Fig.  155,  ap),  which  lie  outside  of  and  overlap  them. 

From  the  above  it  will  be  seen  that  each  ommatidium  of  a  eucone 
eye  is  composed  of  five  kinds  of  cells,  three  of  which,  the  corneal  hypo- 
dermis, the  crystalHne-cone-cells,  and  the  retinular  cells  produce  solid 
structures;    and  three  of  them  are  pigmented. 


THE   INTERNAL   ANATOMY  OF  INSECTS  141 

Three  types  of  compound  eyes  are  recognized:  first,  the  eucone 
eyes,  in  these  each  ommatidium  contains  a  true  crystalHne-cone,  as 
described  above,  and  the  nuclei  of  the  cone-cells  are  in  front  of  the 
cone;  second,  the  pseudocone  eyes,  in  these  the  four  cone -cells  are 
filled  with  a  transparent  fluid  medium,  and  the  nuclei  of  these  cells  are 
behind  the  refracting  body;  and  third,  the  acone  eyes,  in  which 
although  the  four  cone -cells  are  present  they  do  not  form  a  cone,  either 
solid  or  liquid. 

d.       THE    PHYSIOLOGY    OF    COMPOUND    EYES 

The  compound  eyes  of  insects  and  of  Crustacea  are  the  most  com- 
plicated organs  of  vision  known  to  us.  It  is  not  strange  therefore,  that 
the  manner  in  which  they  function  has  been  the  subject  of  much  dis- 
cussion. It  is  now,  however,  comparatively  well-understood; 
although  much  remains  to  be  determined. 

In  studying  the  physiology  of  compound  eyes,  three  sets  of  struc- 
tures, found  in  each  ommatidium,  are  to  be  considered:  first,  the 
dioptric  apparatus,  consisting  of  the  cornea  and  the  crystalline -cone; 
second,  the  percipient  portion,  the  retinula,  and  especially  the  rhab- 
dom;  and  third,  the  envelope  of  pigment,  which  is  found  in  three 
sets  of  cells,  the  iris  pigment-cells,  the  retinular  cells,  and  the  accessory 
or  secondary  pigment -cells. 

The  dioptrics  of  compound  eyes  is  an  exceedingly  complicated 
subject ;  a  discussion  of  it  would  require  too  much  space  to  be  intro- 
duced here.  It  has  been  quite  fully  treated  by  Exner  ('91).  to  whose 
work  those  especially  interested  in  this  subject  are  referred.  The 
im-portant  point  for  our  present  discussion  is  that  by  means  of  the 
cornea  and  the  crystalline-cone,  light  entering  the  cornea  from  within 
the  limits  of  a  certain  angle  passes  through  the  cornea  and  the  crystal- 
line-cone to  the  rhabdom,  which  is  formed  of  the  combined  rhab- 
domeres  of  the  nerve-end-cells,  constituting  the  retinula,  the  precipient 
portion  of  the  ommatidium. 

The  theory  of  mosaic  vision.-^The  first  two  questions  suggested  by 
a  study  of  physiology  of  compound  eyes  have  reference  to  the  nature 
of  the  vision  of  such  an  eye.  What  kind  of  an  image  is  thrown  upon 
the  retinula  of  each  ommatidium?  And  how  are  these  images  com- 
bined to  form  the  image  perceived  by  the  insect?  Does  an  insect 
with  a  thousand  ommatidia  perceive  a  thousand  images  of  the  object 
viewed  or  only  one? 

The  theory  of  mosaic  vision  gives  the  answers  to  these  questions. 
This  theory  was  proposed  by  J.  Miiller  in  1826;   and  the  most  recent 


142 


AN  INTRODUCTION   TO  ENTOMOLOGY 


investigations  confirm  it.  The  essential  features  of  it  are  the  follow- 
ing: only  the  rays  of  light  that  pass  through  the  cornea  and  the 
crystalline -cones  reach  the  precipient  portion  of  the  eye,  the  others  fall 
on  the  pigment  of  the  eye  and  are  absorbed  by  it ;  in  each  ommatidium 
the  cornea  transmits  to  the  crystalline -cone  light  from  a  very  limited 
field  of  vision,  and  when  this  light  reaches  the  apex  of  the  crystaUine- 
cone  it  forms  a  point  of  light,  not  an  image;  hence  the  image  formed 
upon  the  combined  retinulae  is  a  mosaic  of  points  of  light,  which  com- 
bined make  a  single  image,  and  this  image  is  an  erect  one. 

Figure  156  will  serve  to  illustrate  the  mosaic  theory  of  vision. 
In  this  figure  are  represented  the  corneas  (c),  the  crystalline -cones 
(cc),  and  the  rhabdoms  (r.)  of  several  adja- 
cent ommatidia.  It  can  be  seen,  from  this 
diagram,  that  each  rhabdom  receives  a 
point  of  light  which  comes  from  a  limited 
portion  of  the  object  viewed  (O) ;  and  that 
the  image  (I)  received  by  the  percipient 
portion  of  the  eye  is  a  single  erect  image, 
formed  by  points  of  light,  each  of  which 
corresponds  in  density  and  color  to  the 
corresponding  part  of  the  object  viewed. 
The  distinctness  of  vision  of  a  com- 
pound eye  depends  in  part  upon  the  niun- 
ber  and  size  of  the  ommatidia.     It  can  be 

Fig.  156.— Diagram  iUustrat- readily  seen  that  the  image  formed   by 
mg  the    tneory  of    mosaic  a  j 

vision.  many  small  ommatidia  will  represent  the 

details  of  the  object  better  than  one  formed 

by  a  smaller  niunber  of  larger  ommatidia ;   the  smaller  the  portion  of 

the  object  viewed  by  each  ommatidium  the  mere  detailed  "will  be  the 

image. 

The  distinctness  of  the  vision  of  a  compound  eye  depends  also  on 
the  degree  of  isolation  of  the  light  received  by  each  ommatidium, 
which  is  determined  by  the  amount  and  distribution  of  the  pigment. 
Two  types  of  compound  eyes,  differing  in  the  degree  of  isolation  of  the 
light  received  by  each  ommatidium,  are  recognized;  to  one  type  has 
been  applied  the  term  day-eyes,  and  to  the  other,  night-eyes. 

Day-eyes. — The  type  of  eyes  known  as  day-eyes  are  so-called 
because  they  are  fitted  for  use  in  the  day-time,  when  there  is  an 
abundance  of  light.  In  these  eyes  the  envelope  of  pigment  sur- 
rounding the  transparent  parts  of  each  ommatidiiim  is  so  complete 
that  only  the  light  that  has  traversed  the  cornea  and  crystalline -cone 


THE   INTERNAL   ANATOMY  OF  INSECTS 


143 


of  that  ommatidium  reaches  its  rhabdom.  The  image  foiTQed  in 
such  an  eye  is  termed  by  Exner  an  apposed  image;  because  it  is  formed 
by  apposed  points  of  light,  falHng  side  by  side  and  not  overlapping. 
Such  an  image  is  a  distinct  one. 

Night-eyes. — In  the  night-eyes  the  envelope  of  pigment  surround- 
ing the  transparent  parts  of  each  ommatidium  is  incomplete ;  so  that 
rays  of  light  entering  several  adjacent  corneas  can  reach  the  same 
retinula.  In  such  an  eye  there  will  be  an  overlapping  of  the  points  of 
light;  the  image  thus  formed  is  termed  by  Exner  a  superimposed 
image.  It  is  obvious  that  such  an  image  is  not  as  distinct  as  an  ap- 
posed image.  It  is  also  obvious  that  a  limited  amount  of  light  will 
produce  a  greater  impression  in  this  type  of  eye  than  in  one  where  a 
considerable  part  of  the  light  is  absorbed  by  pigment.  Night-eyes  are 
fitted  to  perceive  objects  and  the  movement  of  objects  in  a  dim  light, 
but  only  the  more  general  features  of  the  object  can  be  perceived  by 
them. 

Eyes  with  double  function. — It  is  a  remarkable  fact  that  with 
many  insects  and  Crustacea  the  compound  eyes  function  in  a  bright 
light  as  day-eyes  and  in  a  dim  light  as  night- 
eyes.  This  is  brought  about  by  movements  in 
the  pigment.  If  an  insect  having  eyes  of  this' 
kind  be  kept  in  a  light  place  for  a  time  and  then 
killed  while  still  in  the  hght,  its  eyes  will  be  found 
to  be  day-eyes,  that  is  eyes  fitted  to  form  apposed 
images.  But  if  another  insect  of  the  same 
species  be  kept  in  a  dark  place  for  a  time  and 
then  killed  while  still  in  the  dark,  its  eyes  will  be 
found  to  be  night-eyes,  that  is  eyes  fitted  to 
form  superimposed  images. 

Figure  157  represents  two  preparations 
showing  the  structure  of  the  compound  eyes -of 
a  diving-beetle,  studied  by  Exner.  In  one 
(Fig.  157,  ^),  each  rhabdom.  is  surrounded  by  an 
envelope  of  pigment,  so  that  it  can  receiv  eonly 
:57.— Ommatidia  ^^^  ^^^^^  passing  through  the  crystalline-cone  of 
from  eyes  of  Colym-  the  ommatidiimi  of  which  this  rhabdom  is  a  part. 
coStiont  fif  n^g'lft!  This  is  the  condition  found  in  the  individual 
eye  condition  (From  killed  in  the  light,  and  illustrates  well  the  struct- 
■'^^'^^'"^-  ure  of  a  day-eye.     In  the  other  preparation  (Fig. 

157,5),  which  is  from  an  individual  killed  in  the  dark,  it  can  be  seen 
that  the  pigment  has  moved  up  between  the  crystalline -cones  so  that 


144  AN  INTRODUCTION   TO  ENTOMOLOGY 

the  light  passing  from  the  tip  of  a  cone  may  reach  several  rhabdoms, 
making  the  eye  a  night-eye.  These  changes  in  the  position  of  the 
pigment  are  probably  due  to  amoeboid  movements  of  the  cells. 

Divided  Eyes. — In  many  insects  each  compound  eye  is  divided 
into  two  parts;  one  of  which  is  a  day-eye,  and  the  other  a  night-eye. 
The  two  parts  of  such  an  eye  can  be  readily  distinguished  by  a  differ- 
ence in  the  size  of  the  facets;  the  portion  of  the  eye  that  functions 
as  a  day-eye  being  composed  of  much  smaller  facets  than  that  which 
functions  as  a  night-eye. 

A  study  of  the  internal  structure  of  a  divided  eye  shows  that  the 
distribution  of  the  pigment  in  the  part  composed  of  smaller  facets  is 
that  characteristic  of  day-eyes ;  while  the  part  of  the  eye  composed  of 
larger  facets  is  fitted  to  produce  a  superimposed  image,  which  is  the 
distinctive  characteristic  of  night-eyes. 

Great  differences  exist  in  the  extent  to  which  the  two  parts  of  a 
divided  eye  are  separated.  In  many  dragon-flies  the  facets  of  a  part 
of  each  compound  eye  are  small,  while  those  of  the  remainder  of  the 
eye  are  much  larger ;  but  the  two  fields  are  not  sharply  separated.  In 
some  Blepharocera  the  two  fields  are  separated  by  a  narrow  band  in 
which  there  are  no  facets,  and  the  difference  in  the  size  of  the  facets  of 
the  two  areas  is  very  marked.     The  extreme  condition  is  reached  in 

certain    May-flies,    where   the  two 
parts  of  the  eye  are  so  widely  separa- 
ted that  the  insect  appears  to  have 
'    two  pairs  of  compound  eyes  (Fig  i  s  8) . 
The    tapetum. — In  the  eyes  of 
many  animals  there  is  a  structure 
that  reflects  back  the  light  that  has 
entered  the  eye,  causing  the  well- 
known  shining  of  the  eyes  in  the 
dark.    This  is  often  observed  in  the 
Fig.  158.— Front  of  head  of  Cloeon,     g   gg  ^f  ^^^g  ^^^  -j^  ^^^  ^   gg  ^f  j^oths 
showing  divided  eves;  a,  night-eye;      ;  ,.   , 

&,  day  eye;  c,  ocellus  (From  Sharp),    that  are  attracted  to  our  light  at 

night.  The  part  of  the  eye  that 
causes  this  reflection  is  termed  a  tapetum.  The  supposed  function  of  a 
tapetimi  is  to  increase  the  effect  of  a  faint  light,  the  light  being  caused 
to  pass  through  the  retina  a  second  time,  when  it  is  reflected  from  the 
tapetum. 

The  structure  of  the  tapetum  varies  greatly  in  different  animals; 
in  the  cat  and  other  carnivores  it  is  a  thick  layer  of  wavy  fibrous  tissue; 
in  spiders  it  consists  of  a  layer  of  cells  behind  the  retina  containing 


THE   INTERNAL   ANATOMY  OF  INSECTS 


145 


small  crystals  that  reflect  the  light ;   and  in  insects  it  is  a  mass  of  fine 
tracheae  surrounding  the  retinula  of  each  ommatidium. 


XIII.     THE   ORGANS   OF   HEARING 


Fig.  159. — Side  view  of  a  locust  with  the  wings 
removed;    t,  tympanum. 


a.       THE    GENERAL   FEATURES 

The  fact  that  in  many  insects  there  are  highly  specialized  organs 
for  the  production  of  sounds  indicates  that  insects  possess  also  organs 
of  hearing;    but  in  only  a  few  cases  are  these  organs  of  such  form 

that  they  have  been  gen- 
erally recognized  as  ears. 
The  tympana. — In 
most  of  the  jimiping 
Orthoptera  there  are 
thinned  portions  of  the 
cuticula,  which  are  of  a 
structure  fitted  to  be  put 
in  vibration  by  waves  of 
sound.  For  this  reason  these  have  been  commonly  regarded  as  organs 
of  hearing,  and  have  been  termed  tympana.  In  the  Acridiidse,  there 
is  a  tympantim  on  each  side  of  the  first  abdominal  segment  (Fig. 
159);  and  in  the  Locustidas  and  in  the  Gryllidas,  there  is  a  pair  of 
tympana  near  the  proximal 
end  of  each  tibia  of  the  first 
pair  of  legs  (Fig.  160). 

The  chordotonal  organs. — 
An  ear  to  be  effective  must 
consist  of  something  more  than 
a  membrane  that  will  be  put 
in  vibration  by  means  of 
sound;  the  vibrations  of  such 
a  tympanum  must  be  trans- 
ferred in  some  way  to  a  nerv- 
vous  structure  that  will  be 
influenced  by  them  if  the 
sound  is  to  be  perceived.  Such 
structures,    closely   associated 

with  the  tympana  of  Orthoptera,  were  discovered  more  than  a  half 
century  ago  by  Von  Siebold  (1844)  and  have  been  studied  since  by 
many  investigators.    The  morphological  unit  of  these  essential  auditory 


Fig.  160. — Fore  leg  of  a  katydid;  t,  tympa- 


146 


AN  INTRODUCTION   TO  ENTOMOLOGY 


Fig.  i6i. — Diagrammatic  representation  of  the 
auditory  organs  of  a  locustid  (After  Graber) . 


structures  of  insects  is  a  more  or  less  peg-like  rod  contained  in  a  tubular 
nerve-ending  (Fig.  i6i,  A  and  B);    this  nerve-ending  may  or  may 

not  be  associated  with  a 
specialized  tympaninn. 
To  all  sense-organs  char- 
acterized by  the  presence 
of  these  auditory  pegs, 
Graber  ('82)  applied  the 
term  chordotonal  organs  or 
fiddle-string-like  organs. 
The  scolopale  and 
the  scolopophore. — The 
peg-like  rod 
characteris- 
tic of  a  chor- 
dotonal organ  of  an  insect  was  named  by  Graber  the 
scolopale;  and  to  the  tubular  nerve-ending  containing 
the  scolopale,  he  applied  the  term  scolopophore. 

The  integumental  and  the  subintegumental  scolopo- 
phores. — With  respect  to  their  position  there  are  two 
types  of  scolopophores ;  in  one,  the  nerve-ending  is 
attached  to  the  body-wall  (Fig.  161,  A);  in  the  other,  it 
ends  free  in  the  body-cavity  (Fig.  161,  B).  These  two 
types  are  designated  respectively  as  integumental  scolo- 
pophores and  subintegumental  scolopophores. 

The  structure  of  a  scolopophore. — In  a  scolopophore 
there  can  be  distinguished  an  outer  sheath  (Fig.  161,  I), 
which  appears  to  be  continuous  either  with  the  basement 
membrane  of  the  hypodermis  or  with  that  of  the 
epithelium  of  a  trachea,  and  within  this  sheath  the 
complicated  nerve-ending;  this  nerve-ending  is  repre- 
sented diagrammatically  in  Figure  161  from  Graber  and  in 
detail  in  Figure  162  from  Hess  ('17). 

In  Figure  162  the  following  parts  are  represented:  a 
bipolar  sense-cell  {sc)  with  its  nucleus  (sen) ;  the  proximal 
pole  of  this  sense -cell  is  connected  with  the  central  nerv- 
ous system  by  a  nerve;  and  its  distal  pole  is  connected 
with  the  scolopale  (5)  by  an  axis -fiber  (a/) ;  surrounding 
the  distal  prolongation  of  the  sense -cell  and  the  scolopale 
there  is  an  enveloping  or  accessory  cell  (ec),  in  which 
there  is  a  prominent  nucleus  {ecn) ;   distad  of  the  enveloping  cell  is 


\..aj 


^ 


Fig.  162.— A 
scol op  o- 
phore  of  the 
i  n  t  e  g  u  - 
mental  type 
(From 
Hess). 


THE   INTERNAL   ANATOMY  OF  INSECTS 


14/ 


the  cap-cell  {cc),  in  which  there  is  a  nucleus  {ccn);  extending  from 
the  end -knob  {ek)  of  the  scolopale  and  surrounded  by  the  cap -cell 
there  is  an  attachment  fiber  or  terminal  ligament  {tl),  by  which  the 
scolopophore  is  attached  to  the  body-wall,  the  scolopophore  repre- 
sented being  of  the  integumental  type;  at  the  base  of  the  scolopale 
and  partly  surrounding  it,  there  is  a  vacuole  (v). 

The  structure  of  a  scolopale. — The  scolopalse  or  auditory  pegs  are 
exceedingly  minute  and  are  quite  uniform  in  size,  regardless  of  the  size 
of  the  insect  in  which  they  are ;  but  they  vary  in  form  in  different 
insects.  They  are  hollow  (Fig.  162,5);  but  the  wall  of  the  scolopale 
is  almost  always  thickened  at  its  distal  end,  this  forming  an  end-knob 
(Fig.  162,  e^).  They  are  traversed  by  the  axis -fiber  of  the  sense-cell. 
The  vacuole  at  the  base  of  the  scolopale  connects  with  the  lumen  of 
the  scolopale;  this  vacuole  is  filled  with  watery 
fluid. 

In  Figure  163  is  shown  a  part  of  the  scolopo- 
phore represented  in  Figure  162,  more  enlarged 
(A),  and  three  cross-sections  (B,  C,  D)  of  the 
scolopale.  The  wall  of  the  scolopale  is  composed 
at  either  end  of  seven  ribs  (r),  each  of  which  is 
divided  in  the  central  portion,  making  fourteen 
ribs  in  this  part.  The  entire  scolopale,  except 
possibly  the  terminal  ligament,  is  bathed  in  the 
watery  liquid,  and  is  free  to  vibrate  (Hess  '17). 

It  should  be  remembered  that  the'  scolopalae  of 
different  insects  vary  greatly  in  form;    the  one 
is  merely  given  as  an  example  of 
one  type. 

The  simpler  forms  of  chordotonal  organs. — In  the  simplest  form 
of  a  chordotonal  organ  there  is  a  single  scolopophore;  usually,  how- 
ever, there  are  two  or  more  closely  parallel  scolopophores.  In  figure 
164,  which  represents  a  chordotonal  organ  found  in  the  next  to  the 
last  segment  of  the  body  of  a  larva  of  Chironomus,  these  two  types  are 
represented,  one  part  of  the  organ  being  composed  of  a  single  scolopo- 
phore, the  other  of  several. 

The  chordotonal  ligament. — In  Figure  164  the  nerve  connecting 
the  chordotonal  organ  with  the  central  nervous  system  is  represented 
at  n;  and  at  li  is  shown  a  structure  not  yet  mentioned,  the  chordo- 
tonal ligament,  which  is  found  in  many  chordotonal  organs.  Figure 
165  is  a  diagrammatic  representation  of  the  relations  of  the  chordo- 
tonal organs  of  a  larva  of  Chironomus  to  the  central  nervous  system 


Fig.  163.— Part  of  the 

scolopophore  shown 
in  Figure  162  more 

Hesir^^"^  (^^°"^  figured  here 


148 


AN  INTRODUCTION   TO  ENTOMOLOGY 


and  to  the  body-wall.     Here  each   chordotonal    organ   is  approxi- 
mately T-shaped;   the  proximal  nerve  forming  the  body    of  theT; 

the  scolopophore,  one 

arm;    and   the    chor- 
dotonal ligament,  the 

other  arm. 

It  will  be  observed 

that  in  this   type  of 

chordotonal  organ 

the  scolopophore  and 

the  ligament  form    a 

fiddle- string -like 

structure  between  two 

points  in  the  wall  of 

a  single  segment.     It 

is  believed  that  in  cases 

of  this  kind  the  integu-  Fig.    165.— Diagram 

,        ,                ,  representing    the 

mentactsasatympa-  chordotonal    organs 

Fig.  i64.-Chordotonal  organ    num     or     sounding  of  a  larva  of  CW 

of  a  larva  of   ChironoLs    board.  T'T"    ^ 

(From  Graber).  ,  '^^'^''• 


O.   THE  CHORDOTONAL  ORGANS  OF  LARV.E 

Chordotonal  organs  have  been  observed  in  so  many  larvae  that 
we  may  infer  that  they  are  commonly  present  in  larvce.  These  organs 
are  very  simple  compared  with  those  of  certain  adult  insects,  described 
later.  Those  figured  in  the  preceding  paragraphs  will  serv^e  to  illustrate 
the  typical  form  of  larval  chordotonal  organs.  Even  in  the  more 
complicated  ones,  there  are  comparatively  few  scolopophores ;  and,  as 
a  rule,  they  are  not  connected  with  specialized  t^nnpana,  but  extend 
between  distant  parts  of  the  body- wall,  which  probably  acts  as  a  sound- 
ing board. 

In  certain  larvse,  however,  the  scolopophores  are  attached  to 
specialized  areas  of  the  body-wall.  Hess  ('17)  has  shown  that  the 
pleural  discs  of  cerambycid  larvas,  which  are  situated  one  on  each  side 
of  several  of  the  abdominal  segments,  serve  as  points  of  attachment 
of  scolopophores. 


C.       THE  CHORDOTONAL  ORGANS  OF  THF  LOCUSTID^ 

In  the  Locustidae  there  are  highly  specialized  ears  situated  one  on 
each  side  of  the  first  abdominal  segment.     The  external  vibrating 


THE   INTERNAL   ANATOMY   OF  INSECTS 


149 


Fig.  1 66. — Side  view  of  a  locust  with  the  wings 
removed;    /,  tympanum. 


part  of  these  organs,  the  tympanum,  is  conspicuous,  being  a  thinned 
portion  of  the  body-wall  (Fig.  i66). 

Closely  applied  to  the 
inner  surface  of  each 
tympanum  (Fig.  167,  T), 
there  is  a  ganglion  known 
as  Muller's  organ  {go), 
first  described  by  Muller 
(1826).  This  ganglion 
contains  many  ganglion- 
cells  and  scolopalae  and  is  the  termination  of  a  nerve  extending 
from  the  central  nervous  system,  the  auditory  nerve  {n).  Figure 
168  represents  a  section  of  Muller's  organ,  showing  the  ganglion -cells 
and  scolopalse. 

Intimately  associated  with  the  Muller's  organ  are  two  horny 
processes  (Fig.  167,  o  and  ti)  and  a  pear-shaped  vesicle  (Fig.  167,  bi); 
and  near  the  margin 
of  the  tympantmi, 
there  is  a  spiracle 
(Fig.  167,  st),  which 
admits  air  to  a  space 
inside  of  the  tympa- 
num, the  tympanal 
air-chamber. 

As  the  nerve-end- 
ings in  Muller's  organ 
are  attached  to  the 
t}Tnpanum,  it  is  a 
chordotonal  organ 
of  the  integumental 
type;  it  is  attached 
to  a  vibratile  mem- 
brane, between  two 
air  spaces. 

d.        THE  CHORDOTO- 
NAL ORGANS  OF  THE 
TETTIGONIID^  AND 
OF  THE  GRYLLID^ 

In  the  long-horned  grasshoppers  and  in  the  crickets,  there  is  a  pai  r 
of  tympana  near  the  proximal  end  of  the  tibia  of  each  fore  leg.     In 


Fig.  167  — Ear  of  a  locust,  Caloptenus  ifa/icus,seeniTom 
inner  side;  T,  tympanum;  TR,  its  border;  o,ii,  two 
horn-like  processes;  5x,  pear-shaped  vesicle;  w,  audi- 
tory nerve;  ga,  terminal  ganglion  or  Muller's  organ; 
5<,  spiracle;  M,  tensor  muscle  of  the  tympanum  (From 
Packard  after  Graber). 


150 


AN  INTRODUCTION   TO  ENTOMOLOGY 


many  genera,  these  t>Tnpana  are  exposed  and  easily  obser\^ed  (Fig. 

169) ;   but  in  some  genera  each  is  covered  by  a  fold  of  the  body-wall 

and  is  consequently  within  a  cavity, 
which  communicates  with  the  out- 
side air  by  an  elongated  opening 
(Fig.  170,  a  and  b). 

Within  the  legs  bearing  these 
tympana,  there  are  complicated 
chordotonal  organs.  Very  de- 
tailed accounts  of  these  organs 
have  been  published  by  Graber 
('76),  Adelung  ('92)  and  Schwabe 
(06);  in  this  place,  for  lack  of 
fpace,  only  their  more  general 
features  can  be  described. 

Figure  171  represents  a  longi- 
tudinal section  of  that  part  of  a 
fore  tibia  of  Decticus  verrucivorus  in 
which  the  chordotonal  organs  are 
situated,  and  Figure  172  represents 
a  cross-section  of  the  same  tibia, 
passing  through  the  tympana  and 
scolo-  -(-i^g  air-chambers  formed  by  the 
folds  of  the  body- wall.  In  the  fol- 
lowing account  the  references,  in  most  cases,  are  to  both  of  these  figures. 


g- 


Fig 


168. — Section  of  MuUer's  organ; 
ganglion -cells;    h,  nerve;    s, 
palae  (After  Graber). 


Fore  leg  of  a  katydid;    i,  tympa- 


a 


Fig.  1 70. — Tibia  of  a  locustid 
with  covered  tympana;  a, 
front  view;  6,  side  view;  o, 
opening   (After  Schwabe). 


The  trachea  of  the  leg.— The  trachea  of  the  leg  figured  in  part  here 
is  remarkable  for  its  great  size  and  for  its  division  into  two  branches, 


THE   INTERNAL   ANATOAIY  OF  INSECTS 


151 


the  front  trachea  (Ti)  and  the  hind  trachea  (Te) ;   these  two  branches 

reunite  a  short  distance  beyond  the  end  of  the  chordotonal  organs. 

It  is  an  interesting 
fact  that  these  large 
tracheas  of  the  legs 
containing  the  chor- 
dotonal organs  open 
through  a  pair  of 
supernumery  spir- 
acles, differing  in  this 
respect  from  the  tra- 
chea of  the  other  legs. 
The  spaces  of  the 
leg.  —  By  reference 
to  Figure  172,  it  will 
be  seen  that  the  two 
branches  of  the  leg 
trachea  occupy  the 
middle  space  of  the 
leg  between  the  two 
tympana  (Tie  and 
j'iy  Tii)  and  separate  an 
outerspace,  theupper 
one  in  the  figure,  from 
an  inner  space.  The 
outer  space  (E)  con- 
tains a  chordotonal 
organ,  of  which  the 
scolopale  is  repre- 
sented at  S ;  and  the 
inner  space  contains 
small  trachese  (t) , 
muscles  (m) ,  the 
tibial  nerve  (Ntb), 
and  a  tendon  (Tn). 
The  interstices  of  the 
outer  and  inner  spaces 
are  filled  with  blood. 

In  the  outer  space  some  leucocytes  and  fat-cells  (Gr)  are  represented. 
The  supra-tympanal  or  subgenual  organ. — In  the  outer  space  of 

the  tibia,  a  short  distance  above  the  t>'mpana,  there  is  a  ganglion  (Fig. 


Fig.   171. — Longitudinal   section   of  a  fore  tibia  of 
Decticus  verrucivorus  (From  Berlese  after  Schwabe). 


152  ^iV  INTRODUCTION    TO  ENTOMOLOGY 

171,  Os)  composed  of  nerve-endings,  which  are  scolopophores  of  the 
integumental  type.     Two  nerves  extend  to  this  gangHon,  one  frcm 

each  side  of  the  leg,  and 
each  divides  into  many 
scolopophores.  The 
attachment  fibers  of  the 
scolopophores  converge 
and  are  attached  to  the 
wall  of  the  leg.  Two 
terms  have  been  applied 
to  this  organ,  both  indicat- 
ing its  position  in  the  leg; 
one  refers  to  the  fact  that 
it  is  above  the  tympana, 
the  other,  that  it  is  below 
the  knee. 

The    intermediate   or- 
gan.— Immediatelv  below 
Fig.  172. —Transverse  section  of  the  fore  tibia  of    fUp  oimrp  tvtnnflnal  nro-nn 
Decticus     verrucivorus    (From     Berlese    after   tfie  SUpra-tympanai  organ, 
Schwabe).     In  comparing  this  figure  with  the    and    betw^een    it    and    the 
preceding,  note  that  in  that  one  the  external 


parts  are  at  the  left,  in  this  one,  at  the  right. 


organ  described  in  the  next 


paragraph,  is  a  ganglion 
composed  of  scolopophores  of  the  subintegtmiental  type;  this  is 
termed  the  intermediate  organ  (Fig.  171,  Oi). 

Siebold's  organ  or  the  crista  acustica. — On  the  outer  face  of  the 
front  branch  of  the  large  trachea  of  the  leg  there  is  a  third  chordo- 
tonal  organ,  the  Siebold's  organ  or  the  crista  acusttca.  A  surface  view 
of  the  organ  is  given  in  Figure  171  and  a  cross-section  is  represented  in 
Figure  172.  It  consists  of  a  series  of  scolopophores  of  the  subintegu- 
mental  type,  which  diminish  in  length  toward  the  distal  end  of  the 
organ  (Fig.  171).  The  relation  of  Siebold's  organ  to  the  trachea  is 
shown  in  Figure  172.  It  forms  a  ridge  or  crest  on  the  trachea,  shown 
in  setion  at  cr  in  Figure  172 ;  this  suggested  the  name  crista  acustica, 
usedcby  some  writers. 

e.     THE  Johnston's  organ 

There  has  been  found  in  the  pedicel  of  the  antenna  of  many  insects, 
representing  several  of  the  orders,  an  organ  of  hearing,  which  is  known 
as  the  Johnston's  organ,  having  been  pointed  out  by  Christopher 
Johnston  (1855).     This  organ  varies  somewhat  in  form  in  different 


THE    INTERNAL   ANATOMY   OF   INSECTS 


153 


insects  and  in  the  two  sexes  of  the  same  species ;    but  that  of  a  male 
mosquito  will  serv^e  as  an  example  illustrating  its  essential  features. 

The  following 
account  is 
based  on  an  in- 
vestigation by 
Professor  Ch. 
M.  Child  ('94). 
In  an  an- 
tenna of  a  mos- 
quito (Fig.  173) 
the  scape  or 
first  segment, 
which  contains 
the  muscles  of 
the  antenna,  is 
much  smaller 
than  the  pedicel 
or  second  seg- 
ment, and  is 
usually  over- 
looked, being 
concealed  b  y 
the  large,  glob- 
ular pedicel; 
the  clavola  con- 
sists of  thirteen 
slender  seg- 
ments. Excepting  one  or  two  terminal  segments,  each  segment  of 
the  clavola  bears  a  whorl  of  long,  slender  sets;  these  are  more 
prominent  in  the  male  than  in  the  female. 

Figure  174  represents  a  longitudinal  section  of  the  base  of  an 
antenna;  in  this  the  following  parts  are  shown:  S,  scape;  P,  pedicel, 
C,  base  of  the  first  segment  of  the  clavola;  cp,  conjunctival  plate 
connecting  the  pedicel  with  the  first  segment  of  the  clavola;  pr, 
chitinous  processes  of  the  conjunctival  plate;  m,  muscles  of  the 
antenna;  N,  principal  antennal  nerve;  n,  nerve  of  the  clavola; 
immediately  within  the  wall  of  the  segments  there  is  a  thin  layer 
of  hypodermis;  the  lumen  of  the  pedicel  is  largely  occupied  by  a 
ganglion  composed  of  scolopophores,  the  attachment  fibers  of  which 
are  attached  to  the  chitinous  proce-^ses  of  the  conjunctival  plate. 


Fig.  173. — Antennae  of  mosquitoes,  Culex; 
female;    5,  scape;   p,  pedicel. 


154 


AN  INTRODUCTION   TO  ENTOMOLOGY 


As  to  the  action  of  the  auditory  apparatus  as  a  whole,  it  was  shown 
experimentally  by  Mayer  ('74)  that  the  different  whorls  of  setae  borne 
by  the  segments  of  the  clavola,  and  which  gradually  decrease  in  length 
on  successive  segments,  are  caused  to  vibrate  by  different  notes;  and 
it  is  believed  that  the  vibrations  of  the  setae  are  transferred  to  the 
conjunctival  plate  by  the  clavola,    and  thence   to  the  nerve-end- 

^^  ings. 

It  was  formerly 
believed  that  the 
great  specialization 
of  the  Johnston's  or- 
gan in  male  mosqui- 
toes enabled  the 
males  to  hear  the 
songs  of  the  females 
and  thus  more  readily 
to  find  their  mates. 
But  it  has  been  found 
that  in  some  species, 
at  least,  of  mosquitoes 
and  of  midges  in 
which  the  males 
have  this  organ 
highly  specialized  the 
females  seek  the  m^ales.  This  has  led  some  writers  to  doubt  that  the 
Johnston's  organ  is  auditory  in  function.  But  the  fact  remains  that 
its  distinctive  feature  is  the  presence  of  scolopalcC,  which  is  the  dis' 
tinctive  characteristic  of  the  auditory  organs  of  other  insects. 


Fig.  174. — Longitudinal  section  of  the  base  of  an  anten- 
na of  a  male  mosquito,  Corethra  culiciformis  (After 
Child). 


XIV.     SENSE-ORGANS  OF  UNKNOWN  FUNCTIONS 

In  addition  to  the  sense-organs  discussed  in  the  foregoing  account 
there  have  been  described  several  types  of  supposed  sense-organs 
which  are  as  yet  very  imperfectly  understood.  Among  these  there  is 
one  that  merits  a  brief  discussion  here  on  account  of  the  frequent 
references  to  it  in  entomological  literature.  Many  different  names 
have  been  apphed  to  the  organs  of  this  type;  of  these  that  of  sense- 
domes  is  as  appropriate  as  any,  unless  the  conclusions  of  Mclndoo, 
referred  to  below,  are  confim:ed^  in  which  case  his  term  olfactory  pores 
will  be  more  descriptive. 


THE    INTERNAL    ANATOMY   OF   INSECTS 


155 


Fig. 


a  b 

175. — Sense-domes  (From  Berlese). 


The  sense-domes  are  found  in  various  situations,  but  they  occur 
chiefly  on  the  bases  of  the  wings  and  on  the  legs.  Each  sense-dome 
consists  of  a  thin,  hemispherical  or  more  nearly  spherical  membrane, 

which  either  projects  from  the 
outer  end  of  a  pore  in  the 
cuticula  (Fig.  175,  a)  or  is 
more  or  less  deeply  enclosed 
in  such  a  pore  (Fig.  175,  6); 
intergrades  between  the  two 
types  represented  in  the  accom- 
panying figures  occur. 

When  a  sense-dome  is 
viewed  in  section  a  nerve- 
ending  is  seen  to  be  connected 
with  the  dome-shaped  or  bell- 
like membrane.  A  striking 
feature  of  these  organs  is  the 
absence  of  any  gland -cells  connected  with  them,  such  as  are  found 
in  the  chemical  sense-organs  described  on  an  earlier  page. 

In  one  very  important  respect  there  is  a  marked  difference  in  the 
accounts  of  these  organs  that  have  been  published.  The  organs  were 
first  discovered  long  ago  by  Hicks  ('57);  but  they  have  been  more 
carefully  studied  in  recent  years  by  several  writers,  who  have  been 
able  to  make  use  of  a  greatly  improved  histological  technic;  among 
these  writers  are  Berlese  ('09  a),  Vogel  ('n),  Hochreuter  (12'),  Lehr 
('14),  and  Mclndoo  ('14). 

All  of  the  writers  mentioned  above  except  the  last  named  maintain 
that  the  sense-cell  ends  in  a  structure,  in  the  middle  of  the  sense-dome, 
which  differs  in  appearance  from  both  the  membrane  of  the  sense- 
dome  and  the  body  of  the  sense-cell.  This 
structure  varies  in  form  in  different  sense- 
domes;  in  some  it  is  cylindrical,  and  is 
consequently  described  as  a  peg;  in  others, 
it  is  greatly  flattened  so  that  it  is  semilunar 
in  form  when  seen  in  section.  In  Figure 
175,  ^,  which  represents  a  section  made 
transversely  to  the  long  axis  of  this  part  it 
appears  peglike ;  but  in  Figure  175,0,  which 
represents  a  longitudinal  view  of  it,  it  is 
semilunar  in  form. 

According  to  Mclndoo  (Fig.   176)  no  structure  of  this  kind  is 


Fig.  176 — Olfactory  pore 
of  Mclndoo  (From 
Mclndoo) 


156  AN  INTRODUCTION   TO  ENTOMOLOGY 

present,  but  the  sense- fiber  of  the  sense-cell  pierces  the  bottom  of  the 
cone  and  enters  the  roimd,  oblong,  or  slitlike  pore-aperture.  "It  is 
thus  seen  that  the  cytoplasm  in  the  peripheral  end  of  the  sense- 
fiber  comes  in  direct  contact  with  the  air  containing  odorous  par- 
ticles and  that  odors  do  not  have  to  pass  through  a  hard  membrane 
in  order  to  stimulate  the  sense-cell  as  is  claimed  for  the  antenna! 
organs". 

XV.     THE  REPRODUCTIVE  ORGANS 

a.      THE    GENERAL    FEATURES 

In  insects  the  sexes  are  distinct.  Formerly  Termitoxema,  a  genus 
of  wingless,  very  aberrant  Diptera,  the  members  of  which  live  in  nests 
of  Termites,  was  believed  to  be  hermaphroditic,  but  this  is  now 
doubted. 

individuals  in  which  one  side  has  the  external  characters  of  the 
male  and  the  other  those  of  the  female  are  not  rare ;  such  an  individual 
is  termed  a  gynandromorph;  in  some  gynandromorphs,  both  testes 
and  ovaries  are  present  but  in  no  case  are  both  functional ;  these  there- 
fore are  not  true  hermaphrodites. 

In  females  the  essential  reproductive  organs  consist  of  a  pair  of 
ovaries,  the  organs  in  which  the  ova  or  eggs  are  developed,  and  a  tube 
leading  from  each  ovary  to  an  external  opening,  the  oviduct.  In  the 
male,  the  essential  reproductive  organs  are  a  pair  of  testes,  in  which 
the  spermatozoa  are  developed  and  a  tube  leading  from  each  testis  to 
an  external  opening,  the  vas  deferens.  In  addition  to  these  essential 
organs,  there  are  in  most  insects  accessory  organs,  these  consist  of 
glands  and  of  reservoirs  for  the  reproductive  elements. 

The  form  of  the  essential  reproductive  organs  and  the  number  and 
form  of  the  accessory  organs  vary  greatly  in  different  insects.  It  is 
impossible  to  indicate  the  extent  of  these  variations  in  the  limited 
space  that  can  be  devoted  to  this  subject  in  this  work.  Instead  of 
attempting  this  it  seems  more  profitable  to  indicate  by  diagrams,  one 
for  each  sex,  the  relations  of  the  accessory  organs  that  may  exist  to 
the  essential  organs. 

In  adult  insects  the  external  opening  of  the  reproductive  organs  is 
on  the  ventral  side  of  the  abdomien  near  the  caudal  end  of  the  body. 
The  position  of  the  opening  appears  to  differ  in  different  insects  and  in 
some  cases  in  the  two  sexes  of  the  same  species.  The  lack  of  uni- 
formity in  the  published  accounts  bearing  on  this  point  is  partly  due 
to  differences  in  numbering  the  abdominal  segments;  some  authors 
describing  the  last  segment  of  the  abdomen  as  the  tenth  while  others 


THE    INTERNAL   ANATOMY   OF   INSECTS  157 

believe  it  to  be  the  eleventh;    embryological  evidence  supports  the 
latter   view. 

In  most  insects  there  is  a  single  external  opening  of  the  reproduc- 
tive organs ;  but  in  the  Ephemerida  and  in  a  few  other  insects  the  two 
efferent  ducts  open  separately. 

Secondary  sexual  characters. — In  addition  to  differences  in  the 
essential  reproductive  organs  and  in  the  genital  appendages  of  the 
two  sexes,  many  insects  exhibit  what  are  termed  secondary  sexual 
characters.  Among  the  more  striking  of  these  are  differences  in  size, 
coloring,  and  in  the  form  of  certain  organs.  Female  insects  are 
usually  larger  than  the  males  of  the  same  species;  this  is  due  to  the 
fact  that  the  females  carry  the  eggs ;  but  in  those  cases  where  the  males 
fight  for  their  mates,  as  stag-beetles,  the  males  are  the  larger.  Strik- 
ing differences  in  the  color- 
I  ing  of  the  two  sexes  are 

A  common,  especially  in  the 

/   \  Lepidoptera.       In     many 

y(m  ^  insects  the  antennse  of  the 

/^^^  i^^  male     are     more     highly 

^^^■in  ll'l^^  specialized  than  those   of 

0'm$%,         Im^^^  the   female;      and  this  is 

M^Vi^'\tm  m^wy'^Wk  ^^^^  ^^^°  °^  ^^^  ^^^^  °^ 
P/'/ffllv'^t'l  ItllHt'fPl^  certain  insects.  These  are 
IHIiiflHW  li/i(nnl^  merely  a  few  of  the  many 
UH.\\E^^        ^IImM  known    secondary    sexual 

^^^Mw  i.¥  characters  found  in  insects. 


V^^     ^^  •  #        dc  b.       THE     REPRODUCTIVE 

^••■■%  \\:      1^      ^  Fig.  178  — 

^SX//  /"^^^  ORGANS  OF  THE  Repro- 

^f         /^        M  FEMALE  ductive 

ft  I       ff^iijM^  organs  of 

•  -  -  -  -I  ^0iJ^=^          '^^^  general  features  of  Japyx, 
--.     I  f^--X3)  /p.  the  ovary.— In   the  more  ^f?*^^^ 
fp\    fi'  I      — CZL                                                               •  (After 
H  v^;  v;>'-S5ac=;^  usual  form  of  the  ovaries  Grassi). 

IeJ    ^^  of  insects,  each   ovary  is 

Fig.  177.— Diagram  of  thereproduc-   a    compact,    more    or  less    spindle- 

tive  organs  of  a  female  insect;   o,      .  ,  .      ,  j    j.  . 

ovary;  orf, oviduct;  c,  egg-calyx;  v,  shaped  body  composed  of  many  paral- 

vagina;  5,spermatheca;   6c, bursa   lei  ovarian  tubes  (Fig.  177,  o) ,  which 

copulatrix;      sg,  spermathecal  .    ,  rr         *.  -i.    u 

gland;  eg,  colleterial  glands.  open  mto  a  common  efferent  tube, 

the  oviduct.     In  Campodea,  however, 

there  is  a  single  ovarian  tube;    and  in  certain  other  Thysanura  the 

ovarian  tubes  have  a  metameric  arrangement  (Fig.  178).     The  nimi- 


158 


AN  INTRODUCTION   TO   ENTOMOLOGY 


ber  of  ovarian  tubes  differs  greatly  in  different  insects;  in  many 
Lepidoptera  there  are  only  four  in  each  ovary;  in  the  honeybee, 
about  150;   and  in  some  Termites,  3000  or  more. 

The  wall  of  an  ovarian  tube..— The  ovarian  tubes  are  lined  with 
an  epithelial  layer,  which  is  supported  by  a  basement  membrane;   out- 
side of  this  there  is  a  peritoneal  envelope,  composed  of  connective  tis- 
sue;   and  sometimes  there  are  muscles  in  the  peritoneal  envelope. 
The  zones  of  an  ovarian  tube. — Three  different  sections  or  zones  are 
recognized   in   an   ovarian   tube;     first, 
the    terminal    filament,    which    is    the 
slender  portion  which  is  farthest  from 
the  oviduct  (Fig.   179,  t);    second,  the 
germarium,  this  is  a  comparatively^  short 
chamber,  between  the  other  two  zones 
(Fig.  179,  g);   and  third,  the  vitellarium, 
which  constitutes  the  greater  portion  of 
the  ovarian  tube. 

The  contents  of  an  ovarian  tube. — In 
the  germarium  are  found  the  primordial 
germ-cells  from  which  the  eggs  are  devel- 
oped; and  in  the  vitellarium  are  found 
the  developing  eggs.  In  addition  to  the 
cells  that  develop  into  eggs  there  are 
found,  in  the  ovarian  tubes  of  m.any 
insects,  cells  whose  function  is  to  furnish 
nutriment  to  the  developing  eggs;  these 
are  termed  nurse-cells. 

Depending  upon  the  presence  cr  ab- 
sence of  nurse-cells  and  on.  the  location  of 
the  nurse-cells  when  present,  three  types 
of  ovarian  tubes  are  recognized:  first, 
those  without  distinct  nurse-cells  (Fig. 
179,  A) ;  second,  those  in  which  the  eggs 
and  masses  of  nurse-cells  alternate  in  the 
ovarian  tube  (Fig.  179,  B);  and  third, 
those  in  which  the  nurse-cells  are 
restricted  to  the  germarium  (Fig.  179,  C),  which  thus  becomes  a  nutri- 
tive chamber.  In  the  latter  type  the  developing  eggs  are  each  con- 
nected by  a  thread  with  the  nutritive  chamber. 

The  egg-follicles. — The  epitheliimi  lining  of  the  ovarian  tube 
becomes  invaginated  between  the  eggs  in  such  a  way  that  each  egg  is 


Fig.  179. — Three  types  of 
ovarian  tubes;  e,  e,  e, 
eggs;     n,  n,  n,  nurse-cells 

(After  Berlese). 


THE   INTERNAL   ANATOMY  OF  INSECTS  159 

enclosed  in  an  epithelial  sac  or  egg-follicle,  which  passes  down  the  tube 
with  the  egg  (Fig.  179).  There  is  thus  a  tendency  to  strip  the  tube  of 
its  epithelium,  but  a  new  one  is  constantly  formed. 

The  functions  of  the  follicular  epithelium. — It  is  believed  that  in 
some  cases,  and  especially  where  the  nurse-cells  are  wanting,  the 
follicular  epitheliiun  serves  a  nutritive  function.  Bat  the  most 
obvious  function  of  this  epithelium  is  the  formation  of  the  chorion  or 
egg-shell,  which  is  secreted  on  its  inner  surface.  The  pit-like  mark- 
ings so  common  on  the  shells  of  insect  eggs  indicate  the  outlines  of  the 
cells  of  the  follicular  epithelium. 

The  ligament  of  the  ovary. — In  many  insects,  the  terminal  fila- 
ments of  the  several  ovarian  tubes  of  an  ovary  unite  and  form  a 
slender  cord,  the  ligament  of  the  ovary,  which  is  attached  to  the  dorsal 
diaphragm ;  but  in  other  insects  this  ligament  is  wanting,  the  terminal 
filaments  ending  free  in  the  body  cavity. 

The  oviduct. — The  common  outlet  of  the  ovarian  tubes  is  the  ovi- 
duct (Fig.  177,  od).  In  most  insects  the  oviducts  of  the  two  ovaries 
unite  and  join  a  common  outlet,  the  vagina;  but  in  the  Ephemerida 
and  in  some  Dermaptera  each  oviduct  has  a  separate  opening. 

The  egg-calyx. — In  some  insects  each  oviduct  is  enlarged  so  as  to 
form  a  pouch  for  storing  the  eggs,  these  pouches  are  termed  the  egg- 
calyces  (Fig.  1 7  7 ,  c) . 

The  vagina. — The  tube  into  which  the  oviducts  open  is  the  vagina 
(Fig.  177,  v).  The  vagina  differs  in  structure  from  the  oviducts,  due 
to  the  fact  that  it  is  an  invagination  of  the  body-wall,  and,  like  other 
invaginations  of  the  body-wall,  is  lined  with  a  cuticular  layer. 

The  spermatheca — The  spermatheca  is  a  sac  for  the  storage  of  the 
seminal  fluid  (Fig.  177,5).  As  the  pairing  of  the  sexes  takes  place  only 
once  in  most  insects  and  as  the  egg-laying  period  may  extend  over  a 
long  time,  it  is  essential  that  provision  be  made  for  the  fertilization  of 
the  eggs  developed  after  the  union  of  the  sexes.  The  eggs  become  frll- 
grown  and  each  is  provided  with  a  shell  before  leaving  the  ovarian 
tubis.  At  the  time  an  egg  is  laid  a  spermatozoan  may  pass  from  the 
spermatheca,  where  thousands  of  them  are  stored,  into  the  egg  through 
an  opening  in  the  shell,  the  mncropyle,  which  is  described  in  the  next 
chapter  (Fig.  184  and  185). 

In  some  social  insects,  eggs  that  are  developed  years  after  the 
pairing  took  place  are  fertilized  by  spermatozoa  that  have  been  stored 
in  the  spermatheca. 

The  bursa  copulatrix. — In  many  insects  there  is  a  pouch  for  the 
reception  of  the  seminal  fluid  before  it  passes  to  the  spermatheca. 


160 


AN  INTRODUCTION   TO  ENTOMOLOGY 


This  pouch  is  known  as  the  bursa  copulatrix  or  copulatory  pouch.  In 
some  insects  this  pouch  is  a  diverticulum  of  the  vagina  (Fig.  177,  he); 
in  others  it  has  a  distinct  external  opening,  there  being  two  external 
openings  of  the  reproductive  organs,  the  opening  of  the  vagina  and  the 
opening  of  the  bursa  copulatrix. 

When  the  bursa  copulatrix  has  a  distinct  external  opening  there 
may  or  may  not  be  a  passage  from  it  to  the  vagina.  In  at  least  some 
Orthoptera  {Melanoplus)  there  is  no  connection  between  the  two; 

when  the  eggs  are  laid  they  are 
pushed  past  the  opening  of  the 
bursa  copulatrix  where  they  are 
fertilized. 

In  the  Lepidoptera  (Fig.  180), 
there  is  a  passage  from  the  bursa 
copulatrix  to  the  vagina.  In 
this  case  the  seminal  fluid  is 
I'eceived  by  the  bursa  copulatrix 
at  the  time  of  pairing,  later  it 
passes  to  the  spermatheca,  and 
from  here  it  passes  to  the  vagina. 
A  bursa  copulatrix  is  said  to 


Fig.  180. — Reproductive  organs  of  the 
female  of  the  milkweed  butterfly;  o, 
anus;  b, opening  of  the  bursa  copula- 
trix; ov,  ovarian  tubes;  /,  terminal 
filaments  of  the  ovary;  v,  opening 
of  the  vagina  (After  Burgess). 


be  wanting  in  Hymenoptera,  Diptera,  Heteroptera  and  Homoptera 
except  the  Cicadas. 

The  coUeterial  glands. — There  are  one  or  two  pairs  of  glands  that 
open  into  the  vagina  near  its  outlet  (Fig.  177,  eg) ;  to  these  has  been 
applied  the  general  term  coUeterial  glands.  Their  function  differs  in 
different  insects ;  in  some  insects  they  secrete  a  cement  for  gluing  the 
eggs  together,  in  others  they  produce  a  capsule  or  other  covering 
which  protects  the  eggs. 

The  spermathecal  gland. — In  many  insects  there  is  a  gland  that 
opens  either  into  the  spermatheca  or  near  the  opening  of  the  sperma- 
theca, this  is  the  spermathecal  gland  (Fig.  177,  sg). 


C.       THE  REPRODUCTIVE  ORGANS  OF  THE  MALE 

The  reproductive  organs  of  the  male  are  quite  similar  in  their  more 
general  features  to  those  of  the  female ;  but  there  are  striking  differ- 
ences in  details  of  form. 

The  general  features  of  the  testes. — As  the  reproductive  elements 
developed  in  the  testes,  the  spermatazoa,  always  remain  small,  the 
testes  of  a  male  are  usually  much  smaller  than  the  ovaries  of  the  female 
of  the  same  species. 


THE   INTERNAL   ANATOMY   OF  INSECTS 


161 


In  the  more  common  form,  each  testis  is  a  compact  body  (Fig. 
i8i,  /)  composed  of  a  variable  number  of  tubes  corresponding  with 
the  ovarian  tubes,  these  are  commonly  called 
the  testicular  follicles;  but  it  would  have  been 
better  to  have  termed  them  the  testicular  tubes, 
reserving  the  term  follicle  for  their  divisions. 

The  testicular  follicles  vary  in  number, 
form,  and  in  their  arrangement.  In  many 
insects  as  the  Neuroptera,  the  Hemiptera,  the 
Diptera,  and  in  Campodea  and  Japyx,  each 
testis  is  composed  of  a  single  follicle.  In  some 
beetles,  Carabidae  and  Elateridse,  the  follicle 
is  long  and  rolled  into  a  ball.  In  some  Thy- 
sanura  the  testicular  follicles  have  a  metameric 
arrangement. 

In  some  Coleoptera,  each  testis  is  separated 
into  several  masses,  each  having  its  own  outlet 
leading  to  the  vas  deferens;  while  in  some 
other  insects  the  two  testes  approach  each  other 
during  the  pupal  stage  and  constitute  in  the 
adult  a  single  mass. 

The  structure  of  a  testicular  follicle.— Like 
the  ovarian  tubes,  the  testicular  follicles  are 
lined  with  an  epithelial  layer,  which  is  sup- 
ported by  a  basement  membrane,  outside  of 
which  there  is  a  peritoneal  envelope  composed 
And  in  these  follicles  a  series  of  zones  are 
distinguished  in  which  the  genital  cells  are  found  in  different  stages 
of  development,  corresponding  to  the  successive  generations  of  these 
cells.  In  addition  to  the  terminal  filament  four  zones  are  recog- 
nized as  follows: 

The  germarium. — This  includes  the  primordial  germ-cells  and  the 
spermatogonia. 

The  zone  of  growth. — Here  are  produced  the  spermatocytes  of  the 
first  order  and  the  spermatocytes  of  the  second  order. 

The  zone  of  division  and  reduction. — In  this  zone  are  produced  the 
Spermatids  or  immature  spermatozoa. 

The  zone  of  transformation. — Here  the  spermatids  become  sper- 
matozoa. 

A  discussion  of  the  details  of  the  development  of  the  successive 
generations  of  the  genital  cells  of  the  male,  or  spermatogenesis,  does 
not  fall  within  the  scope  of  this  volimie. 


Fig.  i8i. — Diagram  of 
the  reproductive  or- 
gans of  a  male  insect ; 
the  right  testis  is  shown 
in  section;  ag,  acces- 
sory glands;  ed,  eja- 
culatory  duct ;  sv,  semi- 
nal vesicles;  /,  testes; 
vd,  vasa  deferentia. 

of  connective  tissue. 


162  AN  INTRODUCTION   TO  ENTOMOLOGY 

The  spermatophores. — In  some  insects  the  spermatozoa  become 
enveloped  in  a  sac  in  which  they  are  transferred  to  the  female;  this 
sac  is  the  spermatophore.  Spermatophores  have  been  observed  in 
Gryllidas,  Locustidae,  and  certain  Lepidoptera. 

Other  structures. — A  ligament  of  the  testis,  corresponding  to  the 
ligament  of  the  ovary,  is  often  present ;  the  common  outlet  of  the  testi- 
cular follicles,  corresponding  to  the  oviduct  is  termed  the  vas  deferens 
(Fig.  181,  vd);  an  enlarged  portion  of  the  vas  deferens  serving  as  a 
reservoir  for  the  products  of  the  testis  is  known  as  a  seminal  vesicle 
(Fig.  181,  sv);  the  invaginated  portion  of  the  body-wall,  correspond- 
ing with  the  vagina  of  the  female,  is  the  ejaculatory  duct  (Fig.  181,  ed); 
accessory  glands,  corresponding  to  the  colleterial  glands  of  the  female, 
are  present  (Fig.  181,  ag);  the  function  of  these  glands  has  not  been 
determined,  they  may  secrete  the  fluid  part  of  the  semen,  and  they 
probably  secrete  the  spermatophore  when  one  is  formed;  tJw  penis, 
this  is  merely  the  chitinized  terminal  portion  of  the  ejaculatory  duct, 
which  can  be  evaginated  with  a  part  of  the  invaginated  portion  of  the 
body-wall.  It  is  furnished  with  powerful  muscles  for  its  protrusion 
and  retraction. 

XVI.     THE  SUSPENSORIA  OF  THE  VISCERA 

The  organs  discussed  here  do  not  constitute  a  well-defined  system, 
but  are  isolated  structures  connected  with 
different  viscera.  As  in  most  cases  they 
appear  to  serve  a  suspensory  function,  they 
are  grouped  together  provisionally  as  the  sus- 
pensoria  of  the  viscera. 

The  dorsal  diaphragm. — This  is  a  mem- 
branous structure  which  extends  across  the 
abdominal    cavity    immediately    below   the 

„.      „       ^.  ,  heart,  to  which  it  is  attached  along  its  median 

Fig.  182.— Diagram  show-  o^u     w       1  •  c  ^u-     a-      u 

mg  the  relation  of  the  hne.      The  lateral  margms  of  this  diaphragm 

dorsal  diaphragm  and  are  attached  to  the  sides  of  the  body  by  a 
the  ventral  diaphragm  .  .  ^    .  ,  ,  .  .  ■  ■,   . 

to    other    viscera;    a,  senes  of  triangular  prolongations,  which  have 

ahmentary     canal;    d,  been  commonly  known  as  the  wings  of  the 

dorsal   diaphragm;      h,  ,  ._.  x       ^,        •,  1    i-      ,  • 

heart;  n,  ventral  nerv-  heart  [Fig.  1^9,  c).     The  dorsal  diaphragm  IS 

dS  J^^*^"^'   ^'  ^^"^^^^    composed  largely  of  very  delicate  muscles. 
Its  relation  to  the  heart  is  illustrated  by  the 
accompanying  diagram  (Fig.  182,  d). 

There  are  differences  of  opinion  as  to  the  function  of  the  dorsal 
diaphragm.     An  important  function  is  probably  to  protect  the  heart 


THE   INTERNAL   ANATOMY   OF  INSECTS  163 

from  the  peristaltic  movements  of  the  aHmentary  canal.      It  also 
supports  the  heart;   and  it  may  play  a  part  in  its  expansion. 

The  dorsal  diaphragm  is  also  known  as  the  pericardial  diaphragm. 

The  ventral  diaphragm. — The  ventral  diaphragm  is  a  very  delicate 
membrane  which  extends  across  the  abdominal  cavity  immediately 
above  the  ganglia  of  the  central  nervous  system.  It  is  quite  similar 
in  form  to  the  dorsal  diaphragm;  it  is  attached  along  each  side  of 
the  body,  just  lateral  of  the  great  ventral  muscles,  by  a  series  of  pro- 
longations resembling  in  form  the  wings  of  the  heart.  The  position  of 
the  ventral  diaphragm  is  illustrated  in  Figure  182,  y. 

This  diaphragm  has  been  described  as  a  ventral  heart;  but  I 
believe  that  its  function  is  to  protect  the  abdominal  gangHa  of  the 
central  nervous  system  from  the  peristaltic  movements  of  the  alimen- 
tary canal. 

The  thread-like  suspensoria  of  the  viscera. — Under  this  head  may 
be  classed  the  ligament  of  the  ovary  and  the  ligament  of  the  testis, 
already  described.  In  addition  to  these,  there  is,  in  some  insects  at 
least,  a  thread-like  ligament  that  is  attached  to  the  intestine. 

XVII.     SUPPLEMENTARY   DEFINITIONS 

There  are  found  in  the  bodies  of  insects  certain  organs  not  referred 
to  in  the  foregoing  general  account  of  the  internal  anatomy  of  insects. 
These  organs,  though  doubtless  very  important  to  the  insects  in  which 
they  occur,  are  not  likely  to  be  studied  in  an  elementary  course  in 
entomology  and,  therefore,  a  detailed  account  of  them  may  well  be 
omitted  from  an  introductory  text-book.  This  is  especially  true  as 
our  knowledge  of  the  structure  and  functions  of  these  organs  is  so 
incomplete  that  an  adequate  discussion  of  the  conflicting  views  now 
held  would  require  more  space  than  can  be  devoted  to  it  here.  The 
organs  in  question  are  the  following: 

The  oenocytes. — The  term  cenocytes  is  applied  to  certain  very  large 
cells,  that  are  fotmd  in  clusters,  often  metamerically  arranged,  and 
connected  with  the  tracheae  and  the  fat  body  of  insects.  The  name 
was  suggested  by  the  Hght  yellow  color  which  often  characterizes 
these  cells,  the  color  of  certain  wines ;  but  the  name  is  not  a  good  one, 
as  oenocytes  vary  greatly  in  color.  Several  otlier  names  have  been 
applied  to  them  but  they  are  generally  known  by  the  name  used  here. 
Two  types  of  oenocytes  are  recognized:  first,  the  larval  oenocytes; 
and  second,  the  imaginal  oenocytes. 


164  AN  INTRODUCTION   TO  ENTOMOLOGY 

The  larv'al  oenocytes  are  believed  by  Verson  and  Bisson  ('91)  to  be 
ductless  glands  which  take  up,  elaborate,  and  return  to  the  blood 
definite  substances,  which  may  then  be  taken  up  by  other  cells  of  the 
body.  Other  views  are  held  by  other  writers,  but  the  view  given 
above  seems,  as  this  time  to  be  the  one  best  supported  by  the  evidence 
at  hand. 

As  to  the  function  of  the  imaginal  oenocytes,  there  are  some  obser- 
vations that  seem  to  show  that  they  are  excretory  organs  without 
ducts,  cells  that  serve  as  storehouses  for  excretory  products,  becoming 
more  filled  with  these  products  with  the  advancing  age  of  the  insect. 

The  pericardial  cells. — The  term  pericardial  cells  is  applied  to  a 
distinct  type  of  cells  that  are  found  on  either  side  of  the  heart  in  the 
pericardial  sinus  or  crowded  between  the  fibers  of  the  pericardial 
diaphragm. 

These  cells  can  be  rendered  very  conspicuous  by  injecting  ammonia 
carmine  into  the  living  insect  some  time  before  killing  and  dissecting 
it;  by  this  method  the  pericardial  cells  are  stained  deeply  while  the 
other  cells  of  the  body  remain  uncolored. 

It  is  believed  that  the  pericardial  cells  absorb  albimiinoids  origina- 
ting from  the  food  and  transform  them  into  assimilable  substances. 

The  phagocytic  organs.— The  term  phagocyte  is  commonly  applied 
to  any  leucocyte  or  white  blood  corpuscle  that  shows  special  activity 
in  ingesting  and  digesting  waste  and  harmful  materials,  as  disinte- 
grating tissue,  bacteria,  etc.  The  action  of '  phagocytes  is  termed 
phagocytosis;  an  excellent  example  of  phagocytosis  is  the  part  played 
by  the  leucocytes  in  the  breaking  down  and  rebuilding  of  tissues  in  the 
course  of  the  metamorphosis  of  insects;  this  is  discussed  in  the  next 
chapter. 

Phagocytosis  may  take  place  in  any  part  of  the  body  bathed  by  the 
blood  and  thus  reached  by  leucocj^tes.  In  addition  to  this  widely 
distributed  phagocytosis,  it  is  believed  that  in  certain  insects  there  are 
localized  masses  of  cells  which  perform  a  similar  function;  these 
masses  of  cells  are  known  as  the  phagocytic  organs. 

Phagocytic  organs  have  been  found  in  many  Orthoptera  and  in 
earwigs;  they  are  situated  in  the  pericardial  region;  and  can  be  made 
conspicuous  by  injecting  a  mixture  of  ammonia  carmine  and  India  ink 
into  the  body  cavity ;  by  this  method  the  pericardial  cells  are  stained 
red  and  the  phagocytic  organs  black. 

The  light-organs. — The  presence  of  organs  for  producing  light  is 
widely  distributed  among  living  forms  both  animal  and  vegetable. 


THE    INTERNAL    ANATOMY   OF  INSECTS  165 

The  most  commonly  observed  examples  of  light-producing  insects  are 
certain  members  of  the  Lampyridae,  the  fireflies  and  the  glow-worms, 
and  a  member  of  the  Elateridce,  the  "cucujo"  of  the  tropics.  With 
these  insects  the  production  of  light  is  a  normal  function  of  highly 
specialized  organs,  the  light-organs. 

Examples  of  insects  in  which  the  production  of  light  is  occasionally 
observed  are  larvse  of  mosquitoes,  and  certain  lepidopterous  larvs;. 
In  these  cases  the  production  of  light  is  abnormal,  being  due  either  to 
the  presence  in  the  body  of  light -producing  bacteria  or  to  the  ingestion 
of  luminescent  food. 

The  position  of  the  specialized  light-organs  of  insects  varies 
greatly;  in  the  fireflies,  they  are  situated  on  the  ventral  side  of  the 
abdomen;  in  the  glow-worms,  along  the  sides  of  the  abdomen;  and  in 
the  cucujo,  the  principal  organs  are  in  a  pair  of  tubercles  on  the  dorsal 
side  of  the  prothorax  and  in  a  patch  in  the  ventral  region  of  the 
metathorax. 

The  structure  of  the  light-organs  of  insects  varies  in  different 
insects,  as  is  shown  by  the  investigations  of  several  authors.  A  good 
example  of  highly  specialized  light-organs  are  those  of  Photinus 
marginellus,  one  of  our  common  fireflies.  An  excellent  account  of 
these  is  that  of  Miss  Townsend  ('04),  to  which  the  reader  is  referred. 
A  detailed  accotmt  of  the  origin  ana  development  of  the  light-organs 
of  Phoiurus  pennsylvanica  is  given  by  Hess  ('22). 


CHAPTER   IV. 
THE  METAMORPHOSIS  OF  INSECTS 

Many  insects  in  the  course  of  their  Hves  undergo  remarkable 
changes  in  form ;  a  butterfly  was  once  a  caterpillar,  a  bee  lived  first  the 
life  of  a  clumsy  footless  grub,  and  flies,  which  are  so  graceful  and  active, 
are  developed  from  maggots. 

In  the  following  chapters  considerable  attention  is  given  to 
descriptions  of  the  changes  through  which  various  insects  pass;  the 
object  of  this  chapter  is  merely  to  discuss  the  more  general  features  of 
the  metamorphosis  of  insects,  and  to  define  the  terms  commonly  used 
in  descriptions  of  insect  transformations. 

I.     THE  EXTERNAL  CHARACTERISTICS  OF  THE  META- 
MORPHOSIS OF   INSECTS 

The  more  obvious  characteristics  of  the  metamorphosis  of  insects 
are  those  changes  in  the  external  form  of  the  body  that  occur  during 
postembrv^onic  development.  In  some  cases  there  appears  to  be  but 
little  in  common  between  the  successive  forms  presented  by  the  same 
insect,  as  the  caterpillar,  chrysalis,  and  adult  stages  of  a  butterfly. 
On  the  other  hand,  in  certain  insects,  the  change  in  the  form  of  the 
body  during  the  postembryonic  life  is  comparatively  little.  Based 
on  these  differences,  several  distinct  types  of  metamorphosis  have 
been  recognized;  and  in  those  cases  where  the  insect  in  its  successive 
stages  assumes  different  forms,  distinctive  terms  are  applied  to  the 
different  stages. 

a.       THE    EGG 

Strictly  speaking,  all  insects  are  developed  from  eggs,  which  are 
formed  from  the  primordial  germ-cells  in  the  ovary  of  the  female. 
As  a  rule,  each  egg  is  surrounded  by  a  shell,  formed  by  the  follicular 
epithelium  of  the  ovarian  tube  in  which  the  egg  is  de\-eloped;  and 
this  egg,  enclosed  in  its  shell,  is  deposited  by  the  female  insect,  usually 
on  or  near  the  food  upon  which  the  young  insect  is  to  feed.  In  some 
cases,  however,  the  egg  is  retained  by  the  female  until  it  is  hatched; 
thus  flesh-flies  frequently  deposit  active  larvae  upon  meat,  especially 
when  they  have  had  difficulty  in  finding  it ;  and  t'.  ere  are  other  vivi- 
parous insects,  which  are  discussed  later.       In  tlr'.s  place  is  discussed 

(166) 


THE   METAMORPHOSIS   OF  INSECTS 


167 


i 


the  more  common  type  of  insect  eggs,  those  that  are  laid  while  still 

enclosed  in  their  shell. 

The  shape  of  the  egg. — The  terms  ovoid  and  ovate  have  a  definite 

meaning  which  has  been  derived  from  the  shape  of  the  eggs  of  birds ; 

but  while  many  eggs  of 
insects  are  ovate  in  form, 
many  others  are  not. 

The  more  common 
form  of  insect  eggs  is 
an  elongate  oval,  some- 
what curved;  this  type  is 
illustrated  by  the  eggs 
of  crickets  (Fig.  183,  i); 
many  eggs;  are  approx- 
imately spherical,  as  those 
of  some  butterflies  (Fig. 
183,  2) ;  while  some  are  of 
remarkable  shape,  two  of 
these  are  represented  in 
Figure  183,3,  4. 

The  sculpture  of  the 
shell. — Almost  always  the 
external  surface  of  the  shell 

of  an  insect  egg  is  marked  with  small,  hexagonal  areas;   these  are  the 

imprints  of  the  cells  of  the  follicular  epi- 
thelium, which  formed    the   shell.     In 

many   cases  the  ornamentation  of  the 

shell  is  very  conspicuous,  consisting  of 

prominent  ridges  or  series  of  tubercles ; 

this  is   well -shown  in  the  eggs  of  many 

Lepidoptera  (Fig.  184). 

The  micropyle. — It  has  been  shown, 

in  the  course  of  the  discussion  of    the 

reproductive  organs  of  the  female,  that 

the   egg   becomes  full-grown,    and  the 

protecting  chorion  or  egg-shell  is  formed 

about  it  before  it  is   fertilized.     This 

renders  necessary  some  provision  for  the 

entrance  of  the  male  germ -cell  into  the 

egg;    this  provision  consists  of  one  or 

more  openings  in  the  shell  through  which  a  spermatozoan  may  enter 

This  opening  or  group  of  openings  is  termed  the  micropyle. 


Fig.  183. — Eggs  of  insects;  i,  CEcanthus  nigri- 
cornis;  2,  CEnis  semidea;  3,  Piezosterum 
stibiilatum;   4,  Hydrometra  ntarlini. 


Fig.  184.— Egg  of  the  cotton- 
worm  moth;  the  micropyle  is 
shown  in  the  center  of  the  lower 
figure. 


168  AN  INTRODUCTION   TO  ENTOMOLOGY 

The  number  and  position  of  the  micropylar  openings  varies  greatly 
in  the  eggs  of  different  insects.  Frequently  they  present  an  elaborate 
pattern  at  one  pole  of  the  egg  (Fig.  184);  and  sometimes  they  open 
through  more  or  less  elongated  papillse  (Fig.  185). 

While  in  most  cases  it  is  necessary  that  an  egg  be  fertilized  in  order 
that  development  may  continue;  there  are  many  instances  of  par- 
thenogenesis among  insects. 

The  number  of  eggs  produced  by  insects. — 
A  very  wide  variation  exists  in  the  niimber  of 
eggs  produced  by  insects.  In  the  sheep-tick,  for 
example,  a  single  large  egg  is  produced  at  a  time, 
and  but  few  are  produced  during  the  life  of  the 
insect;  on  the  other  hand,  in  social  insects,  as 
ants,  bees,  and  termites,  a  single  queen  may 
produce  hundreds  of  thousands  of  eggs  during  her 
lifetime. 

These,  however,  are  extreme  examples;    the 
Fig.     185.— Egg  at    peculiar  mode  of  development  of  the  larva  of  the 

Drosophilamelan-    gheep-tick  within  the  body  of  the  female  makes 

ogaster;  m,  micro-  '^  ■' 

pyle.  possible  the  production  of  but  few  eggs;    while 

the  division  of  labor  in  the  colonies  of  social  insects,  by  which  the  func- 
tion of  the  queen  is  merely  the  production  of  eggs,  makes  it  possible 
for  her  to  produce  an  immense  number;  this  is  especially  trae  where 
the  egg-laying  period  of  the  queen  extends  over  several  years. 

The  following  may  be  taken  as  less  extreme  examples.  In  the 
solitary  nest-building  insects,  as  the  fossores,  the  soHtary  wasps,  and 
the  solitary  bees,  the  great  labor  involved  in  making  and  provisioning 
the  nest  results  in  the  reduction  of  the  number  of  eggs  produced  to  a 
comparatively  small  nimiber ;  while  many  insects  that  make  no  pro- 
vision for  their  young,  as  moths,  for  example,  may  lay  several  hundred 
eggs. 

With  certain  chalcis-flies  the  mmiber  of  young  produced  is  not 
dependent  upon  the  number  of  eggs  laid;  for  with  these  insects  many 
embryos  are  developed  from  a  single  egg.  This  type  of  development 
is  termed  polyembryony. 

Modes  of  laying  eggs. — Perhaps  in  no  respect  are  the  wonderful 
instincts  of  insects  exhibited  in  a  more  remarkable  way  than  in  the 
manner  of  lajdng  their  eggs.  If  insects  were  reasoning  beings,  and  if 
each  female  knew  the  needs  of  her  young  to  be,  she  could  not  more 
accurately  make  provision  for  them  than  is  now  done  by  the  great 
majority  of  insects. 


THE    METAMORPHOSIS   OF  INSECTS 


169 


This  is  especially  striking  where  the  life  of  the  young  is  entirely 
different  from  that  of  the  adult.  The  butterfly  or  moth  may  sip 
nectar  from  any  flower;  but  when  the  female  lays  her  eggs,  she  selects 
with  unerring  accuracy  the  particular  kind  of  plant  upon  which  her 
larvae  feed.  The  dragonfly  which  hunts  its  prey  over  the  field,  returns 
to  water  and  lays  her  eggs  in  such  a  position  that  the  young  when  it 
leaves  the  egg  is  either  in  or  can  readily  find  the  element  in  which  alone 
it  is  fitted  to  live. 

The  ichneumon-flies  frequent  flowers;  but  when  the  time  comes 
for  a  female  to  lay  her  eggs,  she  seeks  the  particular  kind  of  larva 
upon  which  the  species  is  parasitic,  and  will  lay  her  eggs  in  no  other. 
It  is  a  remarkable  fact  that  no  larva  leads  so  secluded  a  life  that  it 
cannot  be  found  by  its  parasites.  Thus  the  larvae  of  Tremex  Columba 
bore  in  soHd  wood,  where  they  are  out  of  sight  and  protected  by  a 
layer  of  wood  and  the  bark  of  the  tree  in  which  they  are  boring; 

nevertheless  the  ichneumon-fly 
Thalessa  lunator,  which  is  para- 
sitic upon  it,  places  her  eggs  in 
the  burrows  of  the  Tremex  by 
means  of  her  long  drill-like 
ovipositor  (Fig.  i86). 

In  contrast  with  the  exam- 
ples just  cited,  some  insects 
exhibit  no  remarkable  instinct 
in  their  egg-laying.  Our  com- 
mon northern  walking-stick, 
Diapheromera,  drops  its  eggs-on 
the  ground  under  the  shrubs 
and  trees  upon  which  it  feeds. 
This,  however,  is  sufficient  pro- 
vision, for  the  eggs  are  protected 
throughout  the  winter  by  the 
fallen  leaves,  and  the  young  when  hatched,  readily  find  their  food. 

Many  species,  the  young  of  which  feed  upon  foliage  lay  their  eggs 
singly  upon  leaves;  but  many  others,  and  this  is  especially  true  of 
those,  the  young  of  which  are  gregarious,  lay  their  eggs  in  clusters. 
In  some  cases,  as  in  the  squash  bug,  the  mass  of  eggs  is  not  protected 
(Fig.  187) ;  in  others,  where  the  duration  of  the  egg-state  is  long,  the 
eggs  are  protected  by  some  covering.  The  females  of  our  tent- 
caterpillars  cover  their  eggs  with  a  water-proof  coating;  and  the 
tussock  moths  of  the  genus H enter ocampa  cover  their  egg-clusters  with 
a  frothy  mass. 


Fig.  186. — Thalessa  lunator. 


170 


AN  INTRODUCTION    TO  ENTOMOLOGY 


The  laying  of  eggs  in  compact  masses,  however,  is  not  correlated, 
in  most  cases,  with  gregarious  habits  of  the  larvae.  The  water- 
scavenger  beetles,  Hydrophilids,  make  egg-sacks  out  of  a  hardened 
silk-like  secretion  (Fig.  i88) ;   the  locusts,  Acridiidas,  lay  their  eggs  in 

oval  masses  and  cover  them  with  a 

..    ^,  ,^  tough  substance;    the  scale-insects 

of  the  genus  Pulvinaria   excrete  a 

large   cottony    egg-sac    (Fig.    189); 


^O 


Fig.    187— Egi 
squash-bug. 


-mass    of   the 


Fig.  188. — Egg-sacoiHydrophiliis 

(After  Miall). 


the  eggs  of  the  praying  mantis  are  laid  in  masses  and  overlaid  with 
a  hard  covering  of  silk  (Fig.  190);  and  cockroaches  produce  pod-like 
egg-cases,  termed 
ootheca,  each 
containing  many 
eggs  (Fig.  191). 

Among  the 
more  remarkable 
of  the  methods  of 
caring  for  eggs  is 

that  of  the  lace-winged  flies,  Chrysopa.  These  insects  place 
each  of  their  eggs  on  the  simimit  of  a  stitf  stalk  of  hard  silk 
(Fig.  192). 

Duration  of  the  egg-state. — In  the  life-cycle  of  most  insect  s, 

a  few  days,  and  only  a  few,  intervene  between  the  laying  of 

an  egg  and  the  emergence  of  the  nymph,  naiad,  or  loxxa.  from 

"  it.     In  some  the  duration  of  the  egg-state  is  even  shorter,  the 

'  hatching  of  the  egg  taking  place  very  soon  after  it  is  laid,  or 

as  sometimes  in  flesh-flies,  before  it  is  laid.     On  the 


Fig.  189. — Pulvinaria  inniunerabilis,  females  on 
grape  with  egg  sacs 


Fig.  190. 

-Egg- 

mass 

of     a 

pray-  even 


1 

m  a  n- 

tis. 


^  other  hand,  in  certain  species,  the  greater  part  of  the  life  of  an 
individual   is   passed   within   the   egg-shell.     The   common 
apple-tree    tent-caterpillars,    Clisiocampa    aniericana,    lays 
its  eggs  in  early  summer;    but  these  eggs  do  not  hatch  till  the  fol- 
lowing spring;    while  the  remainder  of  the  life-cycle  occupies  only  a 


THE   METAMORPHOSIS  OF  INSECTS 


171 


few  weeks.  The  eggs  of  Bittacus  axe  said  to  remain  unhatched  for 
two  years;  and  a  similar  statement  is  made  regarding  the  eggs  of 
our  common  walking-stick. 


I'CS*^ 


b.      THE    HATCHING   OF   YOUNG   INSECTS 

Only  a  few  accounts  have  been  published 

regarding  the  manner  in  which  a  young  insect 

frees  itself  from  the  embryonic  envelopes.     In  ^'^cockr7a?h  ^^'"''^  °^  ^ 

some  cases  it  is  evident  that  the  larva  cuts  its 

way  out  from  the  egg-shell  by  means  of  its  mandibles ;  but  in  others,  a 

specialized  organ  has  been  developed  for  this  purpose. 

The  hatching  spines. — 
An  organ  for  rupturing 
the  embryonic  envelopes 
is  probably  commonly  pre- 
sent. It  has  been  des- 
cribed under  several 
names.  It  was  termed  an 
egg-burster  by  Hagen,  the 
ruptor  ovi  by  C.  V.  Riley 
an  egg-tooth  by  Heymons, 
and  the  hatching  spines 
by  Wheeler. 


C.  THE  MOLTING  OF  INSECTS 

Fig.  192.— Eggs,  larva,  cocoon,  and  adult  of  'phe    voung   of   insects 

Chrysopa.  /         ° 

cast  periodically  the  outer 

parts  of  the  cuticula;  this  process  is  termed  molting  or  ecdysis. 

General  features  of  the  molting  of  insects. — The  chitinization  of 

the  epidermis  or  primary  cuticula  adds  to  its  efficiency  as  an  armor,  but 

it  prevents  the  expansion  of  the  body-wall  rendered  necessary  by  the 

growth  of  the  insect;    consequently  as  the  body  grows,  its  cuticula 

becomes  too  small  for  it.     When  this  occurs  a  second  epidermis  is 

formed  by  the  hypodermis;  after  which  the  old  epidermis  splits  open, 

usually  along  the  back  of  the  head  and  thorax,  and  the  insect  works 

itself  out  from  it.     The  new  epidermis  being  elastic,  accommodates 

itself  to  the  increased  size  of  the  body ;  but  in  a  short  time  it  becomes 

chitinized;   and  as  the  insect  grows  it  in  turn  is  cast  off.     The  cast 

skin  of  an  insect  is  termed  the  exuvice,  the  plural  noun  being  used  as  in 

English  is  the  word  clothes. 


172  AN  INTRODUCTION   TO   ENTOMOLOGY 

Coincident  with  the  formation  of  the  new  epidermis,  new  setas 
are  formed  beneath  the  old  epidermis;  these  He  closely  a ppressed  to 
the  ou;:er  surface  of  the  new  epidermis  until  released  by  the  molting 
of  the  old  epidermis. 

In  the  above  account  only  the  more  gsneral  features  of  the  process  of  molting 
are  indicated,  the  details,  according  to  the  observations  of  Tower  ('06)  are  as 
follows.  (See  Figure  113,  p.  99).  In  ths  formation  of  the  new  epidermis  it  appsars 
as  a  thin,  delicate  lamella,  spread  evenly  over  the  entire  outer  surface  of  the 
hypodermis;  it  grows  rapidly  in  thickness  until  finally,  just  before  ecdysis  takes 
place,  it  reaches  its  final  thickness.  After  ecdysis  the  epidermis  hardens  rapidly 
and  its  coloration  is  developed.  As  soon  as  ecdysis  is  over  the  deposition  of  the 
dermis  or  secondary  cuticula  begins.  This  layer  is  a  carbohydrate  related 
to  cellulose,  and  is  deposited  in  layers  of  alternating  composition,  through  the 
period  of  reconstruction  and  growth,  during  which  it  reaches  its  maximum  thick- 
ness. Preliminary  to  ecdysis  a  thin  layer  of  molting  fluid  is  formed,  and  through 
its  action  the  old  dermis  is  corroded  and  often  almost  entirely  destroyed,  thus 
facilitating  ecdysis.  This  dissolving  of  the  dermis,  is,  according  to  Tower,  a  most 
constant  phenomenon  in  ecydsis"  and  has  been  found  in  all  insects  examined  by 
him  in  varying  degrees. 

It  is  said  that  the  CcUembola  molt  after  reacamg  sexual  maturity, 
in  this  respect  agreeing  with  the  Crustacea  and  the  "Myriapoda,"  and 
differing  from  the  Arachnida  and  from  all  other  insects  (Brindley  '98). 

The  molting  fluid. — As  indicated  above,  the  process  of  molting  is 
facilitated  by  the  excretion  of  a  fluid  known  as  the  molting  fluid.  This 
is  produced  by  unicellular  glands  (Fig.  113,  p.  99)  which  are  modified 
hypodermal  cells.  These  glands  are  found  all  through  the  life  of  the 
insect  and  upon  all  parts  of  the  body;  but  are  most  abundant  upon 
the  pronotum,  and  are  more  abundant  at  pupation  than  at  any  other 
period. 

The  number  of  postembryonic  molts. — A  very  wide  range  of  vari- 
ation exists  as  to  number  of  molts  undergone  by  insects  after  they  leave 
the  egg-shell.  According  to  Grassi  ('98,  p.  292),  there  is  only  a  single 
partial  molt  with  Campodea  and  Japyx,  while  the  May-fly  Chloeon 
molts  twenty  times.  Between  these  extremes  every  condition  exists . 
Probably  the  majority  of  insects  molt  from  four  to  six  times;  but 
there  are  many  records  of  insects  that  molt  many  more  times  than  this. 

Stadia. — The  intervals  between  the  ecdyses  are  called  stadia.  In 
numbering  the  stadia,  the  first  stadium  is  the  period  between  hatching 
and  the  first  postembryonic  ecdysis. 

Instars. — The  term  instar  is  appHed  to  the  form  of  an  insect  during 
a  stadium;  in  numbering  the  instars,  the  form  assumed  by  the  insect 
between  hatching  and  the  first  postembryonic  molt  is  termed  the  first 
instar. 


THE   METAMORPHOSIS   OF  INSECTS  173 

Head  measurements  of  larvse.^ — It  was  demonstrated  by  Dyar  ('90) 
that  the  widths  of  the  head  of  a  larva  in  its  successive  instars  follow 
a  regular  geometric  progression  in  their  increase.  The  head  was 
selected  as  a  part  not  subject  to  growth  during  a  stadium;  and  the 
width  as  the  most  convenient  measurement  to  take.  By  means  of 
this  criterion,  it  is  possible  to  determine,  when  studying  the  transfor- 
mations of  an  insect,  whether  an  ecdysis  has  been  overlooked  or  not. 
Experience  has  shown  that  slight  variations  between  the  computed 
and  the  actual  widths  may  occur;  but  these  differences  are  so  slight 
that  the  overlooking  of  an  ecdysis  can  be  readily  discovered.  The 
following  example  will  serve  to  illustrate  the  method  employed. 

A  larva  of  Papilio  thoas  was  reared  from  the  egg;  and  the  widths 
of  the  head  in  the  successive  instars  was  found  to  be,  expressed  in 
millimeters,  as  follov\^s:     .6;    i.i;    1.6;    2.2;    3.4. 

By  dividing  2.2.  by  3.4  (two  successive  members  of  this  series),  the 
ratio  of  increase  was  found  to  be  .676+  ;  the  number,  .68  was  taken, 
therefore,  as  sufficiently  near  the  ratio  for  practical  purposes.  By 
using  this  ratio  as  a  factor  the  following  results  were  obtained : 

Width  found  in  fifth  instar  = 3.4 

Calculated  width  in  fourth  instar  (3.4  X  .68)  = 2.312 

"     "third        "     (2.312  X  .68)  =..  ..      1.57 

"  "     "  second     "     (1.57  X  .68)  = 1.067 

"     "  first  (1.067  X  .68)  = 72s 

By  comparing  the  two  series,  as  is  done  below,  so  close  a  correspond- 
ence is  found  that  it  is  evident  that  no  ecdysis  was  overlooked. 
Widths  found: — .6;   i.i;   1.6;  2.2;  3.4 
"     calculated: — .7;  1.1-;  1.6-;  2.3. 

I  The  reproduction  of  lost  limbs. — The  repro- 

^  duction  of  lost  limbs  has  been  observed  in  many 

insects ;  but  such  reproduction  occurs  here  much 
less  frequently  than  in  the  other  classes  of  the 
Arthropoda.  The  reproduction  takes  place  dur- 
ing the  period  of  ecdysis,  the  reproduced  part 
becoming  larger  and  larger  with  each  molt; 
hence  with  insects,  and  with  Arachnida  as  well, 
the  power  of  reproducing  lost  limbs  ceases  with 
the  attainment  of  sexual  maturity;  but  not  so 
with  the  Crustacea  and  the  "Myriapoda"  which 
molt  after  becoming  sexually  mature.     In  none 

Fig-  93-— A  spider  in    of  the  observed  examples  of  the  reproduction 
which  lost  legs  weie         ^  ^  .  ,.      ,       ,  11 

being  reproduced.       of  appendages  has  an  entire  leg  been  reproduced. 


174  AN  INTRODUCTION   TO   ENTOMOLOGY 

It  appears  to  be  necessary  that  the  original  coxa  be  not  removed  in 
order  that  the  reproduction  may  take  place.  Figure  193  represents 
a  spider  in  our  collection  in  which  two  legs,  the  left  fore  leg  and  the 
right  hind  leg,  were  being  reproduced  when  the  specimen  was  captured. 

d.       DEVELOPMENT    WITHOUT   METAMORPHOSIS 

{Ametabolous*  Development) 

While  most  insects  undergo  remarkable  changes  in  form  during 
their  postembryonic  development,  there  are  some  in  which  this  is 
not  the  case.  In  these  the  young  insect  just  hatched  from  the  egg  is 
of  practically  the  same  form  as  the  adult  insect.  These  insects  grow 
larger  and  may  undergo  slight  changes  in  form  of  the  body  and  its 
appendages ;  but  these  changes  are  not  sufficiently  marked  to  merit 
being  termed  a  metamorphosis.  This  type  of  development  is  known 
technically  as  ametabolous  development. 

Development  without  metamorphosis  is  characteristic  of  the  two 
orders  Thysanura  and  CoUembola,  which  in  other  respects,  also,  are 
the  most  generalized  of  insects. 

The  natiire  of  the  changes  in  form  undergone  by  an  insect  with  an  ametabolous 
development  is  illustrated  by  the  development  of  Machilis  alternata,  one  of  the 
Thysanura.  The  first  instar  of  this  insect,  according  to  Heymons  ('07),  lacks 
the  clothing  of  scales,  the  styli  on  the  thoracic  legs,  and  the  lateral  rows  of  eversi- 
ble  sacs  on  the  abdominal  segments;  and  the  antennae  and  cerci  are  relatively 
shorter  and  consist  of  a  much  smaller  number  of  segments  than  those  of  the  adult. 
These  changes,  however,  are  comparable  with  those  undergone  by  many  animals 
in  the  course  of  their  development  that  are  not  regarded  as  having  a  metamorpho- 
sis. In  common  usage  in  works  on  Entomology  the  term  metamorphosis  is  used 
to  indicate  those  marked  changes  that  take  place  in  the  appearance  of  an  insect 
tha  t  are  correlated  with  the  development  of  wings. 

In  addition  to  the  Thysanura  and  the  CoUembola  there  are  certain 
insects  that  develop  without  metmorphosis,  as  the  Mallophaga 
and  thePediculidae.  But  their  ametabolous  condition  is  believed  to  be 
an  acquired  one.  In  other  words,  it  is  beheved  that  the  bird-lice  and 
the  true  lice  are  descendants  of  winged  insects  whose  form  of  body  and 
mode  of  development  have  been  modified  as  a  result  of  parasitic  life. 

The  Ametabola. — Those  insects  that  develop  without  meta- 
morphosis are  sometimes  referred  to  as  the  Ametabola.  This  term  was 
first  proposed  by  Leach  (18 15),  who  included  under  it  the  Hce  as  well 
as  the  Thysanura  and  CoUembola.  But  with  our  present  knowledge,  if 
it  is  used  it  should  be  restricted  to  the  Thysanura  and  CoUembola 
those  insects  in  which  a  development  without  metamorphosis  is  a 
primitive  not  an  acquired  condition. 

*Ametabolous:     Greek  a,  without;  metabole  (/xerapoXT^),  change. 


IHE   METAMORPHOSIS   OF  INSECTS 


175 


e.      GRADUAL   METAMORPHOSIS 

(Paurometabolous*  Development) 

In  several  orders  of  insects  there  exists  a  type  of  development  that 

is  characterized  by  the  fact  that  the  young  resemble  the  adult  in  the 

general  form  of  the  body  and  in  manner  of  life.     There  is  a  gradual 

growth  of  the  body  and  of  the  wing  rudiments  and  genital  appendages. 


Fig.  194. — Nymph  of  Mela- 
noplus,  first  instar  (After 
Emerton). 


Fig.  195. — Nymph  of  Mela- 
noplus,  second  instar 
(After  Emerton). 


Fig.  196. — Nymph  of  Melano- 
plus,  third  instar  (After  Emer- 
ton) 


Fig.  198. — Nymph  of  Melano- 
plus,  fifth  instar  (After  Emer- 
ton). 


jj^^ 


Fig.  i97.^Nymph  of  Melano- 
plii%,  fourth  instar  (After 
Emerton). 


Fig.  iqg. —  Melanoplus, 
adult. 


But  the  changes  in  form  take  place  gradually  and  are  not  very  great 
between  any  two  successive  instars  except  that  at  the  last  ecdysis 
there  takes  place  a  greater  change,  especially  in  the  wings,  than  at 
any  of  the  preceding  ecdyses.  This  type  of  metamorphosis  is  desig- 
nated as  gradual  metamorphosis  or  paurometabolous  development. 

The  characteristic  features  ol  paurometabolous  development  are 
correlated  with  the  fact  that  the  mode  of  life  of  the  young  and  of  the 


*Paurometabolous:     pauros  (iraCpos),  little;   metabole  (Me^a^oXi}),  change. 


176  AN  INTRODUCTION  TO  ENTOMOLOGY 

adult  are  essentially  the  same;  the  two  living  in  the  same  situation, 
and  feeding  on  the  same  food.  The  adult  has  increased  power  of  loco- 
motion, due  to  the  completion  of  the  development  of  the  wings;  this 
enables  it  to  more  readily  perform  the  functions  of  the  adult,  the  spread 
of  the  species,  and  the  making  of  provision  for  its  continuance;  but 
otherwise  the  life  of  the  adult  is  very  similar  to  that  of  the  young. 

The  development  of  a  locust  or  short-horned  grasshopper  will 
serve  as  an  example  of  gradual  metamorphosis.  Each  of  the  instars 
of  our  common  red-legged  locust,  Melanoplus  femur-rubrum,  is  repre- 
sented in  the  accompanying  series  of  figures.  The  adult  (Fig.  199) 
is  represented  natural  size;  each  of  the  other  instars,  somewhat 
enlarged;  the  hair  line  above  the  figure  in  each  case  indicates  the 
length  of  the  insect. 

The  young  locust  just  out  from  the  egg-shell  can  be  easily  recog- 
nized as  a  locust  (Fig.  194).  It  is  of  course  much  smaller  than  the 
adult;  the  proportion  of  the  different  regions  of  the  body  are  some- 
what different ;  and  it  is  not  furnished  with  wings ;  still  the  form  of  the 
body  is  essentially  the  same  as  that  of  the  adult.  In  the  second  and 
third  instars  (Fig.  195  and  196)  there  are  slight  indications  of  the 
development  of  wing-rudiments;  and  these  rudimentary  wings  are 
quite  conspicuous  in  the  fourth  and  fifth  instars  (Fig.  197  and  198). 
The  change  at  the  last  ecdysis,  that  from  the  fifth  instar  to  the  adult, 
is  more  striking  than  that  at  any  preceding  ecdysis;  this  is  due  to  the 
complete  expansion  of  the  wings,  which  takes  place  at  this  time. 

The  Paurometabola. — Those  orders  of  insects  that  are  characterized 
by  a  gradual  metamorphosis  are  grouped  together  as  the  Paurometa- 
bola. This  is  not  a  natural  division  of  the  class  Hexapoda  but  mer'^l\- 
indicates  a  similarity  in  the  nature  of  the  metamorphosis  in  the  orders 
included.  This  group  includes  the  Isoptera,  Dermaptera,  Orthop- 
tera,  Corrodentia,  Thysanoptera,  Homoptera,  and  Hemiptera. 

The  term  nymph. — An  immature  instar  of  an  insect  that  undergoes 
a  gradual  metamorphosis  is  termed  a  nymph. 

In  old  entomological  works,  and  especially  in  those  written  in  the 
early  part  of  the  last  century,  the  term  nymph  was  used  as  a  synonym 
of  pupa ;  but  in  more  recent  works  it  is  applied  to  the  immature  instar 
of  insects  that  undergo  either  a  gradual  or  incomplete  metamorphosis. 
In  this  book  I  restrict  the  use  of  this  term  to  designate  an  immature 
instar  of  an  insect  that  undergoes  a  gradual  metamorphosis. 

Deviation  from  the  usual  type. — It  is  to  be  expected  that  within  so 
large  a  group  of  organisms  as  the  Paurometabola  there  should  have 


THE  METAMORPHOSIS  OF  INSECTS  177 

been  evolved  forms  that  exhibit  deviations  from  the  usual  type  of 
development.  The  more  familiar  examples  of  these  are  the  following: 
The  Saltatorial  Orthoptera. — In  the  crickets,  locusts,  and  long- 
homed  grasshoppers,  the  wings  of  the  nymphs  are  developed  in  an 
inverted  position ;  that  surface  of  the  wing  which  is  on  the  outside  in 
the  adult  is  next  to  the  body  in  the  nymphal  instars;  and  the  rudi- 
mentary hind  wings  are  outside  of  the  fore  wings,  instead  of  beneath 
them,  as  in  the  adult.  At  the  last  ecdysis  the  wings  assume  the  normal 
position. 

The  Cicadas. — In  the  Cicadas  there  exists  a  greater  difference 
between  the  nymphal  instars  and  the  adult  than  is  usual  with  insects 
in  which  the  metamorphosis  is  gradual.  The  nymphs  live  below  the 
surface  of  the  ground,  feeding  upon  the  roots  of  plants;  the  adults 
live  in  the  open  air,  chiefly  among  the  branches  of  trees.  The  forelegs 
of  the  nymphs  are  fossorial  (Fig.  200);  this  is  an 
adaptation  for  subterranean  life,  which  is  not  needed 
and  not  possessed  by  the  adults.  And  it  is  said  that 
the  last  nymphal  instar  is  quiescent  for  a  period. 

The  Coccidce. — In  the  Coccidas  the  mode  of  develop- 
ment of  the  two  sexes  differ  greatly.      The  female 
never  acquires  wings,  and  in  so  far  as  external  form  is 
concerned  the  adult  is  degenerate.      The  male,  on 
the  other  hand,  exhibits  a  striking  approach  to  com- 
plete metamorphosis,  the  last  nymphal  instar  being 
enclosed  in  a  cocoon,  and  the  legs  of  the  adult  are  not 
those  of  the  nymph,  being  developed  from  imaginal 
Pig.    200.—   disks.     But  the  wings  are  developed  externally. 
^IJ^da  (After         ^^'^  Aleyrodidce.— In  this  family  the  type  of  meta- 
Riley ) .  morphosis  corresponds  quite  closely  with  that  described 

later  as  complete  metamorphosis;  consequently  the 
term  larva  is  applied  to  the  immature  instars  except  the  last,  which  is 
designated  the  pupa. 

The  wings  arise  as  histoblasts  in  the  late  embryo,  and  the  growth 
of  the  wing-buds  diu-ing  the  larval  stadia  takes  place  inside  the  body- 
wall.  The  change  to  the  pupal  instar,  in  which  the  wing-buds  are 
external,  takes  place  beneath  the  last  larval  skin,  which  is  known  as 
the  pupa  case  or  puparium.  The  adult  emerges  through  a  T-shaped 
opening  on  the  dorsum  of  the  puparium.     Both  sexes  are  winged. 

The  AphididcB. — In  the  Aphididas  there  exists  a  remarkable  type 
of  development  known  as  heterogamy  or  cyclic  reproduction.  This  is 
characterized  by  an  alternation  of  several  parthenogenetic  generations 


178 


^.V  INTRODUCTION   TO  ENTOMOLOGY 


with  a  sexual  generation.  And  within  the  series  of  parthenogenetic 
forms  there  may  be  an  alternation  of  winged  and  wingless  forms.  In 
some  cases  the  reproductive  cycle  is  an  exceedingly  complicated  one ; 
and  different  parts  of  it  occur  on  different  food  plants. 

The  Thysanoptera. — In  the  Thysanoptera,  as  in  most  other  insects 
with  a  gradual  metamorphosis,  the  nymphs  resemble  the  adults  in  the 
form  of  the  body,  and  the  wings  are  developed  externally;  but  the  last 
nymphal  instar  is  quiescent  or  nearly  so  and  takes  no  noiuishment. 
This  instar  is  commonly  described  as  the  pupa. 


/.       INCOMPLETE   METAMORPHOSIS 

(Hemtmetabolous*  Development) 

In  three  of  the  orders  of  insects,  the  Plecoptera,  Ephemerida,  and 
Odonata,  there  exists  a  t>^e  of  metamorphosis  in  which  the  changer 


Fig.  20I. — Transformation  of  a  May-fly,  Ephemera  varia;    A, 
adult;  B,  naiad  (After  Needham). 

that  take  place  in  the  form  of  the  body  are  greater  than  in  gradual 
metamorphosis  but  much  less  marked  than  in  complete  metamorpho- 
sis. For  this  reason  the  terms  incomplete  metamorphosis  and  hemi- 
metabolous  development  have  been  applied  to  it. 

Both  incomplete  metamorphosis  and  complete  metamorphosis  are 
characterized  by  the  fact  that  the  immature  instars  exhibit  adaptive 
modifications  of  form  and  structure,  fitting  them  for  a  very  different 
mode  of  life  than  that  followed  by  the  adult.  This  is  often  expressed 
by  the  statement  that  the  imjnature  instars  are  "sidewise  developed" ; 
for  it  is  believed  that  in  these  cases  the  development  of  the  individual 
does  not  repeat  the  history  of  the  race  to  which  the  individual  belongs. 

*Hernimetabolous:    lierni  ("^A"').  lialf;    metabole  (/xerajSoX??'),  change. 


THE   METAMORPHOSIS  OF  INSECTS  179 

This  mode  of  development  is  termed  cenogenesis*  It  contrasts 
strongly  with  gradual  metamorphosis,  where  there  is  a  direct  develop- 
ment from  the  egg  to  the  adult. 

In  each  of  the  orders  that  are  characterized  by  an  incomplete 
metamorphosis,  the  adaptive  characteristics  of  the  young  insects  fit 
them  for  aquatic  life ;  while  the  adults  lead  an  aerial  existence.  The 
transformations  of  a  May-fly  (Fig.  201)  will  serve  to  illustrate  this 
type  of  metamorphosis. 

The  primitive  insects  were  doubtless  terrestrial ;  this  is  shown  by 
the  nature  of  the  respiratory  system,  which  is  aerial  in  all  insects.  In 
the  course  of  the  evolution  of  the  different  orders  of  insects,  the 
immature  forms  of  some  of  them  invaded  the  water  in  search  of  food. 
This  resulted  in  a  sidewise  development  of  these  immature  forms  to 
better  fit  them  to  live  in  this  medium ;  while  the  adult  continued  their 
development  in,  what  may  be  termed  by  contrast,  a  direct  line.  In 
some  of  the  Plecoptera,  as  Capnia  and  others,  the  results  of  the  ceno- 
genetic  development  are  not  marked  except  that  the  immature  forms 
are  aquatic. 

In  the  three  orders  in  which  the  metamorphosis  is  incomplete,  the 
cenogenetic  development  of  the  immature  instars  involved  neither  a 
change  in  the  manner  of  development  of  the  wings  nor  a  retarding  of 
the  development  of  the  compound  eyes ;  consequently  these  immature 
forms,  although  sidewise  developed,  constitute  a  class  quite  distinct 
from  lar^^8e. 

The  Hemimetabola. — The  three  orders  in  which  the  development  is 
a  hemimetabolous  one  are  grouped  together  as  the  Hemimetabola; 
these  are  the  Plecoptera,  Ephemerida,  and  Odonata.  This  grouping 
together  of  these  three  orders  is  merely  for  convenience  in  discussions 
of  types  of  metamorphosis  and  does  not  indicate  a  natural  division  of 
the  class  Hexapoda.  The  radical  differences  in  the  three  types  of 
aquatic  respiratory  organs  characteristic  of  the  three  orders  indicate 
that  they  were  evolved  independently. 

The  term  naiad. — The  immature  instars  of  insects  with  an  incom- 
plete m.etamorphosis  have  been  termed  nymphs;  but  as  a  result  of 
their  sidewise  development  they  do  not  properly  belong  in  the  same 
class  as  the  immature  instars  of  insects  with  a  gradual  metamorphosis. 
I,  therefore,  proposed  to  designate  them  as  naiads  (Comstock  '18,  h). 

The  adoption  of  the  term  naiad  in  this  sense  affords  a  distinctive 
term  for  each  of  the  three  classes  of  immature  insects  corresponding  to 
the  three  types  of  metamorphosis,  i.  e.,  nymphs,  naiads,  and  larv^ae. 


*Ceao2:enesis:     kainos  {Kalvos),  new;  genesis. 


180  AN  INTRODUCTION   TO  ENTOMOLOGY 

Deviation  from  the  usual  type  of  incomplete  metamorphosis. — The 

more  striking  deviations  from  the  usual  type  of  hemimetabolous  devel- 
opment are  the  following: 

The  Odonata. — In  theOdonata  the  wings  of  the  naiads  are  inverted; 
these  insects  resembling  in  this  respect  the  Saltitorial  Orthoptera. 
What  is  the  upper  surface  of  the  wings  with  naiads  becomes  the  lower 
surface  in  the  adults,  the  change  taking  place  at  the  last  ecdysis. 

The  Ephemerida. — In  the  Ephemerida,  there  exists  the  remarkable 
phenomenon  of  an  ecdysis  taking  place  after  the  insect  has  left  the 
water  and  acquired  functional  wings.  The  winged  instar  that  is 
interpolated  between  the  last  aquatic  one  and  the  adult  is  termed  the 
sub-imago. 

g.       COMPLETE    METAMORPHOSIS 

(Holometabolus*  Development) 

The  representatives  of  several  orders  of  insects  leave  the  egg-shell 
in  an  entirely  different  form  from  that  they  assume  when  they  reach 
maturity;  familiar  examples  of  these  are  caterpillars  which  develop 
into  butterflies,  maggots  which  develop  into  flies,  and  grubs  which 
develop  into  beetles.  These  insects  and  others  that  when  they 
emerge  from  the  egg-shell  bear  almost  no  resemblance  in  form  to  the 
adult  are  said  to  undergo  a  complete  metamorphosis  or  a  holometabolous 
development. 

The  Holometabola. — Those  orders  that  are  characterized  by  a 
holometabolous  development  are  grouped  together  as  the  Holometab- 
ola. This  group  includes  the  Neuroptera,  Mecoptera,  Trichoptera, 
Lepidoptera,  Diptera,  Siphonaptera,  Coleoptera,  and  Hymenoptera. 

This  grouping  together  of  these  orders,  while  convenient  for  dis- 
cussions of  metamorphosis,  is  doubtless  artificial.  It  is  not  at  all 
probable  that  the  Holometabola  is  a  monophylitic  group.  In  other 
words  complete  metamorphosis  doubtless  arose  several  times  inde- 
pendently in  the  evolution  of  insects. 

The  term  larva. — The  form  in  which  a  holometabolous  insect 
leaves  the  egg  is  called  larva.  The  term  was  suggested  by  a  belief  of 
the  ancients  that  the  form  of  the  perfect  insect  was  masked,  the  Latin 
word  larva  meaning  a  mask. 

Formerly  the  term  larva  was  applied  to  the  immatiire  stages  of  all 
insects;   but  more  recent  writers  restrict  its  use  to  the  immature  in- 

*Holometabolous :   holos  (^Xos),  complete;   metahole  {ixer a^o\-n) ^  change. 


THE   METAMORPHOSIS  OF  INSECTS  181 

stars  of  insects  with  a  complete  metamorphosis;    and  in  this  sense 
only  is  it  used  in  this  book. 

The  adaptive  characteristics  of  larvae. — The  larvse  of  insects  with 
complete  metamorphosis,  like  the  naiads  of  those  with  incomplete 
metamorphosis,  exhibit  an  acquired  form  of  body  adapting  them  to 
special  modes  of  life;  and  in  this  case  the  cenogenetic  or  "sidewise 
development"  is  much  more  marked  than  it  is  in  insects  with  an 
incomplete  metamorphosis.  Here  the  form  of  the  body  bears  but  little 
relation  to  the  form  to  be  assumed  by  the  adult,  the  nature  of  the 
larval  life  being  the  controlling  factor. 

The  differences  in  form  between  larvse  and  adults  are  augmented 
by  the  fact  that  not  only  have  larvag  been  modified  for  special  modes 
of  life,  but  in  most  cases  the  adults  have  been  highly  specialized  for  a 
different  mode  of  life;  and  so  great  are  these  differences  that  a 
quiescent  pupa  stage,  during  which  certain  parts  of  the  body  can  be 
made  over,  is  necessary. 

Here,  as  in  the  case  of  insects  with  an  incomplete  metamorphosis,  we  have  an 
illustration  of  the  fact  that  natural  selection  can  act  on  any  stage  in  the  develop- 
ment of  animal  to  better  adapt  that  particular  stage  to  the  conditions  under  which 
it  exists.  Darwin  pointed  out  in  his  "Origin  of  Species"  that  at  whatever  age 
a  variation  first  appears  in-  the  parent  it  tends  to  reappear  at  a  corresponding  age 
in  the  oflfspring.     This  tendency  is  termed  homochronous  heredity*. 

It  is  obvious  that  the  greater  the  adaptive  characteristics  of  the  immature 
forms,  the  less  does  the  ontogeny  of  a  species  represent  the  phylogeny  of  the 
race  to  which  it  belongs.  This  fact  led  Fritz  Muller,  in  his  "Facts  for  Darwin", 
to  make  the  aphorism  "There  were  perfect  insects  before  larvae  and  pupae."  The 
overlooking  of  this  principle  frequently  results  in  the  drawing  of  unwarranted  con- 
clusions, by  those  writers  on  insects  who  cite  adaptive  larval  characteristics  as 
being  more  generalized  than  the  corresponding  features  of  the  adult. 

The  more  obvious  of  the  adaptive  characteristics  of  larvag  are  the 
following : 

The  form  of  the  body. — As  indicated  above  the  form  of  the  body  of  a 
larva  bears  but  little  relation  to  the  form  to  be  assumed  by  the  adult, 
the  nature  of  the  larval  life  being  the  controlling  factor  in  determining 
the  form  of  the  body.  As  different  larvee  live  under  widely  differing 
situations,  various  types  of  larvse  have  been  developed;  the  more 
important  of  these  types  are  described  later. 

The  greater  or  less  reduction  of  the  thoracic  legs. — In  the  evolution 
of  most  larvae  there  has  taken  place  a  greater  or  less  reduction  of  the 
thoracic  legs;  but  the  extent  of  this  reduction  varies  greatly.  The 
larvae  of  certain  Neuroptera,  as  Corydalus  for  example,  have  as  perfect 

*Hom6chronous :   homos  {ofio's),  one  and  the  same;   chronos  (xP<^«'<'0.  time. 


182  AN  INTRODUCTION   TO  ENTOMOLOGY 

legs  as  do  naiads  of  insects  with  an  incomplete  m  etamorphosis.  The 
larvag  of  Lepidoptera  have  short  legs  which  correspond  to  only  a  part 
of  the  legs  of  the  adult.  While  the  lar\'as  of  Diptera  have  no  external 
indications  of  legs. 

Tke  development  of  prolegs  in  some  larvce. — A  striking  feature  of 
many  larvee  is  the  presence  of  abdominal  organs  of  locomotion ;  these 
have  been  termed  prolegs;  the  prolegs  of  caterpillars  are  the  most 
familiar  examples  of  these  organs. 

The  prolegs  were  so  named  because  they  were  beheved  to  be  merely  adaptive 
cuticular  formations  and  not  true  legs ;  this  belief  arose  from  the  fact  that  they  are 
shed  with  the  last  larval  skin.  Some  recent  writers,  however,  regard  the  prolegs 
as  true  legs.  It  is  now  known  that  abdominal  appendages  are  common  in  the 
embryos  of  insects;  and  these  writers  believe  that  the  prolegs  are  developed 
from  these  embryonic  appendages,  and  that,  therefore,  they  must  be  regarded  as 
true  legs. 

If  this  is  true,  there  has  taken  place  a  remarkable  reversal  in  the  course  of 
development.  The  abdominal  legs,  except  those  that  were  modified  into  append- 
ages of  the  reproductive  organs,  the  gonapophyses,  were  lost  early  in  the  phylogeny 
of  the  Hexapoda.  The  origin  of  complete  metamorphosis  must  have  taken  place 
at  a  much  later  period;  when,  according  to  this  belief,  the  abdominal  appendages, 
which  had  been  latent  for  a  long  time,  W'ere  redeveloped  into  functional  organs. 

The  development  of  tracheal  gills. — A  strilcing  feature  of  many  larvse 
is  the  possession  of  tracheal  gills.  This  is  obviously  an  adaptive 
characteristic  the  development  of  which  was  correlated  with  the 
assumption  of  aquatic  life  by  forms  that  were  primarily  aerial;  and 
it  is  also  obvious  that  the  development  of  tracheal  gills  has  arisen 
indepandently  many  times;  for  they  exist  in  widely  separated  families 
belonging  to  different  orders  of  insects  that  are  chiefly  aerial.  They 
are  possesssd  by  a  few  lepidopterous  larv^as,  and  by  the  representatives 
of  several  families  of  Neuroptera,  Coleoptera  and  Diptera.  On  the 
other  hand,  in  the  Trichoptera  the  possession  of  tracheal  gills  by  the 
larvce  is  characteristic  of  nearly  all  members  of  the  order. 

The  internal  development  of  wings. — This  is  perhaps  the  most  re- 
markable of  the  sidewise  developments  of  larvae.  Although  larvae 
exhibit  no  external  indications  of  wings,  it  has  been  found  that  the 
rudiments  of  these  organs  arise  at  as  early  a  period  in  insects  with  a 
complete  metamorphosis  as  they  do  in  those  with  an  incomplete 
metamorphosis ;  and  that  during  larval  life  the  wing  rudiments  attain 
an  advanced  stage  in  their  development.  But  as  these  rudiments  are 
invaginated  there  are  no  external  indications  of  their  presence  during 
larval  hfe.  The  details  of  the  internal  development  of  wings  are  dis- 
cussed later. 


THE   METAMORPHOSIS   OF  INSECTS  183 

Occasionally  atavistic  individual  larvae  are  found  which  have 
external  wing-buds. 

As  to  the  causes  that  brought  about  the  internal  development  of  wings  we 
can  only  make  conjectures.  It  has  occurred  to  the  writer  that  this  type  of  wing- 
development  may  have  arisen  as  a  result  of  boring  habits,  or  habits  of  an  analogous 
nature,  of  the  stem  forms  from  which  the  orders  of  the  Holometabola  sprang. 
Projecting  wing -buds  would  interfere  with  the  progress  of  a  boring  insect;  and, 
therefore,  an  embedding  of  them  in  the  body,  thus  leaving  a  smooth  contour, 
would  be  advantageous. 

In  support  of  this  theory  attention  may  be  called  to  the  fact  that  the  larvae 
of  the  most  generalized  Lepidoptera,  the  Hepialida;,  are  borers;  the  larvaj  of  the 
Siricidaj,  which  are  among  the  more  generalized  of  the  Hymenoptera  are  borers; 
so  too  are  many  Coleoptera ;  most  lai-vjE  of  Diptera  are  burrowers ;  and  the  larvag 
of  Trichoptera  live  in  cases. 

The  retarding  of  the  development  of  the  compound  eyes. — One  of  the 
most  distinctively  characteristic  features  of  larvae  is  the  absence  of 
compound  eyes.  The  life  of  most  larvae  is  such  that  only  limited 
vision  is  necessary  for  them ;  and  correlated  with  this  fact  is  a  retard- 
ing of  th.e  development  of  the  greater  portion  of  the  compound  eyes ; 
only  a  few  separate  ommatidia  being  functional  during  larval  life. 

In  striking  contrast  with  this  condition  are  the  well-developed  eyes 
of  nymphs  and  naiads. 

The  larvae  of  Corethra  and  Panorpa  are  the  only  lorva?  known  to 
me  that  possess  compound  eyes. 

The  invaginated  conditions  of  the  head  in  the  larvce  of  the  more 
specialized  Diptera. — The  extreme  of  sidewise  development  is  exhibited 
by  the  larvas  of  the  more  specialized  Diptera.  Here  not  only  are  the 
legs  and  wings  developed  internally  but  also  the  head.  This  phe- 
nomenon is  discussed  later. 

The  different  types  of  larvaB. — As  a  rule,  the  larvae  of  the  insects  of 
any  order  resemble  each  other  in  their  more  general  characteristics, 
although  they  bear  but  little  resemblance  to  the  adult  forms.  Thus 
the  grubs  of  Coleoptera,  the  caterpillars  of  Lepidoptera,  or  the  mag- 
gots of  Diptera,  in  most  cases,  can  be  recognized  as  such.  Still  in 
each  of  these  orders  there  are  larvae  that  bear  almost  no  resemblance 
to  the  usual  type.  As  examples  of  these  may  be  cited  the  water- 
pennies  (Parnidae,  Coleoptera),  the  slug-caterpillars  (Cochlidiids, 
Lepidoptera),  and  the  larvae  of  Microdon  (Diptera). 

To  understand  the  variations  in  form  of  larvs  it  should  be  borne 
in  mind  that  the  form  of  the  body  in  all  larvae  is  the  result  of  secondary 
adaptations  to  peculiar  modes  of  life;  and  that  this  modification  of 
form  has  proceeded  in  different  directions  and  in  varying  degrees  in 
different  insects. 


184 


AN  INTRODUCTION   TO   ENTOMOLOGY 


Among  the  many  types  of  larvae,  there  are  a  few  that  are  of  such 
common  occurrence  as  to  merit  distinctive  names;    the  more  im- 
portant of  these  are  the  following: 

Campodeiform. — In  many  paurometabolous 
insects  and  in  some  holometabolous  ones,  the 
early  instars  resemble  Campodea  more  or  less  in 
the  form  of  the  body  (Fig.  202);  such  naiads 
and  larvae  are  described  as  campodeiform. 

In  this  type,  the  body  is  long,  more  or  less 
flattened,  and  with  or  without  caudal  setae ;  the 
mandibles  are  well  developed;  and  the  legs  are 
not  greatly  reduced.  Among  the  examples  of 
this  type  are  the  larvae  of  most  Neuroptera,  and 
the  active  larvas  of  many  Coleoptera  (Cara- 
bidas,  Dysticidce,  and  the  first  instar  of  Me- 
loidffi). 

Eruciform. — The  eruciform  type  of  larvas  is 
well-illustrated  by  most  larvae  of  Lepidoptera 
and  of  Mecoptera;  it  is  the  caterpillar  form 
(Fig.  203).  In  this  type  the  body  is  cyHndrical ; 
the  thoracic  legs  are  short,  having  only  the 
terminal  portions  of  them  developed;  and  the 
abdomen  is  furnished  with  prolegs  or  with 
proleg-like  cuticular  folds.  Although  these 
larvas  move  freely,  their  powers  of  locomo- 
tion are  much  less  than  in  the  campodeiform 
type. 

Scarabeiform. — The  common  white  grub,  the  larva  of  the  May- 
beetle  (Fig.  204)  is  the  most  famiHar  example  of  a  scarabeiform  larva. 


Fig.  202. — Campodea 

staphylinus    (After 
Lubbock). 


^"^ 


Fig.  203. — The  silk- worm,  an  eruciform  larva  (After  Verson). 


In  this  type  the  body  is  nearly  cylindrical,  but  usually,  especially 
when  at  rest,  its  longitudinal  axis  is  curved;    the  legs  are  short;    and 


THE   METAMORPHOSIS   OF  INSECTS 


185 


prolegs  are  wanting.     This  type  is  quite  characteristic  of  the  larv^ 
of  the  Scarabaeidas,  hence  the  name ;    but  it  occurs  in  other  groups 

of  insects. 

The  movements  of  these  larv«  are 

slow;   most  of  them  Hve  in  the  ground, 

or  in  wood,  or  in  decaying  animal  or 

vegetable  matter. 


Fig.    204. — Larva  of   Melolontha 
vulgaris  (After  Schiodte). 


Vermiform. — Those  larvas   that   are 

more   or   less   worm-like   in    form    are 

termed  vermiform.     The  most  striking 

features  of  this  type  are  the  elongated 

form  of  the  body  and   an  absence  of 

locomotive  appendages  (Fig.  205). 

Naupliiform. — The  term  naupliiform  is  applied  to  the  first  instar 

of  the  larv^a  of  Platygaster  (Fig.  206),  on  account  of  its 

resemblance  to  the  nauplius  of  certain  Crustacea. 

The  prepupa. — Usually  the  existence  of  an  instar 
between  the  last  larval  one  and  the  pupal  instar  is  not 
recognized.  But  such  a  form  exists;  and  the  recogni- 
tion of  it  becomes  important  when  a  careful  study  is 
made  of  the  development  of  holometabolous  insects. 
As  is  shown  later,  during  larval  life  the  develop- 
ment of  the  wings  is  going  on  within  the  body.  As 
the  larva  approaches  maturity,  the  wings  reach  an 
advanced  stage  of  development  within  sac-like  invagi- 
nations of  the  body-wall.  Near  the  close  of  the  last 
larval  stadium  the  insect  makes  preparation  for  the 
change  to  the  pupa  state.  Some  form  a  cell  within 
which  the  pupa  state  is  passed,  the  larvee  of  butter- 
flies suspend  themselves,  and  most  larvee  of  moths  spin 
a  cocoon.  Then  follows  a  period  of  apparent  rest  before 
the  last  larval  skm  is  shed  and  the  pupal  state  assumed. 
But  this  period  is  far  from  being  a  quiet  one;  within 
the  apparently  motionless  body  important  changes  p^ 
take  place.  The  most  easily  observed  of  these 
changes  is  a  change  in  the  position  of  the  wings. 
Kach  of  these  passes  out  through  the  mouth  of  the  sac  in  which  it  has 
been  developed,  and  lies  outside  of  the  newly  developed  pupal  cuti- 
cula,  but  beneath  the  last  larval  cuticula.  Then  follows  a  period  of 
variable  duration  in  different  insects,  in  which  the  wings  are  really 


205.— 
Larva  of  a 
crane-fly. 


^.V  INTRODUCTION   TO  ENTOMOLOGY 


Fig.     206. — 
Lar\'a    of 
Platygaster 
(After  Ganin.) 


outside  of  the  body  although  still  covered  by  the  last  larval  cuticula; 
this  period  is  the  prepupal  stadium.  The  prepupal  instar  differs 
markedly  from  both  the  last  larval  one  and  from  the 
pupa ;  for  after  the  shedding  of  the  last  lar\^al  cuticula 
important  changes  in  the  form  of  the  body  take  place 
before  the  pupal  instar  is  assiimed. 

The  pupa. — The  most  obvious  characteristics  of  the 
pupa  state  are,  except  in  a  few  cases,  inactivity  and  help- 
lessness. The  organs  of  locomotion  are  functionless, 
and  may  even  be  soldered  to  the  body  throughout  their 
entire  length,  as  is  usual  with  the  pupcC  of  Lepidoptera 
(Fig.  207).  In  other  cases,  as  in  the  Coleoptera  (Fig. 
208)  and  in  the  Hymenoptera,  the  wings  and  legs  are 
free,  but  enclosed  in  more  or  less  sac-like  cuticular 
sheaths,  which  put  them  in  the  condition  of  the  pro- 
verbial cat  in  gloves.  More  than  this,  in  most  cases,  the  legs  of  the 
adult  are  not  fully  formed  till  near  the  end  of  the  pupal  stadiimi. 

The  term  pupa,  meaning  girl,  was  applied  to  this  instar  by  Linuceus 
on  account  of  its  resemblance  to  a  baby  that  has  been  swathed  or 
bound  up,  as  is  the  custom  with 
many  peoples. 

Although  the  insect  during  the  pupal 
stadium  is  apparently  at  rest,  this,  from  a 
physiological  point  of  view,  is  the  most 
active  period  of  its  postembryonic  exist- 
ence; for  wonderful  changes  in  the  struc-  p-g_  207.— Pupa  of  a  moth, 
cure  of  the  body  take  plaoe  at  tliis  time. 

In  the  development  of  a  larva  the  primitive  form  of  the  body  has  been  greatly 
modified  to  adapt  it  to  its  peculiar  mode  of  life;  this  sidewise  development  results 
in  the  production  of  a  type  of  body  that  is  not  at  all  fitted  for  the 
duties  of  adult  life.  In  the  case  of  an  insect  with  incomplete  meta- 
morphosis, the  full  grown  naiad  needs  to  be  modified  comparatively 
little  to  fit  it  for  adult  life;  but  the  change  from  a  maggot  to  a  fly, 
or  from  a  caterpiller  to  a  butterfly,  involves  not  merely  a  change 
in  external  form  but  a  greater  or  less  remodeling  of  its  entire 
structiu-e.  These  changes  take  place  during  the  period  of  apparent 
rest,  the  prepupal  and  pupal  stadia. 

The  chrymlis.— The  term  chrysalis  is  often  applied  to 

the  pupae  of  butterflies.     It  was  suggested  by  the  golden 

spots  with  which  the   pups   of   certain   butterflies  are 

ornamented. 

Two  forms  of  this  word  are  in  use:    first,  chrysaHs,  the  plural  of 

which  is  chrysalides;    and  second,  chrysahd,  the  plural  of  which  is 


THE    METAMORPHOSIS   OF   INSECTS 


187 


chrysalids.     The  singular  of  the  first  form  and  the  plural  of  the  second 
are  those  most  often  used. 

Active  pupa. — The  pupas  of  mosquitoes  and  of  certain  midges  are 
remarkable  for  being  active.  Although  the  wings  and  legs  are  func- 
tionless,  as  with  other  pupae,  these  creatures  are  able  to  swim  by 
means  of  movements  of  the  caudal  end  of  the  body. 

In  several  genera  of  the  Neuroptera  {Chrysopa,  Hemerobius,  and 
Raphidia)  the  pupa  becomes  active  and  crawls  about  just  before 
transforming  to  the  adult  state. 

Movements  of  a  less  striking  character  are  made  by  many  pupse, 
which  work  their  way  out  of  the  ground,  or  from  burrows  in  wood, 
before  transforming.  In  some  cases,  as  in  the  pupas  of  the  carpenter- 
moths  (Cossidas)  the  pupa  is  armed  with  rows  of  backward  projecting 
teeth  on  the  abdominal  segments,  which  facilitate  the  movements 
within  the  burrow. 

'^he  cremaster. — Many  pupje,  and  especially  those  of  most  Lepidop- 
tera,  are  provided  with  a  variously  shaped  process  of  the  posterior 
end  of  the  body,  to  which  the  term  cremaster  is  applied.  This  process 
is  cften  provided  with  hooks  which  serve  to  suspend  the  pupa,  as  in 
butterflies,  or  to  hold  it  in  place,  after  it  has  partly  emerged  from  the 
cocoon,  and  while  the  adult  is  emerging  from  the  pupal  skin,  as  in 
cocoon-making  moths.  In  its  more  simple  form,  where  hooks  are 
lacking,  it  aids  the  pupa  in  working  its  way  out  of  the  earth ,  or  from 
other  closed  situations. 

The  msthod  of  fixing  the  cremaster  in  the  disk  of  silk  from  which 
the  pupa  of  a  butterfly  is  suspended  was  well-illustrated  by  C.  V.  Riley 
('79).     The  full  grown  larva  spins  this  disk  and  hangs  from  it  during 

the  prepupal  stadium 
by  means  of  its  anal 
prolegs  (Fig.  209,  a). 
When  the  last  larval 
skin  is  shed,  it  is 
worked  back  to  the 
caudal  end  of  the  body 
(Fig.  209,  b);  and  is 
then  grasped  between 
two  of  the  abdominal 
segments  (Fig.  209,  c,) 
while  the  caudal  end  of  the  body  is  removed  from  it;  and  thus  the 
cremaster  is  freed,  and  is  in  a  position  from  which  it  can  be  inserted 
in  the  disk  of  silk. 


Fig.  209. — Transformations  of  the  milkweed  butter- 
fly (From  Riley). 


188  AN  INTRODUCTION   TO  ENTOMOLOGY 

The  cocoon. — The  pupal  instar  is  an  especially  vulnerable  one. 
During  the  pupal  life  the  insect  has  no  means  of  offence,  and  having 
exceedingly  limited  powers  of  motion,  it  has  almost  no  means  of 
defense  unless  an  armor  has  been  provided. 

Many  larvae  merely  retreat  to  some  secluded  place  in  which  the 
pupal  stadium  is  passed ;  others  bury  themselves  in  the  ground ;  and 
still  others  make  provision  for  this  helpless  period  by  spinning  a  silken 
armor  about  their  bodies.     Such  an  armor  is  termed  a  cocoon. 

The  cocoon  is  made  by  the  full-grown  larva;  and  this  usually 
takes  place  only  a  short  time  before  the  beginning  of  the  pupal  stadium. 
But  in  some  cases  several  months,  elapse  between  the  spinning  of  the 
cocoon  and  the  change  to  pupa,  the  cocoon  being  made  in  the  autumn 
and  the  change  to  pupa  taking  place  in  the  spring.  Of  course  a 
greater  or  less  portion  of  this  period  is  occupied  by  the  prepupal 
stadium. 

Cocoons  are  usually  made  of  silk,  which  is  spun  from  glands 
already  described.  In  some  cases,  as  in  the  cocoons  of  Bombyx,  the 
silk  can  be  unwound  and  utilized  by  man. 

While  silk  is  the  chief  material  used  in  the  making  of  cocoons,  it  is 
by  no  means  the  only  material.  Many  wood-boring 
larvas  make  cocoons  largely  of  chips.  Many  insects  that 
undergo  their  transformation  in  the  ground  incorporate 
earth  in  the  walls  of  their  cocoons.  And  hairy  cater- 
pillars use  silk  merely  as  a  warp  to  hold  together  a 
woof  of  hair,  the  hairs  of  the  larva  being  the  most  con- 
spicuous element  in  the  cocoon. 

In  those  cases  in  which  silk  alone  is  used  there  is  a 
great  variation  in  the  nature  of  the  silk,  and  in  the  den- 
sity of  the  cocoon.  The  well-known  cocoons  of  the 
satumiids  illustrate  one  extreme  in  density,  the  cocoons 
of  certain  Hymenoptera,  the  other. 

The  fiberous  nature  of  the  cocoon  is  usually  obvious; 

but  the  cocoons  of  saw-flies  appear  parchment-like,  and 

Fig.    2IO.—  the  cocoons  of  the  sphecids  appear  like  a  delicate  foil. 

cocoon^ of        While  in  the   more  common  type  of  cocoons  the 

Trichosfibas  wall  is  a  closely  woven  sheet,  there  are  cocoons  that 

from   which  ^^^  lace-like  in  texture  (Fig.  210). 

theadulthas        Modes  of  escape  from  the  cocoon. — The  insect,  having 

emerge  .        walled  itself  in  with  a  firm  layer  of  silk,  is  forced  to  meet 

the  problem  of  a  means  of  escape  from  this  inclostire;  a  problem 

which  is  solved  in  greatly  varied  ways. 


THE   METAMORPHOSIS   OF  INSECTS 


189 


^iK=- 


In  many  insects  in  which  the  adult  has  biting  mouth  parts,  the 
adult  merely  gnaws  its  way  out  by  means  of  its  mandibles  In  some 
cases,  as  the  Cynipidee,  it  is  said  that  this  is  the  only  use  made  of 
its  mandibles  by  the  adult. 

In  some  cases  the  mandibles  with  which  the  cocoon  is  pierced  per- 
tain to  the  pupal  instar,  this  is  true  of  Chrysopa  and  Hemerobius; 
and  the  Trichoptera  break  out  from  their  cases,  by  means  of  their 
mandibles,  while  yet  in  the  pupal  state. 

For  those  insects  in  which  the  adult  has  sucking  mouth  parts,  the 
problem  is  even  more  difficult.     Here  it  has  been  met  in  several  quite 
distinct  ways.     The  pupae  of  many  Lepidop- 
tera  possess  a  specialized  organ  for  breaking 
through  the  cocoon;   in  some  the  anterior 
end  of  the  pupa  is  furnished  with  a  toothed 
crest  {Lithocolletes  hamadryella) ;  in  certain    satur- 
niids  there  is  a  pair  of  large,  stout,  black  spines, 
one  on  each  side 
of  the  thorax,  at 
the  base  of  the 
fore  wings  with 
which  the  f  dult 
fW^-^MW  cuts  a  slit  in  the   Fig.  212. — Cocoon  oi  Megalopvge  oper- 

W      111         cocoon  through      '''^'''''^ 

/iK^  ^fs  which  the  moth  emerges,  this  was  observed  by 
Packard  in  Tropcsa  luna;  but  as  these  spines  are 
present  in  other  saturniids,  where  the  cocoon  is  too 
dense  to  be  cut  by  them,  and  where  an  opening  is 
made  in  some  other  way, 
it  is  probable  that,  as  a 
rule,  their  function  is  loco- 
motive, aiding  the.moth  to 
work  its  way  out  from  the 
cocoon,  by  a  wriggling 
motion. 

One    of   the    ways   in 
which     saturniids     pierce 

their  cocoons  is  that  practiced  by  Bombyx  and  Telea. 
These  insects  soften  one  end  of  the  cocoon  by  a 
liquid,  which  issues  from  the  mouth;  and  then,  by 
forcing  the  threads  apart  or  by  breaking  them,  make  an  opening. 


Fig.  211. — Longi- 
tudinal section 
of  a  cocoon  of 
Callosamia  pro- 
methea;v,valve- 
like  arrange- 
ment for  the 
escape  of  the 
adult. 


Fig.   213. — Old  cocoon  of 
Megalopyge  opercularis. 


190  AN  INTRODUCTION   TO  ENTOMOLOGY 

Far  more  wonderful  than  any  of  the  methods  of  emergence  from 
the  cocoon  described  above  are  those  in  which  the  larva  makes  pro- 
vision for  the  escape  of  the  adult.  The  most  familiar  of  these  is  that 
practiced  by  the  larv^  of  Samia  cecropia  and  Callosamia  promethea. 
These  larvsd  when  they  spin  their  cocoons  construct  at  one  end  a  coni- 
cal valve-like  arrangement,  which  allows  the  adult  to  emerge  without 
the  necessity  of  making  a  hole  through  the  cocoon  (Fig.  2x1,  ?;).  A 
less  familiar  example,  but  one  that  is  fully  as  wonderful,  is  that  of 
a  Megalopyge.  The  larva  of  this  species  makes  a  cocoon  of  the 
form  shown  in  Figure  212.  After  an  outer  layer  of  the  cocoon  has 
been  made,  the  larva  constructs,  near  one  end  of  it,  a  hinged  partition ; 
this  serves  as  a  trap  door,  through  which  the  moth  emerges.  That 
part  of  the  cocoon  that  is  outside  of  the  partition  is  quite  delicate  and 
is  easily  destroyed.  Hence  most  specimens  of  the  cocoons  in  col- 
lections present  the  appearance  represented  in  Figure  213. 

The  puparium. — The  pupal  stadiimi  of  most  Diptera  is  passed 
within  the  last  larval  skin,  which  is  not  broken  till  the  adult  fly  is 
ready  to  emerge.  In  this  case  the  larv^al  skin,  which  becomes  hard 
and  brown,  and  which  serves  as  a  cocoon,  is  termed  a 
puparium.  In  some  families  the  puparium  retains  the 
form  of  the  Xoxysl;  in  others  the  body  of  the  lar\^a 
shortens,  assuming  a  more  or  less  barrel-shaped  form, 
before  the  change  to  a  pupa  takes  place  (Fig.  214), 

Modes  of  escape  from  the  puparium. — The  pupae  of 
the  more  generalized  Diptera  escape  from  the  pupa- 
rium through  a  T-shaped  opening,  which  is  formed  by 
a  lengthwise  split  on  the  back  near  the  head  end  and  a 
crosswise  spHt  at  the  front  end  of  this  (Fig.  215),  or 
rarely,  through  a  cross-wise  split  between  the  seventh 
Fig.  214.— Pupa-  and  eighth  abdominal  segments.  In  the  more  special- 
num  of  Try-  -^g^j  Diptera  there  is  developed  a  large  bladder-like 
organ,  which  is  pushed  out  from  the  front  of  the  head, 
through  what  is  known  as  the  frontal  suture,  and  by  which  the  head 
end  of  the  puparium  is  forced  off.  This  organ  is  known  as  the  ptilinum. 
After  the  adult  escapes,  the  ptiliniim  is  withdrawn  into  the  head. 

The  Different  types  of  pupae . — Three  types  -^ 
of  pupae  are  commonly  recognized;    these 
are  the  following :  Fig.    215.— Puparium  of  a 

Exarate  pupcB.—Vup^  which,  like  those      stratiomyud. 
of  the  Coleoptera  and  Hymenoptera,  have  the  legs  and  wings  free, 
are  termed  exarate  pup«. 


THE   METAMORPHOSIS   OF  INSECTS  191 

Obtected  pupcz. — Pupse  which  Hke  the  pupae  of  Lepidoptera,  have 
the  Hmbs  glued  to  the  surface  of  the  body,  are  termed  obtected  pups. 

Coarctate  Pupcs. — Pupag  that  are  enclosed  within  the  hardened 
larval  skin,  as  is  the  case  with  the  pupae  of  most  of  the  Diptera,  are 
termed  coarctate  pupae. 

The  imago — The  fully  developed  or  adult  insect  is  termed  the 
imago. 

The  life  of  the  imago  is  devoted  to  making  provision  for  the 
perpetuation  of  the  species.  It  is  during  the  imaginal  stadium  that 
the  sexes  pair,  and  the  females  lay  their  eggs.  With  many  species 
this  is  done  very  soon  after  the  last  ecdysis ;  but  with  others  the  egg- 
laying  is  continued  over  a  long  period;  this  is  especially  true  with 
females  of  the  social  Hymenoptera. 

h.       HYPERMETAMORPHOSIS 

There  are  certain  insects,  representatives  of  several  different  orders 
that  exhibit  the  remarkable  peculiarity  in  their  development  that  the 
successive  larval  instars  represent  different  types  of  larvse.  Such 
insects  are  said  to  undergo  a  hypermetamorphosis. 

The  transformations  of  several  of  these  insects  will  be  described 
later  in  the  accounts  of  the  families  to  which  they  belong;  and  for 
this  reason,  in  order  to  avoid  repetition,  are  not  discussed  here.  The 
more  striking  examples  are  Mantispa,  Meloe,  Stylops,  and  Platy- 
gaster. 

i.      VIVIPAROUS   INSECTS 

There  are  many  insects  that  produce  either  nymphs  or  larvee 
instead  of  laying  eggs.  Such  insects  are  termed  viviparous.  This 
term  is  opposed  to  oviparous,  which  is  applied  to  those  insects  that  lay 
eggs  that  hatch  after  exclusion  from  the  body. 

It  has  been  pointed  out  in  the  discussion  of  the  reproductive  organs  that,  from 
the  primordial  germ -cells,  there  are  developed  in  one  sex  spermatoza  and  in  the 
other  eggs;  and  it  should  be  borne  in  mind  that  the  germ-cells  produced  in  the 
ovary  of  a  female  from  the  primordial  germ-cells  are  eggs.  These  eggs  grow  and 
mature;  in  some  cases  they  become  covered  with  a  shell,  in  others  they  are  not 
so  covered ;  in  some  cases  they  are  fertilized  by  the  union  of  a  spermatozoan  with 
them,  and  in  others  they  are  never  fertilized;  but  in  all  these  cases  they  are  eggs. 
We  may  say,  therefore,  that  all  insects  are  developed  from  eggs. 

A  failure  to  recognize  this  fact  has  introduced  confusion  into  entomological 
literature.  Some  writers  have  termed  the  germ-cells  produced  by  agamic  aphids 
pseudova  or  false  eggs.  But  these  germ-cells  are  as  truly  eggs  as  are  those  from 
which  the  males  of  the  honeybee  develop;  they  are  merely  unfertilized  eggs. 
The  term  pseudovum  conveys  a  false  impression;  while  the  phrase,  an  unfer- 
tilized egg,  clearly  states  a  fact. 


192  AN  INTRODUCTION  TO  ENTOMOLOGY 

Some  writers  make  use  of  the  term  ovoviviparous  indicating  the  production 
of  eggs  that  have  a  well -developed  shell  or  covering,  but  which  hatch  within  the 
body  of  the  parent;  but  the  distinction  is  not  fundamental,  since  viviparous  ani- 
mals also  produce  eggs  as  indicated  above. 

Among  viviparous  insects  there  are  found  every  gradation  from 
those  in  which  the  larvae  are  bom  when  very  young  to  those  in  which 
the  entire  larval  life  is  passed  within  the  body  of  the  parent.  There 
also  exist  examples  of  viviparous  larvae,  viviparous  pupae,  and  vivi- 
parous adults.  And  still  another  distinction  can  be  made;  in  some 
viviparous  insects  the  reproduction  is  parthenogenetic ;  in  others  it 
is  sexual. 

Viviparity  with  parthenogenetic  reproduction. — In  certain  vivipar- 
ous insects  the  reproduction  is  parthenogenetic ;  that  is,  the  young  are 
produced  from  eggs  that  are  not  fertilized.  This  type  of  reproduction 
occurs  in  larvae,  pupae,  and  apparently  in  adults. 

Pcedogenetic  Larvcs. — In  1862  Nicholas  Wagner  made  the  remark- 
able discovery  that  certain  larvae  belonging  to  the  Cecidomyiidae  give 
birth  to  living  young.  This  discovery  has  been  confirmed  by  other 
observers,  and  for  this  type  of  reproduction  the  term  pcsdogenesis, 
proposed  by  Von  Baer,  has  come  into  general  use.  This  term  is  also 
spelled  pedogenesis;  the  word  is  from  pcedo  or  pedo,  a  child,  and  genesis. 

The  phenomenon  of  paedogenesis  is  discussed  later  in  the  accounts 
of  the  Cecidomyiidse  and  of  the  Micromalthidag. 

Pcedogenetic  pupce. — The  most  frequently  observed  examples  of 
paedogenetic  reproduction  are  by  larvae;  but  that  pupae  also  are  some- 
times capable  of  reproduction  is  shown  by  the  fact  that  Grimm  ('70) 
found  that  eggs  laid  by  a  pupa  of  Chironomus  grimmii,  and  of  course 
not  fertilized,  hatched. 

Anton  Schneider  ('85)  found  that  the  adults  of  this  same  species  of 
Chironomus  reproduced  parthenogenetically .  This  species,  therefore , 
exhibits  a  transition  frpm  paedogenesis  to  normal  parthenogenesis. 

Viviparous  adult  agamic  females . — There  may  be  classed  under  this 
class  provisionally,  the  agamic  females  of  the  Aphididae ;  as  these  are 
commonly  regarded  as  adults.  It  has  been  suggested,  however,  that 
the  agamic  reproduction  of  the  Aphids  may  be  a  kind  of  paedogenesis ; 
the  agamic  females  being  looked  upon  as  nymphs.  This  however,  is 
not  so  evident  in  the  case  of  the  winged  agamic  generation.  On  the 
other  hand,  the  reproductive  organs  of  the  agamic  aphids  are  incom- 
pletely developed,  as  compared  with  those  of  the  sexual  forms,  lacking 
a  spermatheca  and  colleterial  glands. 


THE   METAMORPHOSIS  OF  INSECTS  193 

This  discussion  illustrates  the  difficulty  of  attempting  to  make  sharp  distinc- 
tions, whereas  in  nature  all  gradations  exist  between  different  types  of  structure 
and  of  development.  Thus  Leydig  ('67)  found  a  certain  aphid  to  be  both  ovipar- 
ous and  viviparous;  the  eggs  and  the  individuals  horn  as  nymphs  being  pro :luced 
from  neighboring  tubes  of  the  same  ovary. 

Viviparity  with  sexual  reproduction. — Although  most  insects  that 
reproduce  sexually  are  oviparous,  there  are  a  considerable  number  in 
which  sexual  reproduction  is  associated  with  viviparity. 

Among  these  sexual  viviparous  insects  there  exist  great  differences 
in  method  of  reproduction ;  with  some  the  young  are  bom  in  a  very 
immature  stage  of  development,  a  stage  corresponding  to  that  in 
which  the  young  of  oviparous  insects  emerge  from  the  egg ;  while  with 
others  the  young  attain  an  advanced  stage  of  development  within  the 
body  of  the  mother. 

Sexual  viviparous  insects  giving  birth  to  nymphs  or  larvce. — That 
type  of  viviparity  in  which  sexual  females  give  birth  to  very  immature 
nymphs  or  larvae  exists  in  more  or  less  isolated  members  of  widely 
separated  groups  of  insects.  As  the  assumption  of  this  type  of  repro- 
duction involves  no  change  in  the  structure  of  the  parent,  but  merely 
a  precocious  hatching  of  the  egg,  it  is  not  strange  that  it  has  arisen 
sporadically  and  many  times.  In  some  cases,  however,  the  change  is 
not  so  slight  as  the  foregoing  statement  would  imply ;  as,  for  example, 
in  the  case  of  the  viviparous  cockroach,  which  does  not  secrete 
ootheccfi  as  do  other  cockroaches. 

Among  the  recorded  examples  of  this  type  of  viviparity  are  repre- 
sentatives of  the  Ephemerida,  Orthoptera,  Hemiptera,  Lepidoptera, 
Coleoptera,  Strepsiptera,  and  Diptera. 

Sexual  viviparous  insects  giving  birth  to  old  larvcu.- — The  mode  of 
reproduction  exhibited  by  these  insects  is  doubtless  the  most  excep- 
tional that  occurs  in  the  Hexapoda,  involving,  as  it  does,  very  import- 
ant changes  in  the  structure  of  the  reproductive  organs  of  the 
females. 

With  these  insects  the  larv^ae  reach  maturity  within  the  body  of  the 
parent,  undergoing  what  is  analogous  to  an  intra-uterine  development, 
and  are  bom  as  full-grown  larvae.  This  involves  the  secretion  of  a 
"milk"  for  the  nourishment  of  the  young. 

This  mode  of  reproduction  is  characteristic  of  a  group  of  flies, 
including  several  famihes,  and  known  as  the  Pupipara.  This  name 
was  suggested  for  this  group  by  the  old  belief  that  the  young  are  born 
as  pupae;  but  it  has  been  found  that  the  change  to  pupa  does  not  take 
place  till  after  the  birth  of  the  larva. 


194  AN  INTRODUCTION   TO  ENTOMOLOGY 

The  reproduction  of  the  sheep-tick,  Melophagus  ovinus,  may  be 
taken  as  an  illustration  of  this  type  of  development;  this  is  described 
in  the  discussion  of  the  Hippoboscidse,  the  family  to  which  this  insect 
belong:s. 

The  giving  birth  to  old  larvae  is  not  restricted  to  the  Pupipara. 
Surgeon  Bruce  (quoted  by  Sharp.  '99)  has  shown  that  the  Tsetse  fly, 
Giossina  morsitans,  reproduces  in  this  way,  the  young  changmg  to 
pups  immediately  after  birth. 

An  intermediate  type  of  development  is  illustrated  by  Hylemyia 
strigosa,  a  dung -frequenting  fly  belonging  to  the  Anthomyiidag. 
This  insect,  according  to  Sharp  ('99),  produces  living  larvae,  one  at  a 
time.  "These  larvae  are  so  large  that  it  would  be  supposed  they  are 
full-grown,  but  this  is  not  the  case,  they  are  really  only  in  the  first 
stage,  an  unusual  amount  of  growth  being  accompHshed  in  this 
stadium." 

j.      NEOTEINIA 

The  persistence  with  adult  animals  of  larval  characteristics  has 
been  termed  neoteinia*  or  neotenia.  When  this  term  first  came  into 
use  it  was  applied  to  certain  amphibians,  as  the  axolotle,  which  retains 
its  gills  after  becoming  sexually  mature;  but  it  is  now  used  also  in 
entomology. 

The  most  familiar  examples  of  neoteinic  insects  are  the  glow- 
worms, which  are  the  adult  females  of  certain  beetles,  the  complemen- 
tal  females  of  Termites,  and  the  females  of  the  Strepsiptera. 


II.     THE   DEVELOPMENT  OF  APPENDAGES 

In  the  preceding  pages  the  more  obvious  of  the  changes  in  the 
external  form  of  the  body  during  the  metamorphosis  of  insects  and 
some  deviations  from  the  more  common  types  of  development  have 
been  discussed.  The  changes  in  the  form  of  the  trunk  that  have  been 
described  are  those  that  can  be  seen  without  dissection;  but  it  is 
impracticable  to  limit  a  discussion  of  the  development  of  the  appen- 
dages of  the  body  in. this  way,  for  in  the  more  specialized  types  of 
metamorphosis  a  considerable  part  of  the  development  of  the  appen- 
dages takes  place  within  the  body-wall. 


"Neoteinia:   neos  {v4o%),  youthful;   teinein  {reiveiv),  to  stretch. 


THE  METAMORPHOSIS   OF  INSECTS  195 

a.      THE   DEVELOPMENT   OF    WINGS 

Two  quite  distinct  methods  of  development  of  wings  exist  in 
insects;  by  one  method,  the  wings  are  developed  as  outward  project- 
ing appendages  of  the  body;  by  the  other,  they  reach  an  advanced 
stage  of  development  within  the  body.  The  former  method  of 
development  takes  place  with  nymphs  and  naiads,  the  latter  with 
larv^ae.* 

I.     The  Development  of  the  Wings  of  Nymphs  and  Naiads 

In  insects  with  a  gradual  or  with  an  incomplete  metamorphosis  the 
development  of  the  appendages  proceeds  in  a  direct  manner.  The 
wings  of  nymphs  and  naiads  are  sac-like  outgrowths  of  the  body-wall, 
which  appear  comparatively  early  in  life  and  become  larger  and  larger 
with  successive  molts,  the  expanding  of  the  wing-buds  taking  place 
immediately  after  the  molt ;  an  illustration  of  this  has  been  given  in 
the  discussion  of  gradual  metamorphosis,  page  175. 

2.     Development  of  the  Wings  in  Insects  with  a  Complete 
Metamorphosis 

Although  there  are  differences  in  details  in  the  development  of  the 
wings  in  the  different  insects  undergoing  a  complete  metamorphosis, 
the  essential  features  are  the  same  in  all.  The  most  striking  feature 
is  that  the  rudiments  of  the  wings,  the  wing-buds,  arise  within  the 
body  and  become  exposed  for  the  first  time  when  the  last  lar\^al  skin 
is  shed.  The  development  of  the  wings  of  the  cabbage  butterfly 
{Pontia  rapce)  will  serve  as  an  example  of  this  type  of  development  of 
wings.  The  tracing  of  that  part  of  this  development  which  takes 
place  during  the  larval  life  can  be  observed  by  making  sections  of  the 
body-wall  of  the  wing-bearing  segments  of  the  successive  instars  of 
this  insect. 

The  first  indication  of  a  wing-bud  is  a  thickening  of  the  hypo- 
dermis;  this  thickening,  known  as  a  histoblast  or  an  imaginal  disc, 
has  been  observed  in  the  embryos  of  certain  insects,  in  the  first 
larval  instar  of  the  cabbage  butterfly  it  is  quite  prominent  (Fig. 
216,  a).  During  the  second  stadium,  it  becomes  more  prominent 
and  is  invaginated,  forming  a  pocket-like  structure  (Fig.  216,  b). 
During  the  third  stadium  a  part  of  this  invagination  becomes 
thickened   and  evaginated  into  the  pocket  formed  by  the  thinner 


*Only  the  more  general  features  of  the  development  of  wings  are  discussed 
here.     For  a  fuller  account  see  "The  Wings  of  Insects"  (Comstock  'i  8,  a). 


196 


AN  INTRODUCTION   TO   ENTOMOLOGY 


portions   of   tne   invagination    (Fig.    216,   c).       During   the   fourth 
stadium,  the    evaginated   part    of   the    histoblast    becomes  greatly 

extended  (Fig.  216,  d). 
It  is  this  evaginated 
portion  of  the  histo- 
blast that  later  be- 
comes the  wing.  Dur- 
ing the  fifth  stadium 
the  wing-bud  attains 
the  form  shown  in 
Figure  216,  e,  which 
represents  it  dissected 
out  of  the  wing-pocket 
At  the  close  of  the  last 
larA^^l  stadium,  the 
fifth,  the  wing  is  pushed 
out  from  the  wing-poc- 
ket, and  lies  under  the 
old  larval  cuticula  dur- 
ing the  prepupal  sta- 
dium. It  is  then  of 
the  form  shown  in 
Figure  216,  /.  The 
molt  that  marks  the 
beginning  of  the  pupal 
stadium,  exposes  the 
wing-buds,  which  in 
I  the  Lepidoptera  be- 
y  come  closely  soldered 
/  to  the  sides  and  breast 
of  the  pupa.  Imme- 
diately after  the  last 
molt  when  the  adult 
emerges,     the     wings 

Fig.  216.— Several  stages  in  the  development  of  the   expand     greatly     and 
wings  of  a  cabbage  butterfly  (After  Mercer).  assume  their  definitive 

form. 

While  this  increase  in  size  and  changes  in  form  of  the  developing 

wing  are  taking  place,  there  occur  other  remarkable  developments  in 

its  structure.     A  connection  is  made  with  a  large  trachea  near  which 

the  histoblast  is  developed,  shown  in  cross-section  in  the  first  four 


THE    METAMORPHOSIS   OF  INSECTS  197 

parts  (a,  b,  c,  and  d)  of  Figure  216;  temporary  respiratory  organs, 
consisting  of  bundles  of  tracheoles,  are  developed  (e  and/) ;  and  later, 
near  the  close  of  the  larval  period,  the  tracheas  of  the  wing  are  devel- 
oped, and  the  bundles  of  tracheoles  disappear.  During  the  later 
stages  in  the  development  of  the  wing  the  basement  membranes  of  the 
hypodermis  of  the  upper  and  lower  sides  of  the  wing  come  together, 
except  along  the  lines  where  the  veins  are  to  be  developed  later,  and 
become  united.  In  this  way  the  wing  is  transformed  from  a  bag-like 
organ  to  a  sheet-like  one.  The  lines  along  which  the  two  sides  of  the 
wing  remain  separate  are  the  vein  cavities ;  in  these  the  trunks  of  the 
wing-trachea  extend.  During  the  final  stages  of  the  development  of 
the  wing,  the  walls  of  the  vein-cavities  are  thickened,  thus  the  wing- 
veins  are  formed ;  and  the  spaces  between  the  wing-vf  ins  become  thin. 

By  reference  to  Figure  216,  c  and  d,  it  will  be  seen  that  the  histo- 
blast  consists  of  two  quite  distinct  parts,  a  greatly  thickened  portion 
which  is  the  wing-bud  and  a  thinner  portion  which  connects  ths  wing- 
bud  with  the  hypodermis  of  the  body-wall,  and  which  constitutes  the 
neck  of  the  sac-like  histoblast,  this  is  termed  the  peripodal  membrane, 
a  term  suggested  by  the  similar  part  of  the  histoblast  of  a  leg ;  and  the 
enclosed  cavity  is  known  as  the  peripodal  cavity. 

In  the  more  specialized  Diptera,  the  peripodal  membranes  are 
very  long  and  both  the  wing-buds  and  the  leg-buds  are  far  removed 
from  the  body-wall.  A  condition  intermediate  between  that  which 
exists  in  the  Lepidoptera,  as  shown  in  Figure  216,  and  that  of  the 
more  specialized  Diptera  was  found  by  Kellogg  (07)  in  the  larva  of 
Holorusia  rubiginosa,  one  of  the 
crane-flies  (Fig.  217). 

h.    THE    DEVELOPMENT    OF    LEGS 

The  development  of  the  legs 
pi  oceeds  in  widely  different  ways 

in    different    insects.     In    the  ^.  „,.      ,,.,,,  c  .u 

Fig.  217. — Wing- bud  in  the  larva  of  the 

more     generalized     forms,      the       giant    crane-flv,     Holorusia    rubiginosa; 

legs    of    the    embryo   reach    an      J>''    hypodermis;    pm    peripodal    mem- 

^  . V,        ,  brane;  t,    trachea;    wb,  wing-bud  (After 

advanced  stage  of  development      Kellogg). 

before    the    nymph    or    naiad 

leaves  the  egg-shell,  and  are  functional  when  the  insect  is  born;  on 
the  other  hand,  in  those  specialized  insects  that  have  vermiform  larvs, 
the  development  of  the  legs  is  retarded,  and  these  organs  do  not 
become  functional  until  the  adult  stage  is  reached.  Almost  every 
conceivable  intergrade  between  these  two  extremes  exist. 


198  AN  INTRODUCTION   TO  ENTOMOLOGY 

I.     The  Development  of  the  Legs  of  Nymphs  and  of  Naiads 

In  insects  with  a  gradual  metamorphosis  and  also  in  those  with  an 
incomplete  metamorphosis  the  nymph  or  naiad  when  it  emerges  from 
the  eggshell  has  well-developed  legs,  which  resemble  quite  closely 
those  of  the  adult.  The  changes  that  take  place  in  the  form  of  the 
legs  during  the  postembyronic  development  are  comparatively  slight ; 
there  may  be  changes  in  the  relative  sizes  of  the  different  parts ;  and 
in  some  cases  there  is  an  increase  in  the  number  of  the  segments  of  the 
tarsus;  but  the  changes  are  not  sufficiently  great  to  require  a  descrip- 
tion of  them  here. 

2.     The  Development  of  the  Legs  -in  Insects  with  a  Complete  Metamor- 
phosis 

It  is  a  characteristic  of  most  larvae  that  the  development  of  their 
legs  is  retarded  to  a  greater  or  less  extent.  This  retardation  is  least 
in  campodeiform  larv^^  more  marked  in  cruciform  larv^se,  and  reaches 
its  extreme  in  vermiform  larvae. 

The  development  of  the  legs  of  insects  with  campodeiform  larvae. — 

Among  the  larvae  classed  as  campodeiform  the  legs  are  more  or  less 
like  those  of  the  adults  of  the  same  species ;  there  may  be  differences 
in  the  proportions  of  the  different  segments  of  the  leg,  in  the  number 
of  the  tarsal  segments,  and  in  the  number  and  form  of  the  tarsal  claws; 
but  these  differences  are  not  of  a  nature  to  warrant  a  discussion  of 
them  here.  These  larvae  lead  an  active  life,  like  that  of  nymphs, 
and  consequently  the  form  of  legs  has  not  been  greatly  modified  from 
the  paurometabolous  type. 

The  development  of  the  legs  of  insects  with  erucif  orm  larvae. — In 

caterpillars  and  other  cruciform  larvae  the  thoracic  legs  are  short  and 
fitted  for  creeping ;  this  mode  of  locomotion  being  best  suited  to  their 
mode  of  life,  either  in  burrows  or  clinging  to  foliage.  This  form  of  leg 
is  evidently  an  acquired  one  being,  like  the  internal  development  of 
wings,  the  result  of  those  adaptive  changes  that  fit  these  lan^ae  to  lead 
a  very  different  life  from  that  of  the  adults. 

In  the  case  of  caterpillars  the  thoracic  legs  are  short,  they  taper 
greatly,  and  each  consists  of  only  three  segments.  It  has  been  com- 
monly believed  and  often  stated  that  the  three  segments  of  the  larval 
leg  correspond  to  the  terminal  portion  of  the  adult  leg;  but  studies  of 
the  development  of  the  legs  of  adults  have  shown  that  the  divisions 
of  the  lar\^al  leg  have  no  relation  to  the  five  divisions  of  the  adult  leg. 


THB   METAMORPHOSIS   OF  INSECTS  199 

It  has  been  shown  by  Gonin  ('92),  Kellogg  ('01  and  '04),  and 
Verson  ('04)  that  histoblasts  which  are  the  rudiments  of  the  legs  of  the 
adult  exist  within  the  body-wall  of  the  caterpillar  at  the  base  of  the 
larval  legs.  Late  in  the  larval  life  the  extremity  of  the  legs  of  the 
adult  are  contained  in  the  legs  of  the  caterpillar.  It  has  been  shown 
that  the  cutting  off  of  a  leg  of  a  caterpillar  at  this  time  results  in  a 
mutilation  of  the  terminal  part  of  the  leg  of  the  adult. 

The  development  of  the  legs  of  the  adult  within  the  body  of  cater- 
pillars has  not  been  studied  as  thoroughly  as  has  been  the  develop- 
ment of  the  wings ;  but  enough  is  known  to  show  that  in  some  respects 
the  two  are  quite  similar;  this  is  especially  true  of  the  development  of 
the  tracheoles  and  of  the  tracheae. 

The  development  of  the  legs  in  insects  with  vermiform  larvae. — In 

vermiform  larv-ee  the  development  of  the  entire  leg  is  retarded.  The 
leg  arises  as  a  histoblast,  which  is  within  the  body  and  bears,  in  its 
more  general  features,  a  resemblance  to  the  wing-buds  of  the  same 
insect.  The  development  of  the  legs  of  vermiform  larvae  has  been 
studied  most  carefully  in  the  larvae  of  Diptera.  During  the  larval 
life  the  leg  becomes  quite  fully  developed  within  the  peripodal  cavity ; 
in  Corethra,  they  are  spirally  coiled;  in  Miisca,  the  different  segments 
telescope  into  each  other.  At  the  close  of  the  larv^al  period,  the 
evagination  of  the  legs  takes  place. 

C.       THE  DEVELOPMENT  OF  ANTENNAE 

/.  The  Transformation  of  the  Antennae  of  Nymphs  and  of  Naiads 
In  the  case  of  nymphs  and  of  naiads  the  insect  when  it  emerges 
from  the  eggshell  has  well-developed  antennae.  The  changes  that 
take  place  during  the  postembryonic  development  are,  as  a  rule, com- 
paratively slight;  in  most  insects,  an  increase  in  the  number  of  the 
segments  of  the  antennae  takes  place ;  but  in  the  Ephemerida,  a  reduc- 
tion in  number  of  the  antennal  segments  occurs. 

2.     The  Development  of  the  Antenna  in  Insects  with  a  Complete 
Metamorphosis 

One  of  the  marked  characteristics  of  larvae  is  the  reduced  condition 
of  the  antennae;  even  in  the  campodeiform  larvae  of  the  Neuroptera, 
where  the  legs  are  comparatively  well-developed,  the  antennae  are 
greatly  reduced. 

In  cruciform  larvae  the  development  of  the  antennae  follows  a 
course  quite  similar  to  that  of  the  legs.     The  larval  antennae  are  small: 


200 


^A^  INTRODUCTION   TO  ENTOMOLOGY 


the  antennas  of  the  adult  are  developed  from  histoblasts  within  the 
head  and  during  the  latter  part  of  the  larval  life  are  folded  like  the 

bellows  of  a  closed  accor- 
dian;  at  the  close  of  this 
period  they  become  eva- 
ginated,  but  the  definitive 
form  is  not  assumed  until 
the  emergence  of  the  adult. 
A  similar  course  of  devel- 
opment of  the  antennae 
takes  place  in  vermiform 
larv£e  (Fig.  218). 

d.  THE  DEVELOPMENT  OF 
Fig.   218. — Sagittal  section  through  headof  old  THE   MOUTH-PARTS 

lar\^a  of  5/mi</2  Mm,  showing  forming  imaginal  , 

head    parts  within.     Ic,   larval   cuticula;    id.  Great   dlfterences   exist 

imaginal  head-wall;    la,  larval  antenna;    ia    among  insects   with   refer- 

imagmal    antenna;     ie,    imagmal    eye;     Imd,  '^ 

■  larval    mandible;     imd,    imaginal    mandible;  ence    to    the    comparative 

Imx    larval  maxilla;    im.v,  imaginal  maxilla;   structure   of   their   mouth- 

lli,  larval  labium;   tk,  imagmal  labium  (trom 

Kellogg).  parts    in    their    immature 

and  adult  instars.  In 
some  insects  the  immature  instars  have  essentially  the  same  type  of 
mou1;h-parts  as  the  adults ;  in  most  of  these  cases,  the  mouth-parts  are 
of  the  biting  types,  but  in  the  Homoptera  and  Heteroptera  both 
nymphs  and  adults  have  them  fitted  for  sucking;  in  many  other 
insects,  the  mouth-parts  of  the  larv^as  are  fitted  for  biting  while  those  of 
adults  are  fitted  for  sucking;  and  in  still  others,  as  certain  maggots,  the 
development  of  the  mouth-parts  is  so  retarded  that  they  are  first 
functional  in  the  adult  insect.  Correlated  with  these  differences  are 
differences  in  the  method  of  development  of  these  organs. 

In  those  insects  that  have  a  gradual  or  incomplete  metamorphosis 
and  in  the  Neuroptera,  the  Coleoptera,  and  the  Hymenoptera  in  part, 
the  mouth-parts  of  the  immature  and  adult  instars  are  essentially  of 
the  same  type.  In  these  insects  the  mouth-parts  of  each  instar  are 
developed  within  the  corresponding  mouth-parts  of  the  preceding 
instar.  At  each  ecdysis  there  is  a  molting  of  the  old  cuticula,  a 
stretching  of  the  new  one  before  it  is  hardened,  a  result  of  the  growth 
in  size  of  the  appendages,  and  sometimes  an  increase  in  the  number 
of  the  segments  of  the  appendage.  In  a  word,  the  mouth-parts  of  the 
adult  are  developed  from  those  of  the  immature  instar  in  a  compara- 
tively direct  manner.     In  some  cases,  however,  where  the  mouth- 


THE    METAMORPHOSIS    OF  INSECTS  201 

parts  of  the  larva  are  small  and  those  of  the  adult  are  large,  only  the 
tips  of  the  developing  adult  organs  are  within  those  of  the  larva  at  the 
close  of  the  larval  period,  a  considerable  part  of  the  adult  organs  being 
embedded  in  the  head  of  the  old  larva. 

In  a  few  Coleoptera  and  Neuroptera  (the  Dytiscidae,  Myrme- 
leonidae,  and  Hemerobiidas)  the  larvae,  although  mandibulate,  have 
the  mouth-parts  fitted  for  sucking.  In  these  cases  the  form  cf  the 
mouth-parts  have  been  modified  to  fit  them  for  a  peculiar  metho  d  of 
taking  nourishment  during  the  larval  life.  The  mouth-parts  of  the 
aduits  are  of  the  form  characteristic  of  the  orders  to  which  these 
insects  belong. 

In  those  insects  in  which  the  larvae  have  biting  mouth-parts  and 
the  adults  those  fitted  for  sucking,  the  development  is  less  direct.  In 
the  Lepidoptera,  for  example,  to  take  an  extreme  case,  there  are  great 
differences  in  the  development;  o:*^.  thc^  different  organs;  within  the 
mandibles  of  the  old  larvas  there  are  no  developing  mandibles,  these 
organs  being  atrophied  in  the  adult;  but  at  the  base  of  each  larval 
maxilla,  there  is  a  very  large,  invaginated  histoblast,  the  developing 
maxilla  of  the  adult;  these  histoblasts  become  evaginated  at  the 
close  of  the  larval  period,  but  the  maxilte  do  not  assimie  their  defini- 
tive form  till  after  the  last  ecdysis. 

The  extreme  modification  of  the  more  usual  course  of  development 
of  the  mouth-parts  is  found  in  the  footless  and  headless  larvce  of  the 
more  specialized  Diptera.  Here  the  mouth-parts  do  not  appear 
externally  until  during  the  pupal  stadium  and  become  functional  only 
when  the  adult  condition  is  reached.  See  the  figures  illustrating  the 
development  of  the  head  in  the  Muscidag  (Fig.  220). 

It  should  be  noted  that  the  oral  hooks  possessed  by  the  larvae  of  the 
more  specialized  Diptera  are  secondarily  developed  organs  and  not 
mouth-parts  in  the  sense  in  which  this  term  is  commonly  used.  These 
oral  hooks  serve  as  organs  of  fixation  in  the  larvas  of  the  CEstridas  and 
as  rasping  organs  in  other  larvas. 


e.       THE    DEVELOPMENT    OF    THE    GENITAL    APPENDAGES 

The  development  of  the  genital  appendages  of  insects  has  been 
studied  comparatively  Httle  and  the  results  obtained  by  the  different 
investigators  are  not  entirely  in  accord ;  it  is  too  early  therefore  to  do 
more  than  to  make  a  few  general  statements. 

In  the  nymphs  of  insects  with  a  gradual  metamorphosis  rudimen- 
tary genital  appendages  are  more  or  less  prominent  and  their  develop- 


202  AN  INTRODUCTION   TO  ENTOMOLOGY 

ment  follows  a  course  quite  similar  to  that  of  the  other  appendages  of 
the  body. 

In  insects  with  a  complete  metamorphosis  the  genital  appendages 
are  represented  in  the  larvag  by  invaginated  histoblasts ;  the  develop- 
ing appendages  become  evaginated  in  the  transformation  to  the  pupa 
state  and  assume  their  definitive  form  after  the  last  ecdysis. 

III.     THE  DEVELOPMENT  OF  THE  HEAD  IN  THE 
MUSCID^ 

In  the  more  generahzed  Diptera  the  head  of  the  larva  becomes, 
with  more  or  less  change,  the  head  of  the  adult ;  the  more  important 
of  these  changes  pertain  to  the  perfecting  of  the  organs  of  sight  and  the 
development  of  the  appendages,  the  antennae  and  mouth-parts. 

But  in  the  more  specialized  Diptera  there  is  an  anomalous  retard- 
ing of  the  development  of  the  head,  which  is  so  great  that  the  lar\-as 
of  these  insects  are  commonly  referred  to  as  being  acephalous.  This 
retarded  development  of  the  head  has  been  carefully  studied  by  Weis- 
man  ('64),  Van  Rees  ('88)  and  Kowalevsky  ('87).  The  accompanying 
diagrams  (Fig.  220)  based  on  those  given  by  the  last  two  authors  illus- 
trate the  development  of  the  head  in  Musca,  which  will  sen-e  as  an 
illustration  of  this  type  of  development  of  the  head. 

The  larv^as  of  Musca 
are  conical  (Fig.  219);  and 
the  head-region  is  repre- 
sented externally  only  by 
the  minute  apical  segment 
Fig.219— Larva  of  the  house-fly,  MM^ca  of  the  conical  bodv.  It 
domeshca  (After  Hewitt) . 

Will  be  shown  later  that 

this  segment  is  the  neck  of  the  insect,  the  developing  head  being 
invaginated  within  this  and  the  following  segments.  This  invagina- 
tion of  the  head  takes  place  during  the  later  embryonic  stages. 

In  Figure  220  are  given  diagrams,  adapted  from  Kowalevsky  and 
Van  Rees,  representing  three  stages  in  the  development  of  the  head  of 
Musca.  Diagram  A  represents  the  cephalic  end  of  the  body  of  a 
larva;  and  diagram  B  and  C,  the  corresponding  region  in  a  young  and 
in  an  old  pupa  respectively;  the  parts  are  lettered  uniformly  in  the 
three  diagrams. 

The  three  thoracic  segments  (i,  2,  and  3)  can  be  identified  by  the 
rudiments  of  the  legs  (/^  /-,  and  P).  In  the  larva  (A)  the  leg-buds 
are  far  within  the  body,  the  peripodal  membrane  being  connected  with 


THE   METAMORPHOSIS  OF  INSECTS 


203 


the  hypodermis  of  the  bodj^-wall  by  a  slender  stalk-Hke  portion.  In 
the  young  pupa  (B)  the  peripodal  membranes  of  the  histoblasts  of  the 
legs  are  greatly  shortened  and  the  leg-buds  are  near  the  surface  of  the 
body;  and  in  the  old  pupa  (C)  the  leg-buds  are  evaginated.  The 
wing-buds  are  omitted  in  all  of  the  diagrams. 

In  the  first  two  segments  of  the  body  of  the  larva  (A)  there  is  a 
cavity  {ph)  which  has  been  termed  the  "pharynx" ;  this  is  the  part  in 
which  the  oral  hooks  characteristic  of  the  larvag  of  the  Muscidas 
develop.  The  name  pharjmx  is  unfortunate  as  this  is  not  a  part  of  the 
ahmentary  canal;  it  is  an  invaginated  section  of  the  head,  into  the 
base  of  which  the  oesophagus  {ce)  now  opens. 

In  the  figure  of  the  lar\^a  (A)  note  the  following  parts:  the 
oesophagus  {ce) ;   the  ventral  chain  of  ganglia  {vg),  the  brain  (6),  and  a 


Fig.  220. — Development  of  the  head  in  the  Muscidae 

C,  old  pupa  (From  Korschelt  and  Heider  after  Kowalevsky  and  Van  Rees). 


pnpa ; 


sac  (6a)  extending  from  the  so-called  pharynx  to  the  brain.  There  are 
two  of  these  sacs,  one  applied  to  each  half  of  the  brain,  but  only  one  of 
these  would  appear  in  such  a  section  as  is  represented  by  the  diagram. 
These  sacs  were  termed  the  brain-appendages  by  Weismann.  In  each 
of  the  "brain-appendages"  there  is  a  disc-like  thickening  near  the 
brain,  the  optic  disc  (od) ;  this  is  a  histoblast  which  develops  into  a 
compound  eye ;  in  front  of  the  optic  disc  there  is  another  prominent 
histoblast ;  the  frontal  disc  (fd) ,  upon  which  the  rudiment  of  an  antenna 
(at)  is  developed. 

In  the  larva  the  brain  and  a  considerable  part  of  the  "brain- 
appendages"  lie  within  the  third  thoracic  segment.  In  the  young 
pupa  (B)  these  parts  have  moved  forward  a  considerable  distance; 
and  in  the  old  pupa  (C)  the  head  has  become  completely  evaginated. 
The  part  marked  p  in  the  two  diagrams  of  the  pupa  is  the  rudiment 
of  the  proboscis. 


204  AN  INTRODUCTION   TO  ENTOMOLOGY 

By  comparing  diagrams  B  and  C  it  will  be  seen  that  what  was  the 
tip  of  the  first  segment  of  the  larva  and  of  the  young  pupa  (++) 
becomes  the  neck  of  the  insect  after  the  head  is  evaginated. 

IV.    THE  TRANSFORMATIONS  OF  THE  INTERNAL 
ORGANS 

Great  as  are  the  changes  in  the  external  form  of  the  body  during 
the  life  of  insects  with  a  complete  metamorphosis,  even  greater  changes 
take  place  in  the  internal  organs  of  some  of  them. 

In  the  space  that  can  be  devoted  to  this  subject  in  this  work,  only 
the  more  general  features  of  the  transformation  of  the  internal  organs 
can  be  discussed;  there  is  an  extensive  and  constantly  increasing 
literature  on  this  subject  which  is  available  for  those  who  wish  to  study 
it  more  thoroughly. 

In  insects  with  a  gradual  or  with  an  incomplete  metamorphosis 
there  is  a  continuous  transformation  of  the  internal  organs,  the  changes 
inform  taking  place  gradually ;  being  quite  comparable  to  the  gradual 
de  velopment  of  the  external  organs ;  but  in  insects  with  a  complete 
metamorphosis,  where  the  manner  of  life  of  the  larva  and  the  adult 
are  very  different,  extensive  changes  take  place  during  the  pupal 
stadium.  The  life  of  a  butterfly,  for  example,  is  very  different  from 
that  it  led  as  a  caterpillar;  the  organs  of  the  larva  are  not  fitted  to 
perform  the  functions  of  the  adult ;  there  is  consequently  a  necessity 
for  the  reconsti-uction  of  certain  of  them ;  hence  the  need  of  a  pupal 
stadium.  Pupae  are  often  referred  to  as  being  quiet ;  but  physiologi- 
cally the  pupal  period  is  the  most  active  one  in  the  post-embryonic 
life  of  the  insect. 

In  those  cases  where  a  very  marked  change  takes  place  in  the 
structure  of  internal  organs,  there  is  a  degeneration  and  dissolution  of 
tissue,  this  breaking  down  of  tissues  is  termed  histolysis. 

In  the  course  of  histolysis  some  cells,  which  are  frequently  leu- 
cocytes or  white  blood  corpuscles,  feed  upon  the  debris  of  the  disin- 
tegrating tissue;  such  a  cell  is  termed  a  phahgocyte,  and  the  process  is 
termed  phagocytosis.  It  is  believed  that  the  products  of  the  digestion 
of  disintegrating  tissue  by  the  phagocytes  pass  by  diffusion  into  the 
surrounding  blood  and  serve  to  nourish  new  tissue. 

After  an  organ  has  been  more  or  less  broken  down  by  histolysis, 
the  extent  of  the  disintegration  differing  greatly  in  different  organs 
and  in  different  insects,  there  follows  a  growth  of  new  tissue;  this 
process  is  termed  histogenesis.. 


THE   METAMORPHOSIS   OF  INSECTS  205 

The  histogenetic  reproduction  of  a  tissue  begins  in  the  differentia- 
tion and  multiplication  of  small  groups  of  cells,  which  were  not  affected 
by  the  histolysis  of  the  old  tissue ;  such  a  group  of  cells  is  termed  an 
imaginal  disc  or  a  htstoblast.  They  were  termed  imaginal  discs  on 
account  of  the  disc-like  form  of  those  that  were  first  described  and 
because  they  are  rudiments  of  organs  that  do  not  become  functional 
till  the  imago  stage ;  but  the  term  histoblast  is  of  more  general  appli- 
cation and  is  to  be  preferred. 

The  extent  of  the  transformation  of  the  internal  organs  differs 
greatly  in  different  insects.  In  the  Coleoptera,  the  Lepidoptera,  the 
Hymenoptera,  and  the  Diptera  Nemocera,  the  mid-intestine  and 
some  other  larval  organs  are  greatly  modified,  but  there  is  no  general 
histolysis.  On  the  other  hand,  in  the  Diptera  Brachycera,  there  is  a 
general  histolysis.  In  Musca  all  organs  break  down  and  are  reformed 
except  the  central  nervous  system,  the  heart,  the  reproductive  organs, 
and  three  pairs  of  thoracic  muscles.  Regarding  the  extent  of  the 
transformations  in  the  other  orders  where  the  metamorphosis  is  com- 
plete we  have,  as  yet,  but  little  data. 


SUPPLEMENTARY  NOTE 

After  the  manuscript  of  this  volume  was  sent  .o  the  printer  there 
appeared  a  very  important  paper  by  Mr.  jR.E.  Snodgrass  on  the 
"Anatomy  and  Metamorphosis  of  the  Apple  Maggot,  Rhagoletis 
pomonella  Walsh."  This  was  published  -n  the  "Journal  of  Agricul- 
tural Research"  Vol.  28,  pp.  1-36,  with  six  plates. 

This  paper  was  received  too  late  to  make  possible  the  incorpora- 
tion of  the  new  material  in  the  preceding  pages. 


PART  II 

THE  CLASSIFICATION  AND  THE  LIFE- 
HISTORIES  OF  INSECTS 


CHAPTER  V 

THE  SUBCLASSES  AND  THE  ORDERS  OF  THE 
CLASS  HEXAPODA 

Insects  constitute  one  of  the  classes  of  the  Arthropoda,  that 
division  of  the  animal  kingdom  in  which  the  body  is  composed  of  a 
series  of  more  or  less  similar  segments  and  in  which  some  of  these 
segments  bear  jointed  legs.    This  class  is  known  as  the  Hexapoda. 

The  distinctive  characteristics  of  the  Class  Hexapoda  and  its 
relation  to  the  other  classes  of  the  Arthropoda  are  discussed  in  the 
first  chapter  of  this  work;  we  have  now  to  consider  the  division  of 
this  class  into  subclasses  and  orders. 

The  orders  that  constitute  the  Hexapoda  represent  two  well-marked 
groups;  this  class  is  divided,  therefore,  into  two  subclasses.  This 
division  was  first  proposed  by  Brauer  ('85),  who  recognized  the  fact 
that  while  the  wingless  condition  of  certain  insects,  the  fleas,  lice, 
bird-lice,  and  the  wingless  members  of  orders  in  which  the  wings  are 
usually  present,  is  an  acquired  one,  the  wingless  condition  of  the 
Thysanura  and  CoHembola  is  a  primitive  one.  In  other  words,  from 
the  primitive  insects,  which  were  wingless,  there  were  evolved  on  the 
one  hand  the  orders  Thysanura  and  Collembola,  which  remained 
wingless,  and  on  the  other  hand,  a  winged  form  from  which  have 
descended  all  other  orders  of  insects. 

An  extended  study  of  the  wings  of  insects  has  shown  that  the 
wings  of  all  of  the  orders  of  winged  insects  are  modifications  of  a 
single  type;  it  is  believed,  therefore,  that  all  of  the  orders  of  winged 
insects  have  descended  from  a  common  winged  ancestor.  As  to  the 
lice,  bird-lice,  and  fleas,  the  relation  of  each  of  these  groups  to  certain 
winged  insects,  as  shown  by  their  structure,  has  led  to  the  belief  that 
their  wingless  condition  is  an  acquired  one,  being  the  result  of  parasitic 
habits.  The  lice  or  Anoplura  are  commonly  regarded  as  closely 
allied  to  the  Homoptera  and  Heteroptera ;  the  bird-lice  or  Mallophaga 
to  the  Corrodentia;  and  the  fleas  or  Siphonaptera  to  the  Diptera. 
Hence  these  wingless  insects  are  placed  with  the  winged  insects  in  a 
single  subclass. 

The  two  subclasses  thus  recognized  were  named  by  Brauer  the 
Apterygogenea  and  the  Pterygogenea  respectively.  The  cumber- 
someness  of  these  names  led  to  the  substitution  for  them  of  the 
shorter  names  Apterygota  and  Pterygota.  The  Apterygota  includes 
the  orders  Thysanura  and  Collembola;  and  the  Pterygota,  all  other 
orders  of  insects.  Some  writers  regard  the  Thysanura  and  Collem- 
bola as  suborders  of  a  single  order,  which  they  term  the  Aptera. 

The  distribution  of  insects  into  orders  is  based  on  the  classification 
of  Linnaeus,  as  set  forth  in  his  "Systema  Naturae"  (1735-1768). 
Linnaeus,  who  has  been  called  the  Adam  of  zoological  science,  divided 

(209) 


210  AN  INTRODUCTION   TO  ENTOMOLOGY 

his  class  Insecta  into  seven  orders;  these  he  named  Coleoptera, 
Hemiptera,  Lepidoptera,  Neuroptera,  Hymenoptera,  Diptera,  and 
Aptera,  respectively. 

Since  the  time  of  Linnasusmany  modifications  of  his  classification 
of  insects  have  been  proposed;  and  new  ones  are  constantly  appear- 
ing. The  result  is  that  now  there  is  a  great  lack  of  uniformity  in  the 
classification  used  by  different  writers. 

The  modifications  of  the  Linnasan  distribution  of  insects  into 
orders  are  based  on  the  belief  that  in  certain  cases  Linnseus  grouped 
into  a  single  order  forms  that  really  represent  two  or  more  distinct 
orders.  The  result  has  been  a  great  increase  in  the  number  of  orders 
recognized. 

Linnaeus  included  in  his  class  Insecta,  under  the  order  Aptera, 
not  only  wingless  insects  but  also  arachnids,  crustaceans,  centipedes, 
and  millipedes.  The  animals  thus  grouped  by  Linnseus  are  now  dis- 
tributed into  several  classes ;  and  to  the  class  composed  of  the  animals 
now  commonly  known  as  insects,  those  characterized  by  the  posses- 
sion of  only  six  legs,  the  term  Hexapoda  is  commonly  applied.  Some 
writers,  however,  apply  the  term  Insecta  to  the  class  of  insects  as 
now  limited. 

Some  of  the  more  recently  recognized  orders  of  insects  are  repre- 
sented among  living  insects  by  comparatively  few  species;  but  in 
each  case  the  structure  of  the  insects  included  in  the  group  is  so  differ- 
ent from  that  of  all  other  insects  that  we  are  led  to  believe  that  they 
represent  a  division  of  the  class  Hexapoda  that  is  of  ordinal  value. 

There  are  given  below  the  names  of  the  orders  of  insects  recognized 
in  this  work.  The  sequence  in  which  these  orders  are  discussed  is  of 
necessity  a  more  or  less  arbitrary  one.  In  general  the  plan  adopted 
here  is  to  make  the  series  an  ascending  one;  that  is,  the  more  gen- 
eralized or  primitive  insects  are  placed  first  and  the  more  highly 
specialized  ones  later  in  the  series;  but  as  the  different  orders  of 
insects  have  been  specialized  in  very  different  ways,  the  relative  de- 
grees of  their  specialization  cannot  be  shown  by  arranging  them  in  a 
single  linear  series,  as  must  be  done  in  a  book.  To  indicate  the 
different  ways  in  which  the  different  members  of  a  group  have  been 
specialized  and  the  relative  rank  of  those  specialized  in  a  similar  way, 
use  must  be  made  of  a  diagram  representing  a  genealogical  tree. 
Many  such  diagrams  have  been  made,  but  no  one  of  them  has  re- 
ceived general  acceptance;  much  remains  to  be  learned  before  such 
a  diagram  can  be  made  that  will  inspire  confidence  in  its  accuracy. 

In  the  course  of  the  preparation  of  a  special  treatise  on  the  wings 
of  insects  (Comstock  '  1 8  a) ,  I  wrote  a  table  indicating  the  more  strik- 
ing of  the  methods  of  specialization  of  the  wings  characteristic  of 
each  of  the  orders  of  winged  insects;  and  in  the  discussion  of  the 
different  orders,  I  followed  the  sequence  indicated  by  this  table.  In 
doing  this  I  did  not  advocate  the  basing  of  a  classification  of  insects 
upon  the  characters  presented  by  the  wings  alone,  but  merely  made 
use  of  these  characters  for  the  purposes  of  that  work. 


11  EX  A  POD  A  211 

A  renewed  study  of  the  relationships  of  the  different  orders  to  each 
other,  in  which  an  effort  has  been  made  to  correlate  other  characters 
with  those  presented  by  the  wings,  has  not  indicated  the  desirability 
of  changes  in  the  sequence  of  the  orders  indicated  in  that  table,  ex- 
cept in  the  allocation  of  those  orders  in  which  wings  are  wanting. 

The  importance  of  the  wings  of  insects  for  taxonomic  purposes 
was  early  recognized  by  entomologists,  as  is  well  shown  by  the  fact 
that  the  names  of  the  Linnsean  orders  are  all  drawn  from  the  nature 
of  the  wings,  except  one,  Aptera,  and  that  from  the  absence  of  wings. 

The  different  methods  of  specialization  of  the  wings  arose  very 
early  in  that  part  of  the  geological  histor}^  of  insects  that  is  known 
to  us.  And  as  most  of  the  fossil  remains  of  the  older  insects  consist 
of  wings,  we  are  forced  to  depend  very  largely  on  the  characters 
presented  by  these  organs  for  data  regarding  the  separation  of  the 
primitive  insects  into  the  groups  from  which  the  orders  of  recent 
insects  have  been  developed.  But  in  characterizing  the  orders  as  they 
now  exist  all  the  results  of  the  study  of  the  structure  of  insects  and 
of  their  transformations  are  available. 

Aside  from  the  structure  of  the  wings,  the  characters  most  used 
in  characterizing  the  orders  of  insects  are  those  presented  by  the 
structure  of  the  mouth-parts  and  the  nature  of  the  post-embryonic 
development.  While  these  characters  are  of  value  in  defining  the 
orders,  but  little  use  has  been  made  of  them,  as  yet,  in  working  out 
the  lines  of  descent  of  the  various  orders  from  the  primitive  insects. 

The  primitive  insects  had  chewing  mouth-parts  and  this  type  has 
been  retained  in  the  greater  number  of  the  orders.  But  although 
many  detailed  accounts  of  the  structure  of  the  mouth-parts  of  chew- 
ing insects  have  been  published,  no  one  has  worked  out  the  various 
ways  in  which  they  have  been  specialized  in  such  a  manner  as  to  in- 
dicate the  phylogeny  of  the  orders. 

Several  different  types  of  sucking  mouth-parts  exist  among  living 
insects;  but  these  are  apparently  of  comparatively  late  origin,  and 
while  they  are  of  great  value  in  defining  the  orders  in  which  they 
occur,  they  do  not  afford  characters  for  determining  the  primitive 
divisions  of  the  Pterygota. 

The  nature  of  the  post-embryonic  development  of  insects,  like 
the  structure  of  the  mouth-parts,  affords  characters  for  defining  the 
orders  of  recent  insects,  but  is  of  little  value  in  determining  the 
phylogeny  of  the  orders. 

The  primitive  insects  doubtless  developed  without  any  marked 
metamorphosis  as  do  the  Thysanura  and  Collembola  of  today.  With 
the  development  of  wings,  there  arose  that  type  of  development 
known  as  gradual  metamorphosis,  and  this  type  is  retained  by  eight 
of  the  orders  recognized  in  this  work.  Incomplete  metamorphosis 
is  the  result  of  a  sidewise  development  of  the  immature  instars  of  the 
insects  exhibiting  it,  in  order  to  fit  them  for  life  in  the  water,  and  it 
doubtless  arose  independently  in  each  of  the  three  orders  in  which 
it  occurs ;  it  is  therefore  an  ordinal  characteristic  in  each  case  and  not 
one  indicating  a  natural  group  of  orders.     This  is  also  true  of  com- 


212  AN  ITRODUCTION   TO  ENTOMOLOGY 

plete  metamorphosis,  which  also  doubtless  arose  independently  in 
different  divisions  of  the  insect  series,  as,  for  example,  intheNeurop- 
tera,  which  it  is  believed  is  a  verv^  ancient  order,  the  origin  of  which 
was  much  earlier  than  the  attainment  of  complete  metamorphosis. 

TABLE    OF     THE    METHODS    OF    SPECIALIZATION    OF    THE    WINGS    CHARACTERISTIC 
OF  THE  ORDERS  OF  WINGED  INSECTS* 

This  table  is  merely  the  result  of  an  effort  to  indicate  the  more  striking  of 
the  methods  of  specialization  of  the  wings  characteristic  of  each  of  the  orders 
of  insects.  It  is  not  a  key  for  determining  the  orders  of  insects.  It  is  not  avail- 
able for  this  purpose;  because,  in  many  cases,  the  wings  of  an  insect  do  not 
show  the  type  of  specialization  characteristic  of  the  order  to  which  the  insect 
belongs.  Thus,  for  example,  while  the  most  characteristic  modification  of  the 
courses  of  the  wing-veins  in  the  Diptera  and  Hymenoptera  is  due  to  the  coales- 
cence of  veins  proceeding  from  the  margin  of  the  wing  towards  the  base  of  the 
wing,  there  is  no  indication  of  this  type  of  coalescence  of  veins  in  some  of  the 
nemocerous  Diptera. 

A.     Wings  specialized  by  the  development  of  .supernumeran,^  veins  in  the  preanal 
area. 
B.     Supernumerary  veins  of  the  accessory  type. 
C.     Wings  developed  externally. 

D.     Wings  retained  throughout  life.     Wings  without  a  striking  contrast 
in  the  thickness  of  the  veins  of  the  anterior  part  of  the  wing  and  those 

of    the    middle    portion Orthoptera 

DD.  Wings  deciduous,  there  being  near  the  base  of  each  wing  a  trans- 
verse suture  along  which  the  wing  is  broken  off  after  the  swarming 
flight.  Wings  with  the  veins  of  the  anterior  part  of  the  wing  greatly 
thickened  and  those  of  the  middle  portion  reduced  to  narrow  lines 

ISOPTERA 

CC.     Wings  developed  internally   Neuroptera 

BB.     Supernumerary  veins  of  the  intercalary  type. 

C.      Flight-function    cephalized;  the    hind    wings    being    greatly    reduced 

in  size Ephemerida 

CC.     Flight-function  not  cephalized;  the  hind  wings  as  large  as  or  larger 

than  the  fore  wings Odonata 

AA.     Wings  specialized  by  a  reduction  in  the  number  of  veins  in  the  preanal 
area. 
B.    Wings  developed  externally. 

C.    The  two  pairs  of  wings  similar  in  texture. 

D.    With  the  tendency  to  develop  accessory  veins  retained. .  Plecoptera 
DD.     With  the  tendencv  to  develop  accessory  veins  in  the  preanal  area 
lost. 
E.     With  the  courses  of  some  of  the  longitudinal  veins  modified  so 

that   they  function  as  cross-veins Corodentia 

EE.  The  transverse  bracing  of  the  wing  attained  in  the  usual  way. 
F.  The  veins  of  the  wing  bordered  with  dark  bands. .  .  Embiidina 
FF.    The  veins  of  the  wing  not  bordered  with  dark  bands. 

G.     Wings  long  and  narrow,  supplemented  by  a  wide  fringe  of 

hairs Thysanoptera 

GG.     Wings  not  greatly  narrowed  and  not   supplemented  by  a 

wide  fringe  of  hairs HoMOPTERA 

CC.    The  front  wings  more  or  less  thickened. 

D.     The  front  wings  not  greatly  reduced  in  length  as  compared  with 
the  hind  wings. 

E.      The  front   wings  thickened   throughout Homoptera 

EE.      The  front   wings  thickened  at   the  base,   the  terminal  portion 

membranous Heteroptera 

DD.     The  front  wings  greatly  reduced  in  length Dermaptera 

*From  "The  Wings  of  Insects,"  pp.  120-122. 


HEX  A  POD  A  213 

BB.    Wings  developed  internally. 
C.    Fore  wings  greatly  thickened. 

D.     Fore  wings  modified  so  as  to  serve  as  covers  of  the  posterior  wings 

COI.EOPTERA 

DD.     Fore  wings  reduced  to  slender,  leathery,  club-shaped  appendages 

Strepsiptera 

CC.    The  two  pairs  of  wings  similar  in  texture. 

D.    With  the  tendency  to  develop  accessory  veins  retained.  .Mecoptera 
DD.    With  the  tendenc}'  to  develop  accessory  veins  lost. 

E.     The  most   characteristic  method  of  reduction  of  the  wing- veins 
of  the  preanal  area  being  by  coalescence  outward. 
F.    Anal  veins  of  the  fore  wings  tending  to  coalesce  at  the  tip.    Wings 

usually    clothed    with  hairs Trichoptera 

FF.     Anal  veins  of  the  fore  wings  not  tending  to  coalesce  at  the 

tip.     Wings  clothed  with  scales Lepidoptera 

EE.  The  most  characteristic  method  of  reduction  of  the  wing-veins 
of  the  preanal  area  being  by  coalescence  from  the  margin  of  the 
wing  inward. 

F.      With  only  one  pair  of  wings Diptera 

FF.      With    two   pairs   of   wings Hymenoptera 

The  sequence  in  which  the  orders  of  insects  are  discussed  in  the 
following  chapters  has  been  determined  by  the  above  table.  This 
sequence,  like  all  linear  arrangements  of  groups  of  organisms,  is  more 
or  less  arbitrary.  Thus  while  there  is  an  effort  to  place  first  the  more 
generalized  orders  and  later  those  that  are  more  specialized,  the 
putting  together  of  orders  exhibiting  the  same  type  of  specialization 
results  in  some  cases  in  the  placing  of  comparatively  generalized 
forms  after  those  that  are  obviously  more  highly  specialized.  The 
position  of  the  Plecoptera  is  an  illustration  of  this.  The  insects  of 
this  order  are  evidently  more  generalized  than,  for  example,  the 
Neuroptera  or  the  Odonata,  which  are  placed  earlier  in  the  linear 
series. 

The  comparatively  high  position  assigned  to  the  Plecoptera  is, 
however,  only  apparent.  A  reference  to  the  table  will  show  that  the 
orders  of  insects  are  grouped  in  two  series,  "A"  and  "AA".  Under 
"A"  are  placed  those  orders  in  which  the  wings  are  specialized  by 
addition  in  the  preanal  area,  and  under  "AA"  those  orders  in  which  the 
wings  are  specialized  by  reduction  in  the  preanal  area.  Each  of  these 
series  includes  some  quite  generalized  insects  and  others  that  are 
highly  specialized.  The  completion  of  the  discussion  of  the  first  series 
before  taking  up  the  second  series  results  in  the  generalized  members 
of  the  second  series  following  the  highly  specialized  members  of  the 
first  series. 

The  more  generalized  members  of  these  two  series,  the  Orthoptera 
of  the  first  series  and  the  Plecoptera  of  the  second  series,  are  probably 
more  closely  allied  to  each  other  than  is  either  of  these  orders  to  the 
more  specialized  orders  of  the  series  in  which  it  is  placed;  the  two 
series  arose  from  a  common  starting  point,  the  Palseodictyoptera,  but 
have  widely  diverged  in  the  course  of  their  development. 

An  even  more  striking  illustration  of  the  difficulty  of  indicating 
the  relative  ranks  of  orders  by  the  use  of  a  single  linear  series  is  the 
position  of  the  Isoptera  in  the  above  table.     This  order  is  a  very 


214  AN  INTRODUCTION   TO  ENTOMOLOGY 

ancient  one;  it  separated  from  the  Palaeodictyoptera  before  definite 
cross-veins  in  the  wings  had  been  developed  and  has  not  attained 
them.  It  is  placed  in  the  table  next  to  the  Orthoptera  because  the 
wings  are  specialized  by  the  development  of  supernumerary  veins  of 
the  accessory  type  and  are  developed  externally;  but  the  peculiar 
specialization  of  the  wings  is  very  different  from  that  of  the  Orthop- 
tera as  is  indicated  in  the  table.  And  in  other  respects  the  termites 
have  reached  a  stage  of  development  far  in  advance  of  that  shown  by 
any  of  the  Orthoptera.  They  have  attained  a  social  mode  of  life, 
with  the  correlated  separation  of  the  species  into  several  castes  and 
the  development  of  remarkable  instincts.  In  this  respect  they  rival 
the  social  Hymenoptera. 

In  fact  the  living  members  of  each  of  the  orders  of  insects  must  be 
regarded  as  a  group  of  organisms  representing  the  results  of  speciali- 
zation in  a  direction  different  from  that  of  any  other  order;  and  to 
attempt  to  decide  which  order  is  the  "highest"  seems  as  futile  as  the 
discussion  by  children  of  the  question:  "Which  is  better,  sugar  or 
salt?"  The  list  below  indicates  the  sequence  in  which  the  orders  are 
discussed  in  the  following  chapters. 

THE   SUBCLASSES   AND   ORDERS   OF   THE   HEXAPODA 

SUBCLASS  APTERYGOTA. — Wingless  insects  in  which  the  wingless  condition  is 
believed  to  be  a  primitive  one,  there  being  no  indication  that  they  descended 
from  winged  ancestors. 
^  ORDER  THYSANURA. — The  Bristlc-tails.  p.  220. 

Y  ORDER  COLLEMBOLA. — The  Spring-tails.  p.  225. 

SUBCLASS  PTERYGOTA. — Winged  insects  and  wingless  insects  in  which  the 
wingless  condition  is  believed  to  be  an  acquired  one;  i.  e.,  those  insects  that 
have  descended  from  winged  ancestors. 

'.  ORDER  ORTHOPTERA. — The  Cockroaches,  Crickets,  Grasshoppers,  and  others, 
p.  230. 

ORDER  zoRAPTERA. — The  genus  Zorotypus.  p.  270. 

ORDER  ISOPTERA. — The  Termites  or  White  Ants.  p.  273. 

ORDER  NEUROPTERA. — The  Dobson,  Aphis-lions,  Ant-lions,  and  others,  p.  281. 
!•    ORDER  EPHEMERiDA. — The  May-flies.  p.  308. 
^  ORDER  ODONATA. — The  Dragon-flies  and  the  Damsel-flies,  p.  314. 
1^  ORDER  PLECOPTERA. — The  Stone-flies.  p.  325. 

ORDER   CORRODENTIA. — The    Psocids.    p.    33 1. 

v^  ORDER  MALLOPHAGA.     The  Bird-lice.  p.  335. 
(/order  embudina. — The  Embiids.  p.  338. 
(/^  order  thysanoptera. — The  Thrips.  p.  341. 
ORDER  anoplura. — The  Lice.  p.  347. 

order  homoptera. — The  Cicadas,  Leaf-hoppers,  Aphids,  Scale-bugs,  and 
others,  p.  394. 

ORDER  hemiptera. — The  True  Bugs.  p.  350. 
order  dermaptera. — The  Earwigs,  p.  460. 
K      order  coleoptera. — The  Beetles,  p.  464. 

/     order  strepsiptera. — The  Twisted  Winged  Insects,  p.  546.      ^ 
X     order  mecoptera. — The  Scorpion-flies,  p.  550. 
>    order  trichoptera. — The  Caddice-flies.  p.  555. 

'     order  lepidotera.— The  Moths,  the  Skippers,  and  the  Butterflies,  p,  571. 
order  diptera. — The  Flies,  p.  773. 

V  order  siphonaptera. — The  Fleas,  p.  877. 

order  hymenoptera. — The  Bees,  Wasps,  Ants,  and  others,  p.  884. 


HEX  A  POD  A  215 

TABLE  FOR  DETERMINING  THE  ORDERS  OF  THE  HEX  A  POD  A 

This  table  is  merely  intended  to  aid  the  students  in  determining  to  which  of 
the  orders  a  specimen  that  he  is  examining  belongs.  No  effort  has  been  made  to 
indicate  in  the  table  the  relation  of  the  orders  to  one  another. 

A.    Winged.     (The   wing-covers,    Elytra,    of   beetles   and  of  earwigs  are  wings.) 
B.    With  two  wings. 

C.    Wings  horny,  leathery,  or  parchment-like. 

D.     Mouth-parts  formed  for  sucking.     Wings  leathery,   shortened,   or 

membranous  at  the  tip.  p.  350 Hemiptera. 

DD.    Mouth-parts  formed  for  biting.    Jaws  distinct. 

E.     Wings  horny,  without  veins.     Hind  legs  not  fitted  for  jumping. 

P-     464 COLEOPTERA 

EE.    Wings  parchment-like  with  a  network  of  veins.    Hind  legs  fitted 

for    jumping,    p.    230 Orthoptera 

CC.     Wings  membranous. 

D.    Abdomen  with  caudal  filaments.    Mouth-parts  vestigial. 

E.      Halteres    wanting,    p.    308 Ephemerida 

EE.     Halteres  present  (males  of  Coccidae).     p.  394 Homoptera 

DD.     Abdomen  without  caudal  filaments.     Halteres  in  place  of  second 

wings.      Mouth-parts    formed    for    sucking,    p.     773 Diptera 

BB.     With  four  wings. 

C.     The  two  pairs  of  wings  unlike  in  structure. 

D.     Fore  wings  reduced  to  slender  club-shaped  appendages;  hind  wings 
fan-shaped  with  radiating  veins.  Minute  insects,   p.  546.  .Strepsiptera 
DD.     Front  wings  leathery  at  base,  and  membranous  at  tip,  often  over- 
lapping.    Mouth-parts  formed   for   sucking,   p.    350.  .. Hemiptera 
DDD.    Front  wings  of  same  texture  throughout. 

E.     Front  wings  horny  or  leathery,  being  veinless  wing-covers.     {Ely- 
tra). 
F.     Abdomen  with  caudal  appendages  in  form  of  movable  forceps. 

p.  460 Dermaptera 

FF.    Abdomen  without  forceps-Hke  appendages,  p.  464.  Coleoptera 

EE.    Front  wings  leathery  or  parchment-like  with  a  network  of  veins. 

F.     Under  wings  not  folded;  mouth-parts  formed  for  sucking. 

G.    Beak  arising  from  the  front  part  of  the  head.  p.  350. Hemiptera 

GG.    Beak  arising  from  the  hind  part  of  the  lower  side  of  the  head. 

p.     394 Homoptera 

FF.      Under    wings   folded   lengthwise.      Mouth-parts    formed    for 

chewing,  p.  230.  •■■••• Orthoptera 

CC.    The  two  pairs  of  wings  similar,  membranous. 

D.     Last  joint  of  tarsi  bladder-like  or  hoof -like  in  form  and  without 

claws,   p.  341 Thysanoptera 

DD.    Last  joint  of  tarsi  not  bladder-like. 

E.    Wings  entirely  or  for  the  greater  part  clothed  with  scales.    Mouth- 
parts  formed  for  sucking,  p.  571 Lepidoptera 

EE.    Wings  naked,  transparent,  or  thinly  clothed  with  hairs. 

F.    Mouth-parts  arising  from  the  hinder  part  of  the  lower  surface  of 
the  head,  and  consisting  of  bristle-like  organs  inclosed  in  a  jointed 

sheath,    p.     394 Homoptera 

FF.     Mouth-parts  in  normal  position.     Mandibles  not  bristle-like. 
G.    Wings  net-veined,  with  many  veins  and  cross-veins. 
H.     Tarsi  consisting  of  less  than  five  segments. 

L     Antennae  inconspicuous,   awl-shaped,   short  and  slender. 
J .    First  and  second  pairs  of  wings  of  nearly  the  same  length ; 

tarsi  three-jointed,  p.  314 Odonata 

JJ.     Second  pair  of  wings  either  small  or  wanting;  tarsi 

four  jointed,  p.  308 Ephemerida 

II.    Antennae  usually  conspicuous,  setiform,  filiform  clavate, 
capitate,  or  pectinate. 
J.    Tarsi  two-  or  three-jointed. 

K.    Second  pair  of  wings  the  smaller,  p.  33 1 .  Corrodentia 


21G  AN  INTRODUCTION  TO  ENTOMOLOGY 

KK.     Second  pair  of    wings  broader,    or    at    least    the 
same  size  as  the  first  pair.  p.   325.  .  .  .  Plecoptera 
JJ.      Tarsi    four-jointed;  wings    equal,    p.    273.  .Isoptera 
HH.    Tarsi  consisting  of  five  segments. 

I.  Abdomen    with    setiform,    many-jointed    anal    filaments. 
(Certain  Way-flies),  p.  308 ." Ephemerida 

II.  Abdomen  without  many-jointed  anal  filaments. 

J.     Head  prolonged  into  a  trunk-like  beak. p.  550.MECOPTERA 
JJ.    Head  not  prolonged  into  a  beak.  p.  281..  .Neuroptera 
GG.     Wings  with  branching  veins  and  comparatively  few  cross- 
veins,  or  veinless. 
H.    Each  of  the  veins  of  the  wing  extending  along  the  middle  of 

a   brown   line.   p.   338 Embiidina 

HH.    Wings  not  marked  with  brown  lines. 

I.  Tarsi  two-or  three-jointed. 

J.    Hind  wings  smaller  than  the  fore  wings. 

K.  Cerci  present;  body  less  than  three  millimeters  in 
length,   p.   270 Zoraptera 

KK.  Cerci  absent;  larger  insects,  p.  331.  .Corrodentia 
JJ.     Posterior  wings  as  large  as  or  larger  than  the  anterior 

ones.     (Certain  Stone-flies),  p.  325 Plecoptera 

II.  Tarsi  four-  or  five-jointed. 

J.     Abdomen  with  setiform,  many-jointed  anal  filaments. 

(Certain    May-flies),    p.    308 Ephemerida 

J  J.      Abdomen    without    many- jointed    anal    filaments. 

K.    Prothorax  horn}-.    First  wings  larger  than  the  second, 

naked  or  imperceptibly  haiTy.     Second  wings  without, 

or  with  few,  unusually  simple,  veins.    Jaws  (mandibles) 

well  developed.   Palpi  small,  p.  884.  .  .  .  Hymenoptera 

KK.    Prothorax  membranous  or,  at  the  most,  parchment - 

like.     Second  wings  as  large  as  or  larger  than  the 

first,  folded  lengthwise,  with  many  branching  veins. 

First  wings  naked  or  thinly  clothed  with  hair.    Jaws 

(mandibles)   inconspicuous.     Palpi  long.     Moth-like 

insects,   p.    555 Trichoptera 

AA.     Wingless  or  with  vestigial  or  rudimentary  wings. 

B.     Insects  with  a  distinct  head  and  jointed  legs,  and  capable  of  locomotion. 
C.    Aquatic  insects. 

D.    Mouth-parts  fitted  for  piercing  and  sucking. 

E.      Free-swimming  nymphs,    p.    350 Hemiptera 

EE.     Larvae  parasitic  in  sponges  (Sisyridse).    p.  281 Neuroptera 

DD.     Mouth-parts  fitted  for  chewing. 

E.    Either  somewhat  caterpillar-like  larvae  that  live  in  portable  cases  or 
campodeiform  larvae  that  spin  nets  for  catching  their  food.    (Caddice- 

worms).   p.  555 Trichoptera 

EE.    Neither  case-bearing  nor  net-spinning  larvae. 

F.  Naiads,  that  is,  immature  insects  that  resemble  adults  in  having 
the  thorax  sharply  differentiated  from  the  abdomen,  and,  except  in 
very  3^oung  individuals,  with  rudimentary  wings. 
G.  Lower  lip  greatly  elongated,  jointed,  capable  of  being  thrust  for- 
ward, and  armed  at  its  extremity  with  sharp  hooks,  p.  314.ODONATA 
GG.     Lower  lip  not  capable  of  being  thrust  forward. 

H.     Usually  with  filamentous  tracheal  gills  on  the  ventral  side 

of  the  thorax,    p.  325 Plecoptera 

HH.     Tracheal  gills  borne  by  the  first  seven  abdominal  seg- 
ments,    p.     308 Ephemerida 

FF.     Larvae,  that  is,  immature  forms  that  do  not  resemble  adults  in 
the  form  of  the  body,  and  in_  which  the  developing  wings  are  not 
visible  externally. 
G.     Several   segments  of   the    abdomen    furnished   with    prolegs. 

p.  571 Lepidoptera 

GG.    With  only  anal  prolegs  or  with  none. 


HEX  A  POD  A  217 

H.     With  paired  lateral  filaments  on  most  or  on  all   of  the  ab- 
dominal segments.    (Sialidas).   p.   281 Neuroptkra 

See  also  HalipHdas  and   Gyrinidae.   p.  464 Coleoptera 

HH.     Without  paired  lateral  filaments  on  the  abdomen,  p.  464. 

Coleoptera 

CC.     Terrestrial  insects. 
D.    External  parasites. 

E.      Infesting   the   honey-bee.    {Braula).    p.    773 Diptera 

EE.     Infesting  birds  or  mammals. 

F.     Body  strongly   compressed.    (Fleas),   p.   877 Siphonaptera 

FF.     Body  not  strongly  compressed. 

G.    Mouth-parts     formed     for     chewing.      (Bird-lice),      p.     335. 

Mallophaga 

GG.     Mouth-parts  formed  for  piercing  and  sucking. 

H.     Antenn.-E  inserted  in  pits,  not  visible  from  above.    (Pupi- 

para).     p.     773 Diptera 

HH.    Antennae  exserted,  visible  from  above. 
G.     Tarsi  with  a  single  claw  which  is  oppo.sed  by  a  toothed  pro- 
jection of  the  tibia.   (Lice),  p.  347 Anoplura 

GG.      Tarsi   two-clawed,   p.    350 Hemiptera 

DD.     Terrestrial  insects  not  parasites. 

E.  Mouth-parts  apparently  retracted  within  the  cavity  of  the  head  so 
that  only  their  apices  are  visible,  being  overgrown  by  folds  of  the  genae. 
F.    Abdomen  consisting  of  ten  or  eleven  segments.  (Campodeidag  and 

Japygidae).    p.    220 Thysanura 

FF.     Abdomen  consisting  of  not  more  than  six  segments,   p.   225. 

Collembola 

EE.      Mouth-parts   mandibulate,    either   fitted   for   chewing   or    with 
sickle-shaped  mandibles  formed  for  seizing  prey.  (See  also  EEE.) 
F.     Larvae  with  abdominal  prolegs. 

G.    Prolegs  armed  at  the  extremity  with  numerous  minute  hooks. 

(Caterpillars),    p.    571 Lepidoptera 

GG.    Prolegs  not  armed  with  minute  hooks. 

H.    With  a  pair  of  ocelli,  one  on  each  side.  (Larvae  of  saw-flies). 

p.  884 Hymenoptera 

HH.     With  many  oceUi  on  each  side  of  the  head.  p.  550 

" Mecoptera 

FF.     Without  abdominal  prolegs. 

G.      Body   clothed  with    scales.      (Machilidae   and    Lepismatidas). 

p.  220 Thysanura 

GG.     Body  not  clothed  with  scales. 
H.    Antennae  long  and  distinct. 

I.  Abdomen  terminated  by  strong  movable  forceps,  p.   460. 
Dermaptera 

II.  Abdomen  not  terminated  by  forceps. 

J.     Abdomen  strongly   constricted  at  base.      (Ants.   etc.). 

p.  884 Hymenoptera 

JJ.    Abdomen  not  strongly  constricted  at  base. 

K.     Head  with  a  long  trunk-like  beak.     {Boreus).  p.  550. 

Mecoptera 

KK.     Head  not  prolonged  into  a  trunk. 

L.    Insects  of  small  size,  more  or  less  louse-like  in  form, 
with    a    very    small   prothorax,    and    without    cerci. 

(Book-lice  and   Psocids).   p.   331 Corrodentia 

LL.      Insects    of    various    forms,    but    not    louse-like, 
prothorax  not  extremely  small;  cerci  present. 
M.     Hind  legs  fitted  for  jumping,  hind  femora  en- 
larged.       (Wingless     locusts,     grasshoppers,     and 

crickets),    p.  230 Orthoptera 

MM.     Hind  femora  not  greatly  enlarged,  not  fitted 
for  jumping. 


218  AN  INTRODUCTION  TO  ENTOMOLOGY 

N.     Prothorax  much  longer  than  the  mesothorax; 
front  legs  fitted  for  grasping  prey.     (Mantidas). 

p.  230 Orthoptera 

NN.     Prothorax  not  greatly  lengthened. 

O.     Cerci  present ;    antennae  usually   with  more 
than  fifteen  joints,  often  many-jointed. 
P.     Cerci  with  more  than  three  joints. 

Q.     Body  flattened  and  oval.      (Blattidas). 

p.  230 Orthoptera 

QQ.    Body  elongate. 

R.    Head  very  large.  (Termopsis) .  p.  273. 

ISOPTERA 

RR.      Head  of  moderate   size.    p.    268. 

Grylloblattid^ 

PP.     Cerci  short,   with  one  to  three  joints. 

Q.     Body  linear  with  very  long  linear  legs. 

(Walking-sticks),    p.  230 ...  Orthoptera 

QQ.     Body  elongate  or  not,  if  elongate  the 

legs  are  not  linear. 

R.     Body  elongate;  front  tarsi  with  first 

joint     swollen,     p.     338.  .  .Embiidina 

RR.    Front  tarsi  not  enlarged. 

S.     Minute  insects,   less  than  3   mm. 
in     length;     antennae     nine- jointed. 

p.    270 Zoraptera 

SS.      Larger  insects;   antennae  usually 
more  than  nine-jointed.  (White-ants) . 

p.  273 Isoptera 

00.    Cerci  absent;  antennae  usually  with  eleven 

joints,    p.  464 Coleoptera 

HH.     Antennae  short,  not  pronounced;  larval  forms. 

I.      Body    cylindrical,    caterpillar-like.    p.    550.MECOPTERA 
n.     Body  not  caterpillar-like. 

J.  Mandibles  sickle-shaped;  each  mandible  with  a  furrow 
over  which  the  maxilla  of  that  side  fits,  the  two  forming 
an  organ  for  piercing  and  sucking.  (Ant-lions,  aphis- 
lions,  hemerobiids).    p.  281 Neuroptera 

J  J.    Mouth-parts  not  of  the  ant-lion  type. 

K.     Larva  of  Raphidia.  p.  281 Neuroptera 

KK.     Larvae  of  beetles,  p.  464 Coleoptera 

EEE.      Mouth-parts   haustellate,    fitted   for    sucking;  mandibles   not 
sickle-shaped. 
F.    Body  covered  with  a  waxy  powder  or  with  tufts  or  plates  of  wax. 

(Mealy-bugs,  Orthezia).    p.  350 Hemiptera 

FF.     Body  more  or  less  covered  with  minute  scales,  or  with  thick 
long  hairs ;  proboscis  if  present  coiled  beneath  the  head.   (Moths) . 

p.  57 1 Lepidoptera 

FFF.    Body  naked,  or  with  isolated  or  bristle-like  hairs. 

G.      Prothorax    not    well   developed,  inconspicuous    or    invisible 

from  above,    p.  773 Diptera 

GG.     Prothorax  well  developed. 

H.     Last  joint  of  tarsi  bladder-like  or  hoof -like  in  form  and 
usually    without    claws;  mouth-parts    forming    a    triangular 

unjointed  beak.    p.  550 Thysanoptera 

HH.    Last  joint  of  tarsi  not  bladder-like,  and  furnished  with  one 
or    two    claws;  mouth-parts    forming    a    slender;    usually 
jointed  beak. 
I.  Beak  arising  from  the    front  part  of  the    head.    p.   350. 

Hemiptera 

n.Beak  arising  from  the  back  part  of  the  head.  p.  394.  .  . 
Homoptera 


HEX A POD A  219 

BB.  Either  without  a  distinct  head,  or  without  jointed  legs,  or  incapable  of 
locomotion. 
C.  Forms  that  are  legless  but  capable  of  locomotion;  in  some  the  head  is 
distinct,  in  others  not.  Here  belong  many  larvee  representing  several  of 
the  orders,  and  the  active  pup£e  of  mosquitoes  and  certain  midges.  It  is 
impracticable  to  separate  them  in  this  key. 
CC.    Sedentary  forms,  incapable  of  locomotion. 

D.     Small  abnormal  insects  in  which  the  body  is  either  scale-like  or  gall- 
like in  form,  or  grub-like  clothed  with  wax.    The  waxy  covering  may  be 
in  the  form  of  powder,  or  large  tufts  or  plates,  or  a  continuous  layer,  or  of 
a  thin  scale,  beneath  which  the  insect  lives.   (Coccidas).  p.  350.HEMIPTERA 
DD.     Pupae,  the  inactive  stage  of   insects   with    a   complete   metamor- 
phosis; capable   only   of   a   wriggling   motion,    and    incapable   of 
feeding. 
E.    Obtected  pupae,  pupae  in  which  the  legs  and  wings  are  glued  to  the 
surface  of  the  body;  either  in  a  cocoon  or  naked,  p.  571 .  Lepidoptera 
EE.      Coarctate   pupae,   pupag  enclosed  in  the  hardened  larval   skin. 

p.  773 DiPTERA 

EEE.  Exarate  pups,  pupas  that  have  the  legs  and  wings  free;  either  in 
a  cocoon  or  naked.  This  type  of  pupa  is  characteristic  of  all  of  the 
orders  in  which  the  metamorphosis  is  complete  except  the  Lepidop- 
tera and  Diptera. 


CHAPTER  VI 
ORDER  THYSANURA^ 


The  Bristle-Tails 

The  members  of  this  order  are  wingless  insects  in  which  the  wingless 
condition  is  believed  to  be  a  primitive  one,  there  being  no  indication  that 
they  have  descended  from  winged  ancestors;  the  mouth-parts  are  formed 
for  chewing;  and  the  adult  insects  resemble  the  young  in  form.  In  these 
three  respects,  these  insects  resemble  the  next  order,  the  Collembola;  but 

they  differ  from  the  Collembola  in 
that  the  abdominal  segments  are 
not  redticed  in  number  and  the 
cerci  are  usually  filiform  and 
many-jointed;  some  members  of 
the  order  have  also  a  caudal  fila- 
ment. 

The  members  of  this  order 
are  known  as  bristle-tails,  a 
name  suggested  by  the  pres- 
ence, in  most  of  them,  of  either 
two  or  three  many-jointed 
filiform  appendages  at  the  cau- 
dal end  of  the  body  (Fig.  221, 
c,  and  mf) .  The  paired  caudal 
appendages  are  the  cerci;  the 
median  one,  when  three  are 
present,  is  the  median  caudal 
filament,  a  prolongation  of  the 
eleventh  abdominal  segment. 
In  fdpyx  (Fig.  222),  the  cerci 
are  not  jointed  but  are  strong, 
curved  appendages,  resembling 
the  forceps  of  earwigs. 

The  bristle-tails  are  most 
often  found  under  stones  and 
other  objects  lying  on  the 
ground;  but  some  species  live 
in  houses.  While  most  species 
prefer  cool  situations,  there  is 
one,  the  fire-brat,  that  fre- 
quents warm  ones,  about  fire- 
places and  in  bakehouses.  The 
antennae  are  long  and  many- 
jointed.      In    the    MachiHdas 


Fig.  221. — Machilis,  ventral  aspect:  c,  cer- 
cus;  Ip,  labial  palpus;  mf,  median  caudal 
filament:  tnp,  maxillary  palpus;  0,  ovi- 
positor; s,  s,  styli. 


"Thysanura:  thysanos  (dvpavos),  a  tassel;  oura  {oipd),  the  tail. 
(220) 


THYSANURA 


221 


-Japyx  sol- 
(After  Lub- 


(Machilis),  the  eyes  are  very  perfect;  for  this  reason,  they  are  used 
in  Chapter  III  to  illustrate  the  structure  of  the  compound  eyes  of 
insects.  In  all  other  Apterygota  they  are  more  or  less  degenerate  or  are 
lost  entirely.  In  the  Lepismatidae  (Lepisma),  the  degeneration  of  the 
eyes  has  progressed  far,  they  being  reduced  to  a  group  of  a  dozen 
ommatidia,  on  each  side  of  the  head.  In  the 
Campodeida?  and  the  Japygida?,  the  eyes  have 
disappeared.  The  mouth-parts  are  formed  for 
chewing ;  those  of  Machilis  will  serve  to  illustrate 
their  form.  The  mandibles  are  elongate  with  a 
toothed  apex  and  a  sub-apical  projection  teimi- 
nated  by  a  grinding  surface  (Fig.  223,  A);  the 
paragnatha  are  comparatively  well  developed 
(Fig.  224);  on  the  outer  edge  of  each  there  is  a 
small  lobe,  which  Carpenter  ('03),  who  regarded 
the  organs  as  true  appendages,  believed  to  be  a 
vestigial  palpus,  and  at  the  tip  there  are  two  dis- 
tinct lobes,  which  this  author  homologized  with 
the  galea  and  the  lacinia  of  a  typical  maxilla ;  the 
maxillce  (Fig.  223,  B)  bear  prominent  palpi. 

In  the  Campodeidas  and  the  Japygidse,  the 
jaws  are  apparently  sunk  in  the  head.  This  con- 
dition is  due  to  their  being  overgrown  by  folds  of  the  genas.  In  the 
Machilidas  and  the  Lepismatida3  the  jaws  are  not  overgrown;  these 
two  families  are  known, 
on  this  account,  as  the 
Ectotrophi  or  Ectotro- 
phous  Thysanura;  while 
the  Campodeidffi  and  the 
Japygidae  are  grouped 
together  as  the  Ento- 
trophi  or  Entotrophous 
Thysanura.  The  over- 
growing of  the  mouth- 
parts  by  folds  of  the 
genae  is  characteristic  of 
the  Collembola  also  and 
is  discussed  more  fully  in 
the  next  chapter. 

The  three  thoracic 
segments  are  distinctly 
separate.  There  is  noth- 
ing in  the  structure  of 
the  thorax  to  indicate 
that  these  insects  have 
descended   from   winged 

ancestors.  The  three  pairs  of  legs  are  well  developed.  In  the  genus 
Machilis  the  coxae  of  the  second  and  third  pairs  of  legs  each  bears  a 
stylus  (Fig.  221,  s). 


Fig.  223. — A,  mandibles  of  Machilis;  B,  maxilla 
of  Machilis.  (After  Oudemans.) 


222 


AN  INTRODUCTION   TO  ENTOMOLOGY 


The  abdomen  consists  of  eleven  segments.  The  eleventh  segment 
bears  the  cerci,  which  are  filiform  and  many-jointed  except  in  the 
Japygidae,  where  they  are  forceps-like.  In  the 
Machilida^  and  the  Lepismatidas  the  eleventh 
abdominal  segment  bears  a  long,  many-jointed 
median  caudal  filament;  styli  and  eversible 
ventral  sacs  are  also  usually  present ;  these  vary 
in  ninnber  in  different  genera. 

The  styli  are  slender  appendages  (Fig.  221, 
s).  Each  stylus  consists  of  two  segments,  a 
very  short  basal  one  and  a  much  longer  termi- 
nal one.  The  maximum  number  of  styli  is 
found  in  Machilis  (Fig.  221),  where  they  are 
borne  by  the  second  and  third  thoracic  legs 
and  the  second  to  the  ninth  abdominal  seg- 
ments. In  Lepisnia  there  are  only  three  pairs; 
these  are  borne  by  the  seventh,  eighth,  and 
ninth  abdominal  segments. 

The  abdominal  styli  are    borne    by    large 
plates,  one  on  each  side  of  the  ventral  aspect 
of  each  abdominal  segment.    These  plates  are 
termed  coxites,  as  they  are  believed  to  be  flat- 
tened coxae  of  abdominal  legs  which  have  otherwise  disappeared. 

A  result  of  the  large  size  and  position  of  the  coxites  is  a  reduction 
in  the  size  of  the  sternum  in  the  abdominal  segments.  This  is  well 
shown  in  Machilis  (Fig.  221);  in  the  first  seven  abdominal  segments, 
there  is  in  each  a  median  triangular  sclerite ;  this  is  the  sternum ;  in 
the  eighth  and  ninth  segments  no  sternum  is  visible. 


Fig.  224. — One  of  the 
paragnatha  of  Ma- 
chilis. (After  Car- 
penter.) 


Fig.  225.- — Cross-section  of  an  abdominal  segment  of  Machilis  showing  the 
styli  and  the  ventral  sacs.  The  ventral  sacs  of  the  left  side  are  retracted ;  those 
of  the  right  side,  expanded.     (After  Oudemans.) 

In  the  families  MachilidcC  and  Lepismatidas  the  females  have  an 
ovipositor,  which  consists  of  two  pairs  of  filiform  gonapophyses  aris- 
ing from  between  the  coxites  of  the  eighth  and  ninth  abdominal 
segments  respectively. 


THYSANURA 


223 


Fig.  226.— 
Ovary  of  Ja- 
pyx.      (After 
Grassi.) 


The  ventral  sacs  are  sac-like  expansions  of  the  wall  of  the  coxites 
which  can  be  everted,  probably  by  blood -pressure,  and  are  withdrawn 
into  the  cavity  of  the  coxite  by  muscles  (Fig.  225).  In  Figure  221, 
the  openings  into  the  retracted  ventral  sacs  are  represented ;  there  is 
one  pair  in  the  first  abdominal  seg- 
ment; two  pairs  in  each  of  the  four 
following  segments;  and  a  single  pair 
each  in  the  seventh  and  eighth  ab- 
dominal segments.  In  Lepisma  the 
ventral  sacs  are  wanting.  The  func- 
tion of  the  ventral  sacs  has  not  been 
definitely  determined;  but  it  seems 
probable  that  they  are  blood-gills. 
The  presence  in  the  Thysanura  of 
styli  and  of  ventral  sacs,  which  are 
evidently  homologous  with  those  of 
the  Symphyla,  is  an  indication  of 
the  primitive  condition  of  these 
insects.  The  generalized  form  of 
the  reproductive  organs  of  the  Thy- 
sanura is  another  indication  of  this. 
In  Japyx  the  ovarian  tubes  have  a 
metameric  arrangement  (Fig.  226); 
and  in  Machilis  (Fig.  227)  we  find  an 
intermediate  form  between  a  metameric  arrange- 
ment of  the  ovarian  tubes  and  a  compact  ovary. 
These  facts,  and  especially  the  presence  of  styli  and 
ventral  sacs,  are  opposed  to  the  view  held  by  some 
writers  that  the  Thysanura  are  degenerate  instead 
of  primitive  insects.  It  is  true  that  degenerate  fea- 
tures are  present  in  the  order,  as  the  loss  of  eyes  in 
Japyx  and  Campodea;  but  this  loss  is  correlated  with 
the  life  of  these  insects  in  dark  places,  like  the  loss  of  eyes  in  certain 
cave-beetles,  and  is  not  important  in  the  determination  of  the 
zoological  position  of  the  order. 

The  young  of  the  Thysanura  resemble  the  adults  in  form,  there 
being  no  marked  metamorphosis.  In  Campodea  and  Japyx  the  molt 
is  partial  (Grassi  '89). 

This  is  a  small  order;  less  than  twenty  American  species  have 
been  described;  these  represent  four  families.      The  distinguishing 
characteristics  of  the  families  are  given  in  the  following  table. 
A      Body  clothed  with  scales.     With  three  filiform  caudal  appendages,  a  pair  of 
cerci  and  a  median  caudal  filament.    Compound  eyes  present.    Jaws  not  over- 
grown by  folds  of  the  genae.     (The  Ectotrophi). 

B.  The  abdominal  tergites  reflexed  to  the  under  surface  so  as  to  form  an 
imbrication  covering  the  sides  of  the  coxites  (Fig.  221).  Compound  eyes 
large  and  contiguous.    Prothorax  smaller  than  the  mesothorax.    Middle  and 

hind   legs   with   styli.      Saltatorial   insects Machilid^ 

BB.  Abdominal  tergites  not  covering  the  sides  of  the  coxites.  Eyes  small  and 
distant.  Prothorax  as  large  as  or  larger  than  the  mesothorax.  Middle  and 
hind  legs  without  styli.     Not  saltatorial  insects Lepismatid^ 


Fig.227. — Ovary 
of  Machilis:  c, 
coxite  of  the 
eighth  abdomi- 
nal segment;  s, 
stylus ;  0,  ovi- 
positor. (After 
Oudemans.) 


224 


^l.V  INTRODUCTION  TO  ENTOMOLOGY 


AA.     Body  not  clothed  with  scales.     Median  caudal  filament   wanting.     Eyes 
wanting.      Jaws    overgrown    by  folds  of  the    genae.     (The  Entotrophi). 

B.       Cerci  many-jointed  and  filiform Campodeid^ 

BB.        Cerci  forceps-like Japygid^ 

Family  Machilid^.. — This  family  is  represented  by  the  genus 

Mdchilis,  of  which  several  species  occur  in  North  America.     These 

insects  are  found  in  heaps  of  stones  and  in  other 

concealed   places;  they    are  very  active  and  leap 

with    agility   when    disturbed.      They    are    about 

12  mm.  in  length. 

Family  Lepismatid^-. — The  best-known  repre- 
sentative of  this  family  is  the  silverfish  or  fish-moth, 

Leptsma  saccharina  (Fig.  228).     It  is  silvery  white 

with  a  yellowish  tinge  about  the  antennae  and  legs 

and  measures  about  8  mm.  in  length.     It  is  often 

a  troublesome  pest  in  laundries,  libraries,  and  mu- 

setims,  as  it  injures  starched  clothes,  the  bindings 

of  books,  labels,  and  other  things  on  which  paste  or 

glue  is  used.  The  popular  names  were  suggested  by 
the  clothing  of  scales  with 
which  the  body  is  covered. 
This  pest  can  be  destroyed 
by  the  use  of  pyrethnim  or 
by  a  poisoned  bait,  consist- 
ing of  a  thin  boiled  starch 
paste  to  which  has  been  add- 
ed from  three  to  five  per 
cent  white  arsenic;  the  paste 
is  spread  on  bits  of  cardboard,  which  are  put 
in  the  places  frequented  by  the  pest. 

Another  common  representative  of  this  fam- 
ily is  the  Hre-hrsit,  Thermobiadomestica.  This 
species  resembles  the  fish-moth  in  general  ap- 
pearance except  that  it  has  dusky  markings  on  its 
upper  surface.  It  is  remarkable  for  frequenting 
warm  and  even  hot  places  about  ovens,  ranges, 
and  fireplaces.  It  can  be  destroyed  in  the  same 
manner  as  the  preceding  species. 

Family  Campodeid^-. — The  best-known 
member  of  this  family  is  Campodea  staphyllnus 
(Fig.  229).  It  lives  in  damp  places  under  stones, 
fallen  trees,  or  in  rotten  wood  and  leaves.  It  is  a 
very  delicate,  small,  white  insect,  about  6  mm. 
in  length.  It  has  on  the  first  abdominal  seg- 
ment a  pair  of  appendages  which  occupy  a 
position  corresponding  to  that  of  the  thoracic 

Fig.  22g.~Campodea  legs  and  each  consists  of  two  or  three  segments. 
ffphyl^nus.  (After  Family  Japygid^..— This  familv  is  repre- 
Lubbock.)  ,11,1  T-  r     1  ■  1   1  ■ 

sented  by  the  genus  Japyx,  of  which  two  species 

have  been  found  in  this  country.  These  insects  can  be  recognized  by 
the  forceps-like  form  of  the  cerci  (Fig.  222).  They  are  small,  deli- 
cate, uncommon  insects,  found  under  stones. 


Fig.  228. — Lepisma 
saccharina.  (After 
Lubbock.) 


CHAPTER  Vir 
ORDER  COLLEMBOLA* 

The  Spring-Tails 

The  members  of  this  order  resemble  the  Thysanura  in  being  wingless 
insects  in  which  the  wingless  condition  is  believed  to  be  a  primitive  one, 
there  being  no  indication  that  they  have  descended  from  winged  ancestors, 
and  in  that  the  adult  insects  resemble  the  young  in  form.     They  differ 


Fig.  230. — Side  view  of  Tomocerus  plumbens: 
(After  Willem.) 


CO,  collophore;  c,  catch;  5   spring. 


from  the  Thysanura  as  follows:  the  abdominal  segments  are  reduced  in 
number,  there  being  only  six  of  them;  the  first  abdominal  segment  bears 
a  ventral  tube,  the  collophore,  furnished  with  a  pair  of  eversible  sacs  which 
assist  the  insects  in  walking  on  smooth  surfaces; 
the  fourth  abdominal  segment  usually  bears  a 
pair  of  appendages,  which  constitute  a  spring- 
ing organ;  and  the  third  abdominal  segment 
Mstially  bears  a  short  pair  of  appendages,  the 
catch,  which  hold  the  spring  when  it  is  folded 
under  the  abdomen. 

The  common  name  spring-tails  has  been 
appHed  to  these  insects  on  account  of  the 
caudal  springing  organ  that  is  possessed  by 
most  members  of  the  order.  The  spring- 
tails  are  minute  insects,  often  of  microscopic 
size  and  rarely  as  large  as  5  mm.  in  length. 
Most  of  the  species  live  on  decaying  matter. 
These  insects  are  common  under  stones 
and  decayed  leaves  and  wood,  in  the  chinks 
and  crevices  of  bark,  among  moss,  and  on 
herbage  in  damp  places.  Sometimes  they 
occur  abundantly  in  winter  on  the  surface 

*Collembola:   colla  (K6XXa),  glue;   embolon  {efj.^o\ov),  a  bolt,  bar; — from  their 
collophores. 

(225) 


Fig.  231 


-An  ommatid- 
ium  of  Podura  aquat- 
ic a.     (After  Willem.) 


226 


AN  INTRODUCTION  TO  ENTOMOLOGY 


of  snow,  where  they  appear  as  minute  black  specks,  which  spring 
away  on  either  side  from  our  feet  as  we  walk;  and  some  species 
collect  in  great  numbers  on  the  surface  of  standing  water.  Sev- 
eral  species   are   known   to   be  photogenic. 

The  body  consists  of  the  head,  three  thoracic  segments,  and  six 
abdominal  segments  (Fig.  230).  The  prothorax  is  usually  small  and 
in  several  genera  is  overlapped  by  the  tergumof  themesothorax;  in 
the  Sminthuridas  the  body-segments  are  more  or  less  fused  together. 
The  structure  of  the  abdomen  is  remarkable,  as  it  consists  of  only  six 
segments;  there  is  no  indication  of  the  manner  in  which  the  reduc- 
tion of  the  number  of  segments  has  taken  place.  The  anus  is  at  the 
caudal  end  of  the  body;  the  genital  opening  is  on  a  small  papilla 
on  the  fifth  abdominal  segment. 

The  antenuce  consist  of  from  four  to  six  segments,  usually  of  four. 
They  vary  greatly  in  their  comparative  length;  in  some  genera  the 
last  segment  or  the  last  two  segments  are  divided  into  many  rings 

or  subsegments(Fig.23o) . 
The  eyes  of  the  Col- 
lembola    are    commonly 
described  as  a  group  of 
eight,  or  fewer,   distinct 
simple  eyes  on  each  side 
of  the  head.     But  these 
so-called  simple  eyes  are 
not  ocelli ;  they  are  more 
or  less  degenerate  omma- 
tidia,   each  group  being 
the   vestige    of   a    com- 
pound  eye.   In     Podura 
aquatica,   these  eyes,   as 
figured  by  Willem  ('00), 
Fig.  232.-^4,  longitudinal  section  of  an  ommatid-    are  clearly  ommatidia  of 
ium  and  of  the  postantennal  organ  oi  Anurida    the     eucone     type     (Fig. 
maritima;  B,  a  surface  view  of  the  postantennal  )      j^^  gome  Other  Col- 

organ.  (After  Willem.)  C),ommatidium;  Pa,  post-    1       u    1  -a  -j 

antennal  organ;  hy,  hypodermal  cells;  N,  optic  lembola,  as  m  Anunda 
nerve;  n,  branch  of  the  optic  nerve;  /,  /,  tuber-  maritima  (Fig.  232,  0), 
cles    surrounding    the   postantennal   organ;    g,    the  reduction  of  the  om- 

wmem')'^"''''""^^^''^^'^''"^^""''^^''^^''"  '^^^^''^  matidia  has    progressed 
'  ^"^  so  far  that  they  present 

the  appearance  of  ocelli ;  and  in  still  others  the  eyes  are  lost  entire- 
ly.    Primary  ocelli  have  not  been  found  in  the  Collembola. 

The  mouth-parts  are  typically  mandibulate;  the  jaws  consisting 
of  a  pair  each  of  mandibles,  paragnatha,  and  maxillae.  The  parag- 
natha  of  Orchesella  cincta  were  described  by  Folsom  ('99) ;  and  those  of 
Anurida  maritima  by  the  same  writer  ('00).  These  organs  were 
termed  the  superlingucB  by  Folsom. 

One  of  the  most  striking  characteristics  of  the  Collembola  is  that 
the  jaws  are  apparently  retracted  into  the  cavity  of  the  head  so  that 
only  their  tips  are  visible.    But  it  has  been  show:n  by  Folsom  ('00), 


COLLEMBOLA 


227 


Fig.  233. — Hind  foot  of  Ach- 
orutes  maturiis.  (After  Fol- 
som.) 


who  studied  the  development  of  the  mouth-parts  of  Anurida  maritima, 
that,  strictly  speaking,  the  jaws  are  not  "retracted,"  as  is  usually 
stated,  but  are  overgrown  by  the  genae.    In  an  early  embryonic  stage, 
a  downward  projection  of  the  gena  ap- 
pears on  each  side  of  the  head,  and  these 
"mouth-folds"  become  larger  and  larger 
in  successive  stages  until  the  condition 
seen    in    the    fully    developed    insect    is 
reached. 

The  development  of  mouth-folds  is 
not  restricted  to  the  Collembola,  but 
occurs  also  in  the  Entotrophous  Thysan- 
ura,  and  to  a  less  marked  extent  in  many 
of  the  Pterygota,  especially  in  some 
Orthoptera,  where  the  gena  of  each  side 
is  prolonged  into  a  small,  but  distinct, 
fiat  fold  over  the  base  of  the  mandible. 

In  some  of  the  Poduridae  the  mouth- 
parts  are  fitted  for  piercing  and  sucking, 
the  mandibles  and  maxillcC  being  stylif orm 
and   projecting   in   a   conspicuous   cone. 

In  some  of  the  Collembola  there  is  a 
sense  organ  situated  between  the  base  of  the  antenna  and  the  ocular 
field ;  this  is  known  as  the  postantennal  organ;  its  presence  or  absence 
and  its  form  when  present  afford  characters  used  in  the  description 
of  these  insects.  In  its  simplest  form  it  is  a  claviform  hyaline  tubercle 
(Sminthurus) .  A  more  complicated  type  is  that  of  Anurida  maritima, 
which  has  been  figured  by  Willem  ('00).  In  Figure  232,  Pa  repre- 
sents a  longitudinal  section  of  this  organ.  It  is  a  nerve-end-cell, 
branching  from  the  optic  nerve  and  extending  to  the  surface  of  the 
body,  where  it  is  covered  by  a  very  thin  cuticular  layer.  It  is  pro- 
tected by  a  ring  of  tubercles  {t,  t),  two  of  which  are  shown  in  the 
sectional  view  (A)  and  eight  in  the  surface  view  (B).  The  function 
of  this  organ  has  not  been  determined;  it  has  been  suggested  that  it 
is  an  organ  of  smell. 

The  legs  of  the  Collembola  consist  each  of  five  segments,  which 
correspond  to  the  five  principal  divisions  of  the  legs  of  the  higher 
insects.  Willem  ('00)  considers  the  two  antecoxal  pieces  as  segments 
of  the  legs  and-  consequently  states  that  the  legs  are  composed  of 
seven  segments.  The  tarsi  in  most  genera  bear  two  claws,  an  outer, 
larger  one,  the  unguis,  and  an  inner,  smaller  one,  the  unguiculus ;  these 
claws  are  apposable  (Fig.  233) ;  in  some  genera  the  inner  claw  is 
wanting. 

One  of  the  most  characteristic  features  of  the  Collembola  is  the 
collophore,  or  ventral  tube,  which  is  situated  on  the  ventral  aspect  of 
the  first  abdominal  segment  (Fig.  230,  co).  This  organ  varies  greatly 
in  form  in  the  different  genera;  in  some  it  is  a  simple  tubercle,  di- 
vided into  two  halves  by  a  central  slit;  in  others  it  is  enlarged  and 
becomes  a  jointed  tube  divided  at  its  free  end  into  two  lobes.    The 


228 


AN  INTRODUCTION  TO  ENTOMOLOGY 


collophore  bears  at  its  extremity  a  pair  of  eversible  sacs  through  the 
walls  of  which  exude  a  viscid  fluid.  By  means  of  this  organ  these 
insects  are  enabled  to  cling  to  the  lower  surface  of  smooth  objects. 
The  collophore  is  developed  from  a  pair  of  appendages,  which  in  the 
course  of  their  development  become  fused  together  at  their  base. 

The  third  abdominal  segment  usually  bears  a  pair  of  short  append- 
ages, whose  basal  segments  are  fused;  this  is  the  tenaculum,  or  catch 
(Fig .  2  3  o ,  c) ,  which  holds  th  e  spring  when  it  is  folded  under  the  abdomen . 

The  spring  or  fur ada  (Fig.  230,  s)  is  formed  by  the 
appendages  of  the  fourth  abdominal  segment  which  are 
united  at  the  base  but  separate  distally.  These  ap- 
pendages are  three-jointed.  The  united  basal  seg- 
ment is  termed  the  manubrium  (Fig.  234,  ma);  the 
intermediate  segments,  the  denies  (Fig.  234,  d);  and 
the  terminal  segments,  the  mucrones  (Fig.  234,  mu). 

In  the  Entomobryidse  the  furcula  appears  to  be 
formed  by  the  appendages  of  the  fifth  abdominal  seg- 
ment; but  a  study  of  the  muscles  that  move  it  shows 
that  it  really  pertains  to  the  fourth  segment.  In  some 
genera  of  the  Poduridee  the  furcula  is  wanting. 

The  order  Collembola  includes  two  quite  distinct 
types  of  insects;  in  one  of  these  types  the  body  is 
elongate  with  distinct  segmentation;  in  the  other 
the  body  is  shortened,  the  abdomen  globose  and  its 
segments  in  part  fused.  Based  on  this  distinction  the 
order  is  divided  into  two  suborders  as  follows : 

A.     Body  elongate Suborder   Arthropleona. 

AA.     Body  globose Suborder  Symphypleona. 

SUBORDER  ARTHROPLEONA* 

In  this  suborder  the  body  is  elongate  with  dis- 
tinct segmentation  (Fig.  235).  The  three  thoracic 
and  six  abdominal  segments  are  distinct  as  a  rule; 
the  exceptions  apply  only  to  the  last  two  or  three 
abdominal  segments.  The  heart  is  furnished 
with  six  pairs  of  ostia.  The  tracheae  are  wanting; 
these  insects  live  in  damp  situations  and  apparent- 
ly breathe  through  the  surface  of  the  body.  This 
suborder  includes  two  families,  which  can  be  sep- 
arated as  follows : 

A.     Furcula  present  or  absent;  when  present  clearly  ap- 
pended to  the  fourth  abdominal  segment.  .Podurid^ 
AA.     Furcula  present  and  apparently  appended  to  the 

fifth  abdominal  segment Entomobryid^ 

Family  Podurid^  . — Among  the  better-known 
members  of  this  family  are  the  following:  The 
"Snow -flea,"  Achorfdes  nivicola,  which  occurs 
abundantly  in  winter  on  the  surface  of  snow  (Fig. 
235);  this  species  is  also  known  as  Achorutes 
socidlis.  Achorutes  armdtus  is  often  found  on  fungi. 
arthron  (&p0ov),  a  joint;  pleon,  a  crustacean's  abdomen. 


Fig.  234.-The 
furcula  of  Ta- 
pir itis:  ma, 
manubrium; 
d,  left  dens; 
mti,  left  muc- 
r  o.  ( A  f  t  e  r 
Lubbock,) 


Fig.  235.— The  snow 
flea,  Achorutes nivi 
cola.  (After  Fol 
som.) 


*Arthropleona: 


COLLEMBOLA  229 

Anurida  marttima  occurs  abundantly  on  the  seashore  chiefly  between 
tide  marks;  several  important  embryological  and  anatomical  mono- 
graphs have  been  published  regarding  this  species.  Podura  aqudtica 
is  one  of  the  most  abundant  members  of  the  Collembola;  it  occurs 
on  the  surface  of  standing  water  on  the  margins  of  ponds  and  streams. 
Family  Entomobryid^. — This  is  the  largest  family  of  the  Collem- 
bola, containing  many  genera  and  species.  In  some  genera  the 
body  is  clothed  with  scales.  To  this  family  belongs  the  genus 
Orchesella,  the  only  genus  in  the  Collembola  in  which  the  antennae 
consist  of  six  segments. 

SUBORDER  SYMPHYPLEONA* 

In  this  suborder  the  body  is  shortened;  the  last  two  abdominal 
segments  are  quite  distinct  but  the  other  body  segments  are  fused 
into  a  globular  mass  in  which  the  seg- 
mentation is  more  or  less  obliterated 
(Fig.  236).  The  heart  is  furnished  with 
only  two  pairs  of  ostia.  Trachea?  are 
present  in  the  typical  genus,  Smintlmms. 
The  external  openings  of  the  tracheee  are 
one  on  each  side  of  the  neck,  in  a  vertical 
fold;  spiracles  properly  speaking  are  not 
present  (Willem  '00). 

This  suborder  includes  a  single  family,  ^^f ;  ,f  36.— Pa^m«5  fuscus- 
,,      o     •    iu      -J  (After  Lubbock.) 

the  SmmthuridcB. 

Family  Sminthurid^. — The  principal  genera  of  this  subfamily 

are  Sminthums,  Paphms,  and  Neelits.    Each  of  these  genera  is  made 

the  type  of  a  separate  family  in  some  classifications  of  the  order. 

These  genera  can  be  separated  as  follows : 

A.    Last  segment  of  the  antennas  long  and  divided  into  subsegments.SMiNTHURUS 
AA.     Last  segment  of  the  antennae  short,  not  divided  into  subsegments. 
B.     Thorax  shorter  than  the  abdomen;  eversible  sacs  of  the  collophore  long. 

Papirius 

BB.     Thorax  longer  than  the  abdomen;  eversible  sacs  of  the  collophore  short. 
Neelus 

In  Sminthurus,  trachese  are  present;  in  the  other  genera  they  are 
absent  or  extremely  vestigial.  The  presence  of  tracheae  in  Sminthurus 
enables  these  insects  to  live  in  drier  situations  than  can  other  Col- 
lembola. The  "garden-flea"  Sminthurus  hortensis  is  found  upon  the 
leaves  of  young  cabbage,  turnip,  cucumber,  and  various  other  plants. 


JUW.^      vSCglilCllLO    aiC    J.UC5CU. 


*Symphypleona;  symphyo,    to    grow    together;  pleon,    a    crustacean's    ab- 
domen. 


CHAPTER  VIII 
ORDER  ORTHOPTERA* 

Grasshoppers,  Crickets,  Cockroaches,  and  others 

The  winged  members  of  this  order  have  two  pairs  of  wings;  the  fore 
wings  are  more  or  less  thickened,  hut  have  a  distinct  venation;  the  hind 
wings  are  folded  in  plaits  like  a  fan  when  at  rest;  there  are  many  forms 
in  which  the  wings  are  vestigial  or  even  wanting.  The  mouth-parts  are 
formed  for  chewing.  The  metamorphosis  is  gradual  (paurometabolous) ; 
the  nymphs  are  terrestrial. 

The  order  Orthoptera  includes  some  of  the  very  common  and  best- 
known  insects.  The  most  familiar  representatives  are  the  long-horned 
grasshoppers,  locusts,  crickets,  katydids,  and  cockroaches. 

With  the  exception  of  a  single  family,  the  Mantida?,  the  members 
of  this  order  are  as  a  rule  injurious  to  vegetation ;  and  many  species 
are  quite  apt  to  multiply  to  such  an  extent  that  their  destruction  of 
plant  life  becomes  of  great  economic  importance. 

The  two  pairs  of  wings  of  the  Orthoptera  differ  in  structure. 
The  front  wings  are  leather}^  or  parchment-like,  forming  covers  for 
the  more  delicate  hind  wings.  These  wing-covers  have  received  the 
special  name  tegmina.  The  tegmina  usually  overlap,  at  least  at  the 
tips,  when  at  rest.  The  hind  wings  are  thinner  than  the  tegmina  and 
usually  have  a  broadly  expanded  anal  area,  which  is  folded  in  plaits 
lilce  a  fan  when  at  rest.  Many  Orthoptera  have  vestigial  wings,  and 
many  are  wingless.  In  the  males  of  the  Saltatorial  Orthoptera,  the 
Locustidffi,  the  Tettigonid^,  and  the  Gr3-llidce,  musical  organs  have 
been  formed  by  modifications  of  certain  parts  of  the  wings;  these 
have  been  described  in  Chapter  II. 

The  mouth-parts  are  of  the  mandibulate  type,  that  is,  they  are 
formed  for  chewing.  The  mouth-parts  of  a  locust  are  figured  on 
page  42. 

In  the  Orthoptera  the  metamorphosis  is  gradual,  paurometabo- 
lous. In  the  case  of  those  species  in  which  the  wings  of  the  adult  are 
either  vestigial  or  wanting,  the  adults  resemble  ver^^  greatly  immature 
insects.  It  is  often  important  to  determine  whether  a  short-winged 
specimen  is  an  adult  or  not.  Fortunately  this  determination  can 
usually  be  made  with  ease  with  the  Saltatorial  Orthoptera,  the 
Locustidas,  the  Tettigonidae,  and  the  Grsdlidae.  In  these  three  families 
the  wing-pads  of  the  nymphs  are  inverted,  as  shown  by  the  curving 
down  of  the  extremities  of  the  wing-veins,  instead  of  up  as  with  the 
adult;  and  the  rudimentary  hind-wings  are  outside  of  the  tegmina, 
instead  of  beneath  them.  The  development  of  the  wings  of  a  locust 
is  described  in  Chapter  IV,  p.  175. 

*0rth6ptera:  orthos  {6pd6i),  straight;  pteron  {nrepSv),  a  wing. 
(230) 


ORTHOPTERA 


231 


The  segmentation  of  the  abdomen  and  the  development  and 
structure  of  the  genitalia  or  gonapophyses  in  the  jumping  Orthoptera 
are  of  especial  interest;  as,  on  account  of  the  generalized  condition 
of  these  parts  in  these  insects,  they,  can  serve  as  a  type  with  which  the 
corresponding  parts  in  more  specialized  insects  can  be  compared.  In 
some  members  of  this  group  of  families  all  of  the  abdominal  segments 
are  preserved  more  or  less  distinct,  and  in  nearly  all  of  them  the 
genitalia  are  well -developed.* 

The  segmentation  of 
the  abdomen  can  be  seen 
best  on  the  dorsal  aspect 
of  this  region;  for  in 
some  cases  the  tergum  of 
a  segment  is  well-pre- 
served while  the  sternum 
is  vestigial.     Figure  237 


Fig.  237.- 
moved: 


-Side  view  of  a  locust  with  the  wings  re- 
/,  tympanum. 

represents  a  side  view  of  a  female  locust  with  the  wings  removed  in 
order  to  show  the  segmentation  of  the  abdomen.  The  first  eight 
segments  of  the  abdomen  of  this  insect  are  very  distinct;  but  the 
caudal  segments  are  much  less  so.  Figure  238  represents  the  caudal 
part  of  the  abdomen  of  the  same  insect  more  enlarged,  in  order  to 
facilitate  the  lettering  of  the  parts. 

In  this  insect  the  eighth  abdominal 
tergtim  resembles  the  preceding  ones. 
The  ninth  and  tenth  abdominal  terga 
are  shorter  and  are  joined  together  on 
each  side ;  but  in  many  other  jumping 
Orthoptera  these  terga  are  not  thus 
imited.  Caudad  of  the  tenth  abdomi- 
nal tergum  there  is  a  shield-shaped  part, 
which  is  commonly  known  as  the 
supra-anal  plate;  this  plate  is  divided 
into  two  sclerites  by  a  transverse  su- 
ture; the  first  of  these  sclerites  is  be- 
lieved to  be  the  tergtmi  of  the  eleventh 
abdominal  segment,  and  the  other  the 
telson  (Fig.  23 S,  /).  Thus  all  of  the 
abdominal  segments  are  preserved,  in 
part  at  least,  in  this  insect. 
The  last  two  abdominal  segments,  the  eleventh  and  the  telson,  are 
even  more  distinctly  preserved  in  the  early  instars  of  some  orthopterous 
insects  than  they  are  in  the  adult  (Fig.  239).  In  many  adult  Orthop- 
tera there  is  no  suture  between  the  eleventh  tergum  and  the  telson. 
On  each  side  of  the  body,  in  the  angle  between  the  supra-anal 
plate  and  the  lateral  part  of  the  tenth  tergum,  there  is  a 
triangular  sclerite  (Fig.  238,  p);  this  pair  of  sclerites  have  long  been 


Fig.  238. — Side  view  of  the  caudal 
end  of  the  abdomen  of  a  female 
locust:  8,  g,  10.  11,  the  tergites 
of  the  eighth,  ninth,  tenth,  and 
eleventh  abdominal  segments ;  t, 
telson;  p,  podical  plate;  c,  cer- 
cus;  d^  i,  V,  dorsal,  inner,  and 
ventral  valves  of  the  oviposi- 
tor. 


*The  genitalia  are  vestigial  in  Tridactylus  and  are  entirely  wanting  in  Gryllo- 
talpa.  In  these  genera  the  reduction  or  loss  of  the  genitalia  is  probably  correlated 
with  the  subterranean  life  of  these  insects,  they  having  no  need  for  an  ovipositor. 


232 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  239. — Caudal  segments  of  a 
nymph  of  a  female  locust,  dorsal 
aspect:  //,  eleventh  abdominal 
segment;  /,  telson;  c,  cercus. 


known  as  the  podical  -plates;  but  they  have  recently  been  named 
the  para  prods  because  they  are  situated  one  on  each  side  of  the 
anus.  They  are  the  sternum  of  the 
eleventh  abdominal  seoment,  which 
is  divided  on  the  midventral  line,  to 
admit  of  the  expansion  of  the  poste- 
rior end  of  the  alimentary  canal  during 
defecation. 

In  this  insect  the  cerci  (Fig.  238,  c) 
project  from  beneath  the  caudal  border 
of  the  tenth  tergtmi ;  they  appear,  there- 
fore, to  be  appendages  of  the  tenth  ab- 
dominal segment;  but  it  is  believed 
that  in  all  insects  where  cerci  are  pres- 
ent they  are  appendages  •  of  the  elev- 
enth abdominal  segment.  This,  for 
example,  is  obviously  the  case  in  the 
Plecoptera  (Fig.  240).  The  homology 
of  the  paraprocts  is  also  well  shown  in 
this  figure. 

The  ovipositor  consists  of  three 
pairs  of  processes  or  gonapophyses ; 
these  are  termed  the  valves  or  vahmlce  of  the  ovipositor;  they  are  dis- 
tinguished as  the  dorsal,  ventral,  and  inner  vahnilae,  respectively. 
In  the  locust  the  dorsal  valvulse  (Fig.  238,  d)  and  the  ventral  valvulse 
(Fig.  238,  v)  are  strong,  curved,  and  pointed  pieces;  the  inner  valvu- 
lee  (Fig.  238,  i)  are  much  smaller. 

The  relation  of  the  gonapophyses  to  the  segments  of  the  abdomen 
can  be  seen  more  clearly  in  the  female  of  Ceuthophilus  (Fig.  241). 
The  ventral  valvulse  arise  from  the  posterior  margin  of  the  eighth 
sternum  and  the  dorsal  and  inner  valvulas  arise  from  the  ninth 
stemimi.  These  relations  can  be  seen  even  more  clearly  in  very  young 
n3niiphs  where  the  rudiments  of  the  gonapophyses  are  mere  tubercles, 
one  pair  on  the  hind  margin  of  the 
eighth  abdominal  sternum  and  two 
pairs  on  the  ninth  sternum  (Fig. 
242). 

In  the  male,  as  in  the  female, 
the  form  of  the  caudal  end  of  the 
abdomen  and  its  appendages  dif- 
fers greatly  in  different  members  of 
this  order.  Space  can  be  taken  here 
to  illustrate  these  parts  in  only  a 
single  species.  For  detailed  ac- 
counts of  these  parts  in  other  mem-  Fig.  240. — End  of  abdomen  of  Pter- 
bers  of  this  order,  special  papers  on  onarcys  dorsata,  female,  ventral 
+ViiQ  Qiihippf  c;br.iilrl  hp  ponsiilted  view:  J7,  77,  the  divided  sternum 
this  subject  should  be  consulted.  ^f  ^he  eleventh  abdominal  segment. 
Among  the  more  recent  and  gen-  the  podical  plates;  c,  c,  basal  parts 
erally  available  of  these  are  those  of     of  the  cerci. 


ORTHOPTERA 


233 


Crampton  ('i8)  and  Walker  ('19  and  '22  b).  These  papers  include 
references  to  the  very  extended  literature  on  this  subject. 

Figures  243  and  244  represent  the  caudal  end  of  the  abdomen 
of  the  male  of  the  Carolina  locust,  Dissosteira  Carolina.  In  this 
insect  the  ninth  and  tenth  terga  are  joined  together  on  each  side 
(Fig.  244)  and  the  eleventh  tergum  is  separated  from  the  apical 
part  of  the  supra-anal  plate  (Fig.  243,  s)  by  a  distinct  suture.  The 
ninth  sternum  is  large,  is  turned  upward  behind,  and  bears  a  large  con- 
ical part  (Fig.  244,  ex)  termed  the  coxale,  which  is  believed  to  be 
united  coxites  of  the  ninth  segment. 

There  are  two  genera  of  rare  and  remarkable  insects,  each  of  which 
has  been  placed  in  the  Orthoptera  by  some  writers  and  each  of  which 


Fig.  242. — Ventral 
view  of  end  of 
abdomen  of 

Fig.  241.— Side  view  of  end  of  abdomen  of  Ceuthophilus        young  nymph  of 
lapidicola:    7,  8,  g,  10,  above,  tergites  of  the  seventh         Conocephalus fas- 
to  the  tenth  abdominal  segments;  7,  8,  below,  sternites         ctatus.    (After 
of  the  seventh  and  eighth  abdominal  segments;  b,  basal         Walker.) 
segment  of  the  ventral  valve  of  the  ovipositor ;  c,  cercus ; 
p,  podical  plate;  d,i,  v,  dorsal,  inner,  and  ventral  valves 
of  the  ovipositor.     (After  Walker.) 

is  regarded  by  others  as  constituting  a  separate  order;  these  are 
Grylloblatta  and  Heniimerus.  These  genera  are  briefly  discussed  at 
the  close  of  this  chapter. 

Leaving  out  of  account  the  two  genera  named  above,  the  order 
Orthoptera  includes  only  six  families,  all  of  which  are  represented  in 
the  United  States.  These  families  can  be  separated  by  the  following 
table.* 


TABLE  OF  FAMILIES  OF   ORTHOPTERA 


A.  Hind  femora  fitted  for  jumping,  i.  e.,  very  much  stouter  or  very  much  longer, 
or  both  stouter  and  longer,  than  the  middle  femora;  organs  of  flight  of  imma- 
ture forms  inverted;  stridulating  insects.     (The  Saltatorial  Orthoptera.) 

*The  limits  assigned  to  the  order  Orthoptera  in  this  work  are  those  that  have 
been  commonly  recognized  for  a  long  period  and  are  those  adopted  in  recently 
published  manuals  treating  of  this  order,  except  that  in  some  of  them  the  Der- 
maptera  is  included  in  the  Orthoptera.  But  Handlirsch  ('08)  in  his  great  work  on 
fossil  insects  proposed  a  new  classification  of  insects,  which  differs  greatly  from 
the  classification  adopted  here.  In  this  classification  the  families  Blattidae, 
Mantidag,  and  Phasmidae  are  removed  from  the  Orthoptera  and  each  is  made  to 
constitute  a  distinct  order. 


234 


AN  INTRODUCTION  TO  ENTOMOLOGY 


B.  Antennae  long  and  setaceous,  except  in  the  mole-crickets  and  sand-crickets ; 
tarsi  three-  or  four-jointed;  organs  of  hearing  situated  in  the  fore  tibiae; 
ovipositor  elongate,  except  in  the  mole-crickets  and  sand-crickets,  with  its 
parts  compact. 

C.  Tarsi  four-jointed;  ovipositor,  when  exserted,  forming  a  strongly- 
compressed,    generally    sword-shaped    blade,    p.    234 Tettigoniid^ 

CC.  Tarsi  usually  three-jointed,  except  in  the  pigmy  mole-crickets  where 
they  are  reduced;  ovipositor,  when  exserted,  forming  a  nearly  cylindrical, 
straight,  or  occasionally   upcurved  needle,   except   in   the   Trigonidiinae. 

p.  242 Grylhd^ 

BB.     Antennae  short;  tarsi  three- jointed;  organs  of  hearing  situated  in  the 
first  abdominal    segment;    ovipositor    short,    with    its    parts    separate. 

p.  252 LocusTiD.*: 

AA.  Hind  femora  closely  resembling  those  of  the  other  legs,  and  scarcely  if  at 
all  stouter  or  longer  than  the  other  femora,  i.  e.,  not  fitted  for  jumping; 
organs  of  flight  in  a  normal  position  when  immature;  stridulating  organs 
not  developed. 
B.  Body  elongate;  head  free;  pronotum  elongate;  legs  slender,  rounded; 
cerci  jointed  or  without  joints;  walking  insects. 

C.      Front    legs   simple;  cerci   without    joints,    p.    260 Phasmid^e 

CC.      Front   legs   fitted   for   grasping;  cerci   jointed,    p.    262.  .  .Mantid^ 

BB.    Body  oval,  depressed;  head  wholly  or  almost  wholly  withdrawn  beneath 

the  pronotum;  pronotum  shield-like,  transverse;  legs  coinpressed ;  cerci 

jointed;  rapidly    running    insects,    p.     263 Bl.\ttid^ 

Fig.  243.— Dorsal  view  of  end  ---;;=£:£»eS5|^^kWg*^'^'^ 

of  abdomen  of  Dissosteira  1      r      ,   ■, 

Carolina,    male:    9T,    loT,  Fig     244.-Side   view    ot    end    ot    abdomen 

II T,  ninth,  tenth,  and  elev-  <^.  Dissosteira  carolma,  male ;  lettenng  as  m 

enth  terga;   5,   supra-anal  figure  243. 

plate;  p,  podical  plate,  c, 
cercus;  ex,  coxale. 

FAMILY   TETTIGONIID^ 
The  Locustidae  of  Authors* 

The  Long-horned  Grasshoppers 

To  this  family  belong  the  most  attractive  in  appearance  of  our 
common  Orthoptera.     In  many  of  them  the  wings  are  graceful  in 

*The  name  Locustidae  has  been  commonly  appHed  to  this  family.  This  usage 
is  the  result  of  an  erroneous  application  of  the  generic  name  Locusta  to  certain 
members  of  this  family.  The  insects  of  the  genus  Locusta,  established  by_  Lin- 
naeus, and  other  insects  commonly  known  as  locusts,  are  members  of  the  farnily  to 
which  the  common  name  short-horned  grasshoppers  is  applied  and  which  is 
properly  termed  the  Locustida. 

The  Tettigoniidae  is  the  Phasgonuridae  of  Kirby's  catalogue. 


ORTHOPTERA  235 

form  and  delicate  in  color,  and  the  antenna?  are  exceedingly  long  and 
slender,  looking  more  like  ornaments  than  like  organs  of  practical  use. 
These  beautiful  creatures  are  much  less  frequently  seen  than  are 
the  crickets  and  locusts  because  of  their  protective  green  color,  which 
renders  them  inconspicuous  in  their  haunts  among  foliage  or  on  the 
blades  of  grass.  Their  presence  is  most  often  indicated  by  the  chirping 
of  the  males. 

The  long-horned  grasshoppers  are  those  jumping  Orthoptera  with 
long,  slender  antenna?,  longer  than  the  body,  in  which  the  tarsi  are 
four-jointed  and  the  ovipositor  is  sword-shaped. 

The  tegmina  of  the  males  are  furnished,  in  nearly  all  winged 
species,  with  stridulating  organs;  but  these  occupy  a  much  smaller 
part  of  the  tegmina  than  with  the  crickets.  The  six  plates  of  which 
the  ovipositor  is  composed  are  closely  united  so  that  this  organ  has 
the  appearance  of  a  single  sword-shaped  blade. 

The  different  members  of  the  Tettigoniidse  exhibit  a  great  variety 
of  methods  of  oviposition;  some  lay  their  eggs  in  the  ground;  some 
in  the  pith  of  twigs ;  some  singly  in  the  edges  of  leaves ;  some  in  rows 
on  leaves  and  stems;  and  others  between  the  root-leaves  and  stems 
of  various  plants. 

The  Tettigoniidse  found  in  America  north  of  Mexico  represent 
eight  subfamilies;  these  can  be  separated  by   the   following   table, 
which  is  based  on  one  by  Scudder  ('97). 
A.     Body  generally  winged;  tarsi  more  or  less  depressed. 

B.     Fore  tibiae  furnished  with  auditory  tympana;  fore  wings  of  male,  when 
present,  furnished  with  stridulating  organs. 

C.    First  two  segments  of  the  tarsi  without  a  lateral  groove;  the  two  series  of 
spines  on  the  hind  side  of  the  posterior  tibias  continued  to  the  apex.  p.  236. 

Phaneropterin^ 
CC.     First  two  segments  of  the  tarsi  with  a  lateral  groove;  one  or  both  of 
the  two  series  of  spines  on  the  hind  side  of  the  posterior  tibiae  not  con- 
tinued to  the  apex. 
D.     Fore  tibiae  without  apical  spines  above. 

E.     The  apex  of  the  vertex  short,  crowded  by  the  prominent  antennary 
fossae;   pronotum  crossed  by   two  distinct   sutures,   p.   238 

PSEUDOPHYLLIN^ 

EE.    The  apex  of  the  vertex  extended  and  free  from  the  not  prominent 

antennary  fossae;  pronotum  without  transverse  sutures,   or  with 

only  one. 

F.    Fore  and  middle  femora  unarmed  beneath ;  the  vertex  terminating 

in  a  rounded  tubercle,  which  is  hollowed  out  on  the  sides,  p.  238. 

CONOCEPH.\LIN^ 

FF.     Fore  and  middle  femora  spined  beneath,  the  vertex  produced 

forward   into   a   long   sharp   cone.   p.    239 Copiphorin^e 

DD.     Fore  tibiae  with  an  apical  spine  above  on  the  outer  side;  usually 

wingless  or  with   vestigial  wings,   p.  239 Decticin^e 

BB.    Fore  tibiae  without  auditory  tympana;  fore  wings  of  male,  when  present, 

without   stridulating  organs,   p.   240 GRYLLACRlNiE 

AA.    Body  usually  wingless;  tarsi  distinctly  compressed. 

B.     Tarsi  without  pulvilli;  inserting' angle  of  the  hind  femora  situated  on  the 

inner  side.  p.  241 Rhaphidophorin.e 

BB.     Tarsi  provided  with  pulvilli;  inserting  angle  of  the  hind  femora  situated 

on  the  outer  side.  p.  242 Stenopelmatin^ 

Some  of  the  more  common  and  better-known  representatives  of 
these  families  are  referred  to  below.    To  save  space  the  distinguishing 


236 


AN  INTRODUCTION  TO  ENTOMOLOGY 


characteristics  of  the  subfamiHes  are  not  repeated ;  these  are  indicated 
in  the  table  above. 

Subfamily  PHANEROPTERIN^ 
The  False  Katydids 


To  this  subfamily  belong  certain  long-horned  grasshoppers  that 
have  broad  leaf-like  wings  and  arboreal  habits.  In  these  respects 
they  resemble  the  well- 
known  katydid  whose  stri- 
dent call  suggested  the  pop- 
ular name.  Several  of  these 
species  have  received  popu- 
lar names  in  which  the  word 
katydid  enters,  as  indicat- 
ed below.  These  species 
may  be  termed  collectively 
the  false  katydids;  the  true 

katydids  constitute  the  next        Yig.2^6.-Arnbhcoryphaohlongifolia.    (From 
subfamily.  Lugger.) 

Blatchley  ('20)  describes  twenty  species  and  varieties  of  the  false 
katydids  that  are  found  in  northeastern  America;  these  represent 
eight  genera.  Among  our  common  species  there  are  representatives 
of  three  genera;  these  can  be  separated  as  follows. 

A.     Tegmina  broadened  in  the  middle;  the  extreme  point  of  the  vertex  much 
broader  than  the  first  segment  of  the  antennae. 


ORTHOPTERA 


237 


Fig.     247. — Scudderi      septentri- 
onalis.     (From  Lugger.) 


B.    Hind  femora  much  shorter  than  the  tegmina;  ovipositor  short  and  turned 

abruptly   upward    (Fig.    245).   p.    237 Microcentrum 

BB.    Hind  femora  but  Httle  if  any  shorter  than  the  tegmina;  ovipo-sitor    well 

developed,  and  curved  gradually  upward,  p.  237 Amblycorypha 

AA.     Tegmina  of  nearly  equal  breadth  throughout;  the  extreme  point  of  the 
vertex  but  little  if  any  broader  than  the  first  segment  of  the  antennae,  p.  237. 

,  SCUDDERIA 

Microcentrum. — Two  species  of  this  genus  are  found  in  the  United 
States  east  of  the  Rocky  Mountains ;  these  are  known  as  the  angular- 
winged  katydids.  Figure  245  repre- 
sents the  female  of  the  larger  angular- 
winged  katydid,  Microcentrum  rhombi- 
folium,  and  the  remarkable  way  in 
which  it  deposits  its  eggs  on  leaves  and 
twigs.  In  this  species  the  slightly  hol- 
lowed front  of  the  pronottmi  has  a  very 
small  central  tooth,  which  is  lacking  in 
smaller  species.  The  smaller  angular- 
winged  katydid,  Microcentrum  retinerve,  is  only  slightly  smaller  than 
the  larger  one. 

Amblycorypha. — The  three  most  common  species  of  the  genus 
are  the  following:  The  oblong-winged  katydid,  Amblycorypha  oblongi- 
folia  (Fig.  246),  is  the  largest  of  the 
three  most  common  species.  The 
tegmina  measure  from  34  to  37  mm. 
in  length;  the  ovipositor  is  less  ser- 
rate and  less  curved  than  in  the  next 
species.  The  round-winged  katydid, 
Amblycorypha  rotundifolia,  is  a  smaller 
species ;  the  tegmina  are  not  more  than 
30  mm.  in  length  and  are  wide  for  their 
length,  as  indicated  by  the  specific 
name;  the  ovipositor  is  quite  broad, 
much  curved,  and  roughly  serrated. 
Uhler's  katj^did,  Amblycorypha  iihleri, 
is  our  smallest  species;  the  body  meas- 
ures from  14  to  16  mm.  in  length;  the 
tegmina  from  24  to  26  mm.;  and  the 
ovipositor  about  8  mm. 

Scuddcria. — Species  of  this  genus 
are  found  throughout  the  United 
States  and  in  Canada;  but  the  greater 
nimiber  of  our  species  are  found  east 
of  the  Great  Plains.  One  species, 
Scuddcria  mexicdna,  is  found  in  Cali- 
fornia and  Oregon.  A  common  eastern 
species  which  may  serve  as  an  ex- 
am.ple  of  the  insects  of  this  genus,  is 
the  northern  bush-katydid,  Scuddcria 
Fig.  248.-Pterophylla  camellifo-  septenirtonalis.^  Figure  247  represents 
lia.    (After  Harris.)  the  male  oi  this  species,  natural  size. 


238 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Subfamily  PSEUDOPHYLLIN^ 
The  True  Katydids 

The  best -known  representative  of  this  subfamily  in  the  United 
States  is  the  northern  true  katydid,  Pterophylla  camellifolia  (Fig. 
248).  This  insect  is  found  throughout  the  United  States  east  of 
the  Rocky  Mountains;  but  in  the  North  it  hves  in  colonies  which 
occupy  quite  limited  areas.  This  is  the  insect  whose  song  suggested 
the  popular  name  katydid.  It  differs  from  members  of  the  preceding 
subfamily  in  having  the  hind  wings  shorter  than  the  tegmina,  and  in 
having  the  tegmina  very  convex,  so  that  it  has  an  inflated  appearance. 
Subfamily  CONOCEPHALIN^ 
The  Meadow  Grasshoppers 

From  the  middle  of  the  summer  to  the  autumn  there  can  be  found 
upon  the  grass  in  our  meadows  and  moist  pastures  many  light-green 
long-homed  grasshoppers  of 
various  sizes;  these,  on  ac- 
count of  the  situations  in 
which  they  are  usualh^  found, 
are  termed  the  meadow-grass 
hoppers.  Our  common  species 
represent  only  two  genera ;  but 
each  of  these  includes  many 
species. 

Orchelimum. — This     genus 
includes  the  larger  and  stouter 
species  of  meadow  grasshoppers 
pared  with  other  Tettigoniidse. 


Fig.      249. — Orchelimum 
(From  Lugger.) 


vidgare,   male. 


but  they  are  of  medium  size  com- 
In  these  the  ovipositor  is  usually 


Cojiocephalns. 


Fig.  250. — Orchelimum  vulgare,  female. 
(From  Lugger.) 

Up-curved.  Our  most  abundant  species  is  the  common  meadow 
grasshopper,  Orchelimum  vulgare.  This  is  found  from  the  Rocky 
Mountains  to  the  Atlantic  Coast.  Figure  249  represents  the  male, 
natural  size;  and  Figure  250,  the  female. 

Conocephalus. — This  genus  comprises,  the  smaller  and  slenderer 
species  of  this  subfamily.  In  these  the  ovipositor  is  slender,  and 
straight  or  slightly  curved  (Fig.  251).  Until  recently  this  genus  has 
been  generally  known  as  Xiphidium.* 

*It  is  unfortunate  that  according  to  the  rules  of  nomenclature  the  name 
Conocephalus  must  be  applied  to  this  genus  instead  of  to  the  typical  genus  of  the 
next  subfamily,  now  known  as  Neoconocephaliis,  with  the  result  that  the  sub- 
family name  Conocephalinee  is  applied  to  the  meadow  grasshoppers  instead  of  to 
the  cone-headed  grasshoppers. 


ORTHOPTERA 
Subfamily  COPIPHORIN^ 


239 


The  Cone-headed  Grasshoppers 

The  cone-headed  grasshoppers  are  so  called  because  the  vertex  is 
prolonged  forward  and  upward  into  a  cone.  These  are  much  larger 
insects  than  the  meadow  grass- 
hoppers and  are  found  in  trees  as 
well  as  upon  grass.  This  sub- 
family is  represented  in  our  fauna 
by  four  genera;  but  three  of 
these  are  found  only  in  the  South. 
All  of  the  northern  species  belong 
to  the  genus  N eoconoce phalns ,  of 
which  eleven  species  occur  in  the 
United  States.  The  most  com- 
mon species  in  the  north,  east  of 


252.  —  Neoconocephaliis    ensiger, 
male.    (From  Lugger.) 


the  Rocky  Mountains,  is  the  sword-bearer,  N eoconocephalus  ensiger. 
Figure  252  represents  the  male  of  this  species,  and  Figure  253  the 
female.  Both  sexes  have  very  long  wings,  and  the  ovipositor  of  the 
female  is  remarkable  for  its  length. 


Fig.  253. — Neoconocephaliis  ensiger,  female.    (From  Lugger.) 

In  most  of  the  species  of  Neoconocephaliis  there  are  two  distinct 
forms :  one  pea-green  in  color  and  the  other  of  a  brownish  straw-color. 


Subfamily  DECTICIN^ 


The  Shield-backed  Grasshoppers 


A  few  members  of  this  subfamily  have  well-developed  wings ;  but 
in  most  species  the  wings  are  small,  especially  in  the  female,  where 
they  are  sometimes  even  absent.  Most  of  the  species  bear  some 
resemblance  to  crickets.  They  present,  however,  a  strange  appear- 
ance, due  to  the  pronotum  extending  backward  over  the  rest  of  the 
thorax,   like    a    sun-bonnet    worn    over    the    shoulders    with    the 


240 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  254. — Atlanticus  testaceus,  male. 
(From  Lugger.) 


back  side  forward.  It  was  the  large  size  of  the  pronotum  that  sug- 
gested for  the  group  the  popular 
name  the  shield-hacked  grass- 
hoppers. 

These  insects  live  in  grassy 
fields  or  in  open  woods,  where 
they  hop  about  in  exposed  posi- 
tions. Even  dn  some  of  the  short- 
winged  forms  the  stridulating  or- 
gans of  the  tegmina  of  the  males 
are  well  developed. 

The  North  American  species 

represent  twenty  genera ;  most  of 

these  are  found  west  of  the  Mississippi  River;  a  few  species  occur  in 

the  east;  nearly  all  of  these  belong  to  the  germs  Atlanticus.     Figure 

254  represents  the  male  of  At- 
lanticus   testaceus,  and  Figure 

255  the  female   of   Atlanticus 
davisi. 

Most  of  the  species  of  this 
subfamily  are  local  or  very 
rare  and  not  of  economic  im- 
portance; but  species  of  the 
genus  Anabrus  and  of  Perana- 
hrus  at  times  invade  cultivated  areas  in  the  western  United  States 
and  do  immense  damage.  Many  popular  names  have  been  applied 
to  these  insects;  perhaps  the  one  in  most  general  use  is  the  western 
cricket. 

A  very  complete  monograph  of  the  North  American  species   of 
this  subfamily  has  been  published  by  Caudell  ('07). 


Fig.  255. — Atlanticus  davisi,  female. 


Subfamily  GRYLLACRIN^ 

The  Leaf -rolling  Grasshoppers 


The  members  of  this  subfamily  agree  with  the  preceding  sub- 
families and  differ  from  the  two  following  in  having  the  tarsi  more  or 

less  depressed.  They 
agree  with  the  fol- 
lowing subfamilies 
and  differ  from  the 
preceding  in  the  ab- 
sence of  auditory 
t3Tnpana  in  the  fore 
tibiae  and  in  the  ab- 
sence of  stridulating 
^.  ^  organs  even  when  the 

filfS^hW  r^^'"'"^""  '''''^''''''''''  ^^"'^^'-    ^^'"°"'  tegmina   are   present. 

Only  a  single  spe- 


Blatchley.) 


ORTHOPTERA 


241 


cies,  the  Carolina  leaf -roller,  Camptondtus  carolinensis  (Fig.  256), 
occurs  in  our  fauna.  This  species  is  wingless;  it  measures  from 
13  mm.  to  15  mm.  in  length.  Its  known  range  extends  from  New 
Jersey  west  to  Indiana  and  south  to  Florida. 

This  insect  is  very  remarkable  in  its  habits.which  have  been  de- 
scribed by  Caudell  ('04)  and  McAfee  ('08).  It  makes  a  nest  by 
rolling  a  leaf  and  fastening  the  roll  with  silken  threads  which  it 
spins  from  its  mouth.  It  remains  in  its  nest  during  the  day  and 
emerges  at  night  to  capture  aphids  upon  which  it  feeds. 


Subfamily  RHAPHIDOPHORIN^ 

The  Cave-Crickets  or  Camel-Crickets 

Many  common  names  have  been  applied  to  members  of  this  sub- 
family; among  these  are  cai)g-crz'<:^^/5,  because  they  abound  in  caves 

and  are  found  in  other 
dark  places;  camel-crick- 
ets, because  of  the  high, 
arched  back  of  some 
species  (Fig.  257);  and 
stone-crickets,  from  their 
habit  of  hiding  beneath 
stones.  This  last  name 
is  not  at  all  distinctive. 
These  are  wingless 
long-horned  grass- 
hoppers that  bear  some 
resemblance  to  the  true 
crickets  (Fig.  258).  They  have  a  short,  thick  body  and  remark- 
ably stout  hind  femora,  like  a  cricket,  but  are  entirely  destitute 
of  tegmina  and  wings,  and  the  females,  like  other  Tettigoniidse.  have 
a  sword-shaped  ovipositor.  The  more  common  species  are  either  of 
a  pale  brown  or  a  dirty  white  color  and  more  or  less  mottled  with 
either  lighter  or  darker  shades. 


Fig.  257. —  Ceuthophilus  uhleri,  male.     (From 
Blatchley.) 


Fig.  258. — Ceuthophilus,  female. 


Fig.  259. — Ceuthophilus  maculatus, 
female.     (From  Lugger.) 


These  insects  live  in  dark  and  moist  places,  under  stones  and 
rubbish,  especially  in  woods,  in  cellars,  in  the  walls  of  wells,  and 
in  caves.  On  one  occasion  I  saw  many  thousands  of  them  on  the 
roof  of  a  cave  in  Texas. 

Caudell  ('16)  in  his  monograph  of  this  subfamily  lists  twelve  gen- 
era including  many  species  that  occur  in  the  United  States.    Most  of 


242  AN  INTRODUCTION  TO  ENTOMOLOGY 

our  common  species  in  the  East  belong  to  the  genus  Ceuthophilus. 
Figure  257  represents  the  male  of  Cew^/zo^Mws  w/z/m,  and  Figure  259 
the  female  of  Ceuthophilus  maculdius. 

Subfamily  STENOPELMATIN^ 

The  Sand-Crickets 


These  are  large,  clumsy 
creatures  with  big  heads  (Fig. 
260).  They  live  under  stones 
and  in  loose  soil.  They  are 
represented  in  our  fauna  by 
a  single  genus,  Stenopebndtus, 
several  species  of  which  are 
found   in   the  Far  West  and  pjg_  260.— Stenopelmatus. 

especially  on  the  Pacific  Coast. 

Family  GRYLLIDAE* 
The  Crickets 

Although  the  word  cricket  forms  a  part  of  some  popular  com- 
pound names  of  members  of  the  Tettigoniidae,  as  "western  crickets" 
and  "sand-crickets,"  when  the  word  is  used  alone  it  is  correctly  ap- 
plied only  to  members  of  this  family. 

In  the  more  typical  crickets,  the  hind  legs  are  fitted  for  leaping; 
the  antennae  are  long  and  slender;  the  tegmina  lie  flat  on  the  back 
and  are  bent  down  abruptly  at  the  sides  of  the  body;  the  ovipositor 
is  spear-shaped;  and  the  tarsi  are  three-jointed.  Wingless  forms  are 
common. 

The  more  striking  departures  from  these  characteristics  are  the 
following:  in  the  Tridactylinas  the  antennae  are  short;  in  the  Tri- 
gonidiinse  the  ovipositor  is  sword-shaped ;  in  the  Gryllotalpinae  and 
the  Tridactylinae  the  ovipositor  is  wanting  in  our  species;  and  in 
the  TridactylinEe  the  tarsi  are  reduced. 

It  is  evident  that  one  step  in  the  reduction  of  the  number  of  tarsal 
segments  is  the  growing  together  of  the  metatarsus  and  the  second 
segment.  This  is  shown  in  the  hind  tarsi  of  Anaxlpha,  CEcdnthus, 
Nemobius,  and  doubtless  others,  where  the  suture  between  these  two 
segments  can  be  seen  although  the  segments  are  anchylosed. 

Tympana  are  usually  present  in  the  fore  tibiae,  one  on  each  side 
of  each  tibia,  as  in  the  TettigoniidcC.  In  some  genera  one  t>Tnpantim 
of  each  pair  is  wanting;  this  is  sometimes  the  outer  and  sometimes  the 
inner  one;  in  the  wingless,  and  therefore  mute,  species,  the  tympana 
are  wanting;  and  in  the  Tridactylinae  there  are  none. 


"This  family  is  termed  the  Achetidae  by  some  writers. 


ORTHOPTERA  243 

With  most  species  of  crickets  the  two  sexes  differ  greatly  in  ap- 
pearance; the  female  has  a  long  ovipositor  and  the  venation  of  the 
wings  is  simple,  while  the  male  has  the  horizontal  part  of  the  fore 
wings  modified  to  form  musical  organs.  The  structure  of  these  has 
been  described  in  Chapter  II. 

The  Gryllidae  includes  eight  subfamilies,  all  of  which  are  repre- 
sented in  the  United  States.  These  subfamilies  can  be  separated  by 
the  following  table. 

A.     The  next  to  the  last  segment  of  the  tarsi  distmct,  depressed,  and  heart- 
shaped. 
B.     Hind  tibiae  armed  with  two  series  of  spines  without  teeth  between  them. 

p.  243 TrIGONIDIIN/E 

BB.     Hind  tibiae  with  teeth  between  the  spines,  p.  244 ENEOPXERiNiE 

AA.     Tarsi  compressed,  the  next  to  the  last  segment  minute,  compressed. 
B.    Fore  legs  fitted  for  walking. 

C.    Hind  tibiae  without  spines  except  the  apical  spurs. 

D.     With  well-developed  wings;  hind  tibiae  with  only  two  very  small 

apical    spurs.      {Neoxabea.)    p.  245 CEcanthin^ 

DD.     Wingless  or  subapterous;  hind  tibiae  with  three  pairs  of  apical 

spurs.       p.    250    MOGOPLISTIN^ 

CC.    Hind  tibis  armed  with  two  series  of  spines. 

D.      Body    subspherical;  wingless;  hind    femora    ovate,    very    strongly 

swollen,    p.    249 Myrmecophilin^ 

DD.     Body  more  elongate,  usually  winged;  hind  femora  more  elongate, 
not  exceptionally  swollen. 
E.    Hind  tibiae  with  minute  teeth  between  the  spines,  p.  245  CEcanthin.« 
EE,     Hind  tibiae  without  teeth  between  the  spines,  p,  247.Gryllin^ 
BB.    Fore  legs  fitted  for  digging. 

C.     Antennae  many-jointed;  all   of  the  tarsi  three-jointed,   p.  250 

Gryllotalpin.^; 

CC.     Antennae  eleven- jointed;  fore  and   middle   tarsi   two-jointed,    hind 
tarsi   one-jointed   or   wanting,    p.    251 Tridactylin^ 

Subfamily  TRIGONIDIIN^ 

The  Sword-bearing  Crickets 

These  are  small  crickets,  our  species  measuring  from  4  mm.  to 
8.5  mm.  in  length  of  body.  They  live  chiefly  on  shrubs  and  tall 
grasses  and  weeds  growing  in  or  near  water.  Their  distinguishing 
features  are  the  following :  The  next  to  the  last  segment  of  the  tarsi 
is  distinct,  depressed,  and  heart-shaped,  the  hind  tibias  are  slender 
with  three  pairs  of  mobile  spines  besides  the  terminal  spurs,  and 
with  no  teeth  between  these  spines ;  and  the  ovipositor  of  the  female 
is  compressed  and  curved  upwards.  In  the  sword-shaped  form  of 
the  ovipositor  these  crickets  present  a  striking  exception  to  the 
characteristics  of  the  Gryllid^. 

The  following  are  our  best-known  representatives  of  this  sub- 
family. 

Anaxlpha  exigua. — This  cricket  resembles  somewhat  in  general 
appearance  the  common  small  field-crickets  {Nemohius) ,  but  unlike 


244  ^iV  INTRODUCTION  TO  ENTOMOLOGY 

them  it  does  not  live  on  the  ground.  The  antennse  are  ver\'  long 
(Fig.  261);  the  ovipositor  is  one  half  as  long  as 
the  hind  femora;  the  hind  femora  of  the  male 
are  longer  than  the  tegmina;  and  the  stridu- 
lating  area  of  the  tegmina  is  large.  The  length  of 
the  body  is  5-8  mm. 

There  are  two  forms  of  this  species:  in  one, 
the  hind  wings  are  wanting  and  only  the  t>-mpana 
on  the  outer  face  of  the  fore  tibiae  are  present ;  in 
the  other,  long  hind  wings  are  present  and  there 
is  a  tympanum  on  each  face  of  the  fore  tibiee. 
This  species  is  found  from  southern  New 
England  west  to  Minnesota  and  Nebraska  and 
south  to  Florida  and  Texas. 

Faldcula  hehdrdi. — This  is  a  smaller  species 
than  the  preceding,  the  body  measuring  only  4-5 
mm.  in  length.  It  is  uniform  pale  yellowish  brown 
in  color.  The  hind  wings  are  wanting.  The 
stridulating  area  is  small,  confined  to  the  basal 
fourth  of  the  tegmina.  The  fore  tibia  are  without 
visible  t\Tnpana.  Its  range  extends  from  New 
Jersey  south  and  southwest  to  Florida  and  Texas. 
Cyrtoxipha  columhidna. — This  is  a  small,  pale 
green  fading  to  brownish  yellow,  cricket;  it  is 
found  on  shrubs  and  small  trees,  usually  near 
water.  The  wings  are  always  present  and  pro- 
longed in  the  form  of  a  tail  or  queue.  Tympana 
are  present  on  both  faces  of  the  fore  tibiae.  The 
tegmina  extend  2-3  mm.  beyond  the  end  of  the 
abdomen.  The  length  of  the  body  to  apices  of 
Yig.  261.— Anaxipha  tegmina  is  8.5  mm.  Its  range  extends  from 
extgua.  (Prom  Lug-  Washington,  D.  C,  to  Florida  and  Texas. 

Phylloscyrtus  pidchellus. — This  cricket  differs 
from  the  three  preceding  species  in  having  the  last  segment  of  the 
maxillary  palpi  spoon-shaped.  The  head  and  the  thorax  are  bright 
crimson-red;  the  margin  of  the  thorax  is  pale  yellow;  the  abdomen 
is  black;  and  the  tegmina  are  chestnut-brown.  The  length  of  the 
body  is  6-7  mm.  This  species  is  found  throughout  the  United  States 
east  of  the  Mississippi  River,  except  in  the  northern  portions. 


Subfamily  ENEOPTERIN^ 

The  Larger  Brown  Bush-Crickets 

These  crickets  resemble  those  of  the  preceding  subfamily  in  the 
heart-shaped  form  of  the  next  to  the  last  segment  of  the  tarsi;  but 
differ  in  having  teeth  between  the  spines  of  the  tibiae,  and  in  the 
ovipositor  being  spear-shaped.  » 


ORTHOPTERA 


245 


Only  a  few  species  are  found  in  our  fauna, 
three  genera:  Orocharis,  in  which  both  t^-m- 
pana  of  the  fore  tibia;  are  present ;  Hdpithns,  with 
a  tympantmi  on  the  inner  face  only  of  the  fore 
tibicc;  and  TafaUsca,  with  no  tympana  and  no 
stridulating  organs. 

The  most  common  species  is  Orocharis  saltator 
(Fig.  262).  This  is  usually  pale  reddish  brown, 
but  some  individuals  are  grayish.  The  length 
of  the  body  is  14-16  mm.  It  is  foimd  from  New 
Jersey  west  to  Nebraska  and  south  to  Florida 
and  Texas. 

The  only  common  species  of  Hapithiis  is  H. 
agitator,  which  is  found  from  Long  Island  west  to 
Nebraska    and    south    to    Florida    and    Texas. 

Our  only  species  of  TafaUsca  is  T.  hlrida, 
which  is  found  in  southern  Florida. 

Subfamily  CECANTHIN.^ 


These  represent 


Fig  262. — Orocharis 
saltator.  (From 
Lugger.) 


The  Tree-Crickets 

These  are  delicate  crickets,  many  of  which  are 
of  a  light  green  color,  with  the  body  and  legs 
sometimes  dusky.  Figm-e  263  represents  a  male;  in  the  females  the 
front  wings  are  more  closely  wrapped  about  the  body,  giving  the  insect 
a  narrower  appearance.  They  live  in  more  or  less  elevated  positions, 
varying,  according  to  the  species,  from  among  herbaceous  plants  to 
the  higher  parts  of  fruit  and  forest  trees,  hence  the  name  tree-crickets 
commonly  applied  to  them.  Their  frequent  occurrence  among  flowers 
suggested  the  name  of  the  principal  genus,  CEcdiithus,  implying  I 
dwell  in  flowers.  Two  genera  of  tree-crickets  are  represented  in  our 
fauna,  Neoxahea  and  CEcanthus;  these  can  be  distinguished  by  differ- 
ences in  the  armature  of  the  hind  tibise. 

Neoxahea. — -In  this  genus  the  hind  tibise  bear 
neither  teeth  nor  spines  except  the  apical  spurs, 
and  the  first  segment  of  the  antennas  is  armed  in 
front  with  a  stout,  blunt  tooth  (Fig.  264,  h). 
Neoxahea  hipunctdta  is  the  only  species  known. 
In  this  species  the  hind  wings  are  almost  twice  as 
long  as  the  fore  wings;  the  fore  wings  of  the  fe- 
male are  each  marked  with  two  rather  large 
blackish  spots;  the  wings  of  the  male  are  un- 
marked. The  general  color  is  pale  pinkish  brown. 
The  length  of  the  body  is  about  16  mm. 

Q^cdnthus. — In  this  genus  the  hind  tibiae  bear 
both  spines  and  teeth.  Several  species  occur  in 
the  United  States  and  Canada;  these  differ  in  the 
color  of  the  body,  in  the  markings  on  the  first  two 
segments  of  the  antenna;,  in  their  song,  and  in  the 


Fig.  263. — CEcanthus 
niveus,  male. 


246 


AN  INTRODUCTION  TO  ENTOMOLOGY 


elevation  above  the  surface  of  the  ground  in  which  they  are  usually- 
found.  Most  of  our  species  are  found  east  of  the  Great  Plains; 
one,  CEcdnthus  calijornicus,  occurs  in  California;  and  one,  CEcanthus 


& 


fl  I 


Fig.  264. — Basal  segments  of  antennae  of  CEcanthus  and  Neoxabea.     (The  lettering 
is  explained  in  the  text.     (After  Lugger  and  Fulton.) 

argentlnus,  in  Texas.  The  species  of  eastern  North  America  can 
be  distinguished  by  the  following  table,  which  is  copied  from  a  de- 
tailed account  of  these  insects  by  B.  B.  Fulton  ('15). 

A.    Basal  segment  of  antennse  with  a  swelling  on  the  front  and  inner  side.    First 
and  second  segments  each  with  a  single  black  mark. 

B.    Basal  antennal  segment  with  a  round  black  spot.   (Fig.  264,  a) .  .  CE.  niveus 
BB.     Basal  antennal  segment  with  a  J-shaped  black  mark.      (Fig.  264,  b) 

CE.  anguslipennis 

BBB.     Basal  antennal  segment  with  a  straight  club-shaped  black  mark. 

(Fig.  264,  e) CE.  exclamationis 

AA.    Basal  antennal  segment  without  a  swelling  on  the  front  and  inner  side. 
First  and  second  antennal  segments  each  with  two  black  marks  or  entirely- 
black.     Tegmina  of  males  5  mm.  or  less  in  width. 
B.    Head  and  thorax  pale  yellowish  green  or  black  or  marked  with  both  colors. 
C.    First  antennal  segment  with  a  narrow  black  line  along  inner  edge  and  a 
black  spot  near  the  distal  end.    Body  entirely  pale  yellowish  green.     (Fig. 

264,  d) CE.  quadripunctatus 

CC.     First  antennal  segment  with  black  markings  similar  to  above,  but 

broader  and  usually  confluent,  sometimes  covering  the  whole  segment. 

Head  and  thorax  often  with  three  longitudinal  black  stripes;  ventral 

side  of  abdomen  always  solid  black  in  life.    (Fig.  264,  c) .  .  CE.  nigriconiis 

BB.    Head,  thorax,  and  antennae  reddish  brown.    Wings  in  life  with  conspicuous 

green  veins.     Marks  on  basal  antennal  segment  broad  but  seldom  con  . 

fluent.     (Fig.  264,  f) CE.  pini 

AAA.  Basal  antennal  segment  without  a  swelling  on  the  front  and  inner  side. 
Basal  portion  of  antenna  red  unmarked  with  black.  (Fig.  264,  g).  Teg- 
mina of  male  about  8  mm.  wide CE.  latipennis 

The  species  of  CEcanthus  that  most  often  attracts  attention  is 
the  snowy  tree-cricket,  CEcanthus  niveus  (Fig.  263).  The  pres- 
ence of  this  insect,  though  usually  unseen,  is  made  very  evident  in  late 


ORTHOPTERA 


247 


summer  and  in  the  autumn  by  the  song  of  the  males.  This  song 
early  in  the  evening  and  is  continued  through- 
out the  night ;  it  consists  of  a  monotonous  series 
of  high-pitched  trills  rhythmically  repeated  in- 
definitely. It  is  a  remarkable  fact  that  all  of 
these  crickets  that  are  chirping  in  any  locality 
chirp  in  unison.  Individual  singers  will  stop 
to  rest,  but  when  they  start  again  they  keep 
time  with  those  that  have  continued  the  chorus. 
Except  where  the  true  katydid  is  heard,  this  is 
the  most  conspicuous  insect  song  heard  in  the 
night  in  the  regions  where  this  species  occurs. 
This  cricket  inhabits  chiefly  high  shrubs  and 
trees;  it  deposits  its  eggs  singly  in  the  bark  or 
cambitim  of  trees  and  bushes. 

While  the  presence  of  the  snowy  tree-cricket 
is  made  evident  by  its  song,  there  is  another 
species  that  has  attracted  much  attention  by 
its  manner  of  oviposition;  this  is  Qicanthus 
nigricdrnis.  The  female  lays  her  eggs  in  a 
longitudinal  series  in  the  twigs  or  canes  of 
various  plants  (Fig.  265).  She  selects  the  rasp- 
berry more  often  than  any  other  plant;  and 
as  that  portion  of  the  cane  beyond  the  incisions 
made  for  the  eggs  usually  dies,  it  often  happens 
that  these  crickets  materially  injure  the  plants. 
In  such  cases  the  dead  canes  should  be  cut  out 
and  burned  early  in  the  spring  before  the  eggs 
hatch. 


is  begun 


Fig.  265. — Stem  of  black 
raspberry  with  the  eggs 
of  CEcanthus  nigricor- 
nis:  c,  d,  egg  enlarged. 
(From  Riley.) 


Subfamily  GRYLLIN^ 


The  Field-Crickets 


The  field-crickets  abound  everywhere,  in  pastures,  meadows,  and 
gardens;  and  certain  species  enter  our  dwellings.  They  lurk  under 
stones  or  other  objects  on  the  ground  or  burrow  into  the  earth. 
They  are  chiefly  solitary,  nocturnal  insects;  yet  many  can  be  seen 
in  the  fields  in  the  daytime.  They  usually  feed  upon  plants  but  are 
sometimes  predacious.  With  most  species  the  eggs  are  laid  in  the 
autumn,  usually  in  the  ground,  and  are  hatched  in  the  following 
summer.  The  greater  number  of  the  old  crickets  die  on  the  approach 
of  winter;  but  a  few  survive  the  cold  season.  In  many  of  the  species 
there  are  both  short-winged  and  long-winged  forms. 

This  subfamily  is  represented  in  our  fauna  by  several  genera; 
but  nearly  all  of  our  common  species  are  included  in  the  two  genera 
Gryllus  and  Nemobius. 


248 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Gryllns  assimilis  liicttio- 


The  larger  field-crickets,  Gryllus. — The  members  of  this  genus  are 

dark-colored,  thick-bodied  insects  of  medium  or  large  size.    In  these 

the  hind  tibiae  are  armed  with  strong 
fixed  spines  and  the  first  segment  of 
the  hind  tarsi  is  armed  with  two 
rows  of  teeth  above.  There  are 
two  auditory  tympana  in  each  fore 
tibia.  The  length  of  the  body  is 
rarely  less  than  14  mm. 

Many  supposedly  distinct 
species  of  Gryllus  have  been  de- 
scribed as  occurring  in  our  fauna; 

biit  now  all  of  our  native  forms  are  believed  to  be  merely  varieties  of 

one  species,  Gryllus  assimilis,  and  the  different  varieties  are  distin- 
guished by  subspecific  names.     Six  of  these  varieties  that  occur  in 

the  East  are  described  by  Blatchley  ('20).     Two  of  these  will  serve 

to  illustrate  our  native  forms. 

Gryllus  assimilis  luctuosus. — This  is  one  of  our  more  common 

forms  of  the  genus.     It  is  distinguished  by  the  great  length  of  the 

ovipositor  of  the  female,  which  is  nearly  or 

fully  half  as  long  again  as  the  hind  femora 

(Fig.  266) ;  and  by  the  fact  that  the  head  of 

the  male  is  distinctly  wider  than  the  front 

of  the  pronotum. 

Gryllus  assimilis   pennsylvanicus . — In 

this  variety  the  ovipositor  is  less  than  half 

as  long  again  as  the  hind  femora,  and  the 

head  of  the  male  is  but  little  if  any  wider 

than  the  front  of  the  pronotum  (Fig.  267). 

In  fresh  specimens  the  color  is  not  shining 

black,  but  with  a  very  fine  grayish  pubes- 
cence. 

In  addition  to  our  native  forms  of  Gryllus, 

there  is  an  Old  World  species  that  has  been 

introduced   into   this   cormtry;  this   is   the 

house-cricket,    Gryllus    domesticus.      Refer- 
ences to  the   "cricket  of  the  hearth"  are 

common  in  English  literature  and  refer  to 

this  species,  which  is  now  widely  distributed 

in  this  country,  though  it  is  rarely  abundant. 

It  is  pale  yellowish  brown  or  straw-colored, 

and  slender  in  form  (Fig.  268).    The  length 

of  the  body  is  15-17  mm. 

Our  native  field-crickets  sometimes  enter 

our  dwellings  in  the  autumn;   but  the  house-cricket  can  be  easily 

distinguished  from  these. 

The  smaller  field-crickets,  Nemohius. — To  this  genus  belong  the 

little  field-crickets,  which  are  the  most  abimdant  of  all  of  our  crickets. 

In  these  the  hind  tibiae  are  furnished  with  long,  mobile,  hairy  spines. 


Fig.  267. — Gryllus  assim- 
ilis pennsylv  ani- 
ens. (From  Lugger.) 


ORTHOPTERA 


249 


and  the  first  segment  of  the  hind  tarsi  is  unarmed  above  or  with  only- 
one  row  of  teeth.  There  is  only  one  tympanum  in  each  fore  tibia. 
The  length  of  the  body  is  less  than  1 2  mm. 

There  are  many  species  and  varieties  of  this  genus  in  our  fauna. 
The  following  enlarged  figures  of  two  of  our  species  will  serve  to 
illustrate  the  form  of  these  insects.     (Fig.  269  and  270.) 


Fig.  268.— Gryllus  do- 
mesticus.  (FromLug- 
ger.) 


Fig.     269. —  Nemo- 
bius  fascial  us. 
(From  Lugger.) 


Fig.     270. —  Nemo- 
bins  palustris. 
(Pom  Blatch- 
ley.) 


Subfamily  MYRMECOPHILIN^ 

The  Ant-loving  Crickets 


The  members  of  this  subfamily  are  very  small  crickets,  which  live 
as  guests  in  the  nests  of  ants. 
The  form  of  these  crickets  is  very 
remarkable.  The  body  is  ovate, 
greatly  convex  above,  and  wing- 
less (Fig.  271);  the  hind  femora 
are  ovate  and  greatly  enlarged, 
the  cerci  are  long;  and  the  ovi- 
positor is  short  and  stout. 

Wheeler  ('00)  states  that 
these  crickets  feed  on  an  oily 
secretion  covering  the  surface  of 
the  body  of  the  ants;  they  also 
obtain  this  substance  from  the 
greasy  walls  of  the  ant-burrows. 
Apparently  the  ants  derive  no  benefit  from  the  presence  of  these 


Fig.    271. — Myrmecopldla    pergandei. 
(From  Lugger.) 


250 


AN  INTRODUCTION  TO  ENTOMOLOGY 


guests,  and  destroy  them  when  they  can;  but  the  crickets  are  very 
agile.    These  are  the  smallest  of  the  true  Orthoptera. 

This  subfamily  includes  a  single  genus,  Myrmecophila,  of  which 
five  species  have  been  described  from  the  United  States.  Only  one 
species  has  been  found  in  the  East;  this  is  Myrmecophila  pergdndei. 
In  this  species  the  length  of  the  body  is  3-5  mm. 


Subfamily  MOGOPLISTIN^ 


The  Wingless  Bush-Crickets 

These  crickets  are  found  chiefly  on  bushes  or  among  rubbish  under 
bushes;  some  are  found  beneath  debris  in  sandy  places.     They  are 

small;  those  found  in  the 

United  States  measure  from 

5  mm.  to  13  mm.  in  length  of 

body.    They  are  either  wing- 
less or  furnished  in  the  male 

sex    with    short    tegmina,    in 

which  the  stridulating  organs 

are  well  developed.    The  body 

is    covered   with    translucent, 

easily  abraded  scales. 

Most    of   the   species    are 

tropical  or  subtropical  in  dis- 
tribution; our  species    are 

found  chiefly  in  the  South  and 

Southwest;  but  the  range  of 

one  of  them  extends  north  to  Fig.  273 
{From  "Rehn    and  Long  Island.     Only  four  spe- 
Hebard.)  ^-^g  j^^ve  been  described  from 

the  East  and  one  of  these  is 
restricted  to  Florida.  A  few  others  are  known  from  the  western  part 
of  our  country.  A  monograph  of  the  North  American  species  was 
published  by  Rehn  and  Hebard  ('12). 

Figure  272  represents  the  male  of  Cryptoptilum  trigonipdlpuni,  a 
wingless  species  found  from  Virginia  southward;  and  Figure  273,  the 
male  of  Holosphyrum  boredle,  found  in  the  Southwest. 


Fig.  272. — Cryptopti- 
lum trigonipalpum. 


Holosphy- 
rum boreale.  (From 
Rehn  and  He- 
bard.) 


Subfamily  GRYLLOTALPIN^ 

The  Mole-Crickets 


The  mole-crickets  differ  greatly  in  appearance  from  the  more 
typical  crickets,  the  form  of  the  body  and  of  the  fore  legs  being 
adapted  to  burrowing  in  the  ground.  The  front  tibiae,  especially, 
are  fitted  for  digging;  they  are  greatly  broadened  and  shaped  some- 


ORTHOPTERA 


251 


Fig.    274.— Gryllotal- 
pa  hexadactyla. 


what  like  a  hand  or  a  foot  of  a  mole;  they  are  terminated  by  strong, 

blade-like  teeth,  termed  the  dactyls  (Fig.  274). 

Two  of  the  tarsal  segments  are  blade-like  and  so  situated  that 

they  can  be  moved  across  the  dactyls  like  the 

cutting  blades  of  a  mowing  machine  (Fig.  275). 

Sharpe  ('95)  states  that  this  organ  enables  the 

mole-cricket  to  cut  the  small  roots  it  meets  in 

digging  its  burrows;  but  this  is  doubted  by  Morse 

('20),  who  believes  that  the  roots  are  cut  by  the 

powerful  mandibles. 

The  antennas  of  mole-crickets  are  much  shorter 

than  the  body;  the  hind  femora  are  but  little 

enlarged,   not  well  fitted  for  jumping;  and  the 

ovipositor  is  not  visible  externally.    The  name  o£ 

the  type  genus,   Gryllotdlpa,  is  from  Gryllus,   a 

cricket,  and  talpa,  a  mole. 

Two  genera  of  mole-crickets  are  found  in  the 

United   States:  Gryllotalpa,   in  which   the  front 

tibiee  are  furnished  with  four  dactyls;  and  Scap- 

tertscus,  in  which  each  fore  tibia  bears  only  two 

dactyls.     Each  of  these  genera  is  represented  in 

our  fauna  by  several  species. 

Our  best -known  and  most  widely  distributed 

species  is  Gryllotdlpa  hexadactyla  (Fig.  274).    This 

species  has  been  generally  known  in  this  country  as  Gryllotdlpa 

horedlis;  but  this  name  is  now  be- 
lieved to  be  a  synonym.  The 
range  of  this  species  extends  from 
British  America  to  the  southern 
part  of  South  America.  The 
length  of  the  body  is  20-30  mm. 
The  mole-crickets  are  not 
common  insects  in  this  country; 
but  occasionally  they  are  found 
in  great  numbers  in  a  limited  lo- 
cality. They  make  burrows  in 
moist  places  from  six  to  eight 
inches  below  the  surface  of  the 
ground,  and  feed  upon  the  tender 
roots  of  various  plants,  and  also 
on  other  insects.  The  eggs  are 
deposited  in  a  neatly  constructed 
subterranean  chamber,  about  the 
size  of  a  hen's  egg. 

Subfamily  TRIDACTYLIN^ 
The  Pigmy  Mole-Crickets 
The  members  of  this  subfamily  resemble  the  mole-crickets  in  the 
form  of  the  body  and  in  their  burrowing  habits;  but  they  are  much 


Fig.  275. — Front  leg  of  a  mole-cricket; 
A,  inner  aspect;  B,  outer  aspect;  e, 
ear-slit.     (From  Sharp.) 


252  AN  INTRODUCTION  TO  ENTOMOLOGY 

smaller,  the  larger  species  measuring  only  lo  mm.  in  length;  and  the 
hind  femora  are  greatly  enlarged,  being  strongly  saltatorial  (Fig.  276). 
The  antennae  are  short  and  composed  of  only  eleven 
segments.     The  fore  wings  are  usually  short  and 
never  extend  to  the  end  of  the  abdomen;  they  are 
homy,  are  almost  veinless,  and  are  not  furnished  with 
stridulating  organs  in  the  male.     The  hind  wings 
are  much  longer,  usually  extending  beyond  the  end 
of   the   abdomen.      The   fore   tibiae   lack    auditory 
t^Tmpana.  The  fore  and  middletarsi,  in  our  genera,  are 
two-jointed;  the  hind  tarsi  are  one-jointed  or  want- 
ing. The  hind  tibite  are  fumishd  with  movable  plates, 
"natatory  lamellae,"  near  the  distal  end;  these  are 
ordinarily  closely  appressed  to  the  tibia  but  can  be 
spread  out  like  a  fan.     It  is  probable  that  these 
plates  are  used  to  aid  the  insect  in  leaping  from  the      ^  Tactylus  api'ca- 
surface  of  water  upon  which  they  have  jumped;        /?.?.  (From Lug- 
they  may  also  serve  a  similar  purpose  on  land,  mak-        ger.) 
ing  a  firm  planting  of  the  end  of  the  leg  upon  the 
groiuid.    The  ovipositor  is  vestigial  in  our  species;  but  Walker  ('19) 
states  that  in  the  exotic  genus  Ripipteryx  there  is  a  well-developed 
ovipositor,  which  is  remarkably  similar  to  that  of  the  short-horned 
grasshoppers.    These  insects  apparently  have  two  pairs  of  cerci ;  this 
is  due  to  the  fact  that  in  addition  to  the  true  cerci  each  of  the  two 
podical  plates  is  greatly  elongated  and  bears  a   terminal  segment, 
which  appears  like  a  stylus  or  cercus. 

These  insects  burrow  rapidly  in  sand  and  possess  great  powers  of 
leaping.  They  live  on  and  in  the  damp  sand  on  the  shores  of  ponds 
and  streams.  Their  burrows  extend  onl}^  a  short  distance  below  the 
surface  of  the  ground. 

Only  two  genera,  each  represented  by  a  single  species,  have  been 
found  in  America  north  of  Mexico. 

Triddctyhis. — In  this  genus  the  hind  tibiae  are  furnished  with  four 
pairs  of  long,  slender  plates,  the  "natatory  lamellae;"  and  the  hind 
tarsi  are  one-jointed.  Our  species  is  Triddctylus  apicdlis  (Fig.  276). 
Thejength  of  the  body  is  6-9.5  ™i^- 

Ellipes. — In  this  genus  the  hind  tibis  are  furnished  with  a  single 
pair  of  "natatory  lamellae";  and  the  hind  tarsi  are  wanting.  Our 
species  is  Ellipes  minuta.    The  length  of  the  body  is  4-5  mm. 

Walker  ('19)  as  a  result  of  his  studies  of  the  genitalia  of  Ripi- 
pteryx believes  that  the  pigmy  mole-crickets  are  more  closely  allied 
to  the  Locustidae  than  they  are  to  the  Gryllidae,  and  ranks  them  as 
constituting  a  distinct  family,  the  Tridactylidae. 

Family  LOCUSTID^* 
The  Locusts  or  Short-horned  Grasshoppers 
The  family  Locustidae  includes  the  locusts  or  short-homed  grass- 


*This  family  is  termed  the  Acrididse  by  some  writers,  this  name  being  based  on 
the  generic  name  Acrida  of  Linnaeus;  other  writers  use  the  family  name  Aery- 


ORTHOPTERA  253 

hoppers.  These  are  common  and  well-lmown  insects.  They  differ 
from  most  of  the  members  of  the  two  preceding  famihes  in  having 
the  antenna)  much  shorter  than  the  body,  and  consisting  of  not  more 
than  twenty-tive  segments.  The  ovipositor  of  the  female  is  short 
and  composed  of  separate  plates;  and  the  basal  segment  of  the 
abdomen  is  furnished  on  each  side  with  a  t^nnpanum,  the  external 
parts  of  the  organs  of  hearing  (Fig.  277,  /). 

It  is  to  these  insects  that  the  term  'locust  is  properly  applied; 
for  the  locusts  of  which  we  read  in  the  Bible,  and  in  other  books 
published  in  the  older  countries,  are  members  of  this  family. 
Unfortunately,  in  the  United  States  the  term  locust  has  been  applied 
to  the  Periodical  Cicada,  a  member  of  the  order  Homoptera,  described 
later.  And,  what  is  more  unfortunate,  the  scientific  name  Locus- 
tidas  has  been  applied  by  many  writers  to  the  long-horned 
grasshoppers. 

Locusts  lay  their  eggs  in  oval  masses  and  cover  them  with  a 
tough  substance.  Some  species  lay  their  eggs  in  the  groimd.  The 
female  makes  a  hole  in  the  ground  with  her  ovipositor,  which  is  a 
good  digging  tool.  Some  species  even  make  holes  in  fence-rails,  logs, 
and  stumps;  then,  after  the  eggs  are  laid  the  hole  is  covered  up  with 
a  plug  of  gummy  material.  There  is  but  one  generation  a  year,  and 
in  most  cases  the  winter  is  passed  in  the  egg-state.  This  family  is 
of  great  economic  importance,  as  the  members  of  it  usually  appear  in 
great  numbers  in  nearly  every  region  where  plants  grow,  and  often 
do  much  damage. 

With  many  species  of  the  Locustidse  the  males  are  furnished  with 
stridulating  organs.  These  have  been  described  in  Chapter  II, 
page  82. 

There  are  very  many  species  of  locusts  in  the  United  States  and 
Canada;  these  represent  four  of  the  subfamilies  of  the  family  Locus- 
tidas,  which  can  be  separated  by  the  following  table. 

A.     Claws  of  the  tarsi  with  a  small  pad  (arolium)  between  them;  pronotum  ex- 
tending at  most  over  the  extreme  base  of  the  abdomen. 
B.    Prosternum  armed  anteriorly  with  a  distinct  conical  or  cylindrical  tubercle- 

p.  254 LOCUSTIN^ 

BB.     Prosternum  without  a  distinct  tubercle;  arolium  usually  small  or  rather 
small. 
C.    Head  rounded  at  the  union  of  the  vertex  and  front ;  front  perpendicular 

or  nearly  so.  p.  257 CEdipodin.« 

CC.    Vertex  and  front  of  head  meeting  at  an  acute  angle;    vertex  extending 

horizontally;  front   strongly  receding,     p.   259 Trux.\lin.e 

AA.    Claws  of  tarsi  without  an  arolium  between  them;  pronotum  extending  over 
the  abdomen,     p.  259 Acrydiin^ 


diidse,  based  on  the  generic  name  Acrydium  of  Fabricius;  and  still  others  use  the 
family  name  Acridiidse,  based  on  Acridium,  an  emended  spelling  of  Acrydium. 
The  oldest  name  given  to  this  family  is  Acrydiana,  appHed  to  it  by  Latreille  in 
1802;  but  the  group  of  insects  that  Latreille  used  as  the  type  of  the  family  is  the 
Locusta  of  Linnaeus  (1758);  for  this  reason  the  name  given  to  the  family  by 
Latreille  has  been  changed  to  Locustidae.     See  also  the  footnote  on  page  234. 


254 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Subfamily  LOCUSTIN^ 

The  Spur-throated  Locusts 

The  members  of  this  subfamily  are  distinguished  from  other 
North  American  locusts  by  the  presence  of  a  tubercle  on  the  pro- 
sternum.  Here  belong 
many  of  our  more  com- 
mon species;  and  among 
them  are  found  the  most 
injurious  insects  of  the 
order  Orthoptera.  Among 
our  best-known  species 
are  the  following. 

The  Rocky  Mountain 


Fig.  277. — Side  view  of  a  female  locust  with  the 
wings  removed. 


locust  or  western  grasshopper,  Meldnoplus  spretus. — The  most  terrible 
of  insect  scourges  that  this  country  has  known  have  been  the  invasions 


Fig.  278. — Egg-laying  of  the  Rocky  Mountain  Locust :  a,  a,  a,  female  in  different 
positions,  ovipositing;  b,  egg-pod  extracted  from  the  ground  with  the  end 
broken  open;  c,  a  few  eggs  lying  loose  on  the  ground;  d,  e,  show  the  earth 
partially  removed,  to  illustrate  an  egg-mass  already  in  place,  and  one  being 
placed;  /  sho\vs  where  such  a  mass  has  been  covered  up.      (From    Riley.) 

of  this  species.    Large  areas  of  country  have  been  devastated,  and  the 
inhabitants  reduced  to  a  state  of  starvation.    The  cause  of  all  this 
suffering  is  not  a  large  insect.     It  is  represented  in  natural  size  by 
Figure  278.    It  measures  to  the  tip  of  its 
wing-covers   20-35  mm.,  and  resembles 
very  closely  our  common  red-legged  lo- 
cust, the  most  abundant  of  all  our  species. 
It  can  easily  be  distinguished  from  this 
species  by  the  greater  length  of  the  wings, 
which  extend  about  one-third  of    their 
length  beyond  the  tip  of  the  abdomen, 
and  by  the  fact  that  the  apex  of  the  last 
abdominal  segment  in  the  males  is  distinctly  notched. 


Fig.  279.- 
rubrum. 


-Melanopltts  femur- 


ORTHOPTERA 


255 


fWr 


bivittatus.       (From 


The  permanent  home  or  breeding  grotinds  of  this  species  is  in  the 
high,  drylands  on  the  eastern  slope  of  the  Rocky  Mountains,  extend- 
ing from  the  southern  limit  of  the  true  forests  in  British  America 
south  through  Montana,  Wyoming,  the  western  part  of  the  Dakotas, 
and  the  Parks  of  Colorado.  There  are  also  regions  in  which  the  species 
exists  permanently  west  of 
the  Rocky  Mountains  in 
Idaho  and  Utah. 

When  the  food  of  this 
insect  becomes  scarce  in  its 
mountain  home,  it  migrates 
to  lower  and  more  fertile  re- 
gions. Its  long  wings  en- 
able it  to  travel  great  dis- 
tances; and  thus  the  larger 

part  of  the  region  west  of  the  Mississippi  River  is  liable  to  be  invaded 
by  it.  Fortunately,  the  species  cannot  long  survive  in  the  low,  moist 
regions  of  the  valleys.  Although  the  hordes  of  locusts  which  reach 
these  sections  retain  their  vigor,  and  frequently  consume  every  bit 
of  green  vegetation,  the  young,  which 
hatch  from  the  eggs  that  they  lay,  perish 
before  reaching  maturity.  In  this  way 
the  invaded  region  is  freed  from  the  pest 
until  it  is  stocked  again  by  another  in- 
cursion. There  is,  however,  a  large  sec- 
tion of  country  lying  immediately  east  of 
the  great  area  indicated  above  as  the 
permanent  home  of  this  species,  which  it 
frequently  invades  and  in  which  it  can 
perpetuate  itself  for  several  years,  but 
from  which  it  in  time  disappears.  This 
sub-permanent  region,  as  it  has  been 
termed,  extends  east  in  British  America 
so  as  to  include  nearly  one-third  of  Mani- 
toba; and,  in  the  United  States,  it  em- 
braces nearly  the  whole  of  the  Dakotas, 
the  western  half  of  Nebraska,  and  the 
northeast  fourth  of  Colorado. 

The  temporary  region,  or  that  only 

periodically  visited  and  from  which  the 

Fig.  281. — Melanoplus  bivitta-  species  gen erallv  disappears  within  a  vear, 

(From'uf  eO    ""    ^''"^''^'   extends  east  and  south  so  as  to  include 

ugger.j  more  than  half  of  Minnesota  and  Iowa, 

the  western  tier  of  counties  of  Missouri, 

the  whole    of    Kansas   and    Oklahoma,    and    the   greater    part   of 

Texas.     The  country  lying  east  of  the  section  thus  indicated  has 

never  been  invaded  by  this  locust,  and  there  is  no  probability  that 

it  will  ever  be  reached  by  it. 


256 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Detailed  directions  for  the  control  of  this  pest  have  been  pub- 
lished in  many  State  and  Federal  Government  reports.    Among  these 

methods  of  control  are 
the  plowing  of  landjin 
which  its  eggs  have 
been  deposited,  the 
use  of  poisoned  bran- 
mash  as  a  bait,  and 
catching  of  the  insects 
Fig.  282.- — Melanoplus  differentialis.  (From  Riley.)  \^y  machines  com- 
monly known  as  "hopper  dozers." 

The  red-legged  locust,  Melanoplus  femur-ruhrum. — This  is  the 


Fig.  283. — Schistocerca  americana.     (From  Riley.) 

most   common   short-homed   grasshopper   throughout   the   United 

States,     except    where     Melanoplus 

spretus    occurs.       It     ravages*    our 

meadows  and  pastures  more  than  all  other 

species  combined.     It  is  found  in  most 

parts  of  North  America.     The  female  is 

represented,  natural  size,  by  Figure  279. 

Melanoplus  hivittdtus . — This  species 
is  also  found  from  the  Atlantic  to  the 
Pacific.  It  is  marked  with  a  yellowish 
stripe,  extending  along  each  side  from 
the  upper  angle  of  the  eye  to  the  tip  of 
the  front  wing  (Fig.  280).  The  length  of 
the  body  varies  from  23  mm.  to  40  mm. 

This  locust  is  often  killed  by  a  para- 
sitic fungus.  Dead  fungus-infected  in- 
dividuals are  frequently  found  clinging  to 
weeds,  up  which  they  have  climbed  to 
die  (Fig.  281). 

Melanoplus  differentialis. — This  spe- 
cies is  slightly  larger  than  the  preceding; 
and  it  lacks  the  prominent  yellow  stripe 
(Fig.  282). 

Schistocerca  americana. — This  magnifi- 
cent species  occurs  in  the  Southern  States  pig_  284^— Brachvstol7  magna 

'  '        -  r         .         r  ,1  ^  (From  Riley.)  ' 


and  has  been  foimd  as  far  north  as  Con- 


ORTHOPTERA 


257 


necticut  and  Iowa.  It  can  be  recognized  by  Figure  283,  which  rep- 
resents it  natural  size.  This  locust  sometimes  assumes  the  migratory 
habit,   and  is  sometimes  injurious  to  agriculture. 

The  lubber  grasshopper,  Brachystola  magna. — This  is  a  large, 
clumsy  species  in  which  the  wings  are  vestigial  (Fig.  284) ;  it  is 
confined  to  the  central  portion  of  North  America. 

Leptysma  marginicolUs. — 
In  most  of  the  spur-throated 
locusts  the  face  is  nearly  ver- 
tical; but  in  a  few  species  it 
is  very  oblique.  This  species 
is  a  good  illustration  of  this 
type  (Fig.  285);  it  is  fomid  in 
the  Southern  States  east  of  the 


Mississippi  River. 


Fig.  285. — Leplysma  marginicolUs. 


Subfamily  (EDIPODIN^ 


The  Band-winged  Locusts 


In  this  subfamily  the  prosternimi  is  without  a  distinct  tubercle; 
the  head  is  rounded  at  the  union  of  the  vertex  and  the  front;  and  the 
front  is  perpendicular  or  nearly  so.  In  most  of  our  species  the  hind 
wings  are  in  part  black,  and  a  portion  of  them  yellow  or  red;  this 
gives  them  a  banded  appearance.  There  are  many  representatives 
of  this  subfamily  in  our  fauna;  the  following  are  some  of  the  more 
common  ones. 

The  clouded  locust,  Encoptolophus  sordidus. — -This  species  (Fig. 
286)  is  very  common  in  the  eastern  United  States  during  the  autumn. 

It  abounds  in  meadows  and  pas- 
tures, and  attracts  attention  by 
the  crackling  soimd  made  by  the 
males  during  flight.  It  is  of  a 
dirty  brown  color,  mottled  with 
spots  of  a  darker  shade.  The 
length  of  the  body  of  the  male  is  i  g- 
Fig.  2m.— Encoptolophus  sordidus.      22  mm. ;  of  the  female,  24-32  mm. 

The  northern  green-striped  locust,  Chortophaga  viridifascidta.  — 
This  is  a  very  common  species  in  the  United  States  and  Canada  east 
of  the  Rocky  Mountains.  There  are  two  well-marked  varieties. 
In  one,  the  typical  form,  the  head,  thorax,  and  femora  are 
green,  and  there  is  a  broad  green  stripe  on  each  fore  wing,  extend- 


258 


AN  INTRODUCTION  TO  ENTOMOLOGY 


ing    from    the    base    to    beyond    the  middle;  this  often     includes 

two  dusky  spots  on  the 
edge.  In  the  other  vari- 
ety, the  ground  color  is 
dusky  brown.  Intergrades 
occur,  in  which  the  head 
and  thorax  are  of  a  reddish 
velvety  brown.  The  length 
of  the  body  is  17-32  mm. 

The  Carolina  locust, 
Dissostelra  Carolina. — Not- 
withstanding its  specific 
name,  this  species  is  com- 
mon throughout  the  United 
States  and  Canada.  It  is 
a  large  species;  the  length 
of  the  body  of  the  males  is 
24-33  mm.,  of  the  females 
33-40  mm.  It  abounds  in 
highways    and    in    barren 

r«-    "  o      n-      ,  •  1-      fv       T  ^      places.       It     takes    flight 

7^g.287.-Drssosteuacarohna.{VromLngger.)       ^^^^.^^^      ^^^      ^^^      ^|^^^ 

stridulate  while  in  the  air.  The  color  of  this  insect  varies  greatly, 
simulating  that  of  the  soil  upon  which 
it  is  found.  It  is  usually  of  a  pale  yel- 
lowish or  reddish  brown,  with  small 
dusky  spots.  The  hind  wings  are  black, 
with  a  broad  yellow  margin  which  is 
covered  with  dusky  spots  at  the  tip 
(Fig.  287). 

Boll's  locust,  Spharagemon  bolli. — 
This  species  is  widely  distributed  in  the 
United  States  and  southern  Ontario 
east  of  the  Rocky  Mountains.  The 
length  of  the  body  of  the  male  is  20-28 
mm.,  of  the  female  27-36  mm.  The 
hind  wings  are  pale  greenish  yellow  at 
the  base  and  are  crossed  by  a  dark 
band;  the  apical  third  is  transparent 
smoky  in  color  (Fig.  288). 

The  coral-winged  locust,  Hipptscus 
apiculdtus. — This  is  one  of  the  larger 
of  our  band-winged  locusts  (Fig.  289). 
The  length  of  the  body  of  the  male  is 
25-30  mm.,  of  the  female  36-44  mm.  The  general  color  is  ash-brown. 
The  basal  portion  of  the  hind  wings  is  bright  coral-red,  rarely  yellow; 
this  part  is  bordered  without  by  a  dark  band.  This  species  is  widely 
distributed  east  of  the  Rockv  Mountains. 


Fig.    288. — spharagemon    bolli 
(From  Lugger.) 


ORTHOPTERA 


259 


Fig.  289. — Hippiscus  apicidatus.     (From  Lugger.) 

Subfamily  TRUXALIN^ 

The  Slant-faced  Locusts 


In  this  subfamily,  as  in  the  preceding  one,  the  prostemum  is 
unarmed  but  the  head  is  of  a  different  form.     In  the  Truxalinaj, 

the  vertex  and  the  front  meet  on  an 
acute  angle.  In  some  species  this 
angle  is  a  sharp  one,  the  shape  of 
the  head  being  similar  to  that  of 
Leptysma  (Fig.  285).  In  other 
species,  however,  the  front  is  less 
receding ;  this  is  the  case  in  the  fol- 
lowing species. 

The  sprinkled  locust,  Chlo'ealtis 
conspersa. — This  is  a  very  abundant 
species     in    the    northern    United 


Fig.  290. — Chloealtis  conspersa, 
male.  (From  Lugger.) 


States  and  Canada  east  of 
the  Great  Plains.  It  is 
brown,  with  the  sides  of  the 
pronotum  and  the  first  two 
or  three  abdominal  seg- 
ments shining  black  in  the 
male;  and  with  the  body 
and  tegmina  of  the  female 
sprinkled  or  mottled  with 
darker  broAvn.  The  teg- 
mina and  hind  wings  are  a 

little  shorter  than  the  abdomen  in  the  male  (Fig.  290), 
shorter  in  the  female  (Fig.  291).  The  males  measure  15- 
length;  the  females,  20-28  mm. 


Fig.  291. — Chloealtis  conspersa,  female.  (From 
Lugger.) 


and  mucli 
20  mm.  in 


Subfamily  ACRYDIIN^ 

TJie  Pigmy  Locusts 

The  Acry'diinse  includes  small   locusts   of  very  tmusual   form. 
They  differ  so  much  from  other  locustids  that  some  students  of  the 


260 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  292.— A  pig- 
my locust.. 


Fig.  293. — Acrydium  graiiulatum. 
ley,  after  Kirby.) 


(From  Blatch- 


Orthoptera  believe  they  constitute  a  separate  family.  The  most 
striking  character  of  the  subfamily  is  the 
shape  of  the  pronotum.  This  is  prolong- 
ed backwards  over  the  abdomen  to  or  beyond 
its  extremity  (Fig.  292).  The  head  is  deeply 
set  in  the  pronotum;  and  the  prostemum  is  ex- 
panded into  a  broad  border,  which  partly 
envelops  the  mouth-parts  like  a  muffler.  The  antennae  are  very 
slender  and  short.  The  tegmina  are  vestigial,  being  in  the  form  of 
small,  rough  scales;  while  the  wings  are  usually  well-developed. 
These  locusts  differ,  also, 
from  all  others  in  having 
no  arolium  between  the 
claws   of  the  tarsi. 

The  pigmy  locusts  are 
commonly  foimd  in  low, 
wet  places,  and  on  the 
borders  of  streams. 
Their  colors  are  usually 
dark,  and  are  often  pro- 
tective, closely  resem- 
bling the  soil  upon  which 
the  insects  occur.  They 
are  very  active  and  pos- 
sess great  leaping  powers. 

Some  of  the  species  vary  greatly  in  coloring;  this  has  resulted 
often  in  a  single  species  being  described  under  two  or  more  names. 
This  is  an  exceedingly  difficult  group  in  which 
to  determine  the  species. 

Figure  293  represents  Acrydium  granuldtum 
with  its  wings  spread,  and  the  pronota  of  two 
color  varieties. 

Figure  294    represents  Acrydium  arenosum 

obscurum,    greath^    enlarged,    with    its   wings 

..     ..  „......^    -^        closed. 

Family   PHASMID^* 
The  Walking-Sticks  and  the  Leaf-Insects 

The  Phasmid£e  is  of  especial  interest  on  ac- 
count of  the  remarkable  mimetic  forms  of  the 
insects  comprising  it.  In  those  species  that 
are  foimd  in  the  United  States,  except  one  in 
Florida,  the  body  is  linear  (Fig.  295),  wingless, 
and  furnished  with  long  legs  and  antennse.  This  peculiar  form 
has  suggested  the  name  walking-sticks  which  is  commonly  applied 

*This  family  is  separated  from  the  Orthoptera  by  Handlirsch  ('o6-'o8)  and 
made  to  constitute  a  distinct  order,  the  Phasmoidea. 


Fig.  294.  —  Acrydium 
arenosum  obscurum. 
(From  Hancock.) 


ORTHOPTERA 


261 


to  these  insects;  they  are  also  known  as  stick-insects.  In  some 
exotic  species  the  body  has  the  appearance  of  being  covered  with 
moss  or  with  Hchens,  which  increases  the  resemblance  to  a  stick 
or  a  piece  of  bark. 

While  our  species  are  all  wingless,  except  Aplopus  mayeri,  found 
in  southern  Florida,  many  exotic  species  are  furnished  with  wings; 
and  with  some  of  these  the  wings  resemble  leaves.  Among  the 
more  remarkable  of  the  leaf-insects,  as  they  are  known,  are  those 
of  the  genus  Phyllimn  (Fig.  296),  the  members  of  which  occur  in 
the  tropical  regions  of  the  Old  World. 

In  the  walking-sticks,  the  body  is  elongate  and  subcylindrical  • 
the  abdomen  consists  of  ten  segments,  but  the  basal  segment  is 
small  and  usually  coalesced  with  the  metathorax  and  sometimes  it 
is  entirely  invisible;  the  legs  are  all  fitted  for  walking;  the  tarsi 
are  five-jointed  except  in  the  genus  Tiniema,  where  they  are  three- 
jointed;    the   cerci   are    without    joints. 

These  insects  are  strictly  herbivorous; 
they  are  slow  in  their  motions,  and  often 
remain  quiet  for  a  long  time  in  one  place. 
They  evidently  depend  on  their  mimetic 
form  for  protection.  In  addition  to  this 
some  species  have  the  power  of  ejecting  a 
stinking  fluid,  which  is  said  to  be  very 
acrid ;  this  fluid  comes  from  glands  placed 
in  the  thorax. 

The  eggs  are  scattered  on  the  ground 
beneath  the  plants  upon  which  the  insects 
feed,  the  female,  unlike  most  Orthoptera, 
making  no  provision  for  their  safety.  In 
our  common  northern  species  the  eggs  are 
dropped  late  in  the  simimer  and  do  not 
hatch  till  the  following  spring,  and  they 
often  remain  till  the  second  spring  before 
they  hatch. 

About  600  species  of  phasmids  have 
been  described;  but  they  are  largely 
restricted  to  the  tropical  and  subtropical 
regions.  Caudell  ('03)  in  his  monograph 
of  the  species  of  the  United  States  enu- 
merates sixteen  species  that  occur  in  our 
fauna;  but  these  are  foimd  chiefly  in  the 
southern  part  of  the  coimtry. 

Our  common  northern  walking-stick 
is  Diapheromera  femordta  (Fig.  295).  The 
range  of  this  species  extends  into  Canada. 
It  is  a  quite  common  insect,  and  on  sev- 
eral occasions  has  appeared  in  such  great 
numbers  as  to  be  seriously  destructive  to 
the  foliage  of  forest  trees;  but  these  outbreaks  have  been  temporary 


Diapheromera  fern- 


262 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Among  the  more  striking  in  ap- 
pearance of  the  walking-sticks  found 
in  the  South  axeMegaphasmadentricus, 
our  largest  species,  measuring  from  125 
to  150mm.  in  length,  and  Anisomorpha 
buprestoides,  a  yellowish  bro^vn  species, 
about  half  as  long  as  the  preceding, 
with  conspicuous,  broad,  black  stripes 
extending  from  the  front  of  the  head 
to  the  tip  of  the  abdomen. 

The  reproduction  of  lost  legs  occurs 
frequently  in  this  family. 


Family  MANTID^^ 


The  Praying  Mantes  or  Soothsayers 


The  praying  mantes  are  easily  rec- 
Fig.  296.— Phyllium  scythe.  (From  ognized  by  the  unusual  form  of  the 
Sharp,  after  Westwood.)  prothoraxand  of  the  first  pair  of  legs 

(Fig.  297).  The  prothorax  is  elongate,  sometimes  nearly  as  long  as 
the  remainder  of  the  body;  and  the  front  legs  are  large  and  fitted 
for  seizing  prey.  The  coxse  of  the  front  legs  are  very  long,  pre- 
senting the  appearance  of  femora;  and  the  femora  and  tibiae  of 
these  legs  are  armed  with  spines;  the  tibia  of  each  leg  can  be 
folded  back  against  the  femur  so  that  the  spines  of  the  two  will 
securely  hold  any  insect  seized  by  the  praying  mantis. 

The  second  and  third  pairs  of  legs  are  simple  and  similar;  the 
tarsi  are  five-jointed;  and  the  cerci  are  jointed. 

With  some  species  the  wings  resemble  leaves  of  plants  in  fomi 
and  coloring.  This  resemblance  is  protective,  causing  the  insects 
to  resemble  twigs  of  the  plants  upon  which  they  are. 

All  of  the  species  are  carnivorous,  feeding  on  other  insects. 
They  do  not  pursue  their  prey  but  wait  patiently  with  the  front 
legs  raised  like  uplifted  hands  in  prayer,  until  it  comes  within  reach, 
when  they  seize  it.  This  position,  which  they  assume  while  waiting, 
gives  them  most  of  their  popular  names,  of  which  there  are  many. 

The  eggs  of  the  Mantidae  are  encased  in  chambered  oothecas, 
which  are  usually  fastened  to  the  stems  or  twigs  of  plants  (Fig.  298). 
In  the  case  of  the  species  that  occur  in  the  North,  there  is  only 
one  generation  in  a  year  and  the  winter  is  passed  in  the  egg-state. 

Most  of  the  members  of  this  family  are  tropical  insects;  a  few 
species,  probably  less   than   twenty,  live  in  the  southern  half  of 


*This  family  is  separated  from  the  Orthoptera  by  Handlirsch  ('o6-'o8)  and 
made  to  constitute  a  distinct  order,  the  Mantoidea. 


ORTHOPTERA  263 

the  United   States;    and  one  of  our  native    species,  Stagmomdntis 


Carolina  (Fig.  297),  is  found  as  far  north  as  Maryland 
and  southern  Indiana. 

Recently  two  exotic  species  have  been  introduced 
into  the  Northern  States,  probably  by  the  importa- 
tion of  o6theca3  on  nursery  stock,  and  have  become 
established  here.  These  are  the  Mantis  religiosa  of 
Europe,  which  was  first  observed  in  this  comitry 
near  Rochester,  N.  Y.,  in  1899,  and  Paratenodera 
sinensis  of  China  and  Japan,  which  was  first  ob- 
served here  at  Philadelphia  about  1895. 


Family  BLATTID^* 

The  Cockroaches 

The  cockroaches  are  such  well-known  insects  that 
there  is  but  little  need  for  a  detailed  account  of  their 
characteristics.  As  already  indicated  in  the  table  of 
families,  the  body  is  oval  and  depressed ;  the  head  is 
nearly  horizontal,  and  wholly  or  almost  wholly 
withdrawn  beneath  the  pronotiim;  the  head  is  bent 
so  that  the  mouth-parts  project  caudad  between 
the  bases  of  the  first  pair  of  legs;  the  antennae  are 
long  and  bristle-like ;  and  the  pronotimi  is  shield-like. 
This  family  includes  only  the  cockroaches ;  but  these  Fig.  298.— Egg- 
insects  are  known  in  some  localities  as  "black  ^^^^^  °^.  *^^"^' 
,       ,1       ,,  1  ,  •         •       J.1  momantts  car- 

beetles,      and   our  most   common   species   m   the       ^n^^^    (From 

northern  cities  bears  the  name  of  Croton-bug.  Riley.) 


*This  family  is  separated  from  the  Orthoptera  by  Handlirsch    ('o6-'o8)   and 
made  to  constitute  a  distinct  order,  the  Blattoidea. 


264  .4iV  INTRODUCTION  TO  ENTOMOLOGY 

In  the  Northern  States  our  native  species  are  usually  found  in 
the  fields  or  forests  under  sticks,  stones,  or  other  rubbish.  But 
certain  imported  species  become  pests  in  dwell- 
^^^^>  /'WSPW^  ings.  In  the  warmer  parts  of  the  coimtry,  how- 
^*-2Si*si<  ?*i44ai#tif^  ever,  native  and  foreign  species  alike  swarm  in 
Fig.  299.-  Ootheca  of  a  buildings  of  all  kinds,  and  are  very  common  out 
cockroach.  ^^  ^^^^^ 

Cockroaches  are  very  general  feeders;  they  destroy  nearly  all 
forms  of  provisions,  and  injure  many  other  kinds  of  merchandise. 
They  often  deface  the  covers  of  cloth-bound  books,  eating  blotches 
upon  them  for  the  sake  of  the  sizing  used  in  their  manufacture ;  and 
I  have  had  them  eat  even  the  gum  from  postage  stamps.  They  thrive 
best  in  warm,  damp  situations ;  in  dwellings  they  prefer  the  kitchens 
and  laundries,  and  the  neighborhood  of  steam  and  water  pipes.  They 
are  chiefly  nocturnal  insects.  They  conceal  themselves  during  the 
day  beneath  furniture  or  the  floors,  or  within  the  spaces  in  the  walls 
of  a  house;  and  at  night  they  emerge  in  search  of  food.  The  de- 
pressed form  of  their  bodies  enables  them  to  enter  small  cracks  in 
the  floors  or  walls. 

Not  only  are  these  insects  very  destructive  to  our  possessions,  but 
owing  to  their  fetid  odor  merely  the  sight  of  them  awakens  disgust ; 
but  it  is  due  them  to  state  that  they  are  said  to  devour  greedily  bed- 
bugs. This  will  better  enable  us :  to  abide  their  presence  in  our 
staterooms  on  ocean  voyages,  or  in  our  chambers  when  we  are  forced 
to  stop  at  poor  hotels.  ^; 

The  eggs  of  cockroaches  are  enclosed  in  purse-hke  capsules  (Fig. 
299).  These  capsules,  or  ootheca?,  vary  in  form  in  difl'erent  genera, 
but  are  more  or  less  bean-shaped.  Within,  the  ootheca  is  divided 
into  two  parallel  spaces,  in  each  of  which  there  is  a  row  of  separate 
chambers,  each  chamber  enclosing  an  egg.  The  female  often  carries 
an  ootheca  protruding  from  the  end  of  the  abdomen  for  several  days. 
It  has  been  found  that  a  single  female  may  produce  several  oothecas. 

The  n^^mphs  resemble  the  adults  except  in  size,  and, 
in  the  case  of  winged  species,  in  the  degree  of  develop- 
ment of  the  wings.  In  adults  also  of  some  species  the 
wings  are  reduced,  atrophied,  or  absent;  this  condi- 
tion exists  more  frequently  in  females  than  in  males 
(Fig.  300). 

As  in  most  other  insects,  the  homologies  of  the 
wing-veins  can  be  most  easily  determined  by  a  study 
of  the  tracheation  of  the  wings  of  n\Tnphs;  Figure  301 
will  serve  to  illustrate  this. 

Experiments  conducted  by  the  Bureau  of  Ento- 
mology at  Washington  have  shown  that  one -of  the   Fig.  300. — A 
most  effective  means  of  ridding  premises  of  cockroaches      wingless 
is  dusting  the  places  they  frequent  with  commercial 
sodium  fluorid.     Several  other  substances  are  used  for  this  purpose; 


ORTHOPTERA 


265 


among  these  are  borax,  pyrethrum,  sulphur,  and  phosphorus  paste. 

Cockroaches  are  chiefly  inhabitants  of  warm  countries;  although 
nearly  one  thousand  species  have  been  described,  few  are  found  in  the 


Fig.  301. — Fore  wing  of  a  nymph  of  a  cockroach. 

temperate  regions.  Only  forty-three  species  have  been  found  in 
North  America  north  of  the  Mexican  boimdary,  and  ten  of  these 
are  probably  introduced  species  (Hebard  '17).  The  cockroaches  that 
are  most  often  found  in  buildings  are  two  introduced  species,  the 
Croton-bug  and  the  Oriental  cockroach,  and  two  native  species,  the 
American  cockroach  and  the  common  wood-cockroach.    The  adults 


Fig.  302. — The  Croton-bug:  a,  first  instar;  b,  second  instar;  c,  third  instar,  d, 
fourth  instar;  e,  adult;  /,  adult  female  with  egg-case;  g,  egg-case,  enlarged; 
h,  adult  with  the  wings  spread.  All  natural  size  except  g.  (From  Howard 
and  Marlatt.) 

of  these  four  species  can  be  separated  by  the  following  table.       For 
tables  separating  all  North  American  species  see  Hebard  ('17). 

A.     With  well-developed  tegmina. 

B.     Tegmina  extending  to  or  beyond  the  tip  of  the  abdomen. 

C.     Body  about    12   mm.   in  length The  Croton-bug 

CC.     Body  16  mm.  or  more  in  length. 


266  AN  INTRODUCTION  TO  ENTOMOLOGY 

D.     Margin  of  the  pronotum  light  in  color  while  the  disk  is  dark.     .  . 

The  commo?i  wood-cockroach,  male 

DD.    Pronotum  reddish-brown   with   two   blotches  of   a   lighter   color. 

The  A  merican  cockroach 

BB.    Wings  not  extending  to  the  tip  of  the  abdomen. 

C.     With  a  light  band  on  each  lateral  border  of  the  pronotum 

The  common  ■wood-cockroach,  female 

CC.    With  no  bands  on  the  pronotum The  Oriental  cockroach,  male 

AA.     Tegmina  represented  by  small  ovate  pads The  Oriental  cockroach, 

female 

The  Croton-bug,  Blattella  germanica  (Fig.  302),  is  the  best-known 
of  all  of  the  cockroaches  in  our  northern  cities.    It  is  easily  recognized 

by  its  small  size,  about 
i?,  ^—-^      *\       ^ — -^       12  mm.  in  length,  and 

^  by  its  pale  color  with 

two  dark,  parallel 
bands  on  the  prono- 
tum. Its  popular 
name  originated  in 
New  York  City,  and 
was  suggested  by.  the 
fact  that  this  pest  is 
^       \/  very  abundant,    in 

houses,  about  water 
pipes  connected  with 
the  Croton  Aqueduct. 
This  is  a  species  intro- 
duced from  Europe; 
it  has  spread  to  nearly 
^         ^^         ^       /      oT     1  ^^^  parts  of  the  world, 

living  upon  ships,  and 

Fig.    303. — The   oriental   cockroach:  a,    female;  b,      spreading  from  them. 

male,  ^,  side  view  of  female;  rf,  half-grown  sped-  -pj^e  oriental  COck- 

men.    All  natural  size,     (rrom  Howard  and  Mar-  ,      -oj^^,         •      ,-t 

latt.)  roach,  BLatta  onentalis 

(Fig.  303),  is  also  a 
cosmopolitan  species ;  its  original  habitat  is  supposed  to  have  been 
in  Asia;  but  it  has  been  distributed  by  commerce  throughout  the 
world  except  in  the  colder  regions.  In  this  coimtry  it  is  most  abun- 
dant in  the  central  latitudes  of  the  United  States ;  it  has  been  found 
in  only  a  few  places  in  Canada.  It  measures  from  18  to  25  mm.  in 
length.  It  is  blackish  brown  in  color.  In  the  male  the  wings  cover 
about  two-thirds  of  the  abdomen;  while  in  the  female  they  are  small, 
ovate-lanceolate,  lateral  pads. 

The  American  cockroach,  Periplaneta  americdna  (Fig.  304),  is  a 
native  of  tropical  or  subtropical  America  that  has  become  distributed 
both  in  tropical  and  mild  climates  over  the  entire  world.  This  is  a 
large  species  measuring  from  25  to  33  mm.  in  length. 

The  common  wood-cockroach,  Parcobldtta  pennsylvdnica,  is  a 
common  species  throughout  the  eastern  half  of  the  United  States, 


ORTHOPTERA  267 

and    its    range    extends     into     southern     Canada.      It    is    a    na- 


Fig.  304. — The  American  cockroach.    (From  Howard  and  Marlatt.) 


tive  of  our  woods  but  is  frequently  attracted  to  lights  in  our  houses. 
The  two  sexes  differ 
so  greatly  in  appear- 
ance that  they  were 
long  believed  to  be 
distinct  species.  In 
both  sexes  the  lateral 
margins  of  the  prono- 
tum  are  light  in  color 
while  the  disk  is  dark. 
In  the  male  the  body 
measures  from  15  to 
25  mm.  in  length  and 
the  wings  extend  be- 
yond the  tip  of  the  ab- 
domen (Fig.  305).  The 

female  is  smaller  and  the  wings  are  much  shorter  than  in  the  male 

(Fig.  306) 


Fig.  305. — The  common 
wood-cockroach,  male. 
(From  Lugger.) 


Fig.  306. — The  com- 
m  o  n  wood-cock- 
roach  ,  female. 
(From  Blatchley.) 


ORTHOPTEROID  INSECTS  OF  UNCERTAIN  KINSHIP 


Under  this  head  are  placed  two  families  of  insects  the  zoological 
position  of  each  of  which  has  not  been  definitely  determined. 


268 


AN  INTRODUCTION  TO  ENTOMOLOGY 
Family  GRYLLOBLATTID^ 


This  family  was  recently  established  by  Dr.  E.  M.  Walker  ('14) 
for  the  reception  of  the  species  described  below,  which,  while  showing 
striking  afifinities  to  the  Orthoptera,  differs  remarkably  from  all 
other  known  members  of  this  order.  Some  writers  who  favor  the 
breaking  up  of  the  order  Orthoptera  into  several  orders,  regard  this 
species  as  the  type  of  a  distinct  order  of  insects,  the  Notoptera. 

Grylloblatta  campodeiformis. — In  this  the  only  species  of  the  family 
known,  the  body  is  elongate,  slender,  depressed,  and  thysanuriform 


Fig.  307. — Grylloblatta  campodeifonnis.     (xAfter  Walker.) 

(Fig.  307).  The  legs  are  fitted  for  running,  the  tarsi  are  five-jointed 
and  lack  pulvilli.  The  cerci  are  long,  about  as  long  as  the  hind  tibiae, 
slender,  and  eight-jointed.  The  ovipositor  is  exserted  and  resembles 
that  of  the  Tettigoniidse.  The  eyes  are  small  and  the  ocelli  are  absent. 
The  adult  male  measures  16.5  mm.  in  length;  the  female,  30mm. 
As  yet,  this  species  has  been  fomid  only  in  the  vicinity  of  Banff, 
Alberta,  and  in  Pliunas  County,  California.  It  is  found  under  stones, 
at  high  altitudes,  and  runs  like  a  centipede. 


ORTHOPTERA 


269 


Family  HEMIMERID^ 

This  family  includes  a  single  genus,  Hemtmerus,  of  which  two  spe- 
cies have  been  found  in  equatorial  West  Africa. 
These  are  blind,  wingless  insects,  of  the  form 
shown  in  Figure  30S.  They  are  remarkable 
in  that  they  exhibit  an  intra-uterine  de- 
velopment. Hansen  ('94),  whose  account  is 
all  the  information  we  have  on  this  subject, 
thinks  that  the  young  are  connected  with  the 
walls  of  the  maternal  passages  by  means  of  a 
process  from  the  neck  of  each ;  about  six  yoimg 
were  found  at  a  time  inside  the  mother,  the 
largest  one  being  next  to  the  external  opening. 
The  species  described  by  Hansen  was  found 
living  on  the  body  of  a  large  rat;  it  runs 
rapidly  among  the  hairs  and  apparently  also 
springs. 

In  an  early  accoimt  of  one  of  the  species  of 
Hemtmerus  this  insect  was  described  erro- 
neously as  possessing  two  lower  lips,  and  for 
that  reason  was  placed  in  a  distinct  order,  the 
Diploglossata,  which  is  no  longer  recognized. 

Although  these  are  exotic  insects,   they  are    y        ^ „     • 

mentioned  here  on  account  of  their  exceptional       jia^i  se  n  i  '^""(From 
manner  of  development  and  mode  of  life.  Hansen.) 


CHAPTER  IX 
ORDER  ZORAPTERA* 

So  little  is  known  regarding  the  insects  of  this  order,  only  a  single 
genus  having  been  found,  that  it  would  be  premature  at  this  time 
to  define  definitely  the  characters  of  the  order.  This  is  well  shown 
by  the  fact  that  recent  discoveries  have  greatly  modified  our  views 
regarding  the  ordinal  characters  of  these  insects. 

This  order  was  established  by  Silvestri  in  1 9 1 3 .  At  that  time  only 
wingless  individuals  were  known;  and  it  was  supposed  by  this  author 
that  the  wingless  condition  was  a  distinctive  ordinal  character;  he, 
therefore,  proposed  the  name  Zoraptera  for  the  order.  But  recently 
Caudell  ('20)  has  described  winged  individuals  of  each  of  the  two 
species  found  in  this  coimtry.  The  name  Zoraptera,  however,  must 
be  retained  even  though  it  is  inappropriate. 

Family  ZOROTYPID^ 

The  single  known  genus,  Zorotypus,  is  the  type  of  this  family  and 
until  other  genera  are  found  the  characters  of  this  genus  must  be 
taken  as  those  of  this  family  and  of  the  order  Zoraptera  as  well. 

At  the  time  this  is  written,  only  six  species  of  Zorotypus  have  been 
described.  These  have  been  found  in  widely  separated  parts  of  the 
world,  one  each  in  Africa,  Ceylon,  Java,  and  Costa  Rica,  and  two  in 
Florida.    One  of  the  species  from  Florida  has  been  found  also  in  Texas. 

The  known  species  are  all  minute,  the  largest  measuring  only  2.5 
mm.  in  length.  In  our  two  species  both  wingless  and  winged  adults 
have  been  found ;  and  it  is  probable  that  these  two  forms  exist  in  the 
other  species.  The  winged  adults  that  have  been  observed  are  all 
females;  but  it  would  not  be  wise  to  conclude  that  only  this  sex  is 
winged.  Of  the  wingless  form  both  male  and  female  have  been  found. 
As  these  are  social  insects,  living  in  colonies  of  various  sizes,  it  may 
be  that  the  wingless  and  the  winged  adults  represent  distinct  castes, 
analogous  to  the  castes  of  termites.  Another  similarity  to  termites 
is  that  the  winged  individuals  shed  their  wings  as  do  the  winged 
termites. 

The  wingless  adults  (Figure  309,  4)  resemble  in  general  appear- 
ance small  worker  termites ;  but  they  have  longer  legs  and  are  more 
active.  The  legs  are  formed  for  running;  the  tarsi  are  two-jointed 
and  each  bears  two  claws.  The  mandibles  are  strong.  The  antennae 
are  moniliform  and  nine-jointed.  Compound  eyes  and  ocelli  are 
wanting.    The  cerci  are  short,  fleshy,  and  unsegmented. 

The  winged  adult  female  (Fig.  309,  1)  has  large  compound  eyes, 
three  ocelli,  nine-jointed  antennEe,  and  two  pairs  of  wings.    The  vena- 

*Zoraptera:  zoros  (x£op6i),  pure;  apterous  (fiTrrepos) ,  without  wings. 

(270) 


ZORAPTERA 


271 


tion  of  the  wings  is  represented  in  the  figure.  As  the  tracheation  of 
the  wings  of  nymphs  has  not  been  studied,  I  will  not  venture  to  make 
any  suggestions  regarding  the  homologies  of  the  wing-veins. 


Fig-  309- — Zorotypus  hiihbardi:  i,  winged  adult  female;  2,  adult  female  that  had 
shed  her  wings;  3,  nymph  of  winged  form;  4,  wingless  adult  female.  5,  An- 
tenna of  adult  wingless  Zorotypus  snyderi.  (From  Caudell,  in  Proc.  Ent.  Soc. 
Wash.,  Vol.  22.) 


272 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Figure  309,  2, represents  an  adult  female  that  had  shed  her  wings 
and  Figure  309,  3,  a  nymph  with  well-developed  wing-pads. 

The  two  known  American  species  are  Zorotypus  huhhardi  and 
Zoroiypus  snyderi.  Detailed  descriptions  of  each  of  the  forms  of 
each  of  these  species  are  given  by  Caudell  ('20),  and  the  external 
anatomy  of  Zorotypus  huhbardi  is  described  by  Crampton  ('20  a), 
who  also  discusses  the  relationships  of  the  order  Zoraptera  to  the 
other  orders  of  insects. 

The  colonies  of  Zorotypus  are  found  under  the  bark  of  logs  and 
stumps  and  frequently  near  the  galleries  of  termites.  For  this 
reason  they  were  formerly  believed  to  live  as  inquilines  in  the  nests  of 
termites;  but  recent  observations  do  not  support  this  view. 


CHAPTER  X 
ORDER  ISOPTERA* 

The  Termites  or  White- Ants 

The  members  of  this  order  are  social  insects,  living  in  colonies  like 
ants.  Each  species  consists  of  several  distinct  castes,  the  number  of 
which  differs  in  different  species.  Each  caste  includes  both  male  and 
female  individuals.  In  most  species  there  are  four  castes  as  follows: 
first,  the  first  reproductive  caste,  in  which  the  wings  become  fully  de- 
veloped and  are  used  for  a  swarming  flight  and  then  shed;  second,  the 
second  reproductive  caste,  in  which  the  wing-buds  remain  short;  the 
members  of  this  caste  are  neoteinic,  becoming  sexually  mature  while 
retaining  the  nymphal  form  of  the  body;  third,  the  worker  caste;  and 
fourth,  the  soldier  caste.  Except  in  a  single  Australian  gemis,  the  two 
pairs  of  wings  are  similar  in  form  and  in  the  more  general  features  of 
their  venation;  they  are  long  and  narrow,  and  are  laid  fiat  on  the  back 
when  not  in  use.  The  abdomen  is  broadly  joined  to  the  thorax;  the 
mouth-parts  are  formed  for  chewing;  the  metamorphosis  is  gradual. 

The  termites  or  white-ants  are  chiefly  tropical  insects;  but  some 
species  live  in  the  temperate  zones.  These  insects  can  be  easily 
recognized  by  the  fact  that  they  live  in  ant-like  colonies,  by  the  pale 
color  of  the  greater  nimiber  of  individuals  of  which  a  colony  is  com- 
posed, and  by  the  form  of  the  abdomen,  which  is  broadly  joined  to 
the  thorax  instead  of  being  pedunculate  as  in  ants. 

The  termites  are  commonly  called  white-ants  on  account  of  their 
color  and  of  a  resemblance  in  form  and  habits  to  the  true  ants. 
These  resemblances,  however,  are  only  very  general.  In  structure 
the  termites  and  ants  are  widely  separated.  In  habits  there  is  little 
more  in  common  than  that  both  are  social,  and  the  fact  that  in  each 
the  function  of  reproduction  is  restricted  to  a  few  individuals,  while 
the  greater  nimiber  differ  in  form  from  the  sexually  perfect  males  and 
females,  and  are  especially  adapted  to  the  performance  of  the  labors 
and  defense  of  the  colony. 

The  cuticula  of  termites  is  delicate  even  in  adults;  the  mature 
winged  forms  can  withstand  exposure  to  dry  air  for  a  limited  period, 
as  is  necessary  during  their  swarming  flight;  but  other  members  of 
a  colony  quickly  become  shriveled  and  die  if  exposed.  It  is  for  this 
reason  that  they  build  tubes  constructed  of  earth  and  excrement  for 
passage-ways,  and  only  rarely  appear  in  the  open,  and  then  m.erely 
for  a  brief  period. 

The  mouth-parts,  which  are  fitted  for  chewing,  are  quite  general- 
ized, resembling  somewhat  those  of  the  Orthoptera;  but  in  the  case 
of  the  soldier  caste  the  mandibles  are  very  large  and  vary  greatly  in 
form  in  the  different  species. 

*Is6ptera:  isos  (f<ros),  equal;  pteron  (Trrepbv),  a  wing. 
(273) 


274 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  antennae  are  moniliform;  in  the  winged  adults  the  number 
of  segments  varies  in  different  species  from  twelve  to  twenty-five  or 
more.  In  newly  hatched  nymphs  the  number  of  antennal  segments 
is  less  than  in  the  later  instars. 

The  members  of  the  winged  sexual  caste  have  pigmented  compound 
eyes  and  a  pair  of  ocelli.  It  is  commonly  stated  that  both  the  workers 
and  soldiers  of  termites  are  blind;  but  in  some  species  the  soldiers 
have  compovmd  eyes;  these,  however,  are  not  pigmented.  There  is 
an  African  species,  the  marching  termite,  in  which  both  workers  and 
soldiers  possess  eyes  (Fuller  '12). 

The  median  ocellus  is  wanting  in  termites;  but  in  many  forms 
there  is  in  its  place  a  more  or  less  distinct  opening  of  a  gland,  the 
frontal  gland,  whose  secretion  is  used  for  defense;  this  opening  of 
the  frontal  gland  is  termed  the  fontanel  or  fontanelle  or  fenestra. 


Fig.  310. — Wings  of  Termopsis  angiisticollis. 

The  wings  are  long  and  narrow,  and,  when  folded  on  the  back  of 
the  insect,  extend  far  beyond  the  end  of  the  abdomen.  In  the  Aus- 
tralian genus  Mastotermes,  the  anal  area  of  the  hind  wings  is  broadly 
expanded;  in  other  termites  the  fore  and  hind  wings  are  similar  in 
form  (Fig.  310).  In  each  case,  the  veins  of  the  anterior  part  of  the 
wing  are  greatly  thickened  and  those  of  the  middle  portion  reduced 
to  indistinct  bands  or  to  narrow  lines.  Regular  cross-veins  are  lack- 
ing, the  membrane  of  the  wings  being  strengthened  by  an  irregular 
network  of  slightly  chitinized  wrinkles.  The  wings  are  deciduous, 
being  shed  after  the  swarming  flight.  The  shedding  of  the  wings  is 
facilitated  by  the  presence  in  each  wing,  except  in  the  hind  wings  of 
certain  genera,  of  a  curved  transverse  suture,  the  humeral  suture. 


ISOPTERA  275 

The  homologies  of  the  wing-veins  are  discussed  by  the  writer  in  his 
"The  Wings  of  Insects,"  Chapter  VIII. 

The  abdomen  consists  of  ten  visible  segments  and  bears  a  pair  of 
two-  to  six-jointed  cerci.  The  genitalia  are  vestigial  and  are 
concealed  by  a  backw-ard  prolongation  of  the  stenium  of  the  seventh 
abdominal  segment. 

If  a  colony  of  termites  be  examined,  many  kinds  of  individuals  will 
be  foimd.  This  multiplicity  of  forms  is  due  partly  to  the  fact  that 
these  insects  imdergo  a  gradual  metamorphosis,  and  nymphs  of  various 
sizes  and  degrees  of  development  will  be  found  running  about  among 
the  mature  individuals.  But  even  if  only  adults  be  considered,  it 
will  be  foimd  that  each  species  consists  of  several  distinct  castes. 

With  the  termites  the  number  of  castes  is  greater  than  with  the 
social  bees,  social  wasps,  and  ants;  and  each  caste  includes  both  male 
and  female  individuals.  The  termites  differ  also  from  other  social 
insects  in  that  there  are  at  least  two  and  sometimes  three  castes 
whose  fimction  is  reproduction.  The  following  castes  have  been 
found  among  these  insects. 

The  first  reproductive  caste. — At  a  certain  season  of  the  year,  late 
spring  or  early  summer  for  our  most  common  species  in  the  eastern 
United  States,  there  can  be  found  in  the  nests  individuals  with  fully 
developed  wings.  These  are  sexually  perfect  males  and  females  and 
constitute  what  is  known  as  the  first  reproductive  caste.  In  these  the 
cuticula  is  black  or  dark  chestnut  in  color,  the  eyes  are  functional, 
and  the  wings  project  more  than  half  their  length  beyond  the  end 
of  the  body.  A  little  later,  these  winged  individuals  leave  the  nest 
in  a  body;  sometimes  clouds  of  them  appear.  After  flying  a  greater 
or  less  distance  they  alight  on  the  ground,  and  then  shed  their  wings. 

At  this  time  the  males  seek  the  females  and  they  become  associated 
in  pairs ;  but  the  fertilization  of  the  females  does  not  take  place  till 
later.  It  seems  probable  that  in  some  cases  swarms  issue  from 
different  nests  at  the  same  time,  as  we  know  to  be  the  case  with  the 
true  ants,  and  that  in  this  way  males  and  females  from  different  nests 
may  pair,  and  thus  the  danger  of  inbreeding  be  lessened;  but 
Holmgren  and  others  doubt  that  this  occurs.  The  greater  number 
of  individuals  comprising  one  of  these  swarms  soon  perish;  they  fall 
victims  to  birds  and  other  insectivorous  animals. 

Each  of  the  more  fortimate  couples  that  have  escaped  their 
enemies,  find  a  suitable  place  for  the  beginning  of  a  nest  and  become 
the  founders  of  a  new  colony.  Such  a  pair  are  commonly  known  as 
the  king  and  the  queen  of  the  colony;  they  are  also  known  as  the 
primary  royal  pair  to  distinguish  them  from  the  second  reproductive 
caste.  The  primary  royal  pair  can  be  recognized  by  the  presence  on 
the  thorax  of  the  stimips  of  the  wings  that  they  have  shed. 

After  the  nest  has  been  begim,  the  abdomen  of  the  female  becomes 
greatly  enlarged,  as  a  result  of  the  growth  of  the  reproductive 
organs  and  their  products;  this  is  greater  in  certain  exotic  species 
than  it  is  in  those  foimd  in  this  coimtry.     Figure  311  represents 


276 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  311-— 
Queen  ter- 
mite, Ter- 
mes  gihms. 


in  natural  size  the  queen  of  a  species  found  in  India.  The  dark  spots 
along  the  middle  of  the  dorsal  wall  of  the  abdomen 
are  the  chitinized  parts  of  that  region;  the  lighter 
portions  are  made  up  of  the  very  much  stretched 
membrane  uniting  the  segments.  This  queen  is  a 
comparatively  small  one ;  in  some  species  the  queens 
become  from  150  to  200  mm.  in  length;  of  course 
such  a  queen  is  incapable  of  locomotion,  but  lives 
with  its  mate  inclosed  in  a  royal  chamber;  their  food 
is  brought  to  them  and  the  eggs  are  carried  away  by 
workers.  In  our  native  species  the  queens  do  not 
become  so  greatly  enlarged  and  do  not  lose  the  power 
of  movement. 

A  remarkable  peculiarity  in  the  habits  of  termites 
is  that  the  association  of  the  male  and  the  female  is 
a  permanent  one ;  the  king  and  the  queen  live  together 
in  the  nest,  and  there  is  repeated  coition. 

TJie  second  reproductive  caste. — There  are  fre- 
quently foimd  in  the  nests  of  termites  neoteinic 
sexual  forms ;  that  is,  individuals  which  are  sexually 
mature  but  which  retain  the  nymphal  form  of  the 
body,  having  short  wing-buds  which  do  not  develop 
further.  These  individuals  constitute  the  second 
reproductive  caste,  which  is  represented  by  both  males 
and  females.  The  members  of  this  caste  are  pale  in 
color;  their  compound  eyes  are  only  slightly  pig- 
mented; and  they  never  leave  the  nest  unless  by  subterranean  tun- 
nels. If  a  primary  king  or  queen  dies,  its  place  is  taken  by  individuals 
of  the  second  reproductive  caste.  For  this  reason,  the  members  of 
this  caste  are  commonly  known  as  substitute  kings  and  queens  or  as 
complemental  kings  and  queens.  The  substitute 
queens  produce  comparatively  few  eggs,  and  conse- 
quently it  requires  several  of  them  to  replace  a  pri- 
mary queen.  Many  pairs  of  substitute  kings  and 
queens  are  commonly  foimd  in  orphaned  nests. 
The  third  reproductive  caste. — In  some  cases  there 
have  been  found  adult  neoteinic  sexual  forms  which 
resemble  workers  in  lacking  wing-buds.  These  are 
known  as  ergatoid  kings  and  queens. 

The  workers. — If  a  termite  nest  be  opened  at  any 
season  of  the  year  there  will  be  fotmd  a  large  number 
of  wingless  individuals  of  a  dirty  white  color,  usually 
blind,  and  of  the  form  represented  by  Figure  312. 
These  are  named  the  workers,  for  upon  them  devolve 
nearly  all  of  the  labors  of  the  colony.  A  study  of  the  internal  anatomy 
of  workers  has  shouTi  that  both  sexes  are  represented  in  this  caste; 
the  reproductive  organs  are,  however,  only  little  developed  as  a  rule; 
but  occasionally  workers  capable  of  laying  eggs  are  foimd.  The 
worker  caste  is  not  always  present;  it  is  absent  in  the  genera  Kalo- 


'\g.  312, 
worker. 


ISOPTERA 


277 


Fig.  313- 
dier. 


-A  sol- 


termes  and  Cryptotermes,  where  the  nymphs  of  the  reproductive  forms 
apparently  attend  to  the  duties  of  workers;  and  in  the  genera 
Tennopsis  and  Neotermes  ordinary  sterile  workers  are  not  found,  but 
the  third  reproductive  caste,  large,  worker-like,  grayish  brown,  fertile 
forms,  with  no  wing-buds,  is  present.  The  n^onphs  of  this  caste  often 
perform  the  duties  of  the  workers  (Banks  and  vSnyder  '20).  In  some 
tropical  species  there  are  two  types  of  workers,  which 
differ  in  size. 

The  soldiers. — ^Associated  with  the  workers,  and 
resembling  them  in  color  and  in  being  wingless,  there 
occur  numerous  representatives  of  another  caste, 
which  can  be  recognized  by  the  enormous  size  of  their 
heads  and  mandibles  (Fig.  313);  these  are  the  sol- 
diers. They  are  so  named  because  it  is  believed  that 
their  chief  function  is  the  protection  of  the  colony; 
but  they  do  not  seem  to  be  very  effective  in  this. 
Among  the  soldiers,  as  among  the  workers,  both  sexes 
are  represented ;  but  as  a  rule  the  reproductive  organs 
are  not  functional.  Sometimes,  however,  soldiers 
capable  of  laying  eggs  are  found.  In  the  genus 
Kalotermes  soldiers  with  small  wing-buds  are  often 
found.  The  soldier  caste  has  not  been  found  in  the  germs  Anoploterines , 
and  in  the  genera  Constrictotermes  and  Nasutitermes  the  soldier  caste 
is  wanting  unless  the  nasuti,  described  in  the  next  paragraph,  are 
regarded  as  soldiers.  In  certain  tropical  species  there 
are  two  types  of  soldiers  which  differ  in  size. 

The  nasuti. — In  certain  species  of  termites  there 

are  found  individuals  in  which  the  head  is  elongated 

into  a  nose-like  process,  from  the  tip  of  which  a  fluid 

^>™™^         exudes,  which  is  used  as  a  means  of  defense  and  also, 

I^^g  it  is  said,  as  a  cement  in  constructing  the  nest  and 

/^^         the  earth-like  tubes  through  which  the  insects  travel 
(Fig.  314).     Such  individuals  are  known  as  nasuti. 
In  this  caste  the  mandibles  are  small,  differing  greatly 
from  those  of  soldiers.    The  nasuti  are  usually  smaller 
than  the  workers  and  are  pigmented.     They  have 
been  commonly  described  as  a  special  type  of  soldiers ; 
Fig.  314-— A  nas-  but  it  seems  better,  in  order  to  avoid  confusion,  to 
utus.    (After  regard  them  as  constituting  a  distinct  caste.    Among 
^^P'^  the  North  American  termites,  nasuti  are  found  in 

the  genera  Constrictotermes  and  Nasutitermes,  which 
lack  the  true  soldier  caste.  In  some  tropical  termites  two  types  of 
nasuti,  large  and  small,  have  been  foimd. 

As  to  the  origin  of  the  different  castes  of  termites  there  has  been 
much  discussion  and  two  radically  different  views  are  held.  The 
first  view  was  probably  suggested  by  the  well-known  fact  that,  in  the 
case  of  the  honey-bee,  queens  can  be  developed  from  eggs  or  young 
larvcB  that  ordinarily  would  produce  workers.  According  to  this  view 
the  newly  hatched  termites  are  not  differentiated  into  castes;  but 


278  AN  INTRODUCTION  TO  ENTOMOLOGY 

this  differentiation  takes  place  later  as  the  result  of  extrinsic  factors, 
such  as  food,  the  presence  or  absence  of  parasitic  protozoa  in  the 
alimentary  tract,  and  the  care  received  frorn  the  older  workers. 
According  to  the  second  view  the  young  of  the  different  castes  are 
different  and  the  castes  are  therefore  "predetermined  in  the  egg  or 
embryo  by  intrinsic  factors." 

Some  comparatively  recent  investigations  support  the  second  view. 
It  was  found  by  Thompson  ('17  and  '19)  that  although  the  newly 
hatched  n\Tiiphs  are  externally  all  alike,  they  are  differentiated  by 
internal  structural  characters  into  two  clearly  defined  types:  first, 
the  reproductive  or  fertile  forms,  with  large  brain  and  large  sex  organs, 
and  usually  a  dense  opaque  body;  and  second,  the  worker-soldier  or 
sterile  forms,  with  small  brain  and  small  sex  organs,  and  usually  a 
clear  transparent  body. 

It  was  also  found  by  Thompson  that  later,  when  the  nymphs  had 
become  from  2  mm.  to  3  mm.  in  length,  they  were  differentiated  into 
"small-headed"  but  large-brained  reproductive  forms,  and  "large- 
headed"  but  small-brained  worker-soldier  forms.  In  the  case  of 
worker-soldier  n\Tiiphs  of  Eutermes  pHifrcus,  a  Jamaican  species,  which 
were  2  mm.  long  and  externally  all  alike,  they  were  distinguishable, 
after  staining,  into  worker  nymphs  with  a  small  vestigial  frontal 
gland,  and  soldier  n\Tnphs  with  a  large  frontal  gland. 

In  a  study  of  Reticulitermes  (Leucotermes)flavipes ,  Thompson  ('17) 
found  that  the  n\Tnphs  of  the  reproductive  forms  that  are  only  1.3 
to  1.4  mm.  in  length  are  differentiated  into  two  groups  by  differences 
in  the  size  of  the  brain  and  sex  organs.  These  are  early  instars  of 
the  first  reproductive  caste  and  the  second  reproductive  caste,  respec- 
tively. The  early  instars  of  the  third  reproductive  caste  have  not 
been  distinguished  from  the  nymphs  of  workers. 

There  is  space  here  for  but  little  regarding  the  nest-building  habits 
of  these  wonderful  insects.  In  the  tropics  certain  species  build  nests 
of  great  size.  Some  of  these  are  moimds  ten  or  twelve  feet  or  more 
in  height.  Other  species  build  large  globular  masses  upon  the  trunks 
or  branches  of  trees  or  upon  other  objects.  Figure  315  represents 
such  a  nest  which  I  observed  on  a  fence  in  Cuba.  Owing  to  the 
delicacy  of  their  cuticula  and  the  consequent  danger  of  becoming 
shriveled  if  exposed,  the  termites  build  covered  ways  from  their 
nests  to  such  places  as  they  wish  to  visit,  if  they  are  in  exposed 
situations  like  that  shown  in  the  figure.  These  exposed  nests  are 
composed  chiefly  of  the  excreted  undigested  wood  upon  which  the 
insects  have  fed.  This  is  molded  into  the  desired  form  and  on  drying 
it  becomes  soHd. 

The  termites  that  live  in  the  United  States  do  not  build  exposed 
nests;  and,  as  the  queens  do  not  lose  the  power  of  movement,  there 
is  no  permanent  royal  cell,  centrally  located,  in  which  the  king  and 
queen  are  imprisoned,  as  is  the  case  with  many  tropical  species. 
Some  of  our  species  mine  in  the  earth,  their  nests  being  made  imder 
stones  or  other  objects  lying  on  the  ground;  some  burrow  only  in 


I  SOFTER A 


279 


wood;  and  others  that  burrow  in  the  ground  extend  their  nests  into 
wood.  To  the  last  category 
belong  the  species  of  the  genus 
Reticulitermes ,  which  includes 
all  of  the  teiTtiites  found  north 
of  Georgia  and  east  of  Nevada. 
These  often  infest  the  foimda- 
tion  timbers  of  buildings,  floor- 
ing in  basements,  and  other 
woodwork  of  buildings  and 
furniture.  These  pests  will 
feed  upon  almost  any  organic 
matter;  books  are  sometimes 
completely  ruined  by  them. 
In  infesting  anything  com- 
posed of  wood,  the}^  eat  out 
the  interior,  leaving  a  thin  film 
on  the  outside.  Thus  a  table 
may  appear  to  be  sound,  but 
crumble  to  pieces  beneath  a 
slight  weight,  entrance  having 
been  made  through  the  floor  of 
the  house  and  the  legs  of  the 
table. 

While  termites  infest 
chiefly  dead  wood,  there  are 
many  records  of  their  infesting 
living  plants.  I  found  them 
common  throughout  Florida, 
infesting  orange-trees,  guava- 
bushes,  pampas-grass,  and  su- 
gar-cane. When  termites  in- 
fest living  plants,  they  attack  that  part  which  is  at  or  just  below  the 
surface  of  the  ground.  In  the  case  of  pampas-grass  the  base  of  the 
stalk  is  hollowed;  with  woody  plants,  as  orange-trees  and  guava 
bushes,  the  bark  at  the  base  of  the  tree  is  eaten  and  frequently  the 
tree  is  completely  girdled;  with  sugar-cane  the  most  serious  injury 
is  the  destniction  of  the  seed-cane. 

Certain  African  termites  have  been  found  to  cultivate  fungus- 
gardens  in  their  nests,  similar  to  those  of  the  well-known  leaf-cutting 
ants. 

The  care  of  the  young  and  of  the  queens  by  the  workers  in  colonies 
of  social  insects  has  attracted  the  attention  and  admiration  of  observ- 
ers in  all  times.  This  care  has  been  quite  generally  attributed  to 
something  resembling  the  parental  feelings  of  our  own  species.  But 
the  observations  of  several  naturalists  in  recent  years  have  shown 
that  with  the  social  insects  the  devotion  of  the  workers  to  the  brood 
and  to  the  queen  is  far  from  being  purely  altruistic;  that  it  is  largely 
or  entirely  due  to  a  desire  to  feed  upon  certain  exudates  produced  by 


Fig.  315. — Nest  of  a  Cuban  termite. 


280  ^A^  INTRODUCTION  TO  ENTOMOLOGY 

the  individuals  that  are  fed;  the  feeding  of  the  youiig  and  the  queens 
being  accompanied  by  a  licking  of  their  bodies  by  the  nurses. 

Among  the  more  important  papers  on  this  subject  are  one  on 
termites  by  Holmgren  ('09)  and  one  on  ants  by  Wheeler  ('18). 
Holmgren  shows  that  all  of  the  castes  of  termites,  but  especially  the 
queens,  have  extensive  exudate  tissues,  consisting  of  the  peripheral 
layers  of  the  abdominal  fat-body,  the  products  of  which  pass  through 
pores  in  the  cuticula,  where  they  are  licked  up  by  other  members  of 
the  colony;  and  that  the  intensity  of  the  licking  and  feeding  of  the 
individuals  of  a  termite  colony  is  directly  proportional  to  the  amount 
of  their  exudate  tissue.  Wheeler  in  his  paper  on  ants  shows  that  the 
larvae  of  certain  species  of  ants  possess  remarkable  exudate  organs, 
and  proposes  for  this  exchange  of  nourishment  the  term  trophallaxis* 

It  is  believed  by  the  writers  quoted  above  and  by  others  that  this 
exchange  of  nourishment  between  those  individuals  that  feed  and 
those  that  are  fed  was  the  source  of  the  colonial  habit  in  social  insects. 
Roubaud  ('16)  in  a  paper  on  the  wasps  of  Africa  points  out  the 
probable  steps  by  which  the  social  habit  was  developed  in  wasps. 
Beginning  with  certain  solitary  etunenids  that  feed  their  larvae  from 
day  to  day  and  while  doing  this  feed  upon  saliva  exuded  by  the  lar^^se, 
he  suggests  that  there  naturally  follows  a  tendency  to  increase  the 
number  of  larvae  to  be  reared  simultaneously  in  order  at  the  same 
time  to  satisfy  the  urgency  of  oviposition  and  to  profit  by  the  greater 
abundance  of  the  secretion  of  the  larvae. 

Now  that  this  explanation  of  the  origin  of  the  social  habit  has 
been  suggested,  it,  doubtless,  will  be  much  discussed.  The  student  is 
urged,  therefore,  to  consult  the  current  literature  for  opinions  regard- 
ing it. 

The  most  extended  account  of  the  termites  of  this  country  is  the 
recently  published  paper  by  Nathan  Banks  and  Thomas  E.  Snyder 
('20).  In  the  first  part  of  this  paper,  Mr.  Banks  gives  a  revision  of 
the  nearctic  termites,  in  which  all  of  our  known  species  are  described, 
seventeen  of  them  for  the  first  time.  This  brings  the  total  number 
of  our  known  species  up  to  thirty-six,  representing  ten  genera. 

In  the  second  part  of  this  paper,  Mr.  Snyder  brings  together  the 
known  data  regarding  the  habits  and  distribution  of  the  termites  of 
the  United  States;  much  of  which  data  is  based  on  his  personal 
observations. 

Many  species  of  insects  live  in  the  nests  of  termites.  The  relations 
of  the  termitophiles,  of  which  several  hundred  species  have  been 
described,  to  their  hosts  vary  greatly;  some  are  predatory,  some  are 
parasites,  and  others  are  guests.  Among  the  guests  some  are  indiffer- 
ently tolerated,  while  others  are  true  guests  which  produce  exudates 
that  are  eagerly  devoured  by  their  hosts  and  in  return  either  receive 
regurgitated  food  or  manage  to  prey  on  the  defenseless  brood. 
Among  the  termitophiles  are  some  that  are  very  remarkable  in  form, 
having  the  abdomen  excessively  enlarged  and  being  furnished  with 
large  exudate  organs. 

*Trophallaxis :  trophe  (rpo^Tjj,  nourishment;  allattem  {aWdrreiv),  to  exchange. 


CHAPTER  XI 

Order  NEUROPTERA* 

The  Horned  Corydalus,  the  Lacewing-FUes,  the  Ant-Lions, 
and  others 

The  members  of  this  order  have  four  wings;  these  are  membranous 
and  are  usually  furnished  with  many  veins  and  cross-veins.  In  most 
members  of  the  order,  the  wings  have  been  specialized  by  the  addition  in 
the  preanal  area  of  many  supernumerary  veins  of  the  accessory  type. 
The  mouth-parts  are  formed  for  chewing.  The  tarsi  are  five-jointed. 
The  cerci  are  absent.    The  metamorphosis  is  complete. 

The  order  Neuroptera  as  now  restricted  differs  greatly  in  extent 
from  the  Neuroptera  of  the  early  entomologists.  Formerly  there  were 
included  in  this  order  many  insects  that  are  no  longer  believed  to  be 
closely  related.  This  has  resulted  in  the  establishment  of  several  dis- 
tinct orders  for  the  insects  that  have  been  removed  from  the  old 
order  Neiiroptera.  This  fact  should  be  kept  in  mind  when  consulting 
the  older  text-books. 

The  wings  of  the  Neuroptera  are  membranous  and  usually  fur- 
nished with  many  wing-veins.  The  two  pairs  of  wings  are  similar 
in  texture  and  usually  in  outline ;  in  some  the  fore  wings  are  slightly 
larger  than  the  hind  wings,  in  others  the  two  pairs  of  wings  are  of  the 
same  size.  The  anal  area  is  small  in  both  fore  and  hind  wings ;  it  is 
rarely  folded  (Sialidcc),  and  then  only  slightly  so.  A  distinct  anal 
furrow  is  rarely  developed.  Definitive  accessory  veins  are  usually 
present,  and,  as  a  rule,  there  are  many  marginal  accessory  veins. 
Intercalary  veins  are  never  developed.  When  at  rest,  with  few  ex- 
ceptions, the  wings  are  folded  roof-like  over  the  abdomen.  In  some 
cases  organs  for  uniting  the  fore  and  hind  wings  are  present. 

Correlated  with  the  extensive  development  of  accessory  veins  in 
the  Neuroptera,  there  has  resulted  in  nearly  all  of  the  families  of  this 
order  the  production  of  a  pectinately  branched  radial  sector;  that  is, 
this  vein  is  so  modified  that  it  consists  of  a  supporting  stem  upon 
which  are  borne  a  greater  or  less  number  of  parallel  branches.  This 
is  shown  in  most  of  the  figures  of  wings  illustrating  this  chapter, 
and  is  a  distinctive  characteristic  of  this  order;  in  no  one  of  the 
other  orders  of  living  insects  in  which  accessory  veins  occur  is  a  well- 
developed  pectinately  branched  radial  sector  found.  Such  a  radial 
sector  existed,  however,  in  many  of  the  Paleozoic  insects.  In  certain 
genera  of  the  Neuroptera  a  dichotomously  branched  radial  sector  has 
been  retained. 

In  many  Neuroptera  one  or  more  series  of  cross-veins  extend 
across  the  wing  and  form  with  sections  of  the  longitudinal  veins  that 
*Neur6ptera:  neuron  (vevpov),  a  nerve;  pteron  (irrepSv),  a  wing. 
(281) 


282 


AN  INTRODUCTION  TO  ENTOMOLOGY 


they  connect  a  very  regular  zigzag  line ;  such  cross-veins  are  termed 
gradate  veins.    Examples  of  series  of  gradate  veins  are  well  shown  in 
the  wings  of  the  Hemerobiidae  and  in  those  of  the  allied  families. 
The  mouth-parts  are  formed  for  chewing.    In  several  families  the 
larvae   suck   the  blood   of  their  pre}^  by 
means  of  their  peculiarly  modified  man- 
dibles and  maxillae.    These  are  very  long 
and  those  of  each  side  form  an  organ  for 
piercing  and  sucking.     The  mouth-parts 
of  the  larva  of  an  ant-lion  will  serve  to 
illustrate  this  type  of  mouth-parts  (Fig. 
316). 

In  this  insect  the  mandibles  (md)  are 
very  long,  curved  at  the  distal  end,  fitted 
for  grasping  and  piercing  the  body  of  the 
prey,  and  armed  with  strong  spines 
and  setse.  On  the  ventral  aspect  of  each 
mandible  there  is  a  furrow  extending  the 
entire  length  of  the  mandible;  and  over 
this  furrow  the  long  and  slender  maxilla 
(mx)  fits.  On  the  dorsal  aspect  of  the 
maxilla  there  is  also  a  furrow.  These  two 
furrows  form  a  tube  which  extends  from 
the  tip  of  the  combined  mandible  and 
maxilla  to  the  base  of  this  organ  where  it 
communicates  with  the  mouth  cavity. 
Through  this  tube  the  blood  of  the  prey 
is  conveyed  to  the  mouth.  On  the  middle 
line  of  the  body,  between  the  mentum  (m) 
and  the  front  margin  of  the  dorsal  wall  of 
the  head  (/),  there  is  a  tightly  closed  slit 
which  is  the  mouth ;  this,  however,  is  not 
functional,  the  food  being  received  into 
lateral  expansions  of  the  mouth-cavity  at 
the  base  of  the  mandibles  and  maxillee. 
For  a  more  detailed  account  of  the  struc- 
ture of  the  mouth-parts  of  an  ant-lion,  see  Lozinski  (08). 

The  metamorphosis  is  complete.  The  larvae  that  are  known  are 
predacious  or  parasitic  and  in  most  cases  are  campodeif orm ;  a  few 
of  them  are  aquatic,  Sialidae,  Sisyrids,  and  certain  exotic  forms,  but 
most  of  them  are  terrestrial ;  some  when  full-grown  enter  the  ground 
and  make  earthen  cells  in  which  they  transform,  but  most  of  them 
spin  cocoons.  The  silk  of  which  these  cocoons  are  made,  in  the  case 
of  those  in  which  the  silk-organs  have  been  described,  is  secreted  by 
modified  Malpighian  vessels  and  is  spun  from  the  anus. 

The  silk-organs  of  Sisyra  will  serve  as  an  example  of  neurojoterous 
silk-organs ;  these  were  described  by  Miss  Anthony  ('02) .  Figure  317 
is  a  diagram  of  a  sagittal  section  of  a  larva  through  the  median  plane. 
In  this  larva  the  posterior  fourth  of  the  mid-intestine  is  merely  a 


Fig.  316. — Head  and  mouth- 
parts  of  a  larva  of  an  ant- 
lion,  ventral  aspect:  c,  car- 
do  of  the  maxilla;  e,  eye;/, 
front  margin  of  the  dorsal 
wall  of  the  head,  labrum 
(?);  m,  mentum;  wJ,  man- 
dible, mx,  maxilla;  p,  la- 
bial palpus;  s,  stipes  of  the 
maxilla. 


NEUROPTERA  283 

solid  cord  of  atrophied  cells;  the  passage  from  the  mid-intestine  to 
the  hind -intestine  is  thus  closed.  The  atrophied  part  of  the  mid- 
intestine  ends  in  the  walls  of  a  dilation,  the  silk-receptacle  {sr). 
Into  this  receptacle  empty  the  five  Malpighian  tubes,  three  of  which 
are  attached  by  both  ends  and  two  of  which  extend  posteriorly  and 
end  free  in  the  body  cavity ;  all  are  modified  in  their  middle  portions 
for  the  secretion  of  silk;  here  the  cells  are  much  larger  and  more 
irregular  in  shape  than  the  ordinary  Malpighian  tubule  cells,  and 
show  singular,  branched  nuclei  like  those  characteristic  of  silk-gland- 


Fig.  317. — Sagittal  section  of  a  larva  of  Sisyra:  a,  b-h',  c-c'.  three  silk-glands 
attached  at  both  ends;  d,  e,  two  silk-glands  attached  at  one  end;  sr,  silk- 
receptacle;  sp,  spinneret;  /,  fat-bodies;  hr,  brain;  g,  subcesophageal  ganglion; 
r,  band  of  regenerative  cells  of  the  stomach;  p,  point  of  junction  of  sucking 
tubes,  s,  sucking  pharynx;  m,  muscle  attachment  of  pharynx;  o,  oesophagus. 
(From  Anthony.) 

cells  of  caterpillars  and  other  insects.  That  part  of  the  hind-intestine 
extending  back  from  the  silk-receptacle  is  a  slender  tube  for  the 
greater  part  of  its  length ;  but  in  the  last  three  abdominal  segments 
it  is  enlarged,  forming  a  reservoir  for  accumulated  silk  {sp),  which 
is  spim  from  the  anus  when  needed  for  making  the  cocoon. 

The  pupae  of  Neuroptera  are  exarate,  that  is,  their  legs  and  wings 
are  free.  In  some  cases  {Chrysopa,  Hemerobius,  and  Mantispa)  the 
pupa  crawls  about  for  a  time  after  leaving  its  cocoon  and  before 
changing  to  the  adult. 

The  known  Neuroptera  of  the  world  represent  twenty  families; 
the  wings  of  one  or  more  members  of  each  of  these  families  have  been 
figured  by  the  writer  in  his  "The  Wings  of  Insects."  Thirteen  of 
these  families  are  represented  in  North  America;  these  can  be  sepa- 
rated by  the  following  table. 

TABLE  OF  THE  FAMILIES  OF  NORTH  AMERICAN  NEUROPTERA 

A.        Prothorax  as  long  as  or  longer  than  the  mesothorax  and  metathorax  com- 
bined. 
B.       Fore  legs  greatly  enlarged  and  fitted  for  grasping,  p.  289.  Mantispid^ 
BB.    Fore  legs  not  enlarged  and  not  fitted  for  grasping,  p.  289.  Raphidiid^ 
AA.    Prothorax  not  as  long  as  the  mesothorax  and  metathorax  combined. 

B.     Hind  wings  broad  at  base  and  with  the  anal  area  folded  like  a  fan  when 

not  in  use.  p.  284 : Sialid^ 

BB.Hind  wings  narrow  at  base  and  not/olded  like  a  fan  when  closed. 

C.    Wings  with  very  few  veins  and  covered  with  whitiish  powder,  p.  307. 

Coniopoterygid^ 

CC.    Wings  with  numerous  veins  and  not  covered  with  powder. 

D.    Antennae  gradually  enlarged  towards  the  end  or  filiform  with  a 
terminal  knob. 


284  AN  INTRODUCTION  TO  ENTOMOLOGY 

E.    Antennae  short;  wings  with  an  elongate  cell  behind  the  point 

of  fusion  of  veins  Sc  and  Ri.   p.  303 Myrmeleonid^ 

EE.    Antennas  long;  wings   without   an  elongate  cell  behind  the 

point  of  fusion  of  veins  Sc  and  Ri.  p.  305 Ascalaphid^ 

DD.    Antennas  not  enlarged  towards  the  end. 

E.       Male  with  pectinate  antennae;  female  with    an  exserted 

ovipositor,  p.  297 Dilarid^e 

EE.    Antenn£E  not  pectinate  in  either  sex;  female  without  ex- 
serted ovipositor. 
F.    Radius  of  the  fore  wings  with  apparently  two  or  more 
sectors. 
G.       Radius  of  the  fore  wings  with  apparently  two  sectors, 
one  of  which  is  vein  R2 +3  and  the  other  veinR4+5. 

p.  293 SVMPHEROBIID.t 

GG.  Radius  of  the  fore  wings  with  three  or  more  sectors. 
Veins  R4  and  Rs  arise  separately  from  vein  Ri; 
one  or  more  definitive  accessory  branches  of  the 

radius  of  the  fore  wings  present,  p.  294 

Hemerobiid.^ 

FF.    Radius  of  the  fore  wings  with  a  single  sector. 

G.        Radial  sector  of  the  fore  wings  without  definitive 
accessory   veins   although   marginal  accessory 

veins  are  present,   p.  291 SiSYRiD.t 

GG.    Radial    sector  of  fore  wings  with  definitive  ac- 
cessory veins. 
H.    Transverse  veins  between  the  costa  and  sub- 

costa  simple,  p.  299 CHRVSOFiDiE 

HH.    JMany  of  the  transverse  veins  between  the 
costa  and  subcosta  forked. 

I.  Humeral  cross- vein  recurved  and  branch- 

ed; first  radio-medial  cross- vein  of  the 
hind  wings  longitudinal  and  sigmoid. 

p.  298 POLYSTCECHOTID^ 

II.  Humeral  cross- vein  not  recurved;  first 
radio-medial  cross-vein  of  the  hind  wings 
transverse,  p.  298 Berothid^ 

Family  vSIALID^* 

The  Sialids 

The  members  of  the  Sialidse  differ  greatly  in  size  and  appearance ; 
but  they  agree  in  having  the  hind  wings  broad  at  the  base  with  the 
anal  area  folded  like  a  fan  when  not  in  use.  In  this  respect  the}' 
diifer  from  all  other  Neuroptera. 

The  type  of  the  wing-venation  of  the  sialids  differs  greatly  in  the 
two  subfamilies  into  which  the  family  is  divided,  as  described  below. 

The  larv«  are  aquatic,  predacious,  campodeiform,  and  possess 
paired,  lateral  filaments  on  most  or  on  all  of  the  abdominal  segments. 
They  leave  the  water  when  full-grown  and  transform  in  earthen  cells 
on  the  banks  of  the  streams  or  lakes  in  which  they  lived  as  larvee. 
The  eggs  are  deposited  in  clusters  on  any  convenient  support  near 
the  water,  in  such  situations  that  the  yoimg  \a.Tx^  can  easily  find 

*This  family  is  separated  from  the  Neuroptera  by  Handlirsch  ('o6-'o8)  as  a 
distinct  order,  the  Megaloptera.  H.  W.  Van  der  Weele  Cio)  also  separates  it 
from  the  Neuroptera,  but  he  associates  with  it  the  family  Raphidiidae  in  his  order 
Alegaloptera. 


NEUROPTERA  285 

access  to  the  water.  The  adults  fly  but  little;  they  are  most  often 
found  resting  on  some  support  near  the  water,  with  the  wings  folded 
over  the  abdomen. 

The  SialidiE  of  the  world  have  been  monographed  by  H.  W. 
Van  der  Weele  ('lo). 

The  family  Sialidaj  is  divided  into  two  subfamilies;  these  can  be 
separated  as  follows : 

A.  Ocelli  wanting;  fourth  tarsal  segment  prominently  bilobed;  radial  sector 
not  pectinatel}^  branched.  Insects  rather  small,  having  an  expanse  of 
wings  of  about  25  mm.  p.  285 Sialin/e 

AA.    With  three  ocelli;  fourth  tarsal  segment  simple,  not  bilobed;  radial  sector 

pectinately  branched.     Insects  large  or  moderately  large,  p.  286 

CORYDALIN^ 

Subfamily  STALING 
The  Alder-Flies 

The  alder-flies  are  so-called  because  the  adults  are  commonly 
foiuid  on  alders  on  the  banks  of  streams;  this  name  was  given  to 
them  by  English  anglers. 

The  subfamily  Sialina}  includes  only  two  genera,  both  of  which 
are  represented  in  this  cotintry,  each  by  a  single  species.  These 
genera  are  distinguished  as  follows : 

A.       Costal  area  of  the  fore  wings  greatly  expanded  before  the  middle  (Fig.318). 

SlALIS 

AA.     Costal  area  of  the  fore  wings  sHghtly  expanded  before  the  middle 

Protosialis 

A', 


Fig.  318. — Wings  of  Sialis  infumata. 


286 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  smoky  alder-fly,  Stalis  in f urn  at  a. —This  is  a  small  insect  hav- 
ing a  wing-expanse  of  about  25  mm. ;  the  males  are  sometimes  smaller 
than  this,  and  the  females  slightly  larger.  It  is  dusky  browTiish  in 
color.  It  can  be  easily  recognized  by  the  form  and  venation  of  its 
wings  (Fig.  318). 

The  costal  area  of  the  fore  wings  is  greatly  expanded  before  the 
middle,  and  most  of  the  wing-veins  are  stout.  A  striking  feature  of 
these  wings,  one  that  is  characteristic  of  the  subfamily  Sialinffi,  is 
that  the  radial  sector  is  nearly  typical  in  form;  the  only  modification 
being  the  development  of  one  or  more  marginal  accessory  veins  upon 
it.  These  accessory  veins,  however,  are  in  a  quite  different  position 
from  that  occupied  by  the  accessory  veins  borne  by  the  radial  sector 
in  the  Corydalinae,  where  a  pectinately  branched 
radial  sector  has  been  developed. 

The  larva  (Fig.  319)  is  furnished  with  the  paired 
lateral  filaments  characteristic  of  the  larvag  of  the 
vSialidfc  on  the  first  seven  abdominal  segments.  These 
filaments  are  more  or  less  distinctly  five-segmented. 
The  last  abdominal  segment  is  prolonged  into  a  taper- 
ing lash-like  filament. 

The  larvae  are  foimd  in  swiftly  flowing  streams 
adhering  to  the  lower  side  of  stones  in  the  bed  of  the 
streams  and  in  trashy  places  filled  with  aquatic  plants 
in  the  borders  of  streams  and  ponds;  they  are  very 
active.  The  larvae  transform  in  earthen  cells  at  some 
little  distance  from  the  water.  Two  or  three  weeks 
after  the  making  of  the  pupal  cell  the  adult  fly 
emerges. 

The  eggs  are  laid  in  patches,  each  consisting 
of  a  single  layer  of  eggs.  The  females  frequently 
add  their  eggs  to  patches  of  eggs  that  have  been  laid 
by  other  females.  The  eggs  when  first  laid  are 
lighter  in  color  than  later. 

Several  specific  names  have  been  given  to  what 
are  now  believed  to  be  merely  varieties  of  this 
species. 
Protosialts  americdna.- — In  this  species  the  costal  area  of  the  fore 
wings  is  only  slightly  expanded  before  the  middle;  and  the  wing- 
veins  are  not  as  stout  as  in  Sialis.    The  early  stages  have  not  been 
described. 


Fig.  319. — Larva 
of  Sialis  infu- 
mata.  (After 
Needham.) 


Subfamily  CORYDALIN^ 

Corydalus  and  the  Fish-Flies 

The  subfamily  Corydalinae  is  represented  in  this  country  by  the 
well-known  horned  corydalus  and  several  smaller  species,  commonly 
known  as  the  fish-flies.  In  these  insects  there  are  three  ocelli;  the 
fourth  tarsal  segment  is  not  bilobed;  and  the  radial  sector  is  pec- 
tinately branched  (Fig.  320).     The  larvae  are  distinguished  by  the 


NEUROPTERA  287 

presence  of  a  pair  of  anal  prolegs,  each  of  which  bears  a  pair  of  hooks. 
Six  species  are  found  in  the  United  States  and  Canada;  these  repre- 
sent four  genera,  which  can  be  separated  as  follows. 
A.       Latero-caudal  angles  of  the  head  with  a  sharp  tooth.    Large  insects,  p.  287 

CORYDALUS 

AA.    Latero-caudal  angles  of  the  head  unarmed.    Insects  moderately  large;  the 
fish-flies. 
B.    Wings  somewhat  ashj'  in  color  with  more  or  less  dusky  markings. 

C.    Veins  of  fore  wings  marked  with  dark  and  light,  uniformly  alternate. 

p.   288 Chauliodes 

CC.    Veins  of  fore  wings  uniform  in  color  except  where  dusky  markings 

cross  them.  p.  288 Neohermes 

BB.    Wings  black  or  brown  with  white  markings,  p.  288 Nigronia 

Corydahts. — The  only  member  of  this  genus  in  our  fauna  is 
Corydalus  cornutus.  This  is  a  magnificent  insect,  which  has  a  wing- 
expanse  of  from  100  to  130  mm.     Figure  321  represents  the  male, 


3<i  A    2d  A  Cui  Cuia 

Fig.  320. — Fore  wing  of  a  pupa  of  Corydalus. 

which  has  remarkably  long  mandibles.  The  female  resembles  the 
male,  except  that  the  mandibles  are  comparatively  short. 

The  larvas  are  called  dobsons  or  heli^rammites  by  anglers  and 
are  used  by  them  for  bait,  especially  for  bass.  Figure  322  represents 
a  full-grown  dobson,  natural  size.  These  larvae  live  imder  stones  in 
the  beds  of  streams.  They  are  most  abundant  where  the  water  flows 
swiftest.  They  feed  upon  the  naiads  of  stone-flies  and  May-flies  and 
on  other  insects. 

The  larvae  of  Corydalus  differ  from  those  of  the  following  genera 
in  the  possession  of  a  tuft  of  hair-like  tracheal  gills  at  the  base  of 
each  of  the  lateral  appendages  on  the  first  seven  abdominal  segments. 

When  about  two  years  and  eleven  months  old,  the  larva  leaves 
the  water  and  makes  a  cell  under  a  stone  or  some  other  object  on 
or  near  the  bank  of  the  stream.  This  occurs  during  the  early  part 
of  the  summer;  here  the  larva  changes  to  a  pupa.  In  about  a  month 
after  the  larva  leaves  the  water,  the  adult  insect  appears.  The  eggs 
are  then  soon  laid;  these  are  attached  to  stones  or  other  objects 
overhanging  the  water.  They  are  laid  in  blotch-like  masses,  which 
are  chalky  white  in  color  and  measure  from  12  mm.  to  nearly  25  mm. 
in  diameter.  A  single  mass  contains  from  two  thousand  to  three 
thousand  eggs.  When  the  larvae  hatch  they  at  once  find  their  way 
into  the  water,  where  they  remain  until  full-grown. 


288 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Chauliodes.—See  the  table  on  page  287  for  the  distinguishing 
characteristics  of  this  genus.  There  are  two  species  in  our  fauna; 
these  are  distinguished  as  follows: 

Chaiiliodes  rastricornis. — In  this  species  the  antennae  are  serrate; 
the  embossed  markings  on  the  head  and  prothorax  are  black  on  a 
paler  groimd;  and  the  prothorax  is  longer  than  wide. 


Fig.    322. — Larva    of 
Corydalus. 


Fig.  321. — Corydalus  cornuttis,  male. 


Chaultodes  pectinicdrnis. — In  this  species  the  antennae  are  serrate; 
the  embossed  markings  on  the  head  and  prothorax  are  yellow  on  a 
black  groimd;  and  the  prothorax  is  not  longer  than  wide. 

Neohermes. — This  genus  is  represented  by  Neohermes  cah'fdrmcus. 
In  addition  to  the  characters  given  in  the  table  of  genera  above,  this 
species  is  distinguished  by  the  great  length  of  its  antennae ,  which  are 
about  two-thirds  as  long  as  the  fore  wings. 

Nigronia. — In  this  genus  the  wings  are  black  or  brown  with  white 
markings.  Two  species  only  are  kno\^Ti;  these  can  be  distinguished 
by  the  form  of  the  white  markings  on  the  wings. 

Nigronia  fascidUis.—ln  this  species  there  is  a  continuous,  broad, 
somewhat  arcuate,  white  band  extending  across  the  middle  of  each 
wing  and  almost  attaining  the  hind  margin. 

Nigronia  serricornis. — In  this  species  there  is  an  irregular  band  of 
white  spots,  generally  broadest  in  front,  extending  across  the  middle 


NEUROPTERA 


289 


of  each  front  wing.    On  the  hind  wings,  the  white  band  is  represented 
by  only  a  few  minute  dots  or  is  entirely  wanting. 


Family  RAPHIDIID^* 


The  Snake-Flies 


Fig.  323. — Raphidia, 

female. 


The  members  of  the  Raphidiid^e  are  found  in  this  country  only 
in  the  Far  West.  They  are  strange-appearing  insects,  the  prothorax 
being  greatly  elongate,  like  the  neck  of  a  camel 
(Fig.  323).  The  female  bears  a  long,  slender, 
sickle-shaped  ovipositor  at  the  end  of  the  ab- 
domen. The  fore  legs  resemble  the  other  pairs 
of  legs,  and  are  borne  at  the  hind  end  of  the  pro- 
thorax.  The  wings  are  long  and  narrow  and  fur- 
nished with  a  pterostigma. 

The  wing-venation  of  a  representative  of  each  of  the  two  genera 
belonging  to  this  family  is  figured  by  the 
writer  in  his  "The  Wings  of  Insects." 

The  larv£e  are  found  under  bark  and 
are  carnivorous.  They  are  common  in  Cali- 
fornia under  the  loose  bark  of  the  eucalyp- 
tus. They  also  occur  in  orchards,  and 
doubtless  do  good  by  destroying  the  larvas 
and  pupas  of  the  codlin-moth.  The  pupas 
are  not  enclosed  in  silken  cocoons  but  lie 
concealed  in  sheltered  places.  Figure  324 
represents  a  larva  and  a  pupa  of  Raphidia 
as  figured  by  Professor  Kellogg. 

This  family  includes  only  two  genera, 
Raphidia  and  Inocellia.  In  the  former  there 
are  three  ocelli  on  the  top  of  the  head  be- 
tween the  compound  eyes ;  in  the  latter  these 
ocelli  are  wa.i3ting.  Six  species  of  Raphidia 
and  three  of  Inocellia  are  foimd  in  America 
north  of  Mexico. 


Fig.  324. — Larva  and  pupa 
of  Raphidia.    (From  Kel- 


Family  MANTISPID^ 
The  Mantis-like  Neuroptera 

The  members  of  the  Mantispida>  are  even  more  strange  in  appear- 
ance than  are  those  of  the  preceding  family.    Here,  as  in  that  family, 


*This  family  is  separated  from  the  Neuroptera  by  Handlirsch  ('o6-'o8)  and 
made  to  constitute  a  separate  order,  the  Raphidioidea. 


290 


AN  INTRODUCTION  TO  ENTOMOLOGY 


the  prothorax  is  greatly  elongated ;  but  the  members  of  this  family  can 

be  easily  recognized  by  their  re- 
markable fore  legs,  which  are  great- 
ly enlarged  and  resemble  those  of 
the  praying  mantes  in  form  (Fig. 
325).  These  legs  are  fitted  for  seiz- 
ing prey;  and,  in  order  that  they 
may  reach  farther  forward,  they  are 
joined  to  the  front  end  of  the  long 
prothorax.  In  the  adult  stage, 
these  insects  are  predacious;  while 
the  larvce,  so  far  as  is  known,  are 
parasitic. 

Brauer  ('69)  described  the  trans- 
formations of  Mantis  pa  styriaca,  a 
European    species.     This    insect 
undergoes  a    hypermetamorphosis. 
It  was  accidentally  discovered  that  the  larvae  were  parasitic  in  the 
egg-sacs  of  spiders  of  the  genus  Lycosa.    These  are  the  large  black 


Fig.  325. — Mantispa.  In  the  speci- 
men figured  the  fore  legs  were 
twisted  somewhat  in  order  to 
show  the  form  of  the  parts. 


Fig.  326. — Hypermetamorphosis  of  ikfawrt'ipa.   (From  Henneguy,  after  Brauer.) 


spiders  which  are  common  tmder  stones,  and  which  carry  their  egg-sacs 
with  them.  Brauer  obtained  eggs  from  a  female  Mantispa  kept  in 
confinement.  These  eggs  were  rose-red  in  color,  and  fastened  upon 
stalks,  like  the  eggs  of  Chrysopa.  The  eggs  were  laid  in  July;  and 
the  larvae  emerged  2 1  days  later.  The  young  larvffi  are  campodeiform 
(Fig.  326,  A);  they  are  very  agile  creatures,  with  a  long,  slender 
body,  well-developed  legs,  and  long,  slender  antennae.  They  pass  the 
winter  without  food.  In  the  spring  they  find  their  way  into  the  egg- 
sacs  of  the  above-named  spiders.  Here  they  feed  upon  the  yoimg 
spiders;  and  the  body  becomes  proportionately  thicker.  Later 
the  larva  molts  and  undergoes  a  remarkable  change  in  form,  becom- 
ing what  is  known  as  the  second  larva;  in  this  stage  the  larva  is 


NEUROPTERA  291 

scarabeiform  (Fig.  326,  B);  the  legs  are  much  reduced  in  size;  the 
antennae  are  short ;  and  the  head  is  very  small.  When  fully  grown  this 
larva  measures  from  7  to  10  mm.  in  length.  It  then  spins  a  cocoon, 
and  changes  to  a  pupa  within  the  skin  of  the  larva.  Later  the  larval 
skin  is  cast;  and,  finally,  after  being  in  the  cocoon  about  a  month, 
the  pupa  becomes  active,  pierces  the  cocoon  and  the  egg-sac,  and 
crawls  about  for  a  time  (Fig.  326,  C) ;  later  it  changes  to  the  adult 
form  (Fig.  326,  D). 

The  life-history  of  Symphasis  varia,  a  Brazilian  species,  is  partly 
known.  The  larvas  of  this  species  live  parasitically  in  the  nests  o'f 
wasps;  when  full-grown  each  larva  spins  a  cocoon  "in  one  of  the  cells 
of  the  nest. 

Only  a  few  representatives  of  this  family  occur  in  the  United  vStates, 
and  all  are  rare  insects. 

Family  SISYRID^ 
The  Spongilla-Flies 

The  Sisyridse  in- 
clude a  very  limited 
number  of  small, 
smoky  brown  insects, 
of  the  form  shoA\Ti  in 
Figure  327.  They  are 
called  Spongilla-flies 
because  the  larvas  live  ^. 
as    parasites    in  fresh-    ^InihonT.j""''''  ''"''  ^"""^  enlarged.     (From 

water  sponges,  the 

typical  genus  of  which  is  Spongilla.  Two  interesting  features  of  these 
insects  are  the  comparative  simplicity  of  the  wing-venation  of  the 
adults,  and  the  anomalous  habits  of  the  larvas. 

The  more  striking  characteristics  of  the  wings  (Fig.  3 28)  are  the 
following :  The  costal  area  of  the  fore  wings  is  not  greatly  broadened; 
the  himieral  vein  is  not  recurrent  and  is  not  branched.  Veins  vSc  and 
Ri  coalesce  near  the  apex  of  the  wing.  The  radial  sector  is  pectinately 
branched;  but  no  definitive  accessory  veins  have  been  developed; 
this  is  the  simplest  form  of  pectinately  branched  radial  sector  foimd 
in  the  fore  wings  in  this  order.    Marginal  accessory  veins  are  present. 

The  larvas  are  aquatic  and  live  in  fresh-water  sponges,  upon 
which  they  feed.  The  life-history  of  a  representative  of  each  of  the 
two  genera,  Sisyra  and  Climacia,  which  constitute  this  family,  was 
worked  out  by  Professor  Needham  ('01);  and  the  anatom}^  and 
transformations  of  a  species  of  Sisyra  were  carefully  studied  by  Miss 
Anthony  ('02).  The  following  notes  are  based  on  the  accounts 
published  by  these  authors. 

Sisyra  umbrdta. — The  form  of  the  adult  is  shown  in  Figure  327; 
its  color  is  nearly  uniform  blackish  brown.  The  legs  and  the  apex 
of  the  abdomen  are  dirty  3'ellowish.  The  length  of  the  male  to  the 
tips  of  the  wings  is  6  mm ;  that  of  the  female,  8  mm. 


292 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  larva   (Fig.   329)   is  campodeiform.     Its  mouth-parts  are 
formed  for  sucking  as  in  the  larvce  of  ant-lions  (see  page  282);  they 


3^^  2d  A     J^^^ 
^\  III  /  r-7 


Fig.  328. — Wings  of  Sisyra  flaviconiis. 

are  very  long;  and  two  sucking  organs,  each  formed  of  the  mandible 
and  maxilla  of  one  side,  are  closely  parallel  for  the  greater  part  of 
their  length.  Each  of  the  first  seven  abdominal  segments  bears  on 
the  ventral  side  a  pair 
of  jointed  filaments 
which  are  believed  to 
be  tracheal  gills. 
When  full-grown,  the 
larva  leaves  the  water 
and  spins  over  itself, 
on  some  object  near 
the  water,  a  hemi- 
spheric cover  of  close- 
ly woven  silk,  at- 
tached by  its  edges  to 
the  supporting  sur- 
face, and  a  complete 
inner  cocoon  of  con- 
siderably smaller  size, 
likewise  closely  woven. 

The  silk-organs  of  the  larva  are  describ- 

t:,.  t  f  c-  ed  on  pages  282-3. 

Fig.  329. — Larva  of  5^5  V-  ^j"  ^  .       ,.  ^^  rr^,. 

ra  umbrata.    (After  An-  Climana  dtctyona— This  species  resem- 

thony.)  bles  the  preceding  in  size  and  is  quite  similar 


Fig.  330. — Cocoon  and 
cocoon-cover  of  Cli- 
macia. 


NEUROPTERA 


293 


in  coloration ;  the  two  can  be  distinguished  by  the  form  of  the  labia 
(Fig.  33 1). 

In  the  larva  of  this  species  the  setse  on  the  dorsum  of  the  tho- 
rax are  situated  on  tubercles;  they  are  sessile  in  the  larva  of  5z5;vm. 
The  habits  of  the  larva  are  similar  to  those  of  Sisyra. 


Cliniacia  dictyona;  h,  Sisyra  umbrata.  (Af t( 


Fig.  331. — Labia  of  Spongilla-flies: 
Needham.) 

Before  spinning  its  cocoon  this  larva  spins  a  hemispheric  cover 
beneath  which  the  cocoon  is  made,  as  does  the  larva  of  Sisyra.  But 
in  the  case  of  Climacia  this  cocoon-cover  is  lace-like ;  it  is  a  beautiful 
object  (Fig.  330). 

Excepting  the  sialids,  the  larvse  of  Sisyra  and  Climacia  are  the 
only  known  aquatic  neuropterous  larvee  found  in  this  country. 


Family  SYMPHEROBIID^ 
The  Sympherobiids 

This  family  includes  certain  insects  which  were  formerly  classed 
with  the  HemerobiidcC  but  which  exhibit  a  type  of  specialization  of 
the  wings  that  is  quite  different  from  that  which  is  distinctively 
characteristic  of  that  family. 

The  distinctive  characteristic  of  the  Sympherobiidee  is  that  vein 
R2+3  of  the  fore  wings  has  become  separated  from  the  remainder 
of  the  radial  sector  and  is  attached  separately  to  vein  Ri.  This 
results  in  the  radius  of  the  fore  wing  having  two  sectors,  each  of  which 
is  forked  (Fig.  332). 

In  this  family  the  number  of  the  branches  of  the  radial  sector  has 
not  been  increased,  this  vein  being  four-branched  in  both  fore  and 
hind  wings ;  but  the  tips  of  all  of  the  branches  are  forked.  The  costal 
area  of  the  fore  wing  is  broad  towards  the  base  of  the  wing ;  and  the 
humeral  vein  is  recurved  and  branched. 

The  North  American  species  of  this  family  represent  two  genera. 


294 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Synipherdbius. — In  this  ^enus  there  are  two  series  of  gradate  veins 
in  the  fore  wings ;  the  outer  series  consists  of  four  cross- veins  (Fig.  332). 
Seven  American  species  have  been  described.  The  wing-expanse  of 
these  insects  ranges  from  9  mm.  to  12  mm. 


Fig.  332. — Wings  of  Sympherobiiis  amiculus. 

Psectra. — In  this  genus  there  is  only  one  series  of  gradate  veins 
in  the  fore  wings.  The  only  species  is  Psectra  diptera.  The  specific 
name  of  this  species  was  suggested  by  the  fact  that  in  the  female  the 
hind  wings  are  atrophied.  This  is  a  widely  distributed  species  both 
in  this  cotmtry  and  in  Europe.  Its  wing  expanse  is  from  5  nun.  to 
6  mm. 

Family  HEMEROBIID^ 

The  Hemerobiids 


The  Hemerobiidaj  include  insects  of  moderate  size;  in  most  of 
our  species  the  wing-expanse  is  between  12  mm.  and  22  mm.;  in 
one  species  of  Megalomus  it  is  only  6  mm.  In  most  of  the  species  the 
body  is  brown  or  blackish  and  is  often  marked  with  yellow;  in  some 


NEUROPTERA 


295 


the  body  is  pale  yellow.     The  wings  are  usually  hyaline  or  pale 
yellowish. 

This  family  has  been  greatly  restricted  in  recent  times ;  formerly 
there  were  included  in  it  the  members  of  the  two  preceding  and  the 
three  following  families. 


/2:^r^rrrrr^^mm22Zm^ 


Fig.  333. — Wings  of  Hcmerohius  humuli. 


■  As  now  restricted  this  family  is  composed  of  a  group  of  genera 
that  are  characterized  by  a  distinctive  manner  of  specialization  of  the 
radius  of  the  fore  wings.  This  feature  is  a  coalescence  of  vein  Ri  and 
the  stem  of  the  pectinately  branched  radial  sector,  which  results  in 
what  I  have  termed  the  suppression  of  the  stem  of  the  radial  sector. 

A  comparatively  simple  example  of  this  condition  is  exhibited 
by  Hemerobius  hUmuli;  in  the  fore  wings  of  this  species  (Fig.  sss)' 
veins  R5,  R4,  and  R2+3  arise  separately  from  what  appears  to  be 
the  main  stem  of  the  radius  but  which  is  really  vein  Ri  and  the  basal 
part  of  the  radial  sector  coalesced. 

An  early  stage  in  the  suppression  of  the  stem  of  the  radial  sector 
is  shown  in  the  hind  wing  oi  Hemerobius  humuli  (Fig.  2>2)Z)-     Here 


296 


AN  INTRODUCTION  TO  ENTOMOLOGY 


vein  R2+3+4  is  bent  forward'  near  its  base  and  is  joined  to  vein  Ri. 
The  extending  of  the  union  of  veins  Ri  and  R2+3+4  from  the  point 
where  the}^  now  anastomose  towards  the  base  of  the  wing:,  so  as  to 
obHterate  the  small  cell  between  them,  and  also  towards  the  apex  of 


Fig.  334. — Wings  of  Megalomtis  mosstus. 


the  wing  for  a  certain  distance,  would  produce  the  condition  that  exists 
in  the  fore  wing. 

The  wings  of  Hemerobius  represent  a  comparatively  simple  type 
of  hemerobiid  wings;  those  of  Megalonms  mcestus  (Fig.  334),  a  more 
complicated  one.  Here  there  have  been  developed  a  larger  ntunber 
of  definitive  accessory  veins  and  of  marginal  accessory  veins. 

Under  the  title  "A  Revision  of  the  Nearctic  Hemerobiidas"  Mr.N. 
Banks  ('05)  has  published  an  account  of  this  family,  the  two  preceding 
families,  and  the  three  following  families,  in  which  all  of  our  species 
kno^vn  at  that  time  are  described. 


NEUROPTERA 


l<d-i 


The  lar\^£c  of  the  hemerobiids,  as  far  as  they  are  known,  resemble 
in  their  general  appearance  aj^his-lions  (Chrysopida?) ,  and,  hke  the 
aphis-lions,  feed  on 
plant-lice  and  other 
small  insects.  Their 
mouth-parts  are 
formed  for  piercing 
and  sucking  (see 
page  282),  and  the 
posterior  part  of 
the  alimentary  ca- 
nal is  transformed 
into  a  silk-organ,  as 
ill  Sisyra  (see  page 
283).  They  are 
found  most  often 
running  about  on 
trees,  and  especial- 
ly on  coniferous 
trees.  vSome,  like 
the  aphis-lions,  are 
naked ;  but  the  lar- 
vse  of  some  species, 
at  least,  of  Hemero- 
biMs  cover  them- 
selves with  a  cloak,  composed  of  the  empty  skins  of  their  victims 
and  other  debris  (Fig.  335).  These  larvee  are  furnished  at  the  sides 
with  projections  which  serve  as  pedicels  to  elongate,  divergent  hairs 
that  help  to  keep  the  cloak  in  place. 

There  are  thirty  described  American  species  belonging  to  this 
family ;  these  represent  four  genera,  Hemerobius,  Boriomyia,  Megalo- 
mus,  and  Mtcromus. 


Fig-  335- — Larva  of  Hemerobius:  A,  the  larva  bare; 
B,  the  same  partially  concealed  by  the  remains  of  its 
victims,  etc.;  a  portion  of  the  covering  has  been  re- 
moved in  order  to  show  the  head.  (From  Sharp.) 


Family  DILARID^ 


The  Dilaridag  is  a  small  family,  representatives  of  which  are  found 
chiefly  in  the  Old  World.  In  this  family  the  antenna  of  the  male 
are  pectinate ;  and  the  female  is  furnished  with  an  exerted  ovipositor. 

Only  a  single,  exceedingly  rare  species,  Dllar  amertcdnus,  has  been 
found  in  North  America;  and  of  this  only  a  single  female  individual 
is  known.  This  is  a  small  insect;  the  length  of  the  body,  not  includ- 
ing the  ovipositor,  is  about  3  mm.;  the  length  of  the  ovipositor  is  a 
little  greater  than  that  of  the  body ;  the  expanse  of  the  wings  is  about 
14  mm.  There  is  a  single  five-branched  radial  sector  in  bothforeand 
hind  wings.  In  several  exotic  species  the  radius  of  the  fore  wings 
bears  two  or  more  sectors. 

The  type  of  our  species  was  taken  at  Bee  Spring,  Kentucky-,  in 
June,  1874. 


298 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Family  BEROTHID^ 

The  Berothidae  is  a  small  family,  which  is  represented  in  North 
America  by  a  single  genus,  Lomamyia,  of  which  only  two  species  are 


Fig.  336. — Wings  of  Beroiha  insolita. 

known.  Figure  336  represents  the  venation  of  the  wings  of  the  type 
species  of  the  family,  Berotha  insolita,  which  is  found  in  India,  and 
to  which  our  species  are  closely  allied. 

The  fore  wings  are  falcate,  which  is  not  true  of  certain  exotic  genera ; 
the  humeral  cross-vein  is  not  recurved ;  many  of  the  transverse  veins 
between  the  costa  and  the  subcosta  are  forked ;  the  radial  sector  bears 
definitive  accessory  veins;  and  there  is  a  single  series  of  gradate 
veins  in  the  radial  area.  In  the  hind  wings  the  first  radio-medial 
cross-vein  is  transverse;  vein  Cuo  is  wanting;  and  the  area  between 
the  margin  of  the  wing  and  veins  ist  A  and  Cui  is  narrow  and  largely 
occupied  by  the  fanlike  tips  of  the  accessory  veins. 

Nothing  is  known  regarding  the  early  stages  of  these  insects. 


Family  POLYSTCECHOTID^ 

The    famih^   Polystoechotidas  was 
established  to  receive  the  genus 
Polystcechotes ,oi\\h\ch  only  two  species, 
both  American,  are  known.     These  are 
larger    insects    than    are    the   members  of  the   allied    families, 


Polystaxhotes  piaicta- 


NEUROPTERj 


!99 


measuring  in  wing-expanse  from  40  mm.  to  75  mm.,  varying  greatly 
in  size.  They  are  nocturnal  and  are  attracted  to  lights.  The  two 
species  can  be  distinguished  as  follows : 

Polystcedwtes  piinctaUts  (Fig.  337).  This  is  blackish,  with  three 
longitudinal  lines  on  the  prothorax,  and  with  the  lateral  margins  of 
this  segment  yellowish. 


Fig.  338. — Wings  of  Polystcechotes  punctahis. 

Polystcechotes  vittdtus. — This  is  pale  yellowish,  with  a  black  stripe 
on  the  sides  of  the  thorax,  and  with  the  abdomen  dark  brown. 

The  larva  of  neither  of  these  species  is  known.  This  is  a  strange 
fact  considering  the  size  and  the  abundance  of  these  insects. 

The  wings  of  Polystcechotes  punctatus  (Fig.  33 8)  represent  the  type 
of  wing-venation  characteristic  of  this  family.  In  these  wings  the 
humeral  cross-vein  is  recurved  and  branched;  veins  Sc  and  Ri  co- 
alesce at  the  tip;  the  radial  sector  is  pectinately  branched;  the  num- 
ber of  cross-veins  is  greatly  reduced;  but  there  is  in  both  fore  and 
hind  wings  a  very  perfect  series  of  gradate  veins. 

In  these  wings  the  development  of  definitive  accessory  veins  on 
the  radial  sector  and  the  regularity  of  the  border  of  marginal  accessory 
veins  have  reached  a  very  high  degree  of  perfection. 

Family  CHRYSOPIDvE 

The  Lacewing-Flies  or  Aphis-Lions 

The  family  Chrysopidag  includes  the  insects  commonly  known 
as  lacewing-flies ;  these  and  their  larvae,  the  aphis-lions,  are  common 


300 


AN  INTRODUCTION  TO  ENTOMOLOGY 


and  well-known  insects;  they  are  found  upon  herbage  and  the  foliage 
_  of  shrubs  and  trees 

throughout  the  summer 
months  (Fig.  330). 

The  adults  are  easily 
recognized  by  their  deh- 
cate  lacelike  wings  and 
their  green  or  yellowish 
green  color.  Members  of 
several  of  the  preceding 
families  have  delicate 
lacelike  wings;  but  with 
those  insects  the  wings 
are  more  or  less  brown  or 
are  hyaline. 

While  these  insects 
are  most  commonly 
known  as  the  lacewing> 
flies, other  popular  names 
have  been  applied  to 
them;  they  are  some- 
times called  golden-eyed  flies,  on  account  of  the  peculiar  metallic 
color  of  their  eyes  while  alive;  and  as  some  species,  when  handled, 
emit  a  very  disagreeable  odor,  they  have  been  called  stink-flies,  an 
undesirable  name  for  such  beautiful  insects. 

The  wings  of  the  Chrysopidas  are  characterized  by  a  very  re- 
markable and  distinctive  type  of  specialization,  the  details  of  which 


Fig.   339. — Eggs,   larva,    cocoon,    and   adult   of 
Chrysopa. 


Fig.   340. — Fore  wing  of  Chrysopa  nigriconiis: 
cubitus. 


JSr,  pseudo-media;  Cui',  pseudo- 


can  be  understood  only  by  a  study  of  the  tracheation  of  the  wings 
of  the  pupae.  Such  a  study  has  been  made  by  McClendon  ('06), 
Tillyard  ('16),  and  R.  C.  Smith  ('22). 

A  superficial  examination  of  a  wing  of  Chrysopa  (Fig.  340)  reveals 
the  presence  of  two  longitudinal  veins  between  the  radial  sector  and 
the  inner  margin  of  the  wing,  one  of  which  appears  to  be  the  media 
and  the  other  vein  Cui;  but  each  of  these,  as  is  shown  later,  is  a 
serial  vein  composed  of  sections  of  several  veins. 


NEUROPTERA 


301 


As  it  would  be  impracticable  to  apply  to  these  serial  veins  names 
indicating  their  composition,  they  have  been  termed  the  pseudo- 
media  or  vein  M'  and  the  pseudo-cuhitus-one  or  vein  Cu/,  re- 
spectively (Fig.  340,  M'  and  Cu/). 


Fig.  341. — Tracheation  of  the  wings  of  a  pupa  of  Chrysopa  iiigricornis. 

An  examination  of  the  tracheation  of  the  wings  of  a  pupa  of 
Chrysopa  nigricornis  reveals  the  nature  of  the  two  serial  veins  M' 
and  Cui'  (Fig.  341). 

In  order  to  show  more  definitely  the  composition  of  the  two  serial 
veins,  a  diagram  of  an  adult  wing  is  given  (Fig.  342),  in  which  the 
elements  of  the  coalesced  veins  are  represented  slightly  separated, 
and  the  cross-veins  connecting  the  coalesced  veins  are  represented 
by  dotted  lines.  By  comparing  this  diagram  with  Figure  340  the 
homologies  of  the  different  veins  can  be  recognized. 

The  larvce  of  the  lacewing-fiies  are  known  as  aphis-lions,  because 
they  feed  upon  aphids;  they  are  found  on  the  foliage  of  plants  in- 
fested by  these  pests;  they  also  feed  upon  other  small  insects  and 
the  eggs  of  insects;  they  are  spindle-shaped  (Fig.  339)  and  are  fur- 
nished with  piercing  and  sucking  mouth-parts  like  those  of  ant-lions. 

Nearly  all  aphis-lions  are  naked;  but  a  few  species  cover  them- 
selves with  the  skins  of  their  victims  and  other  debris,  as  do  the  larvcC 
of  Hemerohius.    This  has  been  observed  by  European  writers  (Sharp 


302 


^A^  INTRODUCTION  TO  ENTOMOLOGY 


'95);  and  recently  jNlr.  R.  C.  Smith  ('21)  has  found  that  the  larvag 
of  several  of  our  native  species  have  a  similar  habit. 

The  cocoons  are  generally  found  on  the  lower  sides  of  leaves  or 
on  the  supports  of  plants;  they  are  spherical  and  composed  of  dense 
layers  of  silk.    In  order  to  emerge  the  insect  cuts  a  circular  lid  from 


''''''^+^^rSr^r^ 


Fig.  342. — Diagram  of  the  wings  of  Chrysopa  nigricomis,  showing  the  coalesced 
veins  slightly  separated. 


one  side  of  the  cocoon;  this  is  done  by  the  pupa  by  means  of  its 
mandibles.  After  emerging  from  its  cocoon,  the  pupa  crawls  about 
for  a  short  time  before  changing  to  the  adult  state. 

The  adults  are  often  attracted  to  lights  at  night.  A  remarkable 
fact  in  the  life-history  of  these  insects  is  the  way  in  which  the  female 
cares  for  her  eggs.  When  about  to  lay  an  egg  she  emits  from  the  end 
of  her  body  a  minute  drop  of  a  tenacious  substance,  which  is  probably 
a  product  of  the  colleterial  glands;  this  she  applies  to  the  object  on 
which  she  is  standing  and  then  draws  it  out  into  a  slender  thread  by 
lifting  the  abdomen ;  then  an  egg  is  placed  on  the  summit  of  this 
thread.  The  thread  dries  at  once  and  firmly  holds  the  egg  in  mid-air. 
These  threads  are  usually  about  12  mm.  in  length,  and  occur  singly 
or  in  groups;  a  group  is  represented  attached  to  a  leaf  in  Figure  339. 

About  fifty  species  belonging  to  this  family  have  been  found  in 
the  United  States  and  Canada ;  the  greater  number  of  these  belong 
to  the  genus  Chrysopa. 


Fig.  343- — Larva,  cocoon  with  pupa-skin  projecting,  and 
adult,  of  an  ant-lion. 


NEUROPTERA  303 

Family  MYRMELEONID^ 
The  Ant-Li ons 

The  members  of  the  family  Myrmeleonidae  are  commonly  known 
as  ant-lions.    This  name  was  suggested  by  the  fact  that  the  larvse  of 
the  best-known 
species,  those  that 
dig  pitfalls,  feed 
chiefly  on  ants. 

The  adults  are 
graceful  creatures. 
The  body  is  long 
and  slender  (Fig. 
343);  the  antennae 
are  short  and  en- 
larged towards  the 
end;  the  wings  are 
long  and  narrow 
and  delicate  in 
structure;  they  are 
furnished  with  many  accessory  veins,  both  definitive  and  marginal, 
and  with  very  many  cross-veins.  A  distinctive  feature  of  the  wings 
of  these  insects  is  the  presence  of  an  elongated  cell  behind  the  point 
of  fusion  of  veins  Sc  and  Ri  (Fig.  344);  this  characteristic  serves  to 
distinguish  this  family  from  the  closely  allied  Ascalaphidse. 

The  determination  of  the  homologies  of  the  wing-veins  of  the 
Myrmeleonidge  was  completed  only  recently.  The  results  of  this  de- 
termination are  set  forth  in  detail  by  the  writer  in  his  "The  Wings 
of  Insects,"  where  they  are  illustrated  by  many  figures. 

Our  native  species,  as  a  rule,  are  not  striking  in  appearance; 
the  wings  are  hyaline  and  are  o^ten  more  or  less  spotted  with  black  or 
brown  marks ;  but  certain  exotic  forms,  as  those  of  the  genus  Pal- 
pares,  are  large  and  have  conspicuously  marked  wings. 

The  larvffi  have  broad  and  somewhat  depressed  bodies  which 
taper  towards  each  end  (Fig.  343).  The  mouth-parts  are  large  and 
powerful  and  are  of  the  piercing  and  sucking  type ;  they  are  described 
on  page  282.  The  pupa  state  is  passed  in  a  spherical  cocoon,  made  of 
sand  fastened  together  with  silk,  and  neatly  lined  with  the  same 
material  (Fig.  343).  The  silk  is  spun  from  the  posterior  end  of  the 
alimentary  canal  and  is  secreted  by  modified  Malpighian  vessels,  as 
in  Sisyra  (see  page  283.) 

This  is  a  large  family  including  several  hundred  described  species. 
In  his  "Catalogue  of  the  Neuropteroid  Insects  of  the  United  States," 
Banks  ('07)  lists  fift^'-eight  species  of  this  family  known  at  that  time 
to  occur  in  our  fauna;  these  are  distributed  among  eleven  genera. 

The  life-histories  of  comparatively  few  of  the  species  are  known; 
but  certain  species,  the  larvas  of  which  dig  pitfalls  in  sandy  places, 
have  attracted  much  attention  since  the  earliest  days  of  entomology. 


304 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Ant-lions  are  much  more  common  in  the  Southern  and  Southwest- 
ern States  than  they  are  in  the  North.  The  pitfalls  of  the  larvae  are 
usually  found  in  sandy  places  that  are  protected  from  rain,  as  beneath 
buildings  or  overhanging  rocks.  In  making  these  pitfalls  the  sand 
is  thrown  out  by  an  upward  jerk  of  the  head,  this  part  of  the  body 


Fig.  344. — Wings  of  Mynncleon. 


serving  as  a  shovel.  The  pits  differ  greatly  in  depth,  according  to  the 
nature  of  the  soil  in  which  they  are  made.  Their  sides  are  as  steep 
as  the  sand  will  lie.  When  an  ant  or  other  wingless  insect  steps  upon 
the  brink  of  one  of  these  pits,  the  sand  crumbles  beneath  its  feet, 
and  it  is  precipitated  into  the  jaws  of  the  ant-lion,  which  is  buried 
in  the  sand,  with  its  jaws  at  the  bottom  of  the  pit  (Fig.  345).  In  case 
the  ant  does  not  fall  to  the  bottom  of  the  pit,  the  ant-lion  undermines 
it  by  throwing  out  some  sand  beneath  it.  I  have  even  seen  an  ant-lion 
throw  the  sand  in  such  a  way  that  in  falling  it  would  tend  to  hit  the 
ant  and  knock  it  down  the  side  of  the  pit.  These  larvae  can  be  easily 
kept  in  a  dish  of  sand,  and  their  habits  watched. 

The  most  common  ant-lion 
in  the  North  is  Myrmeleon  im- 
maculdtiis;  the  larva  of  this 
species  makes  a  pitfall.  The 
habits  of  the  larvae  of  Glenurus, 
Dendroleon,  and  Acanthdclisis, 
three  genera  that  are  repre- 
sented in  this  country,  have 
been  described  by  European 
writers.  These  larvae  do  not 
dig  pitfalls,  but  partially  bury  themselves  in  the  sand,  from  which 
position  they  throw  themselves  quickly  upon  their  victims. 


Fig.  345. — Pitfall  of  an  ant-lion. 


NEUROPTERA  305 

Family  ASCALAPHID^ 

The  Ascalaphids 

The  family  Ascalaphidac  is  quite  closely  allied  to  the  preceding 
family;  but  the  members  of  this  family  can  be  easily  distinguished 
from  myrmeleonids  by 
the  greater  length  of  the 
antennae  (Fig.  346)  and 
by  the  fact  that  in  the 
wings  there  is  not  an 
elongate  cell  behind  the 
point  of  fusion  of  veins 
ScandRi;  compare  Fig- 
ures 347  and  344.  Fig.  T,^6.~-Ululodes  hyalina.  (From  Kellogg,  after 
McClendon.) 

The  adults  are    pre- 
dacious ;  some  species  fly  in  the  daytime  in  bright  sunshine,  but  it  is 
said  that  others  fly  in  the  twilight.    Some  species  resemble  myrmeleon- 


CU2  •-. 


I      rca 

Fig.  347. — Wings  of  Uhdodes  hyalina. 


ids  in  appearance,  while  others  resemble  dragon-flies.  When  at  rest 
they  remain  motionless  on  some  small  branch  or  stalk,  head  down, 
with  the  wings  and  antennae  closely  applied  to  the  branch,  and  the 
abdomen  erected  and  often  bent  so  as  to  resemble  a  short  brown  twig 
or  branch  (Fig.  346). 


306 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  larv£e  resemble  ant-lions  in  the  form  of  the  body  and  possess 
the  same  type  of  mouth-parts  (Fig.  348).  They  have  on  each 
segment  of  the  body  a  pair  of  lateral  finger-like  appendages, 
which  are  clothed  with  hairs.  They  do  not  dig 
pitfalls,  but  lie  in  ambush  on  the  surface  of  the 
ground,  with  the  body  more  or  less  covered,  and 
wait  for  small  insects  to  come  near  them.  When 
a  larva  is  full-grown,  it  spins  a  spherical  silken 
cocoon.  An  account  of  the  life-history  of  one 
of  our  native  species,  Ululodes  hydlina,  has  been 
published  by  McClendon  ('02). 

The  Ascalaphidas  of  the  world  have  been  mon- 
ographed by  H.  W.  Van  der  Weele  ('08).  In  this 
monograph  more  than  two  hundred  species  are  de- 
scribed.    The  members  of  this  family  are  chiefly 

p-         g T  r  tropical  insects,  but   a  few  species  occur  in  the 

illulodes     hyalina.  United  States ;  these  represent  three  genera,  which 
(After McClendon.)  Can  be   separated  by  the  following  table. 


A.       Eyes  entire Neuroptynx 

AA.    Each  eye  divided  into  two  parts  by  a  groove. 

B.       Hind  margin  of  wings  entire Ululodes 

BB.    Hind  margin  of  wings  excised Colobopterus 


Fig-  349- — Wings  of  Semidalis  aleurodiformis.    (After  Enderlein.) 


NEUROPTERA 


307 


Family  CONIOPTERYGID^ 

The  Mealy-winged  Neuroptera 

The  Coniopterygidse  is  a  family  of  limited  extent;  and  it  includes 
only  small  insects,  the  smallest  of  the  Neuroptera;  the  described 
American  species  measure  only  3  mm.  or  less  in  length.  They  are 
characterized  by  a  reduced  wing-venation  (Fig.  349)  and  by  having 
the  body  and  wings  covered  by  a  whitish  powder. 

While  the  adults  resemble  very  slightly  other  neuropterous  insects, 
the  larvae  resemble  those  of  the  Hemerobiida^  and  allied  families  in 
form,  in  the  structure  of  their  mouth-parts,  in  their  predacious  habits, 
and  in  their  metamorphosis. 

The  larvae  have  been  seen  to  feed  upon  coccids,  aphids,  and  the 
eggs  of  the  red-spider;  they  doubtless  feed  on  other  small  insects. 
When  full-grown  they  make  a  double  cocoon  consisting  of  an  outer 
flat  layer  and  an  inner  spherical  case. 

Mr.  Nathan  Banks  ('07)  has  published  a  revision  of  the  species 
that  have  been  found  in  our  fauna.  This  includes  eight  species, 
representing  five  genera. 


CHAPTER  XII 


ORDER  EPHEMERIDA* 

The  May-Flies 

The  members  of  this  order  have  delicate  membranous  wings,  which 
are  triangular  in  outline  and  are  usually  furnished  with  a  considerable 
number  of  intercalary  veins  and  with  many 
cross-veins;  the  hind  wings  are  much  small- 
er than  the  fore  wings  and  are  sometimes 
wanting.  The  mouth-parts  of  the  adults  are 
vestigial;  those  of  the  naiads  are  fitted  for 
chewing.    The  metamorphosis  is  incomplete. 

The  May-flies  or  ephemerids  are  often 
very  common  insects  in  the  vicinity  of 
streams,  ponds,  and  lakes;  frequently  the 
surface  of  such  bodies  of  water  is  thickly 
strewn  with  them.  They  are  attracted  by 
lights ;  and  it  is  not  an  uncommon  occur- 
rence in  summertime  to  see  hundreds  of 
them  flying  about  a  single  street-lamp. 

The  May-flies  are  easily  distinguished 
from  other  net -winged  insects  by  the 
shape  of  the  wings  and  the  relative  sizes 
of  the  two  pairs  (Fig.  350). 

The  mouth -parts  of  the  adult  are 
vestigial,  as  these  insects  eat  nothing  in 
are   very    small;   they  are  composed  of 


Fig.  350— A  May-fly. 


this  state.  The  antennae 
two  short,  stout 
segments  s  u  c- 
ceededbya  slen- 
der, many-joint- 
ed bristle.  The 
thorax  is  robust, 
with  the  meso- 
thorax  predomi- 
nant; the  great 
development  of 
this  segment  is 
correlated  with 
the  large  size  of 
the  fore    wings. 

The  abdomen  is  Fig.  351. — Caudal  end  of  abdomen  of  Siphlurus  alternatus, 
lone  soft  and  ™ale:  p, /o, //,  abdominal  segments;  f,  cerci;  w/,  median 
composed  of  ten 


caudal  filament ;  p,  penis ; /,  forceps-limbs.   (After  Morgan.) 


*Ephemerida,  Ephemera:  ephemeron  (itp-^fj^pov) ,  a  May-fly. 
(308) 


EPIIEMERID. 


309 


visible  segments;  the  eleventh  segment,  which  bears  the  cerci, 
is  overlapped  by  the  tenth  (Fig.  351).  The  cerci  are  long,  slender, 
and  many-jointed;  and  in  some  species  there  is  a  median  caudal 
filament,  which  resembles  the  cerci  inform;  these  three  organs, 
the  two  cerci  and  the  median  caudal  filament,  are  commonly  referred 
to  as  the  caudal  setae.  In  the  male  there  is  a  pair  of  clasping 
organs  placed  ventrally  at  the  extremity  of  the  tenth  segment;  these 
are  usually  two-,  three-,  or  four-jointed  and  are  termed  the  forceps- 
limbs.  Eachvas  deferens  and  each  oviduct  has  a  separate  opening; 
in  the  male  these  openings  are  at  the  caudal  end  of  the  body;  in 
the  female,  between  the  seventh  and  eighth  stemites. 

In  some  May -flies  the  compound  eyes  are  divided;  one  part  of 
each,  in  such  cases,  is  a  dav-eve,  and  the  other  a  night-eve  ('seepage 
144). 

As  the  adult  May-fly  takes  no  food,  its  alimentary  canal  is  not 
needed  in  this  stage  for  purposes  of  digestion,  and,  instead  of  serving 
this  function,  acts  as  a  balloon,  being  inflated  with  air, 
thus  lessening  the  specific  gravity  of  the  bod}^  and  aid- 
ing in  flight. 

In  this  order  a  marked  cephalization  of  the  flight 
function  has  taken  place,  which  has  resulted  in  a  great 
reduction  of  the  hind  wings  in  all  living  forms.  In 
some  cases  {Ccsnis  et  al.),  this  has  gone  so  far  that  the 
hind  wings  are  wanting  (Fig.  352);  but  at  least  one 
pair  of  wings  is  present  in  all  members  of  this  order. 

When  at  rest,  the  wings  are  held  upright;  they  are 
never  folded  over  the  abdomen.     No  anal  furrow  has 
been  developed.    A  striking  feature  of  the  wings  of  May-flies  is  their 
well-known  corrugated    or  fan-like  form,  there  being  a  remarkably 


Fig.  352.— 
Cams,  a 
t  w  o- winged 
May-fly. 


Fig.  353. — Fore  wing  of  Chirotonetes  albonianicatus. 

perfect  alternation  of  so-called  convex  and  concave  veins.  Correlated 
with  the  development  of  the  fan-like  form  of  the  wings  has  been  the 
development  of  intercalary  veins,  that  is,  veins  that  did  not  arise  as 
branches  of  the  primitive  veins,  but  were  developed  in  each  case  as 
a  thickened  fold,  more  or  less  nearly  midway  between  two  preexisting 


310 


AN  INTRODUCTION  TO  ENTOMOLOGY 


veins,  with  which  primarily  it  was  connected  only  by  cross-veins. 
The  veins  labeled  IMi,  IM3,  and  ICu,  in  Figures  353  and  354  are 
good  illustrations  of  this  type  of  veins.  The  initial  I  in  these  designa- 
tions is  an  abbreviation  of  the  word  intercalary.  Thus  the  intercalary 
vein  between  veins  Cui  and  Cu2,  i.  e.,  in  the  area  Cui,  is  desig- 
nated as  vein  ICui. 

Figures  353  and  354  will  aid  in  the  determination  of  the  homol- 
ogies of   the  wing-veins  of  May-flies.     In  these  figures  convex  veins 

are  designated  by 
plus  signs  and  con- 
cave veins  by  minus 
signs.  In  attempt- 
ing to  determine 
the  homology  of  a 
vein  in  a  wing 
where  the  venation 
is  reduced,  it  should 
first  be  determined 
whether  the  vein  is 
convex  or  concave, 
as  the  corrugations 
of  the  wings  of 
May-flies  are  the 
most  persistent  fea- 
albomanicatus.  tures  of  them.  For 
a  more  detailed  ac- 
count of  this  subject,  see  Chapter  X  of  "The  Wings  of  Insects." 

The  Greek  name  Ephemeron  applied  to  these  insects  in  the  days 
of  Aristotle  was  derived  from  ephemeras,  signif^dng  lasting  but  a  day; 
and  from  that  time  to  this,  frequent  references  have  been  made  to  the 
insects  that  live  only  a  single  day.  This  brevity  of  the  life  of  these 
insects  is  true  only  of  their  existence  in  the  adult  state.  Strictly  speak- 
ing, the  May-flies  are  long-lived  insects;  some  species  pass  through 
their  life-cycle  in  a  few  weeks  in  midsimmier;  but  as  a  rule  one,  two,  or 
even  three  years  are  required  for  the  development  of  a  generation. 
The  greater  part  of  this  time  is  passed,  however,  beneath  the  surface 
of  water,  and  after  the  insect  emerges  into  the  air  and  assumes  the 
adult  form  its  existence  is  very  brief.  With  many  species  the  indi- 
viduals leave  the  water,  molt  twice,  mate,  lay  their  eggs,  and  die  in 
the  course  of  an  evening  or  early  morning;  and  although  the  adults 
of  many  genera  live  several  days,  the  existence  of  these  insects  is 
very  short  compared  with  that  of  the  adults  of  other  insects. 

The  females  lay  their  eggs  in  water.  Some  short-lived  species 
discharge  the  contents  of  each  ovary  in  a  mass.  Individuals  are  often 
found  in  which  there  project  from  the  caudal  end  of  the  body  two 
parallel  subcylindrical  masses  of  eggs,  one  protruding  from  each  of 
the  openings  of  the  oviducts.  "The  less  perishable  species  extrude  their 
eggs  gradually,  part  at  a  time,  and  deposit  them  in  one  or  the  other 
of  the  following  manners :  either  the  mother  alights  upon  the  water 


Fig.    354. — Hind    wing    of    Chirotonetes 


EPHEMERIDA 


311 


at  intervals  to  wash  off  the  eggs  that  have  issued  from  the  mouths  of 
the  oviducts  during  her  flight  or  else  she  creeps  down  into  the  water — 
enclosed  within  a  film  of  air  with  her  wings  collapsed  so  as  to  overlie 
the  abdomen  in  the  form  of  an  acute  narrowly  linear  bundle,  and 
with  her  setae  closed  together- — to  lay  her  eggs  upon  the  under  side  of 
the  stones,  disposing  of  them  in  rounded  patches,  in  a  single  layer 


Fig-  355- — Metamorphosis  of  a  ATay-fly,  Ephemera  varia:  A,  adult;  B,  naiad. 
(After  Needham.) 

evenly  spread,  and  in  mutual  contiguity."  (Eaton  'S3.) 

The  metamorphosis  of  May-flies  is  incomplete.  The  wings  are 
developed  externally,  as  in  the  Orthoptera;  the  development  of  the 
compound  eyes  is  not  retarded;  but  the  immature  forms,  or  naiads, 
are  "sidewise  developed"  to  fit  them  for  aquatic  life.  In  most  species 
the  form  of  the  body  of  the  naiads  is  elongate  and  furnished  with  two 
or  three  long  "caudal  setfe,"  that  is,  the  cerci  and  in  some  a  median 
caudal  filament;  in  these  respects  the  naiads  resemble,  to  a  greater 
or  less  degree,  the  adults  (Fig.  355);  but  except  in  the  early  instars 
the  abdomen  of  a  naiad  is  furnished  with  tracheal  gills  (Figs.  355  and 
356). 

The  tracheal  gills  are  usually  large  and  prominent;  in  most 
species  there  are  seven  pairs,  borne  by  the  first  seven 
abdominal  segments.  They  vary  greatly  in  form  in  the 
different  genera.  In  some  each  gill  is  divided  into  two 
long  narrow  branches,  which  lie  in  one  plane  (Fig.  355) ; 
in  others  the  gills  consist  of  a  scoop-shaped  covering 
piece  beneath  which  is  a  more  delicate  part  consisting 
of  many  thread-like  branches.  A  detailed  account  of 
the  various  forms  of  tracheal  gills  of  May-flies  is  given 
by  Miss  Morgan  ('13). 

The  naiads  of  May-flies  are  all  aquatic;  they  are 

very    active;  and    are    almost    entirely    herbivorous,    ^.  ^ 

feeding  largely  on  the  decaying  stems  and  leaves  of      ^\'^\   o  f  ^a 
aquatic  plants,  the  epidermis  of  moss  and  of  roots,        May-fly. 


312 


AN  INTRODUCTION  TO  ENTOMOLOGY 


algae,  and  diatoms.    The  variations  in  the  details  of  their  habits  are 
described  as  follows  by  Dr.  Needham  ('i8). 

"A  few,  \\]<.&  Hexagenia,  Ephemera,  and  Po/jmiVarcv^  are  burrowers beneath  the 
bottom  silt.  A  few  like  Ccenis  and  Ephemerella,  are  of  sedentary  habits  and  live 
rather  inactively  on  the  bottom,  and  on  silt-covered  stems.  Alany  are  active 
climbers  among  green  vegetation;  such  are  Callibails  and  Blasturiis;  and  some 
of  these  can  swim  and  dart  about  by  means  of  synchronous  strokes  of  tail  and  gills 
with  the  swiftness  of  a  minnow.  The  species  of  Leptophlebia  love  the  beds  of 
slow-flowing  streams,  and  all  the  flattened  nymphs  of  the  Heptageninae  live  in 
swiftly  moving  water,  and  manifest  various  degrees  of  adaptation  to  withstanding 
the  wash  of  strong  currents.  The  form  is  depressed,  and  margins  of  the  head  and 
body  are  thin  and  flaring,  and  can  be  appressed  closely  to  the  stones  to  deflect  the 
current." 

There  are  two  features  of  special  interest  in  the  structure  of  the 
naiads  of  May -flies:  first,  the  hypopharj-nx  bears  a  pair  of  lateral 

lobes,  which  are  believed  to  be 
vestiges  of  paragnatha;  and  sec- 
ond, the  presence  of  accessor}^ 
circulatorv^  organs  in  the  cerci 
and  median  caudal   filament 

(Fig.  35  7) • 

May -flies  exhibit  a  remark- 
able peculiarity  in  their  develop- 
ment. After  the  insect  leaves  the 
water  and  has  apparently  as- 
sumed the  adult  form,  that  is, 
after  the  wings  have  become  fully 
expanded,  it  molts  again.  These 
are  the  only  insects  that  miolt  af- 
Fig-  357-— A,  caudal  end  of  abdomen  of  tev  they  have  attained  functional 


Clo'eon  dipterum:  h,  heart;    a,    acces 
sory  circulatory   organs.    B,  twenty 


wings.    The  term  stibimago  is,  ap- 

^  -^      -  -n     -■     plied  to  the  instar  between  the 

sixth  segment  of  a  cercus :  o,  orince  m         ■     -,         j   w-i_     £      i   x  -c  j-v,^ 

blood  vessel.   (After  Zimmerman.)       naiad  and  the  final  fomi  of  the 

msect,  the  adult.  With  some 
species  the  duration  of  the  subimago  stage  is  only  a  few  minutes ; 
the  insect  molts  on  leaving  the  water;  flies  a  short  distance;  and 
molts  again.  In  others  this  stage  lasts  twenty-four  hours  or  more. 
With  many  species  of  May-flies  there  is  great  uniformity  in  the 
date  of  maturing  of  the  individuals.  Thus  immense  swarms  of  them 
will  leave  the  water  at  about  the  same  time,  and  in  the  course  of  a  few 
days  pass  away,  this  being  the  only  appearance  of  the  species  until 
another  generation  has  been  developed.  The  great  swarms  of  "lake- 
flies,"  Ephemera  smmlans,  which  appear  along  our  northern  lakes 
about  the  third  week  of  July,  afford  good  illustration  of  this  peculi- 
arity. 

Family  EPHEMERID^ 

The  May-Flies 

The  order  Ephemerida  includes  a  single  family,  the  Ephemeridas; 
the  characteristics  of  this  family,  therefore,  are  those  of  the  order, 
which  are  given  above. 


EPHEMERIDA  313 

Comparatively  few  writers  have  made  extended  studies  of  the 
classification  of  the  ephemerids ;  this  is  doubtless  partly  due  to  the  fact 
that  pinned  specimens  usually  become  shriveled  and  are  very  fragile; 
consequently  this  order  is  poorly  represented  in  most  collections  of 
insects.  In  spite  of  this,  more  than  one  hundred  species  have  been 
described  from  the  United  States.  An  important  paper  on  the 
classification  of  May-flies  is  that  by  Dr.  Needham  (05)  in  Bulletin_86 
of  the  New  York  State  Museum.  Here  are  given  keys  for  separating 
the  North  American  genera,  one  for  the  adult  insects  and  one  for 
the  naiads. 


CHAPTER  XIII 
ORDER  ODONATA* 


The  Dragon-Flies  and  the  Damsel-Flies 

The  members  of  this  order  have  Jour  membranous  wings,  which  are 
finely  netted  with  veins;  the  hind  wings  are  as  large  as  or  larger  than 
the  fore  wings;  and  each  wing  has  near  the  middle  of  the  costal  margin  a 
joint-like  structure,  the  nodus.  There  are  no  wingless  species.  The 
mouth-parts  are  formed  for  chewing.  The  metamorphosis  is  incomplete. 
Dragon-flies  and  damsel-flies  are  very  common  insects  in  the 
vicinity  of  streams,  ponds,  and  lakes; they  are  well  known  to  all  who 
frequent  such  places.    The  dragon-flies,  especially,  attract  attention 

on  account  of  their 
largesize(Fig.  358) 
and  rapid  flight, 
back  and  forth, 
over  the  water  and 
the  shores ;  the 
damsel-flies  (Fig. 
359)  are  less  likely 
to  be  noticed,  on 
account  of  their  less 
vigorous  flight. 

The  name  of 
this  order  is  evi- 
dently from  the 
Greek  word  odous, 
a  tooth;  but  the 
reason  for  applying 
it  to  these  insects  is 


Fig.  358. — A  dragon-fly,  Plathemis  lydia.  (From  San- 
born.) 


obscure;  it  may  refer  to  the  tusk-like  form  of  the  abdomen. 

In  these  insects,  the  head  is  large;  it  differs  in  shape  in  the  two 
suborders  as  described  below.  The  compound  eyes  are  large;  they 
often  occupy  the  greater  part  of  the  surface  of  the  head ;  in  many 
cases  the  upper  facets  of  the  eye  are  larger  than  the  lower,  and  in  a 
few  forms  the  line  of  division  between  the  two  kinds  is  sharpl\' 
marked.  It  is  probable  that  the  ommatidia  with  the  larger  facets 
are  night-eyes,  and  those  with  the  smaller  facets,  day-eyes.  See 
pages  142  and  1 43 .  Three  ocelli  are  present.  The  antennte  are  short ; 
they  consist  of  from  five  to  eight  segments;  of  these  the  two  basal 
ones  are  thick,  the  others  form  a  bristle-like  organ.  The  mouth- 
parts  are  well  developed ;  the  labnrni  is  prominent ;  the  mandibles 
and  maxillae  are  both  strongly  toothed;  and  the  labium  consists  of 


"Odonata:  odous  {65oCs),  a  tooth. 


(314) 


ODONA TA 


315 


Fig.   359.  —A    damsel-fly. 


three  large  lobes,  which  with  the  labrum  nearly  enclose  the  jaws  when 
at  rest.     The  thorax  is  large.     The  wings  are,  as  a  rule,  of  nearly 
similar  size  and  structure ;  they  are  richly  netted  with  veins;  and  the 
costal  border  of  each  is  divided  into  basal 
and  apical  parts  by  what  is  termed  the  nodus 
(Fig.  364,  n).    The  legs  are  rarely  used  for 
walking,  but  are  used  chiefly  for  perching, 
and  are  set  far  forward ;  the  tarsi  are  three- 
jointed.    The  abdomen  is  long,  slender,  and 
more  or  less  cylindrical;  the  caudal  end  is 
furnished  with  clasping  organs  in  the  males. 

A  remarkable  peculiarity  of  the  order  is 
the  fact  that  the  copulatory  organs  of  the 
male  are  distinct  from  the  opening  of  the 
vasa  deferentia;  the  former  are  situated  on 
the  second  abdominal  segment,  the  latter  on 
the  ninth.  Before  pairing,  the  male  conveys 
the  seminal  fluid  to  a  bladder-like  cavity  on 
the  second  abdominal  segnnent;  this  is  done 
by  bending  the  tip  of  the  abdomen  forward. 
Except  in  the  subfamily  Gomphince,  the  pair- 
ing takes  place  during  flight.  The  male 
seizes  the  prothorax  or  hind  part  of  the  head 
of  the  female  with  his  anal  clasping  organs; 
the  female  then  curves  the  end  of  the  abdomen  to  the  organs  on  the 
second  abdominal  segment  of  the  male.  Pairs  of  dragon-flies  thus 
united  and  flying  over  water  are  a  common  sight. 

The  Odonata  are  predacious,  both  in  the  immature  instars  and 
as  adults.  The  adults  feed  on  a  great  variety  of  insects,  which  they 
capture  by  flight;  and  the  larger  dragon -flies  habitually  eat  the 
smaller  ones,  but  a  large  part  of  their  food  consists  of  mosquitoes 
and  other  small  Diptera. 

The  eggs  are  laid  in  or  near  water.  All  of  the  damsel-flies  and 
many  dragon-flies  are  provided  with  an  ovipositor,  by  means  of 
which  punctures  are  made  in  the  stems  of  aquatic  plants,  in  logs,  in 
wet  mud,  etc.,  for  the  reception  of  the  eggs.  The  females  of  those 
dragon-flies  that  lack  a  well-developed  ovipositor  deposit  their  eggs 
in  various  ways.  In  some  species  the  female  flies  back  and  forth 
over  the  surface  of  the  water,  sweeping  down  at  intervals  to  touch  it 
with  the  tip  of  her  abdomen  and  thus  wash  off  one  or  more  eggs  into 
it.  In  other  species  the  eggs  are  laid  in  a  mass  on  some  object  just 
below  the  surface  of  the  water;  some  species  do  this  by  alighting 
upon  a  water-plant,  and,  pushing  the  end  of  the  abdomen  below  the 
surface  of  the  water,  glue  a  bunch  of  eggs  to  the  submerged  stem  or 
leaf;  in  other  species  the  mass  of  eggs  is  built  up  gradually;  the 
female  will  poise  in  the  air  a  short  distance  above  the  point  where  the 
mass  of  eggs  is  being  laid,  and  at  frequent  intervals  descend  with  a 
swift  curved  motion  and  add  to  the  egg-mass  and  then  return  to  her 
former  position  to  repeat  the  operation.    Still  other  species  hang  their 


316 


AN  INTRODUCTION  TO  ENTOMOLOGY 


eggs  in  long  gelatinous  strings,  on  some  plant  stem  at  the  surface  of 
the  water. 

The  metamorphosis  is  incomplete.  The  naiads  are  all  aquatic 
except  those  of  a  few  Hawaiian  damsel-flies,  which  live  on  moist  soil 
under  the  leaves  of  liliaceous  plants.  The  wings 
are  developed  externally,  and  the  development  of 
the  compound  eyes  is  not  retarded,  as  it  is  with 
larvae.  The  adaptations  for  aquatic  life  differ  in 
the  two  suborders  and  are  described  later. 

All  naiads  of  the  Odonata  are  predacious. 
The  mouth  is  furnished  with  well-developed 
mandibles  and  maxillse,  all  of  which  are  armed 
with  strong  teeth.  But  none  of  these  is  visible 
when  the  insect  is  at  rest.  The  lower  lip  is  greatly 
enlarged,  and  so  formed  that  it  closes  over  the 
jaws,  concealing  them.  For  this  reason  it  has  been 
termed  the  mask.  But  it  is  much  more  than  a 
mask;  it  is  a  powerful  weapon  of  offence.  It  is 
greatly  elongated  and  is  jointed  in  such  a  way  that 
it  can  be  thrust  out  forward  in  front  of  the  head. 
It  is  armed  at  its  extremity  with  sharp  hooks, 
for  seizing  and  retaining  its  prey  (Fig.  360). 

The  order  Odonata  is  divided  into  three  sub- 
orders.   One  of  these  suborders,  the  Anisozygop- 
tera,  is  composed  almost  entirely  of  fossil  forms, 
-Underside  being  represented  among  living  insects  by  a  single 
of  head  of  a  nmad  g^^us,  Epiophlebia,  which  is  found  in  Japan.    The 
?abium"^  unfolded.  Other  two  suborders  are  well  represented  in  this 
(After  Sharp.)       '  country ;  one  of  them  consists  of  the  dragon-flies, 
the  other  of  the  damsel-flies. 


Fig.  360. 


Suborder  ANISOPTERA* 


The  dragon-flies 
are  easily  recognized 
by  the  relative  size  of 
the  two  pairs  of  wings, 
and  by  the  attitude  of 
the  wings  when  at 
rest  (Fig.  361).  The 
hind  wings  are  larger 
than  the  fore  wings 
and  are  of  a  somewhat 
different  shape ;  but 
the  most  striking  char- 
acteristic is  the  fact 
that  the  wings  are  ex- 


The  Dragon-Flies 


Fig.  361. — A  dragon-fly,  Lihellula  luctuosa. 


tended  horizontally  when  at  rest. 

*Anis6ptera:  anisos  {ivuros),  unequal;  pteron  {Trrepov),  a  wing. 


ODONA TA 


817 


The  head  is  large,  broad,  often  semi-globose,  and  concave  behind. 
The  wings  are  very  strong.    An  important  factor  in  the  strengthening 


Fig.  362. — Wings  of  naiads  of  Gomphus  descriptus,  early  stages.  (From  Comstock 
and  Needham.) 

of  the  wings  of  these  insects  is  the  development  of  a  series  of  corruga- 
tions, which  has  resulted  in  certain  veins  becoming  convex  and  others 
concave ;  this  has  progressed  so  far  that  there  is  a  very  perfect  alterna- 
tion of  convex  and  concave  veins. 

The  habits  of  dragon-flies  have  been  carefully  studied  by  Professor 
Needham  ('18),  who  writes  as  follows: 

"Among  the  dragon-flies  are  many  superb  flyers.  The  speed  on  the  wing  of 
Trdmea  and  Anax  equals,  and  their  agility  exceeds,  that  of  swallows.  They  all 
capture  their  prey  in  flight ;  and  are  de]:)endent  on  their  wings  for  getting  a  living. 
But  the  habit  of  flight  is  very  different  in  different  groups.     Only  a  few  of  the 


Fig.  363. — Tracheation  of  the  wings  of 
(After  Needham.) 


grown  naiad  of  Gomphus  descriptus. 


318 


AN  INTRODUCTION  TO  ENTOMOLOGY 


strongest  forms  roam  the  upper  air  at  will.  There  is  a  host  of  beautiful  species,  the 
skimmers  or  Libellulida,  that  hover  over  ponds  in  horizontal  flight,  the  larger 
species  on  tireless  wings,  keeping  to  the  higher  levels.  The  stronger  flying  ^schni- 
dae  course  along  streams  on  more  or  less  regular  beats;  but  the  Gomphines  are 
less  constantly  on  the  wing,  flying  usually  in  short  sallies,  from  one  resting  place 
to  another,  and  alighting  oftener  on  stones  or  other  fiat  surfaces  than  on  vertical 
stems." 

The  characters  presented  by  the  venation  of  the  wings  of  the 
Odonata  are  much  used  in  the  classification  of  these  insects.  In 
general  the  veins  and  areas  of  the  wings  are  designated  as  in  the 
accounts  of  the  wings  of  other  orders  of  insects ;  but  there  are  certain 
features  in  the  wings  of  these  insects  that  are  peculiar  to  them. 

The  most  distinctive  feature  of  the  wings  of  the  Odonata  is  the 
fact  that  in  the  course  of  their  development  one  or  more  branches, 
usuallv  two,  of  the  medial  trachea  invade  the  area  of  the  radial  sector. 


Fig.  364. — Wings  of  Gomphus  descripHis.     In  the  front  wing,  cells  or  areas  are 
labeled;  in  the  hind  wing,  veins. 

This  results  in  vein  Rs  occupying  a  position  behind  one  or  more, 
usually  two,  of  the  branches  of  media.  Figure  362  represents  the 
tracheation  of  the  wings  of  two  naiads  of  Gomphus  descnptus;  the 
wing  shown  at  A  is  of  a  ver}^  young  naiad;  that  at  B  is  of  a  somewhat 
older  one.  In  the  wing  shown  at  A,  the  branches  of  trachea  M  are  in 
their  typical  position;  in  the  wing  shown  at  B,  trachea  Mi  is  in  front 
of  trachea  Rg.  Figure  363  represents  the  tracheation  of  a  full-grown 
naiad  of  the  same  species.  In  this  stage  of  the  development  of  the 
wings,  both  trachese  Mi  and  M2  are  in  front  of  trachea  Rs;  and  it  is 
in  this  position  that  the  veins  of  the  adult  wing  are  developed  (Fig. 
364). 


ODONA  TA 


319 


By  comparing  the  figure  of  the  wing  of  an  adult  (Fig.  364)  with 
that  of  the  full-grown  naiad  (Fig.  363),  it  will  be  seen  that  the 
oblique  vein  marked  o  is  not  a  cross-vein  but  a  section  of  vein  Rs ; 
so  too,  what  appears  to  be  another  cross- vein,  labeled  s  n,  \s  also  a 
section  of  vein  Rs;  this  section  of  vein  Rs  is  known  as  the  siibnodus. 
It  will  also  be  seen  that  what  appears  to  be  the  base  of  the  radial 
sector,  labeled  6  r,  is  a  secondarily  developed  vein  which  connects  the 
radial  sector  with  a  branch  of  media;  this  secondary  vein  is  known 
as  the  bridge.  The  beginning  of  the  formation  of  the  bridge  is  shown 
in  Figure  363.* 

The  more  important  of  the  other  special  terms  used  in  descriptions 
of  the  wings  of  dragon-flies  are  the  following :  Much  use  is  made  in 
taxonomic  work  of  the  two  series  of  cross-veins  that  are  nearest  the 
costal  margin  of  the  wing ;  those  of  these  cross-veins  that  are  situated 
between  the  base  of  the  wing  and  the  nodus  are  termed  the  antenodal 
cross-veins;  the  first  of  these  two  series  of  antenodal  cross-veins  ex- 
tend from  the  costa  to  the  subcosta;  the  second  from  the  subcosta 
to  the  radius;  the  antenodal  cross-veins  are  termed  the  anteciibital 
cross-veins  by  some  writers.    The  two  series  of  cross-veins  nearest  to 
the  costal  margin  of  the  wing  and  between  the  nodus  and  the  apex 
of  the  wing  are  termed 
the    postnodal    cross- 
veins;  the  first  of  the 
two  series  of  postnodal 
cross-veins  extend 
from  the  costa  to  vein 
Ri;   the  second,  from 
vein  Ri  to  vein   Mi; 
the    postnodal    cross- 
veins  are  termed  the 
postcubital  cross-veins 
by  some  writers.  Near 
the  base  of  the  wing 
there  is  in  dragon-flies 
a  well-marked  area  of 
the  wing,  which  is  usu- 
ally triangular  in  out- 
line (Fig.  364,  t);  this  . 
is  the  triangle;  ive-^'f  366.- Exuviae 
,1     , ,      ,  *.         1     .      of  a  naiad  of  a  drag- 
quently  the  triangle  is   on-fly,  Tetr  ago- 
divided    by    one    or  neuria. 
Fig.365.-Hmd-mtestineand  part  more  cross-veins   into 
of  the  tracheal  system  of  a  naiad  two  or  more  cells.    The  area  lying  imme- 
oi.^schnacyanea:  R,  R,  R,  R,Tec-  diatelvin  front  of  the  triangle  (Fig.  364, 
tumM  anus; /./  dorsal  tracheal  ^)  ^g  1^,-^^^  the  super  triangle;  like  the 
tubes; /z',  ventral  tracheal  tubes-     ^.        ,     ^1  •                   ^             .  ^    '  -        .      , 
M,  Malpighian    tubes.    (From  triangle  this  area  may  consist  of  a  single 
Sharp,  after  Oustalet.)                 cell  or  may  be  divided  by  one  or  more 

*The  conclusions  regarding  the  homologies  of  the  wing-veins  given  here  are 
based  on  investigations  by  Dr.  Needham  the  results  of  which  were  published  by 


320  AN  INTRODUCTION  TO  ENTOMOLOGY 

cross-veins.    Other  named  areas  are  the  basal  anal  area  (Fig.  364,  ha) 
and  the  cubital  area  (Fig.  364,  ca). 

The  writer  has  given  in  his  "The  Wings  of  Insects"  an  extended 
discussion  of  the  wings  of  Odonata,  illustrated  by  many  figures,  in- 
cluding a  plate  in  which  adjacent  veins  are  represented  in  different 
colors,  so  that  the  course  of  each  can  be  easily  followed. 

With  the  naiads  of  dragon-flies  there  is  a  remarkable  modification 
of  the  organs  of  respiration,  which  fits  these  insects  for  aquatic  life. 
The  caudal  part  of  the  alimentary  canal,  the  rectum,  is  modified  so 
as  to  constitute  a  tracheal  gill.  It  is  somewhat  enlarged ;  and  its  walls 
are  abundantly  supplied  with  tracheae  and  tracheoles  (Fig.  365). 
Water  is  alternately  taken  in  and  forced  out  through  the  anal  opening; 
by  this  process  the  air  in  the  tracheae,  with  which  the  walls  of  the 
rectiim  are  supplied,  is  purified  in  the  same  manner  as  in  an  ordinary 
tracheal  gill. 

The  rectal  tracheal  gill  of  the  naiads  of  dragon-flies  is  an  organ  of 
locomotion,  as  well  as  of  respiration.  By  drawing  water  into  the  rec- 
timi  gradually,  and  expelling  it  forcibly,  the  insect  is  able  to  dart 
through  the  water  with  considerable  rapidity.  This  can  be  easily 
observed  when  naiads  are  kept  in  an  aquariimi. 

When  the  naiad  of  a  dragon-fly  is  fully  grown  it  leaves  the  water 
to  transform.  The  skin  of  the  naiad  splits  open  on  the  back  of  the 
thorax  and  head,  and  the  adult  emerges,  leaving  the  empty  skin  of 
the  naiad  clinging  to  the  object  upon  which  the  transformation 
took  place.  Figure  366  represents  such  a  skin  clinging  to  the  stem 
of  a  water  plant. 

The  suborder  Anisoptera  includes  two  families,  the  y^schnidae 
and  the  Libellulidae ;  each  of  these  families  is  represented  in  our 
fauna  by  many  genera  and  species.  These  are  enumerated  in  the 
"Catalogue  of  the  Odonata  of  North  America"  by  Muttkowski  ('10). 
The  two  families  can  be  separated  by  the  characters  given  below. 

Family  ^SCHNID^ 
The  Mschnids 

In  this  family  the  triangle  (Fig.  364,  t)  is  about  equally  distant 
frorn  the  arculus  (Fig.  364,  ar)  in  the  fore  and  hind  wings;  and, 
except  in  the  genus  Cordulegdster,  there  is  an  oblique  brace-vein 
extending  back  from  the  inner  end  of  the  stigma  (Fig.  364). 

The  seschnids  are  mostly  large  species ;  among  them  are  the  largest, 
fleetest,  and  most  voracious  of  our  dragon-flies.  Some  of  them  roam 
far  from  water  and  are  commonly  seen  coursing  over  lawns  in  the 
evening  twilight;  but  most  of  them  fly  over  clear  water. 


Comstock  and  Needham  ('gS-'gg)  and  by  Needham  ('03).  These  conclusions 
have  been  questioned  by  Tillyard  ('22)  and  by  Schmieder  {'22);  but  I  do  not  feel 
that  it  would  be  wise  to  modify  them  before  a  much  more  extended  investigation 
of  the  subject  has  been  made. 


ODONATA  321 

Family  LIBELLULID^ 

The  Lihellulids  or  Skimmers 

In  this  family  the  triangle  in  the  hind  wing  is  much  nearer  the 
arculus  than  is  the  triangle  of  the  fore  wing;  and  there  is  no  oblique 
brace- vein  extending  back  from  the  inner  end  of  the  stigma,  as  in 
the  ceschnids. 

This  is  a  large  family  including  many  of  our  commonest  and 
best-known  species  of  dragon-flies ;  many  of  them  are  familiar  figures 
flying  over  ponds  and  ditches  and  by  roadsides.  Most  of  them  are 
of  well-sustained  flight,  and  are  seen  continually  hovering  over  the 
surface  of  still  water;  this  suggested  the  common  name  skimmers 
which  has  been  applied  to  them. 


Fig-  367. —  A  damsel-fly. 


Suborder  ZYGOPTERA* 
The  Damsel-Flies 

The  damsel-flies  differ  from  the 
dragon-flies  in  that  the  two  pairs 
of  wings  are  similar  in  form  and 
are  either  folded  parallel  with  the 
abdomen  when  at  rest  (Fig.  367) 
or  up  tilted  {Testes).  The  head  is 
transverse,  each  eye  being  borne 
by  a  lateral  prolongation  of  the 
head.  The  females  possess  an 
ovipositor  by  means  of  which  the 
eggs  are  placed  in  the  stems  of 
aquatic  plants,  sometimes  beneath 
the  surface  of  the  water. 

The  name  of  the  suborder 
probably  refers  to  the  fact  that 
the  wings  are  brought  together 
when  at  rest. 


Fig.  368. — Wing  of  Lestes  rectangularis:  0,  oblique  vein;  br,  the  bridge. 


*Zyg6ptera:  zyg07i  (^vy6v),  yoke;  pteron  {wrepbu),  a  wing. 


322 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Unlike  the  dragon-flies,  the  damsel-flies  are  comparatively  feeble 
in  their  flight.  They  are  found  near  the  margins  of  streams  and 
ponds,  in  which  the  immature  stages  are  passed. 

Most  of  the  features  in  the  venation  of  the  wings  of  dragon-flies 
described  on  earlier  pages  are  also  characteristic  of  the  wings  of  damsel- 
flies.     Figure  368  represents  an  entire  wing  of  Lestes  rectangularis; 


Fig.  369. — Base  of  fore  wing  of  Lestes  rectangularis:  br,  the  bridge;  q,  quadrangle; 
sq,  subquadrangle. 

in  this  figure  o  indicates  the  oblique  vein,  and  br  the  bridge.  In 
Figure  369  the  base  of  this  wing  is  represented  more  enlarged,  and 
the  principal  veins  are  lettered. 

In  the  suborder  Zygoptera  the  cubitus  and  the  first  branch,  vein 
Cui,  extend  in  a  comparatively  direct  course  from  the  base  of  the 
wing  outward  (Fig.  369);  the  abrupt  bends  in  these  veins  in  the 
region  of  the  triangle,  which  are  so  characteristic  of  the  Anisop- 
tera,  are  only  sHghtly  developed  here.  This  results  in  the  areas 
corresponding  to  the  triangle  and  the  supertriangle  of  the  Anisop- 
tera  being  in  direct  line  and  forming  an  area  which  is  often 
quadrangular;  this  area  is  termed  the  quadrangle  (Fig.  369,  q).    In  a 

large  part  of  this  or- 
der the  cross-vein  sep- 
arating the  parts  of 
the  quadrangle  corre- 
spond ingtothetriangle 
and  the  supertriangle 
of  the  Anisoptera  is 
lacking,  in  which  case 
the  quadrangle  con- 
sists of  a  single  cell 
Fig.  370.— Base  of  wing  of  Heliocharis.        ^""'■"-^       (Fig.  369,  q).    In  some 

members  of  this  sub- 
order it  is  present;  in  Figure  370,  representing  the  base  of  a  wing 
of  Heliocharis,  the  two  cells  of  the  quadrangle  are  labeled  /  and  .y  to 


ODONA TA 


323 


facilitate  comparison  with  figures  of  wings  of  Anisoptera.     In  certain 
other  members  of  this  subor- 
der the  quadrangle  is  divided 
into  several  cells  by  cross-veins 
(Fig.  371). 

The  cubital  area  of  the 
wing  is  usually  quadrangular 
in  outline  in  the  Zygoptera, 
and  is  termed  the  subquad- 
rangle  (Fig.  369,  sq).  Like 
the  quadrangle,  it  may  con- 
sist of  a  single  cell  or  it  may 
be  divided  by  cross-veins  (Fig. 
371)- 

The  naiads  of  damsel-flies  have  three  plate-like  tracheal  gills  at 
the  caudal  end  of  the  body  (Fig.  372).  The  structure  of  these  gills 
is  illustrated  by  Figure  373 ;  at  A  is  represented  an  entire  gill  showing 
the  tracheas;  and  at  B,  part  of  a  gill  more  magnified,  showing  both 
tracheae  (T)  and  tracheoles  (t). 


Fig.  371. — Base  of  wing  of  Helcerina. 


Fig.  372.— Naiad  of  a 
damsel-fly,  Argia. 


Fig.  373. — Tracheal  gill  of  a  damsel-fly: 

A,  entire  gill  showing  the  tracheas; 

B,  part  of  gill  more  magnified,  show- 
ing both  tracheae  (T)  and  tracheoles 
(t). 


The  suborder  Zygoptera  includes  two  families,  the  Agrionidas 
and  the  Coenagrionidae.  The  genera  and  species  of  these  families  are 
enumerated  by  Muttkowski  ('10).  The  two  families  can  be  separated 
as  follows. 

A.       Wings  with  many,  at  least  five,  antenodal  cross-veins .Agrionid^ 

AA.    Wings  usually  with  only  two  antenodal  cross-veins,  rarely  with  three  or 

four CcENAGRIONIDiE 


324  AN  INTRODUCTION  TO  ENTOMOLOGY 

Family  AGRIONID^ 
TJte  True  Agrionids 

In  the  Agrionidas  the  wings  are  furnished  with  many  antenodal 
cross-veins;  and,  although  the  wings  are  narrow  at  the  base,  they 
are  not  so  distinctly  petiolate  as  in  the  next  family.  These  insects 
may  be  termed  the  true  agrionids,  as  owing  to  a  misapplication  of  the 
generic  name  Agrion  the  members  of  the  next  family  have  been 
incorrectly  known  as  the  agrionids. 

Here  belong  the  most  beautiful  of  our  damsel-fiies,  whose  metallic 
blue  or  green  colors  are  sure  to  attract  attention.  They  are  feeble  in 
flight  and  do  not  go  far  from  the  banks  of  the  pond  or  stream  in 
which  they  were  developed. 

There  are  only  two  genera  of  this  famih'  in  our  fauna.  These  are 
Agrion,  whjch  has  been  commonly  known  as  Calopteryx,  and  HetcB- 
rina.  In  Agrion  the  wings  are  broad  and  spoon-shaped.  In  Hetce- 
rlna  the  wings  are  rather  narrow,  and  in  the  males  the  base  of  one  or 
both  pairs  is  red. 

Family  CCENAGRIONID^ 

The  Stalked-winged  Damsel-Flies 

The  members  of  this  famiily  are  easily  recognized  by  the  shape 
of  their  wings,  which  are  long,  narrow,  and  very  distinctly  petiolate 
(Fig.  368);  and  by  the  fact  that  in  each  wing  there  are  only  twc 
antenodal  cross-veins,  except  in  a  few  cases  where  there  are  three  or 
four. 

To  this  family  belong  the  smallest  of  our  damsel-flies;  but  while 
our  species  are  of  small  or  moderate  size,  there  exist  in  the  tropics 
species  that  are  the  largest  of  the  Odonata.  Some  of  our  species  are 
dull  in  color;  but  many  are  brilliant,  being  colored  with  green,  blue, 
or  yellow.    This  family  includes  the  greater  number  of  our  damsel-flies. 


CHAPTER  XIV 


ORDER  PLECOPTERA* 

The  Stone-Flies 

The  members  of  this  order  have  four  membranous  wings.  In  some 
genera  the  branches  of  the  principal  veins  are  reduced  in  number  and 
there  are  comparatively  few  cross-veins;  in  others,  accessory  veins  are 
developed  and  there  are  many  cross-veins;  in  most  genera  the  hind  wings 
are  much  larger  than  the  fore  wings,  and  are  folded  in  plaits  and  lie 
upon  the  abdomen  when  at  rest.  The  mouth-parts  are  of  the  chewing 
type  of  structure,  btit  are  frequently  vestigial  in  the  adult.  The  cerci  are 
usually  long  and  many-joi^ited.      The  metamorphosis  is  incomplete. 

Members  of  this  order  are  common  insects  in  the  vicinity  of  rapid 
streams  and  on  wave-washed  rocky  shores  of  lakes;  but  they  attract 
httle  attention  on  account  of  their  inconspicuous  colors  and  secretive 
habits.  They  are  called  stone-flies  because  the  immature  forms  are 
very  abundant  under  stones  in  the  beds  of  streams. 

In  the  adults  the  body  is  depressed,  elongate,  and  with  the  sides 
nearly  parallel  (Fig.  374). 
The  prothorax  is  large.  The 
antennas  are  long,  tapering, 
and  many-jointed.  The 
mouth-parts  are  usually 
greatly  reduced.  In  some 
genera  the  mandibles  are  al- 
most membranous,  but  in 
others  they  are  firm  and 
toothed,  being  well  fitted 
for  biting.  The  maxillse 
exhibit  variations  in  the  de- 
gree of  their  reduction  simi- 
lar to  those  shown  by  the 
mandibles.  The  maxillary 
palpi  are  five-jointed.  The 
labial  palpi  are  three-joint- 
ed. The  legs  are  widely 
separated,  except  the  fore 
legs  in  the  Pteronarcidaj; 
the  tarsi  are  three-jointed.  The  hind  wings  are  a  little  shorter  than 
the  fore  wings,  but  usually,  owing  to  the  expansion  of  the  anal  area, 
they  are  considerably  larger  than  the  fore  wings;  in  a  few  genera  the 
hind  wings  are  smaller  than  the  fore  wings ;  in  some  species  the  wings 
of  the  male  are  greatly  reduced  in  size,  and  in  others  the  males  are 
wingless.    When  at  rest,  the  wings  are  folded  in  plaits  and  lie  upon  the 

*Plec6ptera:  plecos  {irXiKos),  plaited;  pleron  (jrTepSv),  a  wing. 
(325) 


Fig.  374. — A  stone-fly,  Pteronarcys  dorsata. 


326  AN  INTRODUCTION  TO  ENTOMOLOGY 

abdomen,  as  shown  on  the  left  side  of  Figure  374.  The  cerci  are  usu- 
ally long  and  many-jointed;  but  they  are  rudimentary  in  the 
Nemouridae. 

The  stone-flies  are  unattractive  in  appearance;  in  most  of  them 
the  colors  are  obscure,  being  predominantly  black,  brown,  or  gray;  but 
some  of  them  that  are  active  in  the  da>i:ime  and  inhabit  foliage  are 
green.  Their  powers  of  flight  are  quite  limited;  they  are  usually 
found  crawling  about  on  stones  or  on  plants  near  streams.  Several 
of  the  smaller  species  appear  in  the  adult  state  upon  snow  on  warm 
days  in  the  latter  half  of  winter.  They  become  more  nimierous  in 
early  spring  and  often  find  their  way  into  our  houses.  The  most 
common  one  of  these  in  central  New  York  is  the  small  snow-fly, 
Cdpnia  pygnKsa. 

It  is  probable  that  most  adult  stone-flies  eat  nothing;  this  can 
be  inferred  from  the  reduced  condition  of  their  mouth-parts.  But  it 
has  been  shown  by  Newcomer  ('18)  that  several  species  of  Tceniopteryx, 
which  are  equipped  with  well-developed  mouth-parts,  feed  upon  the 
buds  and  leaves  of  plants.  One  species  in  particular,  T.  pactfica,  is  a 
serious  pest  in  the  Wenatchee  Valley,  Wash.,  where  it  bites  into  the 
buds  of  fruit  trees. 

One  of  the  more  striking  features  of  the  venation  of  the  wings  of  the  Plecoptera 
is  a  lack  of  uniformity  in  the  number  and  courses  of  the  subordinate  veins.  Not 
only  are  striking  differences  in  wing-venation  to  be  observed  between  different 
individuals  of  the  same  species,  but  frequently  the  wings  of  the  two  sides  of  an 
individual  will  vary  greatly  in  venation.  This  is  especially  true  as  to  the  number 
of  cross-veins  and  the  branching  of  the  veins  in  the  distal  parts  of  the  wings. 
On  the  other  hand,  the  characters  presented  by  the  trunks  of  the  principal  veins 
are  quite  constant. 

There  is  one  characteristic  of  the  wings  of  the  Plecoptera  that  is  so  constant 
that  it  may  be  considered  an  ordinal  character.  This  is  the  fact  that  in  the  wings 
of  the  adult  the  radial  sector  of  the  hind  wings  is  attached  to  media  instead  of  to 
radius  (Fig.  376b).  This  switching  of  the  radial  sector  of  the  hind  wings  is  true 
only  of  the  venation  of  the  adult.  In  the  wings  of  naiads  the  trachea  Rs  is  a 
branch  of  trachea  R. 

There  are  certain  features  of  the  wings  of  Plecoptera,  which,  although  not 
always  constant,  occur  in  so  large  a  portion  of  the  members  of  the  order  that  they 
may  be  considered  characteristic;  these  are  the  following,  all  of  which  are  repre- 
sented in  Figure  376/?.-  The  presence  of  the  radial  cross-vein  (/-).  The  absence  of 
cross- veins  in  cell  R  and  in  the  basal  part  of  area  Ri.  (Cross- veins  are  found  in 
cell  R  in  Pleronarcys.)  The  strengthening  in  the  fore  wings  of  the  area  between 
media  and  vein  Cui  and  of  that  between  veins  Cuj  and  Cu^  by  the  development 
of  many  cross- veins.  The  reduction  of  media  to  a  two-branched  condition.  The 
reduction  of  the  radial  sector  to  a  two-branched  condition.  (This  reduction  of  the 
radial  sector  is  apparent  only  after  an  extended  study  of  the  wings  of  stone-flies. 
In  many  cases,  of  which  the  form  represented  by  Figure  3766  is  one,  accessory 
veins  have  been  developed  on  vein  R2  -I-3  which  appear  to  be  the  primitive  branches 
of  the  radial  sector;  but  these  accessory  veins  are  very  inconstant  in  number  and 
position.)    And  the  unbranched  condition  of  the  first  anal  vein. 

In  concluding  this  brief  summary  of  the  special  features  of  the  wings  of  the 
Plecoptera  it  seems  desirable  to  define  some  terms  frequently  used  by  writers  on 
this  order. 

The  transverse  cord. — In  many  genera  of  this  order  there  is  a  nearly  continuous 
series  of  cross-veins  extending  across  each  wing  just  beyond  the  middle  of  its 
length;  this  series  of  cross- veins  is  termed  the  anastomosis  by  many  writers  on 
the  Plecoptera.  As  it  is  not  formed  by  an  anastomosing  of  veins,  the  use  of  the 
term  transverse  cord  is  preferable. 


PLECOPTERA 


327 


The  pterostigma. — In  most  members  of  this  order  a  specialized  pterostigma  has 
not  been  developed;  but  the  term  pterostigma  is  commonly  applied  to  the  cell 
beyond  the  end  of  the  subcosta  and  between  the  costa  and  vein  Rj,  even  though 
it  is  of  the  same  color  and  texture  as  the  remainder  of  the  wing. 

The  basal  anal  cell. — A  very  constant  feature  of  the  anal  area  of  the  wings  of 
Plecoptera  is  the  presence  of  a  cross- vein  near  the  base  of  the  wing,  which  extends 
from  the  first  anal  vein  to  the  second.  The  cell  that  is  closed  by  this  cross- vein  is 
termed  the  basal  anal  cell  (Fig.  376^,  ba). 

The  females  drop  their  eggs  in  a  mass  in  water.  I  have  taken 
females  of  Perla  and  of  Pteronarcys  at  lights,  each  with  a  mass  of 
eggs  hanging  from  the  abdomen. 

The  metamorphosis  is  incomplete.    The  immature  forms  are  all 
aquatic.    These  naiads  are  common  on  the  lower  surface  of  stones  in 
rapids.  They  can  be  found  easily  by  lifting  stones  from  such  situations 
and  turning  them  over  quickly,  when  the  na- 
iads  will  be  found  clinging  to  the  stones 
with  their  fiat  bodies  closely  appressed  to 
them  and  their  legs,  antennse,  and  cerci  ra- 
diating on  the  surface  of  the  stone,  but  they 
are  apt  to  run  away  quickly. 

The  naiads  of  stone-flies  live  only  in 
well-aerated  water ;  they  are  not  found  in 
stagnant  water  or  in  foul  streams.  They  are 
said  to  feed  on  other  aquatic  insects,  includ- 
ing smaller  individuals  of  their  own  species ; 
but  according  to  the  observations  of  Dr. 
P.  W.  Claassen  they  are  largely  vegetable 
feeders. 

The  body  is  depressed  (Fig.  375);  the 
antennge  are  long,  so  too  are  the  cerci.  Most 
species  possess  tracheal  gills,  situated  usually 
on  the  ventral  side  of  the  thorax  just  be- 
hind the  base  of  each  leg ;  but  tracheal  gills 
are  found  in  some  species  either  on  the  un- 
der side  of  the  head,  on  the  basal  abdom- 
inal segments,  or  at  the  tip  of  the  abdo- 
men. A  large  number  of  the  smaller  species  are  destitute  of 
tracheal  gills;  in  these  the  air  supply  is  absorbed  through  the  thin 
cuticula  of  the  ventral  surface.  The  colors  of  naiads  are  often  brighter 
than  those  of  adults. 

When  full-grown  the  naiads  leave  the  water  and  transform  on  some 
near-by  object.  The  empty  exuvise  are  often  found  clinging  to  stones 
or  logs  projecting  from  water  or  on  the  banks  of  streams. 

According  to  a  recent  classification  of  this  order,  that  of  Tillyard 
('21),  it  includes  seven  families;  but  only  four  of  these  families  are 
represented  in  our  fauna.  A  monograph  of  the  North  American 
species  of  the  order  is  in  preparation  by  Professor  J.  G.  Needham 
and  Professor  P.  W.  Claassen ;  this  is  nearly  completed  and  probably 
will  be  published  soon.  The  four  families  of  our  fauna  can  be  separat- 
ed by  the  following  table. 


Fig-  375-  —  Naiad  of  a 
stone-fly,  Acroneura. 


328 


AN  INTRODUCTION  TO  ENTOMOLOGY 


A.       Anal  area  of  the  fore  wings  with  two  or  more  series  of  cross-veins  (Fig. 

376a).  p.  328 Pteronarcid^ 

AA.    Anal  area  of  the  fore  wings  with  not  more  than  a  single  series  of  cross- veins, 
usually  with  no  cross-veins  beyond  the  basal  anal  cell. 
B .    Media  of  the  fore  wings  separating  from  radius  gradually,  the  two  forming 

a  sharp  angle  (Fig.  3766).  p.  328 Perlid^e 

BB.    Media  of  the  fore  wings  separating  from  radius  abruptly,  the  two  form- 
ing a  blunt  angle  (Fig.  376c). 
C.       Anal  area  of  the  fore  wings  with  a  forked  vein  arising  from  the  basal 
anal  cell  (Fig.  376a).    Cerci  vestigial,  p.  330.  Nemourid^e 

CC.    Anal  area  of  the  fore  wings  with  only  simple  veins  arising  from  the 

basal  anal  cell  (Fig.  376^).     Cerci  well  developed,  p.  330 

Capniid^ 

Family  PTERONARCID^ 

This  is  a  small  family  which  is  represented  in  North  America  by 
only  two  genera  and  by  but  few  species. 

Pterondrcys. — This  genus  includes  the  largest  of  our  stone-flies. 
Figure  374  represents  a  common  species.    The  venation  of  the  wings 


Fig.  376a. — Wings  of  Pteronarcella  badia. 

is  reticulate ;  the  reticulation  is  irregular  and  extends  in  the  fore  wings 
from  the  costa  through  the  anal  area. 

A  remarkable  feature  of  members  of  this  genus  is  that  vestiges  of 
tracheal  gills  are  retained  by  the  adults. 

Pteronarcella. — This  genus  includes  smaller  species  than  the  pre- 
ceding one,  and  the  venation  of  the  wings  is  more  regular  than  in 
Pteronarcys  (Fig.  376a). 

Family  PERLID^ 


The  members  of  this  family  differ  from  the  Pteronarcidae  in  the 
smaller  number  of  cross-veins  in  the  anal  area  of  the  fore  wings, 


PLECOPTERA 


329 


there  being  usually  no  cross-veins  beyond  the  basal  anal  cells  (Fig. 
3766);  and  they  differ  from  the  following  families  in  that  media  of 


2d  A 
Fig.  3766. — Wings  of  Isogeniis  sp. 


Fig.  376c. — Wings  of  Nemoiira  sp. 


330 


AN  INTRODUCTION  TO  ENTOMOLOGY 


the  fore  wings  separates  from  radius  gradually,  the  two  forming  a 
sharp  angle  (Fig.  3766). 

This  is  the  largest  of  the  families,  including  a  large  portion  of  the 
genera  and  species  found  in  our  fauna;  fourteen  genera  have  been 
described  from  this  region. 

Family  NEMOURID^ 

In  this  and  the  following  family  the  media  of  the  fore  wings 
separates  from  radius  abruptly,  the  two  forming  a  blunt  angle  (Fig. 
376c).  In  this  family  the  second  and  third  anal  veins  of  the  fore 
wings  coalesce  for  some  distance  beyond  the  basal  anal  cell,  forming  a 
forked  vein  (Fig.  376c),  and  the  cerci  are  vestigial. 

The  family  is  represented  in  our  fauna  by  nine  genera.  Our  more 
common  representatives  are  small,  dusky,  and  grayish  species  that 
are  found  emerging  throughout  the  spring  of  the  year. 

Family  CAPNIID^ 

In  this  family,  as  in  the  Nemouridae,  the  media  of  the  fore  wings 
separates  from  radius  abruptly,  the  two  forming  a  blunt  angle  (Fig. 
376(i) ;  but  in  this  family  there  are  in  the  anal  area  of  the  fore  wings 


A'4+5 


Fig.  376<f. — Wing  of  Capnia  sp. 

only  simple  veins  arising  from  the  basal  anal  cell  (Fig.  376c/),  and  the 
cerci  are  well  developed.  This  is  a  small  family  which  is  represented 
in  our  fauna  by  only  three  genera. 

The  members  of  this  family  that  are  most  often  seen  are  the  little 
black  species  of  Capnia  that  appear  on  snow  on  warm  days  in  the 
latter  half  of  winter  and  in  early  spring.  The  naiads  of  these  live  chiefly 
in  small  brooks. 


CHAPTER  XV 
ORDER  CORRODENTIA* 


Fig.  377. — A  winged   psocid, 
Cerastipsocus    venosus. 


The  Psocids  and  the  Book-Lice 

The  winged  members  of  this  order  have  Jour  membranous  wings, 
with  the  veins  prominent,  but  with  comparatively  Jew  cross-veins;  the 
Jore  wings  are  larger  than  the  hind  wings; 
and  both  pairs  when  not  in  use  are  placed 
rooj-like  over  the  body,  being  almost  vertical, 
and  not  Jolded  in  plaits.  The  mouth-parts 
are  formed  Jor  chewing.  The  metamorphosis 
is  gradual. 

The  best-known  representatives  of  this 
order  are  the  minute,  soft-bodied  insects 
which  are  common  in  old  papers,  books, 
and  neglected  collections  and  which  have 
received  the  popular  name  book-lice. 
These  low,  wingless  creatures  fonn,  how- 
ever, but  a  small  part  of  the  order.  The  more  typical  winged  forms 
(Fig.  377)  bear  a  strong  resemblance  to  plant-lice  or  aphids.  The  body 

is  oval,the  head  free, and  the  pro  tho- 
rax small.  The  fore  wings  are  larger 
than  the  hind  wings;  and  both 
pairs  when  not  in  use  are  placed  roof- 
like over  the  body,  being  almost 
vertical,  and  not  folded  in  plaits. 
The  wing-veins  are  prominent,  but 
the  venation  of  the  wings  is  reduced. 
The  tarsi  are  two-  or  three-jointed. 
Cerci  are  wanting. 

The  mouth-parts  are  of  especial 
interest  on  account  of  the  presence 
of  well-preserved  paragnatha.  Fig- 
ure 378  represents  the  mouth-parts 
of  the  common  book-louse,  Troctes 
divinatdrius,  as  figured  by  Snodgrass 
('05).  The  mandibles  (B)  are  of  the 
ordinary,  strong,  heavy,  biting  type. 
The  maxilla  (m)  consist  each  of  a 
body  piece,  a  weakly  chitinized  terminal  lobe,  and  a  four-jointed 
palpus.  The  paragnathus  (f,  J)  is  represented  in  the  figure  at  A, 
with  the  maxilla;  it  hes  above  the  maxilla  and  is,  therefore,  in  its 
typical  position  between  the  maxilla  and  the  mandible  of  the  same 

*Corrodentia :  Latin  corrodens,  gnawing. 
fS.Sl) 


Fig-  378. — Mouth-parts  of  a  book- 
louse,  Troctes  divinatorius:  A ,  max- 
illa and  paragnathus  of  right  side, 
ventral  view;  w,  maxilla;  /,  /, 
paragnathus;  p,  protractor  mus- 
cle; r,  retractor  muscle.  5,  man- 
dibles. C,  labium,  ventral  view; 
p,  palpus.   (After  Snodgrass.) 


332 


AN  INTRODUCTION  TO  ENTOMOLOGY 


side.     Note  that  the  figure  is  a  ventral  view,  hence  the  paragnathus 
is  represented  as  passing  beneath  the  maxilla.    The  paragnatha  have 


Fig.  379. — The  wings  of  a  psocid. 

been  known  as  the  fitrccc  maxillares.    The  labium  {C)  bears  a  pair  of 
one-jointed  palpi. 

The  venation  of  the  wings  is  distinctively  characteristic  in  this  order. 
The  venation  is  more  or  less  reduced;  "but  its  most  characteristic 
feature  is  the  bracing  of  the  wing  by  anastomoses  of  the  principal 


Fig.  380. — Fore  wing  of  a  full-grown  nymph  of  a  psocid. 

veins  instead  of  b}'  cross-veins.  This  is  well  shown  by  the  vvings  of 
Psocus  (Fig.  379).  The  determination  of  the  homologies  of  the 
wing-veins  in  this  insect  was  accomplished  by  a  study  of  the  trach ca- 
tion of  the  wings  of  nymphs.  Figure  380  represents  the  tracheation 
of  a  fore  wing  of  a  full-grown  nymph  of  Psocus. 

There  are  no  cross-veins  in  the  wings  of  Psocus;  the  arculus  (ar) 
in  the  fore  wing  is  merely  the  base  of  media,  and  what  appear  as 


CORRODENTIA  333 

cross-veins  in  the  central  portion  of  the  wing  are  sections  of  media 
and  cubitus.  In  some  genera,  however,  the  radial  cross-vein  is  present, 
and  in  some,  instead  of  an  anastomosis  of  veins  M  and  Cui,  these 
veins  are  connected  by  a  medio-cubital  cross- vein.     - 

The  metamorphosis  is  gradual.  The  nymphs  resemble  the  adults 
in  the  form  of  the  body,  but  lack  wings  and  ocelli  in  those  species 
that  are  winged  in  the  adult;  in  the  wingless  species  the  differences 
between  the  young  and  the  adult  are  even  less  marked. 

The  Corrodentia  of  the  United  States  and  Canada  represent  two 
families,  which  can  be  separated  as  follows. 

A.       Wings  well  developed;  ocelli  present Psocid^ 

AA.    Wings  absent  or  vestigial;  ocelli  absent AtropiD/E 

Family  PSOCID^ 
The  Psocids 

The  family  Psocidae  includes  the  more  typical  members  of  the 
Corrodentia,  those  in  which  the  wings  are  well  developed  (Fig.  377). 
Usually  the  wings  extend  much  beyond  the  end  of  the  abdomen;  but 
short-winged  forms  occur  in  species  which  ordinarily  are  long-winged. 
Of  course  the  young  of  all  are  wingless,  and  there  is  a  gradual  develop- 
ment as  the  insect  matures.  The  antenna  consist  of  only  thirteen 
segments;  this  will  enable  one  to  separate  the  immature  forms  from 
the  Atropidce,  in  which  the  antennae  have  a  greater  ntmiber  of  segments. 

The  psocids  occur  upon  the  trunks  and  leaves  of  trees,  and  on 
stones,  walls,  and  fences.  They  feed  upon  lichens,  fungi,  and  probably 
other  dry  vegetable  matter.  They  are  sometimes  gregarious.  I  have 
often  seen  communities  of  a  hundred  or  more  closely  huddled  together 
on  the  trunks  of  trees,  feeding  on  lichens. 

The  eggs  are  laid  in  heaps  on  leaves,  branches,  and  the  bark  of 
trunks  of  trees.  The  female  covers  them  with  a  tissue  of  threads. 
It  is  believed  that  both  sexes  have  the  power  of  spinning  threads. 
The  silk  is  spun  from  the  labium. 

More  than  seventy  species,  representing  eleven  genera,  have  been 
described  from  our  fauna. 


Family  ATROPIDCE 
The  Book-Lice  and  Their  Allies 

The  family  Atropidai  includes  small  Corrodentia,  which  are 
wingless  or  possess  only  vestigial  wings.  The  most  commonly  ob- 
served species  are  those  known  as  book-lice,  which  are  the  minute 
soft-bodied  insects  often  found  in  old  books  (Fig.  381).  Of  these  the 
two  following  species  are  the  best  known. 

Troctes  divinatorius. — This  is  a  wingless  species  which  measures 
about  I  mm.  in  length;  it  is  grayish  white,  with  black  eyes. 


334 


AN  INTRODUCTiaN  TO  ENTOMOLOGY 


Atropos  pulsatoria. — In  this  species  the  fore  wings  are  represented 
by  small  convex  scales;  it  is  of  a  pale  yellowish  white  color  and  is  a 
little  more  than  i  mm.  in  length. 

Each  of  these  species  has  been  known  as  the  death-watch,  as  they 
have  been  believed  by  superstitious  people  to  make  a 
ticking  sound  that  presaged  the  death  of  some  person 
in  the  house  where  it  is  heard.  It  is  not  probable  that 
such  minute  and  soft  insects  can  produce  sounds 
audible  to  human  ears.  The  sounds  heard  were  prob- 
ably made  by  some  wood-boring  beetles,  Anobiidce, 
which  are  also  known  as  the  death-watch. 

Book-lice  are  found  chiefly  in  damp,  well-shaded 
rooms,  not  in  general  use.  They  do  not  attack  man, 
but  feed  upon  dead  vegetable  and  animal  matter,  as 
the  paste  in  book-bindings,  wall-paper,  and  photo- 
graphs. They  rarely  occur  in  sufficient  numbers  to 
do  serious  injury.  They  can  be  destroyed  by  fimiigating  the  infected 
room  with  hydrocyanic  acid  gas.  This,  however,  should  be  used  only 
by  experienced  persons.  Ordinarily  a  prolonged  heating  and  drying 
of  the  room  will  be  sufficient  to  destrov  them. 


CHAPTER  XVI 
ORDER  MALLOPHAGA* 

The  Bird-Lice 

The  members  of  this  order  are  wingless  parasitic  insects  with  chewing 
mouth-parts.     Their  development  is  without  metamorphosis. 

The  bird-lice  resemble  the  true  lice  in  form,  being  wingless,  and 
having  the  body  more  or  less  flattened ;  certain  species  that  infest 
domestic  fowls  are  well-known  examples.  These  insects  differ  from 
the  true  lice  in  having  chewing  mouth-parts.  They  feed  upon  feath- 
ers, hair,  and  dermal  scales,  while  the  true  lice,  which  constitute  the 
order  Anoplura,  have  sucking  mouth  parts,  feed  upon  blood,  and 
infest  only  mammals. 

The  Mallophaga  infest  chiefly  birds,  and  on  this  account 
the  term  bird-lice  is  applied  to  the  entire  group;  a  few  genera, 
however,  are  parasitic  upon  mammals.  Some  writers  term  the  Mallo- 
phaga the  biting  lice,  which  is  a  more  accurate  designation;  but  the 
name  bird-lice  is  more  generally  used. 

The  bird-lice  are  small  insects.  The  more  common  species  range 
from  I  mm.  to  5  mm.  in  length.  The  mouth-parts  are  on  the  under 
side  of  the  head,  the  most  anterior  part  of  the  head  being  a  greatly 
enlarged  clypeus;theyareof  the  mandibulate  type;  and  paragnatha 
("furcce  maxillares")  have  been  found  in  several  species  (Snod- 
grass  '05).  There  is  a  pair  of  "simple  eyes"  located  in  the  lateral 
margins  of  the  head.  The  structiire  of  these  eyes  has  not  been  de- 
scribed ;  but  judging  from  their  position  they  are  probably  degenerate 
ommatidia  and  not  ocelli.  The  front  legs  are  shorter  than  the  others 
and  are  used  to  convey  food  to  the  mouth. 

There  is  an  interesting  correlation  between  the  habits  of  these 
insects  and  the  structure  of  their  feet.  The  tarsi  of  those  species 
that  feed  on  mammals  are  one-clawed  and  fitted  for  folding  against 
the  tibiae;  they  are  organs  well  adapted  for  clinging  to  hairs.  Those 
species  that  feed  on  birds  have  two-clawed  tarsi  and  are  better  fitted 
for  running.  The  above  distinction  is  not  quite  accurate,  as  a  few 
two-clawed  species  feed  on  kangaroos,  wallabies,  and  wombats. 


"Mallophaga:  niallos  (fiaWis),  wool;  phagein  (^a7etv),  to  eat. 
(335) 


336  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  accompanying  figures  represent  some  of  our  common  species. 


Fig.  ^82.— Goniodes  sty  lif- 
er. (From  Law.) 


Fig.  383.— Tricho- 
de  c  t  e  s  I  at  u  s. 
(From  Law.) 


Fig.  384-— 
Tnchodectes 
spheroceph- 
alus.    (From 
Law.) 


Fig.  385-  — 7^"- 
chodectes  sca- 
I'lris.  (From 
Law.) 


Fig.  386. — Tricho- 
dectes  equi. 
(From  Law.) 


Goniddes  stylifer  (Fig.  382)  infests  turkeys;  Tnchodectes  Idtus  (Fig. 
383),  dogs;  Tnchodectes  spherocephalus  (Fig.  384), 
sheep;  Tnchodectes  scaldris  (Fig.  385),  domestic  cat- 
tle ;  and  Tnchodectes  equi  (Fig.  386),  horses  and  asses. 
The  eggs  of  the  Mallophaga  are  glued  to  the 
hairs  or  feathers  of  their  hosts.  The  development 
takes  place  on  the  body  of  the  host  and  is  without 
metamorphosis.  The  young  are  not  so  dark  in  color 
as  the  adults  and  the  cuticula  is  less  densely  chitin- 
ized.  The  ametabolous  condition  of  these  insects  is 
believed  to  be  an  acquired  one,  a  result  of  their 
parasitic  habits. 

The  bird-lice  are  well  known  to  most  people  who 
have  pet  birds  or  who  keep  poultry.  It  is  to  free 
themselves  from  these  pests  that  birds  wallow  in 
dust.  When  poultry  are  kept  in  closed  houses  they  should  be  provided 
with  a  dust-bath.  All  poultry  houses  should  be  cleaned  at  least  twice 
a  year,  and  the  old  straw  burned.  Sprinkling  powdered  sulphur  in 
the  nests  and  oiling  the  perches  with  kerosene  will  tend  to  keep  the 
pests  in  check.  If  a  poultry  house  becomes  badly  infected,  it  should 
be  cleaned  thoroughly,  every  part  whitewashed,  and  the  poultry  dust- 
ed with  either  insect-powder  or  sodium  fluoride. 

The  Mallophaga  is  a  small  order.  Professor  V.  L.  Kellogg  in  his 
"Mallophaga"  (Kellogg  '08  b)  estimates  the  niunber  of  known  species 
to  be  1250;  these  represent  twenty-seven  genera.  But  there  are 
doubtless  many  species  not  yet  discovered,  as  comparatively  few 
birds  and  mammals  have  been  thoroughly  searched  for  these  pests. 

The  work  just  quoted  is  the  latest  and  most  complete  systematic 
treatise  on  this  order.  It  followed  a  long  series  of  papers  on  these 
insects  published  by  this  author.  A  more  generally  accessible  ac- 
count of  the  species  that  have  been  found  in  North  America  is  a 


MALLOPHAGA  337 

chapter  in  Professor  Herbert  Osborn's  "Insects  Affecting  Domestic 
Animals"  (Osborn  '96). 

The  chief  divisions  of  the  order  adopted  by  Kellogg  ('08  b)  are  as 
follows. 

A.       With  filiform,  3-  or  5-segmented,  exposed  antennae;  no  maxillary  palpi; 

mandibles  vertical Suborder  Ischnocera 

B.       With  3-segmented  antennae;  tarsi  with  one  claw;  infesting  mammals. 

Family  Trichodectid^ 

BB.    With  5-segmented  antennas;  tarsi  with  two  claws;  infesting^  birds 

Family  Philopterid^ 

AA.    With  clavate  or  capitate,  4-segmented,  concealed  antennae ;  with  4-segmented 

maxillary  palpi ;  mandibles  horizontal Suborder  Amblycera 

B.       Tarsi  with  one  claw;  infesting  mammals Family  Gyropid^ 

BB.    Tarsi  with  two  claws;  infesting  birds,  excepting  a  few  species  that  infest 
kangaroos,  wallabies,  and  wombats Family   Liotheid^ 


CHAPTER  XVII 


ORDER  EMBIIDINA=* 


The  Emhiids 

This  order  is  composed  of  small  and  feeble  insects  in  which  the  body 
is  elongate  and  depressed.  The  winged  members  of  the  order  have  two 
pairs  of  wings,  which  are  quite  similar  in  form  and  structure;  they  are 
elongate,  membranous,  extremely  delicate,  and  folded  on  the  back  when 
at  rest;  the  venation  of  the  wings  is  considerably  reduced.  The  mouth- 
parts  are  formed  for  chewing.  Cerci  are  present  and  consist  each  of  two 
segments.    The  metamorphosis  is  of  a  peculiar  type. 

This  is  a  small  order  of  insects;  Enderlein  ('12  a)  in  his  monograph 
of  the  Embiidina  of  the  world  lists  only  sixty-one  species.  The  body 
is  elongate  and  depressed  (Figs.  387  and  388),  Only  the  males  are 
winged;  and  in  some  genera  this  sex  also  is 
wingless .  The  venation  of  the  wings  is  re- 
duced; this  reduction  has  been  brought      |  "x 


I)/"" 

^^ 

^^ 

i^i 

^^^^v" 

1/   v\ 

i< 

1 
1 

Fig.  387. — Enibia  sabulosa,  male.   (After  En- 
derlein.) 


Fig.    388. — Enibia    sabulosa, 
female.    (After  Enderlein.) 


about  both  by  the  coalescence  of  veins  and  by  the  atrophy  of  veins. 
Each  of  the  veins  of  the  wings  extends  along  the  middle  of  a  brown  band ; 
between  these  bands  the  membrane  of  the  wing  is  pale  in  color.  The 
alternating  brown  and  pale  bands  give  the  wing  a  very  characteristic 

*Embiidina:  Embiidae,  Embia,  embios  (e/x^hs),  lively. 

(338) 


EMBIIDINA 


339 


appearance  (Fig.  3  89) .  In  those  forms  where  the  venation  of  the  wings 
has  been  reduced  by  the  atrophy  of  veins,  the  brown  bands  persist 
after  the  veins  have  faded  out ;  hence  it  is  easy  to  determine  by  these 
bands  the  former  position  of  veins  that  have  been  lost.  A  discussion 
of  the  venation  of  the  wings  of  the  Embiidina  is  given  in  my  "The 
Wings  of  Insects." 

The  antenuce  are  filiform  and  are  composed  of  from  sixteen  to 
thirty-two  segments.    The  compound  eyes  consist  of  many  ommatidia, 


.^^yy'^y^^^.y^^^. 


Fig.  389. — Fore  wing  of  Oligotoma  saundersi:  A,  the  wing;  B,  outline  of  the  wing 
showing  the  existing  venation;  C,  outline  of  the  wing  showing  the  venation 
restored.      (After  Wood- Mason.) 

which  are  of  the  eucone  type.  Ocelli  are  always  wanting.  The 
mouth-parts  are  mandibulate;  the  maxillary  palpi  are  five-jointed 
and  the  labial  palpi  three-jointed.  The  abdomen  is  composed  of  ten 
distinct  segments  and  bears  at  its  tip  a  pair  of  two-jointed  cerci. 

Figure  387  represents  the  male  of  Emhia  sabulosa,  with  the  wing 
of  one  side  removed;  and  Figure  388,  the  female  of  this  species. 

The  metamorphosis  is  of  a  type  intermediate  between  gradual  and 
complete.  This  was  shown  by  Melander  ('02  b),  who  studied  the 
development  of  Embia  texdna.  The  3'oung  resemble  the  adults  in 
the  form  of  the  body,  except  that  the  body  is  cylindrical  instead  of 
depressed;  and  the  cuticula  of  the  young  is  less  densely  chitinized 
and  pigmented  than  is  that  of  the  adult.    In  the  case  of  the  females 


340  AN  INTRODUCTION  TO  ENTOMOLOGY 

and  of  those  males  that  are  wingless  in  the  adult  instar,  it  might  be 
said  that  these  insects  develop  without  metamorphosis.  But  in  the 
case  of  the  winged  males  the  development  resembles  that  of  insects 
with  a  complete  metamorphosis  in  one  important  respect;  that  is, 
the  development  of  the  wings  is  internal  until  the  penultimate  molt 
is  reached.  Melander  states  that  he  sectioned  the  fully  grown  larv^a 
and  found  the  wings  as  large  invaginated  pockets  completely  beneath 
the  hypodermis.  In  the  penultimate  instar  of  the  winged  females 
there  are  well-developed,  external  wing-pads.  This  instar  may  well 
be  termed  a  pupa. 

The  embiids  are  very  active  insects  both  in  running  and  in  flight. 
They  are  often  gregarious.  They  live  in  silken  nests  or  galleries  under 
stones  or  other  objects  lying  on  the  ground,  and  burrow  into  the  soil 
when  the  surface  becomes  too  dry.  Imms  found  in  his  studies  of 
Embia  major  in  the  Himala3"as  that  maternal  care  on  behalf  of  the  ova 
and  larvce  is  strongly  exhibited  by  the  females,  in  much  the  same 
manner  as  is  known  to  occur  among  the  Dermaptera. 

Writers  differ  as  to  the  source  of  the  silk  of  which  the  nests  are 
made.  Melander  ('02  a)  and  others  have  described  glands  in  the 
metatarsi  of  the  forelegs,  which  open  through  hairs,  and  have  ob- 
served that  in  spinning  its  nest  the  insect  uses  its  fore  feet.  But 
Enderlein  maintains  that  the  chief  source  of  the  silk  is  from  glands 
that  open  through  a  spinneret  on  the  labium,  although  the  secretion 
of  the  metatarsal  glands  may  play  a  part  in  the  formation  of  the 
silken  tissues. 

The  embiids  are  widely  distributed  in  the  warmer  parts  of  the 
world.  A  few  species  have  been  found  in  Florida,  Texas,  and 
California. 


CHAPTER  XVIII 
ORDER  THYSANOPTERA* 

The  Thrips 

The  members  of  this  order  are  minute  insects  with  wings  or  wingless. 
The  winged  species  have  Jour  wings;  these  are  similar  in  form,  long, 
narrow,  membranous,  not  plaited,  with  but  few  or  with  no  veins,  and 
only  rarely  with  cross-veins;  they  are  fringed  with  long  hairs,  and  in 
some  species  are  armed  with  spines  along  the  veins  or  along  the  lines 
from  which  veins  have  disappeared.  The  mouth-parts  are  formed  for 
piercing  and  sucking.  The  tarsi  are  usually  tivo-jointed  and  are  bladder- 
like at  the  tip.  The  metamorphosis  is  gradual,  but  deviates  from  the 
usual  type. 

These  insects  are  of  minute  size,  rarely  exceeding  2  mm.  or  3  mm. 
in  length .  They  can  be  obtained  easily ,  however,  from  various  flowers , 
especially  those  of  the  daisy  and  clover.  Ordinarily  it  is  only  necessary 
to  pull  apart  one  of  these  flowers  to  find  several  thrips.  They  are  in 
many  cases  very  active  insects,  leaping  or  taking  flight  with  great 
agility.  In  case  they  do  not  leap  or  take  flight  when  alarmed,  they 
are  apt  to  run  about  and  at  the  same  time  turn  up  the  end  of  the 
abdomen  in  a  threatening  manner,  as  if  to  sting.  In  this  respect  they 
resemble  the  rove-beetles. 

The  body  is  long  (Fig.  390) .  The  head  is  narrower  than  the  thorax, 
without  any  distinct  neck.  The  antennae  are  filiform  or  monilifomi 
and  consist  of  from  six  to  nine  segments ;  they 
are  always  much  longer  than  the  head  and  may 
be  two  or  three  times  as  long.  The  compound 
eyes  are  large,  with  conspicuous  facets,  which 
are  circular,  oval,  or  reniform  in  outline.  Three 
ocelli  are  usually  present  in  the  winged  forms, 
but  sometimes  there  are  only  two  ocelli ;  wing- 
less species  lack  ocelli.  The  mouth-parts  are 
fitted  for  piercing  and  sucking ;  they  are  in  the 
form  of  a  cone  which  encloses  the  piercing  or- 
gans.    The  cone  is  composed  of  the  clypeus,        ^.  .    ,   . 

labrum,  maxillary  sclerites,  and  labium.     The  ^^'  "^^^'  ^^^^* 

piercing  organs  consist  of  the  left  mandible  (the  right  mandible  is 
vestigial)  and  the  two  maxillae.  Each  maxilla  is  composed  of  two 
parts:  first,  the  palpus-bearing  maxillary  sclerite;  and  second,  the 
maxillary  seta.  For  detailed  accounts  of  the  mouth-parts  see  Hinds 
('02)  and  Peterson  ('15).  The  above  statement  regarding  the  mouth- 
parts  is  based  on  the  paper  by  Peterson.  The  mouth-parts  of  the 
Thysanoptera  bear  a  striking  resemblance  to  those  of  the  Hemiptera 

*Thysan6ptera:  thysanos  {diaavoi),  fringe;  pteron  {irrepby),  a  wing. 

(341) 


342  AN  INTRODUCTION  TO  ENTOMOLOGY 

and  the  Homoptera,  which  are  described  in  detail  in  later  chapters. 
The  three  thoracic  segments  are  well  developed.  The  wings  are 
laid  horizontally  on  the  back  when  not  in  use;  they  are  very  narrow, 
but  are  fringed  with  long  hairs  (Fig.  391),  which,  diverging  in  flight, 
compensate  for  the  smallness  of  the  membrane.  The  fringing  of  the 
wings  suggested  the  name  Thysanoptera,  by  which  the  order  is  known . 
The  two  longitudinal  veins  that  traverse  the  disk  of  the  wing  in 


Fig.  391 . — Fore  wing  of  yElolhrips  nasturtii.  (After  Jones.)  The  lettering  is  original. 

the  more  generalized  forms  I  believe  to  be  the  radius  and  the  media 
respectively.  The  costal  vein  is  continued  by  an  ambient  vein,  which 
margins  the  entire  preanal  area  of  the  wing  (Fig.  391,  am).  The 
ambient  vein  is  termed  the  "ring  vein"  by  writers  on  this  order,  al- 
though the  term  ambient  vein  has  been  long  in  use  for  veins  in  this 
position.  There  is  a  short  longitudinal  vein  separating  the  anal  and 
preanal  areas;  this  is  doubtless  the  anal  vein  (Fig.  391,  A).  An  organ 
for  uniting  the  two  wings  of  each  side,  and  consisting  of  hooked  spines 
situated  near  the  base  of  the  wings  and  a  membranous  fold  on  the  under 
side  of  the  anal  area  of  the  fore  wing,  is  described  byHinds  ('02). 

In  some  species  one  or  both  sexes  are  wingless  in  the  adult  state ; 
and  in  others,  short -winged  forms  occur. 

The  legs  are  well  developed,  but  are  furnished  with  ven,''  peculiar 
tarsi.  These  are  usually  composed  of  two  segments;  the  last  seg- 
ment terminates  in  a  cup-shaped  or  hoof-like  end  and  is  usually 
without  claws.  Fitted  into  the  cup-shaped  end  of  the  tarsus  there  is 
a  very  delicate,  protrusile,  membranous  lobe  or  bladder,  which  is 
withdrawn  into  the  cup  when  not  in  use  but  is  protruded  when  the 
tarsus  is  brought  into  contact  with  an  object.  This  is  one  of  the 
most  distinctively  characteristic  features  of  the  members  of  this  order. 
It  was  this  feature  that  suggested  the  name  Physopoda  which  is  ap- 
plied to  this  order  by  some  writers.* 

The  abdomen  consists  of  ten  distinct  segments.  The  form  of  the 
caudal  segments  differs  in  the  two  suborders  as  indicated  below. 

The  manner  of  oviposition  differs  in  the  two  suborders.  In  the 
Terebrantia  the  female  cuts  slits  with  her  saw-like  ovipositor  and 
deposits  her  eggs  singly  in  the  tissue  of  the  infested  plant.  In  the 
Tubulifera  it  is  evident  that  the  eggs  must  be  deposited  on  the  surface. 

*Physopoda:  physao  {(pvffdw),  to  blow  up;  pous  (irovs),  a  foot. 


THYSANOPTERA 


343 


The  metamorphosis  of  these  insects  is  in  some  respects  peculiar; 
but  it  conforms  more  closely  to  the  paurometabolous  type  than  to 
any  other,  the  newly  hatched  youn*^  resembling  the  adult  in  the 
form  of  its  body  (Fig.  392,  A)  and  in  having  similar  mouth-parts  and 
food  habits.  The  first  two  or  three  instars  have  no  external  wings; 
these  instars  are  commonly  referred  to  as  larvce.  The  use  of  the  term 
larva  in  this  connection  is  not  inappropriate  if  the  wings  are  de- 
veloping internally  during  these  early  stadia.  That  this  may  be  the 
case  is  indicated  b\'  the  large  size  of  the  wing-pads  when  they  first 


Fig.  392. — Immature  forms  of  the  citrus  thrips:  A,  first  larval  instar;  B,  second 
larval  instar;  C,  propupa;  D,  pupa.  (After  Horton.) 

appear  externally.  After  the  last  larval  molt  the  insect  assumes  a 
form  known  as  the  propupa  (Fig.  392,  C").  This  resembles  the  larva 
in  form ;  the  antennae  are  slender,  and  the  insect  is  moderately  active. 
Its  most  striking  feature  is  the  presence  of  large  wing-pads,  which 
extend  at  first  to  about  the  end  of  the  second  abdominal  segment  and 
increase  in  length  somewhat  during  this  stadium.  With  the  next 
molt  the  insect  becomes  what  is  known  as  the  pupa.  In  this  stage 
the  wing-pads  are  longer  (Fig.  392,  D),  the  antennas  extend  back 
over  the  head  and  prothorax,  and  the  insect  is  quiescent.  With  the 
next  molt  the  adult  form  is  assumed. 

The  different  species  of  thrips  vary  greatly  in  habits,  some  being 
injurious  to  vegetation,  while  others  are  carnivorous,  feeding  on 
aphids  and  other  small  insects,  the  eggs  of  insects,  and  mites,  es- 
pecially the  "red  spider."  Their  most  important  economic  role,  how- 
ever, is  that  of  pests  of  cultivated  plants.  The  thrips  that  infest 
plants  puncture  the  tissue  of  the  plant  by  their  piercing  mouth-parts 
and  suck  out  the  sap. 

The  order  Thysanoptera  is  divided  into  two  suborders,  which  can 
be  separated  as  follows : 

A.       Female  with  a  saw-like  ovipositor;  terminal  abdominal  segment  of  female 

conical;  that  of  the  male  bluntly  rounded Terebrantia 

AA.    Female  without  a  saw-like  ovipositor;  terminal  abdominal  segment  tubular 
in  both  sexes,  p.   345 Tubulifera 


344 


^A'  INTRODUCTION  TO  ENTOMOLOGY 


Suborder  TEREBRANTIA* 

In  this  suborder  the  female  has  a  four-valved,  saw-like  ovipositor; 
the  terminal  abdominal  segment  of  the  female  is  conical ;  that  of  the 
male  bluntly  rounded.  Wings  are  usually  present;  the  front  wings 
are  stronger  than  the  hind  wings  and  usually  have  more  or  less  well- 
developed  veins;  the  membrane  of  the  wings  is  clothed  with  micro- 
scopic hairs. 

The  members  of  this  suborder  are  more  agile  than  those  of  the 
other  one.  They  run  rapidly;  and  spring,  by  bending  under  the  tip 
of  the  abdomen  and  suddenly  straightening  it  out. 

This  suborder  includes  two  families. 


Fig- 393-- 


Fore  wing  of  Erythrothrips  arizona. 
(After  Aloulton.) 


Family  ^OLOTHRIPID^ 

In  this  family  the  wings  are  comparatively  broad.  Each  fore 
wing  has  two  longitudinal  veins  extending  from  its  base  to  near  the  tip, 
where  they  unite 
with  a  prominent 
ambient  vein 
on  each  side 
of  the  tip  (Fig. 
391);  four  or  five 
cross-veins  are 
present  in  each 
fore  wing,  in 
some  species 
(Fig.  393);  in 
others,  cross- 
veins  are  want- 
ing (Fig.  391).    The  ovipositor  is  upcurved. 

Comparatively  few  species  belonging  to  this  family  have  been 
found  in  our  fauna;  the  best-known  one  is  the  following. 

The  banded  thrips,  /Eolothrips  fascidhis. — This  species  is  widely 
distributed  both  in  this  country  and  in  Europe.  The  adult  is  yellow- 
ish brown  to  dark  brown  in  color,  with  three  white  bands  on  the  wings, 
one  at  the  base,  one  in  the  middle,  and  one  at  the  tip.  The  larva  is 
yellow  with  the  abdomen  deeper  orange  behind.  This  species  infests 
many  plants ;  it  is  common  in  the  heads  of  red  clover. 

Family  THRIPID^ 

In  this  family  the  wings,  when  present,  are  usually  narrow  and 
pointed  at  the  tip.  The  radius  and  cubitus  of  the  front  wings,  when 
present,  usually  coalesce  for  about  one  third  their  length,  so  that 
cubitus  appears  to  be  a  branch  of  radius.  The  ovipositor  is  down- 
curved. 

To  this  family  belong  most  of  the  species  of  thrips  that  have  at- 
tracted attention  on  account  of  their  economic  importance.  The 
better-known  of  these  are  the  following. 


'^Terebrantia:  terebro,  to  bore  through. 


THYSANOPTERA  345 

The  onion  thrips,  Thrips  tabdci. — This  is  a  serious  pest  of  the  onion. 
It  is  found  on  the  bulbs  in  loose  soil  and  at  the  axils  of  leaves,  causing 
the  disease  known  as  white  blast  on  account  of  the  whitish  appearance 
of  the  infested  fields.  Although  called  the  onion  thrips,  it  infests  a 
great  variety  of  plants. 

The  greenhouse  thrips,  Heliothrips  hcsmorrhoidalis. — This  is  a 
tropical  insect,  which  is  often  a  serious  pest  in  greenhouses;  it  is  also 
found  out  of  doors  in  the  milder  California  climate.  Drops  of  a 
reddish  fluid  which  turns  black  cover  the  infested  leaves. 

The  bean  thrips,  Heliothrips  fascidUts. — This  is  a  serious  pest  on 
oranges,  alfalfa,  pear  trees,  and  various  garden  crops  in  California. 

The  orange  thrips,  Eiithrips  citri. — This  is  a  serious  orange  pest  in 
California  and  Arizona ;  it  deforms  the  new  growth  of  foliage  and  causes 
scabbing  and  scarring  of  the  fruits. 

The  pear  thrips,  Euthrips  pyri. — This  thrips  infests  pears,  prunes, 
peaches,  and  other  deciduous  fruits,  both  in  California  and  in  the 
East.  It  infests  the  opening  buds  and  blossoms,  stunting  the  leaves 
and  blasting  the  blossoms. 

The  tobacco  thrips,  Euthrips  fuscus . — This  is  a  destructive  enemy 
of  shade-grown  tobacco  causing  the  injury  known  as  white  vein. 
The  white  veins  of  the  leaves  show  in  the  wrapper  when  manufactured 
into  cigars. 

The  strawberry  thrips,  Euthrips  trltici. — This  species  was  first 
described  as  a  pest  of  wheat,  hence  its  specific  name;  but  on  account 
of  its  extensive  injury  to  the  flowers  of  strawberry  it  is  now  known  as 
the  strawberry  thrips.  It  is  found  in  the  flowers  of  almost  all  wild 
and  cultivated  plants  and  is  the  commonest  and  most  widely  distribut- 
ed of  all  American  species  of  thrips. 

The  grass  thrips,  Andphothrips  stridtus. — This  species  infests  June 
grass,  timothy,  and  other  grasses  by  destroying  the  heads  of  the 
infested  plants.  The  young  insect  pierces  the  stem  just  above  the 
upper  node,  where  it  is  tender,  causing  it  to  shrivel  and  all  the  parts 
above  the  injury  to  die.  The  dead  and  yellow  heads  of  grasses  thus 
destroyed  can  be  seen  in  early  summer  ever^'where  in  grass-growing 
regions.    This  disease  is  known  as  silver-top. 

Control. — Thrips  are  destroyed  in  those  cases  where  it  is  prac- 
ticable to  spray  the  infested  plants  by  the  use  of  contact  poisons,  such 
as  nicotine  or  kerosene  emulsion,  and  soap  solution.  Detailed  di- 
rections for  making  and  applying  these  sprays  are  given  in  many 
published  bulletins  and  in  special  text-books.  The  burning  of  old 
grass  in  early  spring  would  probably  destroy  the  hibernating  grass 
thrips. 

Suborder  TUBULIFERA* 

In  this  suborder  the  female  is  without  a  saw-like  ovipositor  and 
the  terminal  abdominal  segment  is  tubular  in  both  sexes.  The  wings 
are  usualh^  present ;  the  fore  pair  only  with  a  single  vestigial,  longi- 

*Tubulifera:  tubulus,  a  little  tube;  fero,  to  bear. 


346  AN  INTRODUCTION  TO  ENTOMOLOGY 

tudinal  vein;  the  membrane  of  the  wings  is  not  clothed  with  micro- 
scopic hairs.     This  suborder  includes  a  single  family. 

Family  PHLCEOTHRIPID^ 

The  members  of  this  family  are,  as  a  rule,  considerably  larger  and 
more  powerfully  formed  than  the  Terebrantia,  some  of  them  being 
the  giants  of  the  order.  They  live  usually  in  secluded  places,  as  be- 
tween the  parts  of  composite  flowers,  under  the  bark  of  trees,  on  the 
underside  of  foliage,  in  galls,  moss,  turf,  fungi,  etc.  Their  movements 
are  very  deliberate  and  they  never  run  or  spring  (Hinds  '02). 

Nearly  as  many  species  and  genera  of  this  family  have  been  found 
in  this  country  as  of  the  other  suborder;  but  this  family  appears  to 
be  of  much  less  economic  importance  than  is  the  Thripidee.  One 
species,  Aleurddothripsfasciapennis,  which  is  common  in  Florida,  feeds 
IS,  larv^,  and  pupse  of  the  citrus  white  fly,  Dialeurodes  citri. 


CHAPTER  XIX 
ORDER  ANOPLURA* 

The  True  Lice 

The  members  of  this  order  are  wingless  parasitic  insects  with  piercing 
and  sucking  mouth-parts.    Their  development  is  without  metamorphosis. 

The  order  Anoplura  is  composed  of  the  true  lice.  These  are  small 
wingless  insects,  which  live  on  the  skin  of  mammals  and  suck  their 
blood.  They  are  sharply  distinguished  from  the  Mallophaga  or  bird- 
lice  by  the  possession  of  piercing  and  sucking  mouth-parts.  The  most 
familiar  examples  of  the  Anoplura  are  three  species  that  infest  man 
and  several  species  that  are  found  on  domestic  animals. 

The  name  Siphunculata  was  proposed  for  this  order  by  Meinert 
in  189 1  and  is  now  used  by  some  authors;  but  the  name  Anoplura  is 
much  the  older  name,  having  been  proposed  by  Leach  in  181 5,  and 
is  more  generally  used. 

The  body  is  more  or  less  flattened  (Fig.  394).  The  head  is  free 
and  horizontal.  The  compound  eyes  are  vestigial  or  are  wanting. 
There  are  no  ocelli.  The  antennee  are  three-,  four-,  or  five-jointed. 
The  mouth  is  furnished  with  a  fleshy,  un jointed  proboscis,  which  can 
be  withdrawn  into  the  head  or  extended  to  a  considerable  length. 
Within  this  proboscis  are  two  knife-like  stylets;  and  at  its  base, 
when  extended,  there  is  a  wreath  of  recm-ved  hooks.  These  hooks 
serve  to  anchor  firmly  the  proboscis  when  inserted  in  the  skin  of  the 
infested  animal.  Authors  do  not  agree  as  to  the  homologies  of  the 
different  mouth -parts  of  these  insects. 

The  thoracic  segments  are  fused.  The  legs  are  similar;  the  tarsi 
consist  of  a  single  segment,  which  is  often  greatly  reduced.  There  is 
a  single  tarsal  claw,  which  is  opposed  by  a  toothed  projection  of  the 
tibia,  forming  an  efficient  organ  for  clinging  to  the  hairs  of  the  host. 
The  abdomen  consists  of  nine  segments;  there  are  no  cerci. 

The  eggs  of  the  true  lice  are  commonly  known  as  "nits."  They 
are  attached  to  the  hairs  of  the  host  by  a  glue-like  substance.  The 
young  lice  resemble  the  adults  except  in  size.  As  with  the  Mallophaga, 
the  ametabolous  condition  of  these  insects  is  believed  to  be  an  ac- 
quired one,  a  result  of  their  parasitic  life. 

This  is  a  small  order.  Dalla  Torre  ('08)  in  his  monograph  of  the 
Anoplura  of  the  world  lists  only  sixty-five  species.  These  represent 
fifteen  genera,  which  are  grouped  in  four  families.  The  two  following 
families  include  all  of  the  species  that  infest  man  and  the  common 
domestic  animals. 


*Anoplura:  anoplos  ((StottXcj),  unarmed;  oura  {oiipd),  tail. 
(347) 


348  AN  INTRODUCTION  TO  ENTOMOLOGY 

Family  PEDICULID^ 

In  this  family  the  eyes  are  comparatively  large,  convex,  and  dis- 
tinctly pigmented;  and  the  proboscis  is  short,  hardly  reaching  the 
thorax.  Here  belong  the  three  well-known  species  of  lice  that  are 
parasites  of  man.    These  are  the  following. 

The  head-louse,  Pedtculus  capitis. — This  is  the  most  common 
species  infesting  man.  It  lives  in  the  hair  of  the  head,  and  is  most 
common  on  the  heads  of  neglected  children.  Under  ordinary  circum- 
stances, cleanliness  and  the  use  of  a  fine-toothed  comb  are  all  that  is 
necessary  to  insure  freedom  from  this  disgusting  pest.  But  sometimes 
adults  of  most  cleanly  habits  become  infested  b^dt.  It  can  be  destroyed 
by  the  use  of  tincture  of  larkspur  or  a  larkspur  lotion,  which  can  be 
obtained  from  druggists. 

The  body -louse,  Pedicuhis  corporis. — This  insect  lives  upon  the 
skin  of  most  parts  of  the  body,  but  especially  on  the  chest  and  back. 
It  is  often  troublesome  on  ships,  in  military  camps,  in  prisons,  and 
in  the  apartments  of  uncleanly  people  who  neglect  to  change  their 
clothes.  It  was  a  terrible  scourge  during  the  World  War,  when  troops 
were  obhged  to  live  under  most  unsanitary  conditions  in  trenches  and 
camps.  The  female  attaches  her  eggs  to  fibers  in  the  seams  of  under- 
garments, from  which  the  young  hatch  in  about  a  week.  This  species 
is  exceedingly  prolific.  It  is  known  under  several  common  names; 
among  these  are  "clothes-louse,"  "gray  backs,"  "crumps,"  and 
"cooties." 

The  method  of  destroying  these  vermin  commonly  employed  in 
hospitals  and  poorhouses  is  to  rub  mercurial  ointment  in  the  seams 


Fig.  394. — The  short-  ,,,,^  ^, 

nosed  ox-louse.    (From  -r^.                TVi^-hnrc^^  ^^S-    396.— The    hog- 
Law.)  1^  ig.  395-— 1  he  horse-  j             (From  Law.) 
^  louse.  (From  Law.)  "• 

of  undergarments.  During  the  W^orld  War  much  attention  was  de- 
voted to  the  problem  of  control  of  this  pest  and  hundreds  of  papers 
were  published  on  this  subject.  It  has  been  found  that  both  the  lice 
and  their  eggs  are  destroyed  by  the  ordinarv'  laundering  process  used 
in  washing  clothes. 


ANOPLURA 


349 


The  crab-louse,  Phthirius  piibis. — The  common  name  of  this  spe- 
cies is  su<jgested  by  the  form  of  the  body,  which  is  nearly  as  broad  as 
long.  When  hi<:hly  magnified,  the  resemblance  of  this  insect  to  a 
crab  is  quite  striking;  but  to  the  unaided  eye  it  appears  more  like  a 
large  scale  of  dandruff.  These  offensive  vermin  aft'ect  the  pubic 
region  and  armpits  of  man,  stretching  themselves  out  flat,  holding 
tight  to  the  cuticle,  and  inflicting  most  irritating  punctures.  They 
can  be  destroved  bv  mercurial  ointment. 


Family  H^MATOPINID^ 

In  this  famih'  the  eyes  are  vestigial  or  wanting  and  the  proboscis 
is  very  long.  Here  belong  the  true  lice  that  infest  our  common  domes- 
tic animals;  the  more  important  of  these  are  the  following. 

The  short-nosed  ox-louse,  Hcematoplnns  eurystcrnus  (Fig.  394). 
The  horse-louse,  Hamatophms  asini  (Fig.  395). 
The  hog-louse,  Hcematoplnus  silis  (Fig.  396). 
The  long-nosed  ox -louse,  Linognathus  vttuli  (Fig.  397). 
The  dog-louse,  Linognathus  piUferus  (Fig.  398). 
For  the  destruction  of  these  pests  upon  cattle,  poisonous  sub- 
stances must  not  be  used,  as  injur}-  would  result  from  the  animals 
licking   themselves.      They 
may  be  safely  treated  by 
washing  with  a  strong  in- 
fusion of  tobacco  leaves,  or 
by  rubbing  with  an  oint- 
ment made  of  one  part  sul- 
phur and  four  parts  lard,  or 
by  sprinkling  with  Scotch 
snuff    or    powdered    wood- 
ashes.      Stavesacre    lotion 
and  larkspur  lotion  are  also 
used.  The  insecticide  should 
be  applied  thoroughly, 
leaving  no  spot  untouched 
where   the  lice   can  gather 
and  remain  and  from  which 
they  can  spread  over    the 
body  again.     The   applica- 
tion should  be  repeated  several  times  at  intervals  of  three  or  four  days, 
in  order  to  destroy  the  young  which  may  hatch  after  the  first  applica- 
tion.    It  is  also  necessarv%  in  order  to  make  sure  of  eradicating  the 
pests,   to  dress  with  similar  agents,  or  with  strong  lye  or  kerosene,  all 
places  where  the  cattle  have  .been  in  the  habit  of  rubbing,  and  the 
cracks  in  the  stables  where  they  have  stood;  or  to  whitewash  the 
stables  and  rubbing-places. 

For  a  more  extended  account  of  the  true  lice  found  in  North 
America,  see  Professor  Herbert  Osbom's  "Insects  Affecting  Domestic 
Animals,"  pp.  164-188  (Osborn  '96). 


Fig.  397-—  The 
long-nosed  ox- 
louse.  (From 
Law.) 


J^ 


Fig.     398.— The    dog- 
louse.    (From  Law.) 


CHAPTER  XX 
ORDER  HEMIPTERA* 

The  True  Bugs 

The  winged  members  of  this  order  have  four  wings;  the  first  pair  of 
wings  are  thickened  at  the  base,  with  thinner  extremities  which  overlap 
on  the  back.  The  mouth-parts  are  formed  for  piercing  and  sucking;  the 
beak  arises  from  the  front  part  of  the  head.    The  metamorphosis  is  gradual. 

People  who  know  but  little  regarding  entomology  are  apt  to  apply 
the  term  bug  to  any  kind  -of  insect ;  but  strictly  speaking,  only  mem- 
bers of  the  order  Hemiptera  are  bugs. 

The  bugs  are  very  common  insects.  Many  species  abound  on  grass 
and  on  the  foliage  of  other  plants;  some  species  live  on  the  surface  of 
water;  others  live  within  water;  and  a  few  are  parasitic  on  birds  and 
mammals. 

This  order  is  a  very  important  one;  it  includes  many  species  in- 
jurious to  vegetation ;  among  these  are  some  of  our  more  important 
pests  of  cultivated  plants.  On  the  other  hand,  some  of  the  species 
are  ranked  among  beneficial  insects  on  account  of  their  predac'ous 
habits;  for  many  of  them  feed  upon  noxious  insects. 

The  name  Hemiptera  was  suggested  by  the  form  of  the  front 
wings.  In  these  the  basal  half  is  thickened  so  as  to  resemble  the 
elytra  of  beetles,  only  the  terminal  half  being  wing-like.  The  hind 
wings  are  membranous,  and  are  folded  beneath  the  front  wings.  On 
this  account  the  front  wings  are  often  termed  wing-covers;  they  are 
also  termed  hemelytra,  a  word  suggested  by  their_ structure. 

Formerly,  when  the  Homoptera  was  included  in  the  order  Hemip- 
tera, the  true  bugs  constituted  the  suborder  Heteroptera;  this  name 
indicated  the  remarkable  difference  in  the  texture  of  the  two  pairs  of 
wings  of  the  true  bugs  and  served  to  contrast  this  condition  with  that 
found  in  the  Homoptera,  where  the  two  pairs  of  wings  are  usually 
similar  in  structure. 

In  the  Hemiptera  the  front  wings  present  characters  much  used 
in  the  classification  of  these  insects ;  and  consequently  special  names 
have  been  applied  to  the  different  parts  of  them  The  thickened  basal 
portion  is  composed  of  two  pieces  joined  together  at  their  sides;  one 
of  these  is  narrow  and  is  the  part  next  to  the  scutellimi  when  the 
wings  are  closed;  this  is  distinguished  as  the  clavus  (Fig.  399,  cl);  the 
other  part  is  the  corium  (Fig.  399,  co).  The  terminal  portion  of  the 
front  wing  is  termed  the  membrane  (Fig.  399,  m).  In  certain  families, 
the  Anthocoridae  for  example,  a  narrow  piece  along  the  costal  margin 
of  the  wing  is  separated  by  a  suture  from  the  remainder  of  the 

*Hemiptera :  hemi-  (wO.  half;  pleron  (irTepov),  a  wing. 

The  order  Hemiptera  as  now  restricted  includes  only  one  of  the  suborders  of 
the  old  order  Hemiptera,  the  suborder  Heteroptera.  The  following  order,  the 
Homoptera,  was  formerly  regarded  as  a  suborder  of  the  Hemiptera. 

(350) 


HEMIPTERA 


351 


corimn;  this  is  the  embolium  (Fig.  400,  e).    In  certain  other  cases,  as 
the  Miridae  for  example,  a  triangular  portion  of  the  terminal  part  of 


Fig.  399-— Diagram  of  a  front  wing  of       Fig.  400.— Diagram  of  a  front  wing  of 
a  bug:    cl,    clavus;  co,    corium;    m,  an  anthocorid:  e,  embolium. 

membrane. 


the  coritmi  is  separated  as  a  distinct  piece;  this  is  the  cuneus  (Fig. 
401,  cm). 

The  wings  of  the  Hemiptera  exhibit  remarkable  departures  from 
the  primitive  type  of  wing- venation.  So  great  are  these  that,  at 
first,  one  sees  very  little  in  com- 
mon between  the  wings  of  a 
bug  and  those  of  insects  of  any 
other  order.  But  an  examina- 
tion of  the  tracheation  of  the 
wings  of  nymphs  of  bugs  shows 
that  these  wings  are  merely 
modifications  of  the  primitive 
type  of  insect  wings.  This  is 
more  obvious  in  some  families 

than  in  others;  it  is  well  shown  Fig.  401-— Diagram  of  a  front  wing  of  a 
in  the  tracheation  of  a  fore     "'^"^^  ^«'  '^""^^^• 
wing  of  a  pentatomid  nymph 
(Fig.  402). 

The  head  in  the  Hemiptera  varies  greatly  in  form  in  the  different 
families;  but  the  accompanying  figures  of  the  head  of  one  of  the 
Belostomatidse,  Lethocerus  (Figs.  403  and  404),  will  serve  to  illustrate 
the  position  and  form  of  the  parts  that  are  commonly  referred  to  in 
descriptions  of  members  of  this  order. 

There  are  two  factors  which  make  difficult  the  determination  of 
the  areas  of  the  surface  of  the  head  in  these  insects  that  have  been 
recognized  and  defined  in  the  more  generalized  insects  (see  pages  3  7 
to  40) :  first,  in  some  cases  the  sutures  that  limit  these  areas  in  the 
more  generalized  insects  are  here  obsolete;  second,  the  basal  part  of 
each  mandible  and  of  each  maxilla  enters  into  the  composition  of  the 
wall  of  the  head. 

A  similar  modification  of  the  head  and  mouth-parts  exists  in  the 
Homoptera,  and  the  students  of  the  Hemiptera  should  study  the 
relations  of  the  mouth-parts  to  the  head-capsule  in  that  order,  where 
they  are  more  easily  seen  than  in  the  Hemiptera. 


352 


AN  INTRODUCTION  TO  ENTOMOLOGY 


An  important  feature  of  the  head  in  the  Hemiptera  is  the  extended 
development  of  the  gular  regions,  which  results  in  the  beak  being 


Fig.  402. — Tracheation  of  a  fore  wing  of  a  pentatomid  nymph. 

borne  by  the  front  part  of  the  head.    This  contrasts  strongly  with  the 
condition  found  in  the  Homoptera,  where  the  gula  is  so  reduced  that 


Fig.  403. — Head  of   Lelhocerus,  dorsal       Fig.  404. — Head  of  Lethocerus,  ventral 
aspect.  aspect. 

the  beak  arises  from  the  hind  part  of  the  lower  side   of  the  head. 

In  Lethocerus  the  occiput  (Fig.  403,  o)  is  separated  from  the  vertex 

by  a  distinct  transverse  suture.     The  vertex  (Fig.  403,  v,  v)  is  very 


HEMIPTERA  353 

short  on  the  middle  hne  of  the  body  but  is  much  longer  on  each  side 
next  to  the  compound  eye;  the  epicranial  suture  is  very  indistinct  in 
the  adult.  In  those  bugs  in  which  the  paired  ocelli  are  present  they 
are  borne  by  the  vertex.  Immediately  in  front  of  the  vertex  is  the 
front  or  frons  (Fig.  403,  /).  The  dypeus  is  a  narrow,  elliptical  sclerite 
which  is  well  defined  (Fig.  403,  c).  Some  writers  on  the  Hemiptera 
and  Homoptera  term  the  clypeus  the  tylus;  but,  for  the  sake  of 
uniformity,  the  use  of  this  name  should  be  discontinued. 

The  four  regions  of  the  head  referred  to  in  the  preceding  paragraph, 
the  occiput,  the  vertex,  the  front,  and  the  clypeus,  are  easily  homol- 
ogized  with  the  corresponding  regions  in  the  more  generalized  insects. 
We  will  now  consider  certain  modifications  of  the  structure  of  the 
wall  of  the  head  that  are  correlated  with  the  development  of  the  type 
of  mouth -parts  characteristic  of  the  Hemiptera  and  Homoptera. 

On  either  side  of  the  clypeus  there  is  what  appears  to  be  a  pro- 
longation of  the  front.  In  Lethocerus  (Fig.  403,  x,  x),  each  of  these 
prolongations  extends  about  half  the  length  of  the  clypeus  and 
bounds  the  eye  in  front.  It  is  believed  that  each  of  them  represents 
the  basal  part  of  a  mandible ;  they  are  termed,  therefore,  the  mandibu- 
lar sclerites.  In  some  Homoptera  the  mandibular  sclerites  are  dis- 
tinct ;  this  condition  exists  in  the  head  of  a  cicada  figured  in  the  next 
chapter  (Fig.  463).  The  mandibular  sclerites  were  so  named  by 
Smith  ('92),  who  first  recognized  that  they  pertain  to  the  mandibles. 
Before  that  time  several  different  names  were  applied  to  them,  which 
are  still  in  use  by  some  writers;  these  are  jugcB,  lores,  and  fulcra. 

In  Lethocerus  there  is  a  pair  of  sclerites  in  front  of  the  mandibular 
sclerites  and  bounding  the  distal  end  of  the  cl}'peus;  each  of  these  is 
the  basal  part  of  a  maxilla;  for  this  reason  they  are  termed  the 
maxillary  sclerites  (Fig.  403,  y,  y).  In  Lethocerus  the  tips  of  these 
sclerites  meet  on  the  dorsal  wall  of  the  head  covering  the  tip  of  the 
clypeus. 

On  the  ventral  aspect  of  the  head,  the  gula  occupies  the  median 
area  (Fig.  404,  gu);  and  the  gencB,  the  lateral  areas  (Fig.  404,  ge). 
In  each  gena  there  is  a  deep  groove  in  which  the  very  remarkable 
antenna  rests. 

At  the  front  end  of  the  ventral  wall  of  the  head  there  is  a  pair  of 
sclerites,  each  of  which  is  articulated  with  a  maxillary  sclerite;  these 
are  known  as  the  hucculce  and  are  believed  to  represent  the  maxillary 
palpi  (Fig.  404,  hu).  In  Lethocerus  the  caudal  margin  of  each  buccula 
is  solidly  joined  to  the  front  end  of  the  gula. 

From  the  above  account  it  can  be  seen  that  only  a  portion  of 
the  mouth-parts  enters  into  the  constitution  of  the  beak.  The  beak 
consists  of  the  following  parts :  the  labrum,  the  labitmi,  and  four  very 
slender  lancet-like  organs  enclosed  in  the  labnun  and  labium,  the 
mandibular  setas  and  the  maxillary  setae. 

The  labrum  is  joined  to  the  distal  end  of  the  clypeus;  in  Lethocerus 
the  base  of  the  labrum  is  covered  by  the  maxillary  sclerites,  where 
they  overlap  the  tip  of  the  clypeus,  and  its  distal  end  extends  into  the 
furrow  of  the    labium,    but    the    intermediate    portion    is    exposed 


354 


^A^  INTRODUCTION  TO  ENTOMOLOGY 


(Fig.  403,  /).  It  is  a  slender,  pointed,  transversely  striated  organ. 
The  labium  constitutes  the  most  prominent  part  of  the  beak;  in 
most  Hemiptera  it  consists  of  four  segments ; 
but  in  several  families  it  is  reduced  to  three 
segments.  At  the  distal  end  of  the  third 
segment  in  Lethocerus  and  some  other  aquatic 
Hemiptera  there  is  a  pair  of  small  append- 
ages, each  of  which  consists  of  a  single  seg- 
ment (Fig.  403,  Ip);  these  were  described 
by  Leon  ('97)  as  vestiges  of  the  labial  palpi.* 
The  dorsal  surface  of  the  labium  is  deeply 
grooved,  forming  a  channel  which  encloses 
the  mandibular  and  maxillary  setae.  The 
labium  is  not  a  piercing  organ;  its  function 
is  to  protect  and  direct  the  setK  and  to  de- 
termine, by  means  of  tactile  hairs  at  its  tip, 
the  place  where  the  puncture  should  be  made 
by  the  setee  (Fig.  405,  t). 

The  mandibular  setcs  and  the  maxillary 
setcs  are  four  slender,  lance-like  organs 
which  arise  within  the  head-capsule  and  pass 
out  from  the  head  through  a  furrow  in  the 
lower  side  of  the  la- 
brumandextendon  in 
a  furrow  on  the  upper 
side  of  thelabiimito 
the  tip  of  this  organ, 
from  which  they  are 
Fig.  405.-Last  segment  of  Pushed  out  when  not 
the  beak  of  Lethocerus,  in  use  (Fig.  405).  As 
with  seta; projecting:  md,  the  four  setffi  emerge 
from  the  head  they 
lie  side  by  side;  the 
outer  pair  are  the  mandibular  setae,  the  inner  Fig.^  406. 
pair  the  maxillary  sets.  Farther  from  the  head 
the  maxillary  setae  become  twisted  so  that  one 
of  them  lies  above  the  other.  Figure  406  repre- 
sents a  cross-section  of  the  setEe  of  a  squash- 
bug  as  figured  by  Tower  ('14);  the  setas  are 
fastened    together    by    interlocking  grooves 

*There  has  been  much  discussion  regarding  the  homologies  of  the  parts  of  the 
labium  in  the  Hemiptera  and  the  Homoptera.  The  early  entomologists  believed 
that  the  lower  lip  of  bugs  was  composed  of  the  labium  and  the  grown-together 
labial  palpi;  but  this  view  is  no  longer  held.  Leon,  who  published  a  series  of 
papers  on  the  labium  of  aquatic  bugs,  believes  that  the  first  two  segments  of  the 
labium  consists  of  the  submentum  and  the  mentum;  the  third  segment,  of  the 
palpiger,  which  bears  vestiges  of  the  labial  palpi;  and  the  fourth  segment,  of  the 
remainder  of  the  ligula.  Heymons  ('99)  argues  at  great  length  against  the  con- 
clusions of  Leon.  He  believes  that  the  segmentation  of  the  labium  is  merely  the 
result  of  secondary  divisions  of  this  organ  and  that  labial  palpi  do  not  exist  in  the 
Hemiptera  and  Homoptera. 


mandibular  seta : 
maxillary  seta. 


md" 


-Cross-section 
of  the  setae  of  Anasa 
Irlstis:  md,  mandibular 
setas;  m,  maxillary  se- 
tas; fc,  food  canal;  sc, 
salivary  canal.  (From 
Tower.) 


HEMIPTERA 


355 


Fig.  407. — Articulation  of  a  mandibular 
seta  with  the  wall  of  the  head :  md,  man- 
dibular seta;  a  and  i,  chitinous  levers; g, 
wall  of  the  head;  ?-w,  retractor  muscles; 
pm,  protractor  muscle    (From  Tower.) 


and  ridges;  and  between  the  maxillary  setae  are  two  canals,  the  upj^er 
one  (/c)  for  the  passajre  in  of  food,  the  lower  one  {sc)  for  the  passage 
out  of  saliva.  The  tip  of  the  mandibular  seta?  are  barbed  (Fig.  405, 
md);  their  function  is  that  of  piercing  the  tissue  fed  upon  and  holding 
the  setc-ein  place;  while  the  tips  of  the  maxillary  seta?,  which  are  acute 
and  fluted,  probe  the  tissue,  take  up  the  fluid  food,  and  eject  the  saliva. 

Within  the  head  each  seta  is  connected  with  a  chitinous  lever,  or 
with  a  series  of  two  levers  which  in  turn  articulate  with  the  head- 
capsule  ;  the  in-and-out  move- 
ments of  the  seta;  are  produced 
by  muscles  extending  from  the 
head-capsule  to  them  and  to 
the  levers  conrecting  them 
with  the  wall  of  the  head.  Fig- 
ure 407  represents  the  articu- 
lation of  a  mandibular  seta  of 
a  squash-bug,  as  represented 
by  Tower;  and  in  the  next 
chapter  the  relations  of  both 
the  mandibular  setse  and  the 
maxillary  setae  to  the  head- 
capsule  in  a  cicada  are  rep- 
resented (Fig.  465). 

Correlated  with  the  de- 
velopment of  the  hemipterous 
type  of  mouth-parts  there  is  a  remarkable  specialization  of  the  phar- 
ynx, which  fits  it  as  a  sucking  organ,  and  the  development  of  an 
organ  for  forcing  out  the  saliva,  which  is  known  as  the  salivary  pump. 
A  detailed  account  of  these  organs  is  given  bv  Bugnion  and  Popoff 

Cii). 

A'lost  of  the  Hemiptera  protect  themselves  by  the  emission  of  a 
disagreeable  odor.  In  the  adult  stink-bugs  (Pentatomidae)  this  is 
caused  by  a  fluid  which  is  excreted  through  two  openings,  one  on 
each  side  of  the  ventral  aspect  of  the  thorax,  behind  or  near  the  middle 
coxa.  These  openings  are  termed  the  osteoles.  Each  of  these  is 
usually  in  some  kind  of  an  open  channel  styled  the  osteolar  canal, 
and  this  is  surrounded  by  a  more  or  less  rugged  and  granulated 
space,  the  evaporating  surface.  In  the  nymphs  the  stink-glands 
open  on  the  dorsal  aspect  of  the  abdomen.  In  the  bedbug  (Cimex), 
the  stink -glands  open  in  the  dorsal  wall  of  the  first  three  abdominal 
segments.  The  legs  of  the  Hemiptera  vary  greatly  in  form,  but  the 
tarsi  are  rarely  more  than  three-jointed.  The  lateral  margin  of  the 
abdominal  segments  is  much  developed  in  several  families,  and  forms 
a  flat,  reflexed  or  vertical  border  to  the  abdomen,  which  is  called  the 
connexivum. 

In  the  Hemiptera  the  metamorphosis  is  gradual;  the  newly 
hatched  young  resembles  the  adult  in  the  form  of  its  body  but  lacks 
wings.  After  one  or  two  molts  the  wing-buds  appear  and  become 
larger  and  larger  at  successive  molts.    With  the  last  molt  there  takes 


356  AN  INTRODUCTION  TO  ENTOMOLOGY 

place  a  great  expansion  of  the  wings,  the  change  at  this  time  being 
much  greater  than  at  either  of  the  previous  molts.  There  are  many- 
forms  in  this  order  in  which  wings  are  not  developed.  In  some 
species  all  individuals  are  wingless;  in  others  there  are  two  forms  of 
adults,  the  winged  and  the  wingless. 

In  this  order  we  find  variations  in  structure  which  correspond 
closely  with  variations  in  habits.  There  are  certain  families  the 
members  of  which  are  truly  aquatic,  living  within  the  water,  through 
which  they  swim  and  to  the  surface  of  which  they  come  occasionally 
for  air.  There  are  others  which  are  truly  terrestrial,  living  upon  the 
surface  of  plants,  or  in  other  positions  away  from  water.  There  are 
still  other  families  the  members  of  which  hold  an  intermediate  position 
between  the  aquatic  and  the  terrestrial  forms,  living  upon  the  surface 
of  water  or  in  marshy  places. 

In  the  systematic  arrangement  of  the  families  of  the  Hemiptera 
adopted  here  the  aquatic  forms  are  placed  first;  the  terrestrial  forms, 
last;  and  the  semiaquatic  forms  hold  an  intermediate  position.  The 
sequence  of  the  families  is  more  fully  indicated  in  the  following 
synopsis. 

SYNOPSIS  OF  FAMILIES 

The  Short-horned  Bugs.    Bugs  with  short  antennae,  which  are  nearly  or  quite 

concealed  beneath  the  head. 
Bugs  that  live  luithin  water. 

The  Water-boatmen,  Family  Corixid^.    p.  360. 
The  Back-swimmers,  Family  NoxoNECTiDiE.    p.  362. 
The  Water-scorpions,  Family  Nepid/E.    p.  364. 
The  Giant  Water-bugs,  Family  Belostom.vtid.-e.    p.  365. 
The  Creeping  Water-bugs,  Family  Naucorid.'E.    p.  367. 
Bugs  that  live  near  water. 

The  Toad-shaped  Bugs,  Family  GELASTOCORiDyE.    p.  368. 
The  Ochterids,  Family  Ochterid^.    p.  368. 
The  Long-horned  Bugs.    Bugs  with  antennae  at  least  as  long  as  the  head,  and 

prominent  except  in  the  Phj^matid^,  where  they  are  concealed  under  the 

sides  of  the  prothorax. 
The  Semi-aquatic  Bugs 

The  Shore-bugs,  Family  Saldid.e.    p.  369. 

The  Broad-shouldered  Water-striders,  Family  Veliid^.    p.  369. 
The  Water-striders,  Family  Gerrid.-e.    p.  370. 
The  Alesoveliids,  Family  Mesovelhd^.    p.  372. 
The  Hebrids,  Family  Hebrid^.    p.  372. 
The  Water-measurers,  Family  Hydrometrid.'E.    p.  373. 
The  Land-bugs. 

The  Land-bugs  with  four-jointed  antennce. 

The  Schizopterids,  Family  Schizopterid.^.    p.  373. 

The  Dipsocorids,  Family  Dipsocorid^.    p.  374. 

The  Isometopids,  Family  Isometopid.-e.    p.  374. 

The  Leaf-bugs,  Family  Mirid^.    p.  375. 

The  Termatophylids,  Family  Termatophylid.-e.    p.  377. 

The  Flower-bugs,  Family  Anthocorid/E.    p.  377. 

The  Bedbugs,  Family  Cimicid.e.    p.  378. 

The  Many-combed  Bugs,  Family  Polyctexid.'E.    p.  379. 

The  Nabi'ds,  Family  Nabid.-e.    p.  380. 

The  Assassin-bugs, "Family  Reduvud^.    p.  380. 

The  Ambush-bugs,  Family  Phymatid^.    p.  382. 

The  Unique-headed  Bugs,  Family  Enicocephalid.^.  p.  383. 


HEMIPTERA  357 

The  Lace-bugs,  Family  Tingid/E.    p.  384. 
The  Cotton-stainer  Family,  Family  Pyrrhocorid-^.    p.  385. 
The  Chinch-bug  Family,  Family  Lyg^id^.    p.  386. 
The  wStilt-bugs,  Family  Neidid^.    p.  388. 
The  Flat-bugs,  Family  Aradid/e.    p.  388. 
The  Squash-bug  F'amily,  Family  Coreid^.    p.  389. 
The  Land-bugs  tvith  five-jointed  antennce. 

The  Stink-bug  Family,  Family  Pentatomid.e.    p.  390. 

The  Burrower-bugs  and  the  Ncgro-bvigs,  Family  CvDNiDiE.    p.  391. 

The  Shield-bticked-bugs,  Family  Scutellerid^.    p.  392. 

TABLE  FOR  SEPARATING  THE  FAMILIES  OF  THE  HEMIPTERA 

A.    Antennae  shorter  than  the  head,  and  nearly  or  quite  concealed  in  a  cavity 

beneath  the  eyes. 

B.    Hind  tarsi  with  indistinct   setiform  claws  (except  in  Plea,  of  the  family 

Notonectidce,  which  is  less  than  3  mm.  in  length). 

C.    Fore  tarsi  consisting  of  one  segment,  which  is  flattened  or  shovel-shaped, 

and  without  claws;  head  overlapping  the  prothorax  dorsally.    p.  360. 

CORIXID^ 

CC.    Fore  tarsi  of  the  usual  form,  and  with  two  claws;  head  inserted  in  the 

prothorax.     p.  362 Notonectid^ 

BB.    Hind  tarsi  with  distinct  claws. 

C.     Ocelli  absent;  bugs  that  live  within  water. 

D.    Membrane  of  the  hemelytra  with  distinct  veins. 

E.    Caudal  appendages  of  the  abdomen  long  and  slender;  tarsi  one- 
segmented,  p.  364 Nepid^ 

EE.    Caudal  appendages  of  the  abdomen  short,  flat,  and  retractile; 

tarsi  two-segmented,     p.  365 Belostomatid^ 

DD.    Membrane  of  the  hemelytra  without  veins.      p.  367..Naucorid^ 
CC.  I  Ocelli  present;  bugs  that  live  on  shores  of  streams  and  ponds. 

D.    Fore  legs  stout,  fitted  for  grasping;  antennae  concealed,  p.  368. 

Gelastocorid^ 

DD.    Fore  legs  slender,  fitted  for  running;  antennae  exposed,    p.  368. 

Ochterid/e 

AA.      Antennae  at  least  as  long  as  the  head,  usually  free,  rarely  (Phymatidae) 
I-  "  .  flitting  in  a  groove  under  the  lateral  margin  of  the  pronotum. 
B.    Body  linear;  head   as   long  as   the   three  thoracic   segments,      p.   373. 

Hydrometrid^ 

BB.     Body  of  various  forms,  but,  when  linear,  with  the  head  shorter  than  the 
- '  <i(    thorax. 

C.    Last  segment  of  the  tarsi  more  or  less  split,  and  with  the  claws  of  at 
least  the  front  tarsi  inserted  before  the  apex. 
D.     Hind  femora  extending  much  beyond  the  apex  of  the  abdomen; 
intermediate  and  hind  pairs  of  legs  approximated,  very  distant 

from  the  front  pair;  beak  four-jointed,     p.  370 Gerrid.e 

DD.  Hind  femora  not  extending  much  beyond  the  apex  of  the  ab- 
domen ;  intermediate  pair  of  legs  about  equidistant  from  front 
and   hind   pairs    (except   in  Rhagovelia) ;  beak  three-jointed. 

p.  369 Veliid^ 

CC.     Last  segment  of  the  tarsi  entire,  and  with  the  claws  inserted  at  the 
apex. 
D.    Antennae  four-jointed.* 

E.    Hemelytra  resembling  network,  and  very  rarely  with  any  dis- 
tinction between  the  corium  and  the  membrane,     p.  384. 

TlNGID^ 

EE.     Hemelytra  of  various  forms  or  absent,  but  not  of  the  form 
presented  by  the  Tingidae. 

*In  certain  families  there  are  minute  intermediate  joints  between  the  principal 
joints  of  the  antennae;  for  the  purposes  of  this  table,  these  intermediate  joints 
are  not  counted. 


358  AN  INTRODUCTION  TO  ENTOMOLOGY 

F.    Beak  three-jointed. 

G.    Hemelytra  when  well-developed  with  an  embolium  (Fig. 
408);  those  forms  in  which  the  adult  has  vestigial 
hemelytra  have  no  ocelli. 
H.    Hemelytra  vestigial;  parasitic  bugs  preying  on  man, 

bats,  and  birds,     p.  378 Cimicid.-e 

HH.    Hemelytra    usually    well  developed;  not    parasitic 

bugs.    p.  377 Anthocorid^e 

GG.    Hemelytra  when  well  developed  without  an  embolium ; 
those  forms  in  which  the  adult  has  vestigial  hemely- 
tra have  ocelli. 
H.     Ocelli  wanting. 

I.  Body  greatly  flattened,    p.  388 Ar.\did^ 

II.  Body  not  greatly  flattened,   p.  380. .  Reduviid.e 
HH.    Ocelli  present,  though  sometimes  difficult  to  see. 

I.  Antenna     whip-like,    the    first    two    segments 

short  and  thick,  the  third  and  fourth  long  and 
very  slender  and  clothed  with  long  hairs,  the 
third  segment  thickened  towards  the  base. 
J.  Head  when  viewed  from  above  wider  than  long, 
strongly   defiexed;  beak   short,      p.    373. 

SCHIZOPTERID^ 

JJ.     Head   extended  horizontally   or  slightly  de- 
flexed;  beak  long.    p.  374.  . .  Dipsocorid^ 

II.  Antennae  not  of  the  form  described  above. 

J.    Beak  long,  reaching  to  or  beyond  the  inter- 
mediate coxae. 
K.    Membrane  of  hemelytra  with  looped  veins. 

p.  369 ..Saldid^ 

KK.    Membrane  of  hemelytra  without  veins. 

L.    Hemelytra    with    the    clavus  similar  in 

texture   to   the   membrane  (Fig.  409). 

p.  372 Hebrid^ 

LL.    Clavus    and    membrane    distinct,     p. 

372 Mesoveliid^ 

JJ.    Beak  not  reaching  the  intermediate  coxas. 
K.      Front  legs  with  greatly  thickened   fem- 
ora,    p.  382 Phymatid^ 

KK.    Front     femora     somewhat     thickened, 
but  much  less  than  half  as  wide  as 

long.    p.  380 Reduviid^ 

FF.    Beak  four-jointed. 

G.     Front  legs  fitted  for  grasping  prey. 

H.    The  fore  tarsi,  which  are  one-jointed,  capable  of  be- 
ing closed  upon  the  end  of  the  broad  tibiae,    p.  383. 

Enicocephalid^ 

HH.  The  fore  tibiae  armed  with  spines  and  capable  of 
being  closed  tightly  upon  the  femora,  which  are 
stout.  In  the  forms  with  long  wings  the  mem- 
brane is  usually  furnished  with  four  long  veins 
bounding  three  discal  cells  which  are  often  open. 
From  these  cells  diverge  veins  which  form  sev- 
eral marginal  cells  (Fig.  410).  p.  38o..NABiDyE 
GG.    Front  legs  fitted  for  walking. 

H.    Hemelj'tra  with  a  cuneus;  membrane  with  one  or 
two  closed  cells  at  its  base,  otherwise  without 
veins  (Fig.  411). 
I.    Ocelli  wanting. 
J.    Membrane  of  the  hemelytra  with  two  closed 

cells,     p.  375 MiRiD^ 

JJ.    Membrane  with  only  one  closed  cell. 


HEM  I PT  ERA  359 

K.     Tarsi  furnished  with  an  arolium.     p.  375. 

MiRink 

KK.    Tarsi  without  an  arohum.    p.  377 

Termatophylid/e 

II.    OcelH  present,     p.  374 Isometopid/e 

HH.  Hemclytra  without  a  cuneus;  membrane  with 
four  or  five  simple  or  anastomosing  veins  aris- 
ing from  the  base,  or  with  a  large  number  of 
veins  arising  from  a  cross-vein  at  the  base. 

I.  Ocelli  wapting. 

J.    Exceedingly  flat  bugs,  p.  .788 Aradid^ 

JJ.  Rather  stout  and  heavily  formed  bugs.  p. 
3*^5 Pyrrhocorid^ 

II.  Ocelli  usually  present. 

J.  Head  with  a  transverse  incision  in  front  of 
the  ocelli,  which  are  always  jjresent  (Fig. 
449)-    V-  i>i^ Neidid/e 

JJ.     Head  without  transverse  incision. 

K.  Membrane  with  four  or  five  simple  veins 
arising  from  the  base  of  the  membrane, 
the  two  inner  ones  sometimes  joined  to 
a  cell  near  the  base  (Fig.  413).    p.  386. 

LyC'EID^ 

KK.  Membrane  with  many,  usually  forked 
veins,  springing  from  a  transverse 
basal  vein  (Fig.  414).     p.   389.  .  .  . 

Coreid^ 

HHH.     Hemelytra   vestigial;  parasitic   bugs  preying 
on  bats.    p.  379 Polyctenid^ 

DD.    Antennae  five- jointed.* 

E.  Hemelytra  with  the  clavus  similar  in  texture  to  the  membrane, 
which  is  without  veins  (Fig.  409);  small  semiaquatic  bugs, 
measuring  less  than  3  mm.  in  length  (Hebrus).  p.  372 
Hebrid.'E 

EE.    Hemelytra   with   the   clavus   markedly   thicker   than   the 
membrane. 

F.     Tibia;  armed  with  strong  spines,  p.  391 CydniD/E 

FF.     Tibige  smooth  or  with  small  spines. 

G.     Scutellum  narrowed  behind,  only  rarely  almost  cover- 
ing the  abdomen,  p.   390 PENTATOMiDiE 

GG.  Scutellum  not  narrowed  as  in  the  Pentatomidas, 
very  convex,  nearly  or  quite  covering  the  ab- 
domen,   p.  392 Scutellerid^ 

*ln  some  cases  there  are  minute  intermediate  joints  between  the  principal 
joints  of  the  antennas;  for  the  purposes  of  this  table  these  intermediate  joints  are 
not  counted. 


360 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  410. — Nabi 


Fig.  411. — Miridae. 


Fig.  412. — Pyrrhocoridse. 


Fig.  413.— Lygagidse. 


Fig.  414. — Coreidae. 
Figures  408  to  414. — Diagrams  illustrating  the  types  of  hemelytra  characteristic 
of  several  families  of  Hemiptera. 

Family  CORIXID^* 


The  Water-Boatmen 

The  family  Corixidae  includes  oval,  gray-and-black  mottled  bugs, 
usually  less  than  half  an  inch  in  length,  which  live  in  lakes,  ponds, 
and  streams,  in  both  stagnant  and  running  water.  The  characteristic 
form  and  markings  of  these  insects  are  shown  in  Figure  415. 

The  name  of  the  typical  genus  of  this  family,  Corixa,  is  evidently 
from  the  Greek  word  coris,  meaning  a  bug.  For  this  reason  many 
writers  have  spelled  the  generic  name  Corisa  and  the  family  name 
Corisidse.  This  name  was  probably  given  to  these  insects  iDCcause 
they  have  an  odor  like  that  of  the  bedbug. 

The  water-boatmen  exhibit  some  striking  peculiarities  in  struc- 

*Corixidae,  Corixa,  a  misspelling  of  Corisa:  coris  (kVO,  a  bug. 


IIEMIPTERA  361 

ture:  the  head  overlaps  the  prothorax  instead  of  being  inserted  in 
that  segment;  the  beak  is  ver>^  short  and  scarcely  distinguishable 
from  the  face,  the  opening  to  the  mouth  being  on  the  front  of  the  so- 
called  beak;  the  tarsi  of  the  front  legs  (termed  palce)  are  flattened 
or  scoop-like  in  form;  each  consists  of  a  single  se^^ent  and  bears  a 
comb-like  fringe  of  bristles;  the  middle  legs  are  long,  slender,  and 
end  in  two  claws ;  the  hind  legs  are  flattened  and  fringed  for  swimming ; 
and,  in  the  males,  the  abdominal  sterna,  especially  the  four  caudal 
ones,  are  very  uns\  mmetrical,  being  on  one  side  broken  into  irregular- 
shaped  fragments. 

The  water-boatmen  have  the  body  flattened  above,  and  swim 
upon  their  ventral  surface;  they  differ  in  these  respects  from  the 
members  of  the  next  family.  They  swim  with  a  quick,  darting 
motion ;  they  use  for  this  purpose  chiefly  their  long,  oar-like,  posterior 
legs.  When  in  their  favorite  attitude,  they  are  anchored  to  some 
object  near  the  bottom  of  the  pond  or  aquarium  by  the  tips  of  their 
long,  slender,  intermediate  legs;  at  such  times  the  fore  legs  hang 
slightly  folded,  and  the  posterior  legs  are 
stretched  out  horizontally  at  right  angles  to 
the  length  of  the  body.  The  body  of  these 
insects,  with  the  air  which  chngs  to  it,  is  much 
lighter  than  water;  consequently  whenever 
they  lose  hold  upon  the  object  to  which  they 
have  been  clinging,  they  rise  quickly  to  the 
surface,  unless  they  prevent  it  by  swimming. 
They  occasionally  float  on  the  surface  of  the 
water,  and  can  leap  into  the  air  from  the 
water  and  take  flight.  Fig.  415.— A  water-boat- 

The  bodies  of  these  insects,  as  they  swim 
through  the  water,  are  almost  completely 

enveloped  in  air.  The  coating  of  air  upon  the  ventral  surface  and  sides 
can  be  easily  seen,  for  it  glistens  like  silver.  By  watching  the  insects 
carefully  when  they  are  bending  their  bodies,  the  air  can  be  seen  to  fill 
the  spaces  between  the  head  and  the  prothorax,  and  between  the  pro- 
thorax  and  the  mesothorax.  The  space  beneath  the  wings  is  also  filled 
with  air.  When  these  insects  are  in  impure  water,  they  must  come 
to  the  surface  at  intervals  to  change  this  supply  of  air.  But  I  have 
demonstrated  that  in  good  water  it  is  not  necessary  for  them  to  do 
this.  The  air  with  which  the  body  is  clothed  is  purified  by  contact 
with  the  fine  particles  of  air  in  the  water ;  so  that  the  insect  can  breathe 
its  coat  of  air  again  and  again  indefinitely. 

It  has  been  commonly  believed  that  the  corixids  are  carnivorous ; 
but  Hungerford  ('19)  has  shown,  by  an  extended  series  of  experiments, 
that  these  insects  gather  their  food  supply  from  the  ooze  at  the 
bottom  of  pools  in  which  they  live.  This  flocculent  material  they 
sweep  into  their  mouths  by  means  of  the  flat  rakes  of  their  fore  tarsi. 
This  material  is  largely  of  plant  origin ;  but  the  protozoa  and  other 
minute  animals  living  on  it  are  also  consimied.  This  author  also 
found  that  the  corixids  feed  on  the  chlorophyll  of  Spirogyra. 


362  AN  INTRODUCTION  TO  ENTOMOLOGY 

In  most  cases  the  eggs  of  corixids  are  attached  to  the  steins  of 
aquatic  plants;  but  Ramphocorixa  acuminata  usually  attaches  its 
eggs  to  the  body  of  a  cra^Tfish. 

The  males  of  most  of  the  Corixidas  are  furnished  with  stridulating 
organs.  These  consist  of  one  or  two  rows  of  chitinous  "pegs"  on  the 
fore  tarsi  and  a  roughened  area  on  the  inner  surface  of  the  fore  femora 
near  the  base.  By  rubbing  the  tarsal  comb  of  one  leg  over  the 
roughened  area  of  the  femur  of  the  opposite  leg,  a  chirping  sound  is 
I^roduced.    These  stridulating  organs  dififer  in  form  in  different  species. 

In  addition  to  the  stridulating  organs  of  the  fore  legs  there  is  in 
certain  species  a  more  or  less  curry-comb-like  organ  near  the  lateral 
margin  of  the  dorsal  wall  of  the  sixth  abdominal  segment;  this  has 
been  termed  the  "strigil."  It  is  situated,  when  present,  on  the  left 
side  in  Corixa  and  on  the  right  side  in  several  other  genera.  Its  func- 
tion has  not  been  definitely  determined. 

Both  the  adults  and  the  eggs  of  Corixa  are  used  for  food  for  man 
and  for  birds  in  Mexico  and  in  Egypt.  The  eggs  are  gathered  from 
water-plants.  Glover  states  that  in  Mexico  the  natives  cultivate  a 
sedge  upon  which  the  insects  will  deposit  their  eggs;  this  sedge  is 
made  into  bundles,  which  are  floated  in  the  water  of  a  lake  until 
covered  with  eggs;  the  bundles  are  then  taken  out,  dried,  and  beaten 
over  a  cloth ;  the  eggs,  being  thus  disengaged,  are  cleaned  and  powdered 
into  flour.  Kirkaldy  ('98)  reports  the  importation  into  England  of 
Corixa  mercenaria  and  its  eggs  for  food  of  insectivorous  birds,  game, 
fish,  etc.,  by  the  ton;  and  computes  "that  each  ton  of  the  adults  will 
contain  little  short  of  250  million  individuals!!  As  to  the  ova,  they 
are  beyond  computation."  The  adults  are  captured  at  night  with 
nets  when  they  leave  the  water  in  swarms. 

It  is  difficult  to  separate  the  different  species  of  water-boatmen  on 
account  of  their  close  resemblance  to  each  other;  this  is  especially 
true  of  the  females.  Fifty-five  species  are  listed  in  the  Van  Duzee 
check-list;  these  represent  six  genera. 

Family  NOTONECTID^ 

The  Back-Swimmers 

The  NotonectidcC  differ  from  all  other  aquatic  Hemiptera    in  the 
fact  that  they  always  swim  on  their  backs;  and  there 
is  a  corresponding  difference  in  the  form  of  these  in- 
sects.    The  body  is  much  deeper  than  in  the  allied 
families,  and  is  more  boat-shaped.    The  back,  from 
the  peculiar  attitude  of  the  insect  when  in  the  water, 
^^S-  Y^'^J^I^^f'     corresponds  to  the  bottom  of  a  boat,  and  is  sloped 
nee  a  un  u  a  a.    ^^  ^^  ^^  greatly  resemble  in  form  this  part  (Fig.  416). 
The  eyes  are  large,  reniform,  twice  sinuated  on  the  outer  side, 
and  project  a  little  way  over  the  front  margin  of  the  prothorax.  Ocelli 
are  absent.     The  prothorax  has  the  lateral  margins  shari^  and  pro- 


HEMIPTERA  303. 

jecting.  The  legs  are  all  long;  the  hind  ])air  are  mueh  the  longest  and 
fitted  for  swimming.  The  tarsi  consist  each  of  three  segments,  but 
the  basal  segment  is  so  small  that  it  is  often  overlooked.  There  is  a 
ridge  along  the  middle  line  of  the  venter  which  is  clothed  with  hairs, 
and  along  each  side  of  this  a  furrow.  Along  the  upper  edge  of  the 
outside  of  this  furrow  and  a  short  distance  from  the  side  of  the  body, 
there  is  a  fringe  of  long  hairs,  and  beneath  this  fringe  the  abdominal 
spiracles  are  situated. 

The  features  presented  by  the  ventral  side  of  the  abdomen  just 
referred  to  can  be  seen  on  dead  specimens;  but  it  is  well  to  examine 
them  on  living  insects.  This  can  be  done  by  placing  a  back-swimmer 
in  a  glass  of  water,  and,  when  it  is  resting  at  the  surface  of  the  water, 
stud>'ing  it  b\'  means  of  a  lens  of  low  power.  Under  these  conditions 
it  can  be  seen  that  the  furrow  on  either  side  of  the  venter  is  an  air- 
chamber,  which  is  enclosed  by  the  two  fringes  of  hairs,  one  borne 
by  the  ridge  of  the  middle  line  on  the  body  and  the  other  by  the 
outer  margin  of  the  furrow.  It  can  also  be  seen  that  there  is  a  hole 
near  the  tip  of  the  abdomen  through  which  the  air  passes  into  the 
chambers  beneath  the  fringes  of  hairs.  Sometimes  when  watching 
an  individual  under  these  conditions  it  will  be  seen  to  force  the  air 
out  of  the  chambers  beneath  the  fringes  of  hair,  using  the  hind  legs 
for  this  purpose,  and  sometimes  an  entire  fringe  will  be  lifted  like  a  hd. 

By  examining  the  first  ventral  abdominal  segment  of  a  dead  indi- 
vidual a  little  furrow  can  be  seen  on  each  side;  these  are  air-passages 
extending  between  the  chambers  on  the  ventral  side  of  the  abdomen 
to  that  beneath  the  wings. 

Air  is  also  carried  among  the  hairs  on  the  lower  side  of  the  thorax, 
and  in  the  spaces  between  the  head  and  the  prothorax  and  between  the 
prothorax  and  the  mesothorax;  this  is  probably  expired  air. 

In  collecting  back-swimmers,  care  must  be  taken  or  they  will  inflict 
painful  stings  with  the  stylets  of  their  beak. 

The  manner  of  oviposition  of  these  insects  differs  in  different  spe- 
cies. Some  merely  attach  their  eggs  to  the  surface  of  aquatic  plants 
by  means  of  a  colorless,  water-proof  glue;  others  have  a  long  oviposi- 
tor by  means  of  which  they  insert  their  eggs  in  the  tissue  of  these 
plants. 

The  males  of  some  back-swimmers  possess  stridulating  areas; 
these  are  located  on  the  femora  and  tibias  of  the  fore  legs  and  on  the 
sides  of  the  face  at  the  base  of  the  beak. 

The  notonectids  of  our  fauna  represent  three  genera ;  these  can  be 
separated  by  the  following  table : 

A.     Legs  dissimilar;  hind  legs  flattened  and  fringed  for  swimminp. 

B.    Last  segment  of  the  antennas  much  shorter  than  the  penultimate  segment. 

NOTONECTA 

BB.     Last  segment  of  the  antennae  longer  than  the  penultimate  segment. 

BUENOA 

AA.     Legs  quite  similar Ple.\ 

Notonecta. — To  this  genus  belong  the  greater  number  of  our 
species,  of  which  twelve  have  been  described.     These  are  the  back- 


364  AN  INTRODUCTION  TO  ENTOMOLOGY 

swimmers  that  are  commionly  seen  floating  at  the  surface  of  the  water, 
with  the  caudal  part  projecting  sufficiently  to  admit  of  the  air  being 
drawn  into  the  air  chambers.  When  in  this  position,  their  long, 
oar-like,  hind  legs  are  stretched  outward  and  forward  ready  for  action; 
when  disturbed  they  dart  away  toward  the  bottom  of  the  pond, 
carry-^ing  a  supply  of  air  with  them. 

Buenoa. — This  genus,  of  which  six  species  have  been  found  in  this 
country',  is  composed  of  much  more  slender  forms  than  is  the  preceding. 
The  habits  of  two  of  our  species  have  been  studied  by  Hungerford  ('  19) . 
These  insects  do  not  rest  at  the  surface  of  the  water  as  do  some  species 
of  Notonecta,  but  may  be  seen  swimming  slowly,  or  even  poising  in 
midwater  some  distance  beneath  the  surface.  They  abound  in  water 
teeming  with  Entomostraca,  upon  which  they  largely  feed. 

Plea. — The  members  of  this  genus  are  small  insects,  not  exceeding 
3  mm.  in  length.  The  shape  of  the  body  is  quite  different  from  that 
of  other  back-swimmers,  being  highly  arched  behind.  They  are 
found  in  tangles  of  aquatic  vegetation,  to  the  filaments  of  which  they 
cling  when  at  rest.  They  feed  on  small  Crustacea.  Only  one  species. 
Plea  striola,  has  been  described  from  our  fauna. 


Family  NEPID^ 

The  Water-Scorpions 

The  members  of  this  family  can  be  distinguished  from  other 

aquatic  Hemiptera  by  the  presence  of  a  long  respiratory  tube  at  the 

end  of  the  abdomen.    This  tube  consists  of  two  long  filaments,  each 

with  a  groove  on  its  mesal  side.    By  applying  these 

^^        ^"jjX        filaments  together  the  grooves  form  a  tube,  which 

^^V^/^^        conducts  the  air  to  two  spiracles  situated  at  the 

'^'-N^^^^-^       caudal  end  of  the  abdomen.    By  means  of  this  ap- 

j^HT  paratus  these  insects  are  able  to  rest  on  the  bottom 

^^^H^S|         of  a  shallow  pond,  or  among  rubbish  or  plants  in 

r  H^SP     I        water,  and  by  projecting  this  tube  to  the  surface 

/    ^Br      \       obtain  what  air  they  need. 

J  With  regard  to  the  form  of  the  body,  two  very 

I  different  types  exist  in  this  family.     In  one,  repre- 

I  sented  by  the  genus  Nepa,  the  body  is  a  long  oval, 

pjg  .jy ^gp^      flat,  and  thin  (Fig.  417);  in  the  other,  represented 

apiculata.  by  the  genus  Ranatra,  the  body  is  almost  linear  and 

cylindrical  (Fig.  418).  An  intermediate  form, 
Curicta,  represented  by  two  species,  is  found  in  Louisiana,  Texas,  and 
Arizona. 

The  water-scorpions  are  carnivorous ;  and  with  them  the  first  pair 
of  legs  is  fitted  for  seizing  prey.  In  these  legs  the  coxae  are  very  long, 
especially  in  Ranatra;  the  femora  are  furnished  with  a  groove  into 
which  the  tibiee  and  tarsi  fit  like  the  blade  of  a  pocket-knife  into  its 
handle. 


HEMIPTERA 


365 


Although  the  Nepidae  are  aquatic  insects,  the  second  and  third 
pairs  of  legs  are  fitted  for  walking  rather  than  for  swimming. 

Of  the  genus  Nepa  we  have  only  a  single  species,  Nepa  apiculdta. 
This  insect  is  about  i6  mm.  in  length,  not 
including  the  respiratory  tube,  which 
measures  a  little  more  than  6  mm.  It 
lives  in  shallow  water  concealed  in  the 
mud  or  among  the  dead  leaves  and  twigs, 
lying  in  wait  for  its  prey.  The  eggs  are 
inserted  in  the  tissues  of  decaying  plants ; 
they  are  an  elongate  oval  and  bear  near 
one  end  a  crown  of  eleven  slender  fila- 
ments. 

Of  the  genus  Ranatra  eight  American 
species  have  been  described.  These  in- 
sects are  found  in  the  same  situations  as 
Nepa;  where,  owing  to  the  linear  form  of 
the  body  and  to  the  dirt  with  which  it  is 
usually  covered,  it  is  quite  difficult  to  de- 
tect their  presence.  They  have  also  been 
observed  in  deep  water  clinging  to  the 
stems  of  rushes  and  grasses,  with  the  re- 
spiratory tube  piercing  the  surface  film 
(Bueno) ;  and  also  upon  floating  dead 
leaves  and  stalks  of  cat-tail,  where  they 
were  basking  in  the  sun  and  entirely  dry 
(Hungerford). 

Ranatra  has  stridulating  organs;  these  consist  of  a  roughened 
patch  on  the  outside  of  each  fore  coxa  and  a  rasp  on  the  inner  margin 
of  each  shoulder  of  the  prothorax ;  by  means  of  these  organs  a  squeak- 
ing sound  is  produced. 

The  eggs  of  Ranatra  have  been  described  by  Pettit;  they  are 
elongate  oval,  about  3.5  mm.  in  length,  and  bear  at  one  end  a  pair  of 
slender  appendages,  about  4  mm.  long;  they  are  embedded  in  the 
rotting  stems  of  aquatic  plants,  from  which  the  appendages  of  the 
eggs  project. 

A  monograph  of  the  Nepidfe  of  North  America  was  published  by 
Hungerford  ('22). 


Fig.  418. — Ranatra  fusca. 


Family  BELOSTOMATID^E 
The  Giant  Water-Fugs 


The  common  name  "giant  water-bugs"  was  applied  to  this  family 
because  to  it  belong  the  largest  of  the  Hemiptera  now  living;  a 
species  that  is  found  in  Guiana  and  Brazil  measures  from  75  to  100 
mm.  in  length;  and  the  larger  of  our  species  exceed  in  size  our  other 
water-bugs. 


366 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.    419. — Lethocenis  america- 
nus. 


The  members  of  this  family  are  all  wide  and  flat-bodied  aquatic 
insects,  of  more  or  less  ovate  outline.  The  fore  legs  are  raptorial ; 
the  middle  and  hind  legs  are  fitted  for 
swimming,  being  flattened  and  ciliated; 
this  is  especially  true  of  the  hind  legs. 
At  the  caudal  end  of  the  body  there  is, 
in  the  adult,  a  pair  of  narrow,  strap-like 
respiratory  appendages,  which  are  re- 
tractile. 

These  insects  are  rapacious  creatures, 
feeding  on  other  insects,  snails,  and  small 
fish.  Like  other  water-bugs,  they  fly  fi  om 
pond  to  pond  and  are  frequently  attracted 
to  lights.  This  is  especially  the  case  where 
electric  lights  are  used,  into  which  they 
sometimes  fly  and  are  killed  by  hundreds. 
On  this  account  they  are  known  in  man}' 
parts  of  the  country  as  "electric-light 
bugs." 

The  family  Belostomatid^e  is  repre- 
sented in  this  country  by  four  genera. 
Recent  studies  of  the  nomenclature  of  the 
genera  of  this  famiily  have  resulted  in  the 
making  of  changes  in  some  of  the  generic 

names.    This  should  be  kept  in  mind  when  using  the  older  text-books. 
Our  genera  are  separated  by  Hungerford  ('19)  as  follows: 
A.    Mesothorax  with  a  strong  midventral  keel;  membrane  of  the  hemelytra  re- 
duced   Abedus 

AA.    Mesothorax  without  a  midventral  keel;  membrane  of  the  hemelytra  not 
reduced. 

B.  Basal  segment  of  the  beak  longer  than  the  second;  base  of  the  wing- 
membrane  nearly  or  quite  straight.  Body  about  25  mm.  or  less  in 
length ' Belostoma 

BB.    Basal  segment  of  the  beak  shorter  than  the  second;  base  of  the  wing- 
membrane  sinuous.     Body  more  than  37  mm.  in  length. 
C.    Anterior  femora  grooved  for  the  reception  of  the  tibia.  ..Lethocercs 
CC.    Anterior  femora  not  grooved  for  the  reception  of  the  tibia..  Benacus 

Lethocerus: — To  this  genus 
and  the  following  one  belong  our 
larger  members  of  this  family. 
The  appearance  of  these  insects 
is  indicated  by  Figure  419,  which 
represents  Lethocenis  americaniis. 
In  this  genus  the  anterior  femora 
are  furnished  with  a  groove  for 
the  reception  of  the  tibia.  Five 
species  have  been  described  from 
the  United  States  and  Canada. 
In  most  of  the  references  to  these 
420.  — Belos-  insects  in  our  literature  the  gener- 
ic name  Belostoma  is  used.  p-  .^^  —Male  of 
Benacus. — Only  a  single  spe-      Abedus,  with  eggs. 


Fig. 

toma    flunnnea. 


IIEMIPTERA  367 

ciesoi  this genxxs,  Bendcus  gnseus,  is  found  in  our  fauna.  This  close- 
ly resembles  Lethocerus  americanus  (Fig.  419),  but  can  be  distinguish - 
ed  from  that  species  by  the  absence  of  the  groove  in  the  femora  of  the 
fore  legs. 

Belostoma. — To  this  genus  as  now  recognized  belong  our  more  com- 
mon representatives  of  the  smaller  members  of  this  family.  These 
have  long  been  known  incorrectly  under  the  generic  name  Zaitha. 
Our  most  common  species  is  Belostoma  flummea  (Fig.  420). 

In  this  genus  and  the  following  one  the  eggs  are  carried  by  the 
males  on  their  backs,  where  they  are  placed  by  the  females,  sometimes 
in  spite  of  vigorous  opposition  on  the  part  of  the  male. 

Ahedus. — Five  species  of  this  genus  have  been  found  in  the  south- 
western parts  of  the  United  States.  Figure  421  represents  the  male 
of  one  of  these  carrying  his  load  of  eggs. 


Family  NAUCORID^ 
The  Creeping  Water-^iigs 

The  Naucorida:  includes  flat-bodied,  chiefly  oval  insects,  of 
moderate  size.  The  abdomen  is  without  caudal  appendages.  The 
front  legs  are  fitted  for  grasping,  the  femora  being  greatly  enlarged; 
the  middle  and  hind  legs  are  suited  for  crawling  rather  than  for 
swimming.  There  are  no  ocelli ;  the  antennas  are  very  short,  and -well 
concealed  beneath  the  eyes;  the  beak  is  three-jointed  and  covered 
at  the  base  by  the  large  labnmi ;  and  the  hemely  tra  are  furnished  with 
a  distinct  embolium. 

Although  these  are  aquatic  insects,  they  have  been  comparatively 
little  modified  for  such  a  life.  They  carry  air  beneath  their  wings 
and  obtain  this  air  by  pushing  the  tip  of  the  abdomen 
above  the  surface  of  the  water. 

They  are  predac'ous  and  are  fond  of  reedy  and 
grassy,  quiet  waters,  where  they  creep  about  like  the 
dytiscid  beetles,  creeping  and  swimming  around  and  Fig.422.--Pf/- 
between  the  leaves  and  spravs  of  the  submerged  plants,  oconsfemor- 
seekmg  their  prey. 

Only  two  genera  of  this  family  are  represented  in  our  fauna;  these 
are  Pelocoris  and  Ambry sus.  In  Amhrysus  the  front  margin  of  the 
prothorax  is  deeply  excavated  for  the  reception  of  the  head;  in 
Pelocoris  this  is  not  the  case. 

Pelocoris. — Only  three  speciesof  thisgenus  are  found  in  this  country 
and  these  are  restricted  to  the  eastern  half  of  the  United  States. 
The  most  common  one  is  Pelocoris  femordtiis  (Fig.  422).  It  measures 
about  Q  mm.  in  length,  and  when  alive  is  more  or  less  greenish  testa- 
ceous in  color;  but  after  death  it  is  pale  yellow  or  brownish  in  color, 
with  black  or  dark  brown  markings. 

Ambrysus. — Ten  species  of  this  genus  have  been  found  in  this 
country;  thev  are  restricted  to  the  Far  West. 


368  AN  INTRODUCTION  TO  ENTOMOLOGY 

Family  GELASTOCORID^ 

The  Toad-shaped  Bugs 

The  GelastocoridcB  was  formerly  known  as  the  GalguHdae;  conse- 
quently most  of  the  references  to  these  insects  will  be  found  under 
the  older  family  name,  which  has  been  dropped,  as  the  generic  name 
Galgulus,  on  which  it  was  based,  is  not  tenable. 

In  these  insects  the  body  is  broad  and  short,  and  the  eyes  are 
prominent  and  projecting;  the  form  of  the  body  and  the  protuberant 
eyes  remind  one  of  a  toad  (Fig.  423).     Ocelli  are  present.     The  an- 
tennas are  short  and  nearly  or  quite  concealed  beneath  the  eyes.    The 
beak  is  short,  stout,  and  four-segmented.    The  fore  legs  are  raptorial. 
The  toad-shaped  bugs  live  on  the  muddy  margins 
of  streams  or  other  bodies  of  water.    Some  of  them  make 
holes  for  themselves,  and  live  for  a  part  of  the  time 
beneath  the  ground.     They  feed  upon  other  insects, 
which  they  capture  by  leaping  suddenly  upon  them. 
Their  colors  are  protective  and  vary  so  as  to  agree  with 
Fig.423-7-Ge/-   -f-j-^g  color  of  the  soil  on  which  thev  live.     Hungerford 
/a/?/'"  "''''  has  found  that  the  eggs  are  buried  in  the  sand.     Only 
five  species  are  known  to  occur  in  this  country. 
The  most  common  and  most  widely  distributed  representative  of 
the  family  found  in  this  country  is  Gelasiocoris  oculdtus  (Fig.  423). 
Two  other  species  of  Gelasiocoris  are  found  in  the  Southern  and 
Western  States.     In  this  genus  the  hemelytra  are  not  fused  and  the 
fore  tarsi  are  two-clawed. 

In  the  genus  Mononyx,  of  which  a  single  species,  Mononyxjiiscipes, 
is  found  in  California,  the  hemelytra  are  free,  but  the  fore  tarsi  are 
one-clawed. 

The  genus  NMhra  is  also  represented  in  this  country  by  a  single 
species,  Nerthra  styglea,  which  is  found  in  Georgia  and  Florida.  In 
this  genus  the  hemelytra  are  fused  together  along  a  straight  suture 
indicated  by  a  groove. 

Family  OCHTERID^ 

The  Ochterids 

These  are  shore-inhabiting  bugs,  which  are  closely  allied  to  the 
preceding  family,  in  which  they  were  formerly  classed.  They  differ 
from  the  toad-shaped  bugs  in  having  the  fore  legs  slender  and  fitted 
for  running,  and  in  having  the  short  antennae  exposed.  They  resemble 
the  following  family,  the  Saldidae,  in  having  the  beak  long,  reaching 
the  hind  coxae.    The  eyes  are  prominent,  and  two  ocelli  are  present. 

The  family  includes  a  single  genus,  Ochterus,  which,  due  to  an 
error,  has  been  commonly  known  as  Pelogonus.  Only  three  species 
occur  in  the  United  States;  one  of  these  was  described  from  Virginia, 
one  from  Florida,  and  the  third  is  widely  distributed  from  the  At- 
lantic Coast  to  Arizona. 


HEMIPTERA  369 

The  widely  distributed  species  is  Ochterns  americanus.  It  measures 
5  mm.  in  length,  and  is  blackish  in  color  sprinkled  with  golden  yellow 
points.  On  each  side  of  the  prothorax,  behind  the  front  angles,  there 
is  a  bright  yellow  spot. 

The  members  of  this  family  are  predacious. 


Family  SALDID^ 

The  Shcre-Fngs 

With  the  Saldida?  we  reach  the  beginning  of  the  extensive  series 
of  families  of  Hemiptera  in  which  the  antennae  are  prominent  and 
are  not  concealed  beneath  the  head.     In  this  family  the  insects  are  of 
small  size,  and  of  dark  colors  with  white  or  yellow  markings.     The 
head  stands  out  free  from  the  thorax  on  a  cylindrical  base.    The  an- 
tennae are  four-jointed;  there  are  two  ocelli;  the  rostrum  is  three- 
jointed  and  very  long,  reaching  to  or  beyond  the  middle 
coxae.     The  membrane  of  the  wing-covers  is  furnished 
with  looped  veins,  forming  four  or  five  long  cells  placed 
side  by  side.    Occasionally  there  is  little  or  no  distinc- 
tion between  the  corium  and  the  membrane.  Two  forms 
sometimes  occur  in  the  same  species,  one  with  a  dis- 
tinct membrane,  and  another  with  the  membrane  thick-  ^^S-  424— A 
ened  and  almost  as  coriaceous  as  the  corium  proper.       ^'loreoug. 
The  shape  of  these  shore-bugs  is  shown  by  Figure  424. 

These  insects  abound  in  the  vicinity  of  streams  and  other  bodies 
of  water,  and  upon  damp  soils,  especially  of  marshes  near  our  coasts. 
Some  of  the  shore  bugs  dig  burrows,  and  live  for  a  part  of  the  time 
beneath  the  ground.  They  take  flight  quickly  when  disturbed,  but 
alight  after  flying  a  short  distance,  taking  care  also  to  slip  quickly  into 
the  shade  of  some  projecting  tuft  of  grass  or  clod  where  the  soil 
agrees  with  the  color  of  their  bodies. 

Thirty-three  species  belonging  to  this  family  have  been  found  in 
the  United  States  and  Canada;  these  represent  eight  genera. 


Family  VELIID.^ 

The  Broad-shouldered  Water-Striders 

The  Velliidse  includes  insects  which  are  very  closely  allied  to  the 
following  family,  the  water-striders,  both  in  structure,  and  in'^habits. 
In  both  families  the  distal  segment  of  the  tarsi,  at  least  of  the  fore 
tarsi,  is  more  or  less  bifid,  and  the  claws  are  inserted  before  the  apex ; 
these  characters  distinguish  these  two  families  from  all  other  Hemip- 
tera. In  the  Veliidje  the  body  is  usually  stout,  oval,  and  broadest 
across  the  prothorax  (Fig.  425).  The  beak  is  three- jointed;  the  legs 
are  not  extremely  long,  the  hind  femora  not  extending  much  beyond 


370  AN  INTRODUCTION  TO  ENTOMOLOGY 

the  end  of  the  abdomen.  In  fact,  the  legs  are  fitted  for  running  over 
the  water,  instead  of  for  rowing,  as  with  the  Gerridas.  The  intermedi- 
ate legs  are  about  equidistant  from  the  front  and  hind  pairs,  except 
in  Rhcgovelia.  These  insects  are  dimorphic,  both  fully  winged  and 
short -winged  or  wingless  adults  occurring  in  the  same  species. 

About  twenty  species  of  this  family  have  been  found  in  America 
north  of  Mexico;  these  represent  four  genera. 

The  broad-shouldered  water-striders  are  found  both  on  the  banks 
of  streams  and  ponds  and  on  the  surface  of  water.  About  one-half 
of  our  species  belong  to  the  genus  Microvelia.  These  are  very  small, 
plump-bodied  bugs,  which  are  usually  black  and  silvery  in  color  or 
mottled  with  brown.  They  are  found  at  the  water's  edge  but  run 
out  on  the  water  when  disturbed ;  and  they  are  also  often  found  upon 
rafts  of  floating  vegetation. 

To  the  genus  Rhagovelia  belong  somewhat  larger  forms,  which  are 

characteri2ed  by  the  long,  deeply  split,  terminal 

segment  of  the  tarsi  of  the  middle  legs.    Our  most 

common  species  of  this  genus  is  Rhagovelia  ohesa 

(Fig.  425).     These  bugs  are  found  running  over 

the  surface  of  rapidly  moving  waters  in  streams. 

They  can  also  dive  and  swim  well  under  water. 

Four   species    of   Rhagovelia   are    found    in    this   ^.  „,         ,. 

,     ^  '^  Fig.  42s. — Kliapovelia 

country.  *>  -+  o 

The  genus  Velia  includes  the  larger  members 
of  the  family.  In  these  the  tarsi  of  the  middle  legs  are  not  cleft. 
Four  species  of  this  genus  occur  in  our  fauna.  They  are  found  on 
moderately  rapid  streams  or  little  bogs  and  eddies  connected  there- 
with. 

The  fourth  genus  occurring  in  our  fauna  is  represented  by  a  single 
species,  Mocrovelia  harrisii,  which  is  restricted  to  the  Far  West. 

Family  GERRID^ 
The  Water-Striders 

This  family  includes  elongated  or  oval  insects  which  live  upon  the 
surface  of  water.  Their  legs  are  long  and  slender;  the  hind  femora 
extend  much  beyond  the  apex  of  the  abdomen;  the  middle  and  hind 
pairs  of  legs  are  approximated  and  distant  from  the  fore  legs;  the 
terminal  segment  of  the  tarsi,  at  least  of  the  fore  tarsi,  is  more  or 
less  bifid,  and  the  claws  are  inserted  before  the  apex.  The  beak  is 
four-jointed.    The  antenna  are  long  and  four-jointed. 

The  water-striders  prefer  quiet  waters,  upon  which  they  rest  or 
over  which  they  skim  rapidly;  they  often  congregate  in  great 
numbers.  There  are  commonly  two  forms  of  adults  belonging  to  the 
same  species,  the  winged  and  the  wingless;  sometimes  a  third  form 
occurs  in  which  the  adult  has  short  wings. 

These  insects  are  predacious;  they  feed  on  insects  that  fall  into 
the  water,  and  I  have  seen  them  jump  from  the  water  to  capture  flies 
and  other  insects  tliat  were  flying  near  them. 


II  KM  I PT  ERA  371 

Twenty  species  of  water-striders  ha\^e  been  found  in  America 
north  of  Mexico;  these  represent  seven  genera.  These  genera  are 
separated  by  Hungerford  ('19)  as  follows: 

A.    Inner  margin  of  the  eyes  sinuate  behind  the  middle.     Body  comparatively 
long  and  narrow;  abdomen  long.     (Subfamily  Gerrinse). 
B.    Pronotum  sericeous,  dull;  antennae  comparatively  short  and  stout. 

C.     First  segment  of  the  antennae  shorter  than  the  second  and  third  taken 
together. 
D.    Antennae  half  as  long  as  the  body;  sixth  abdominal  segment  of  the 

male  roundly  emarginate Limnoporus 

DD.    Antennae  not  half  as  long  as  the  body,  not  extending  beyond  the 
thorax;  sixth  abdominal  segment  of  the  male  doubly  emarginate. 

Gerris 

CC.    First  segment  of  the  antennae  longer  than  the  second  and  third  taken 

together Gerris 

BB.     Pronotum  glabrous,  shining;  antenna  long  and  slender.  .  .Tenagogonus 
AA.     Inner  margin  of  the  eyes  convexly  rounded.     Body  comparatively  short 
and  broad;  abomen  so  short  as  to  appear  almost  nymjjhal  in  some  forms. 
(Subfamily  Halobatinae). 
B.     First  antennal  segment  much  shorter  than  the  other  three  taken  together; 
not  much  longer  than  the  second  and  third  taken  together,  and  some 
times  shorter. 
C.    Fourth  (apical)  segment  of  the  antennas  longer  than  the  third. 
D.    Eyes  fairly  prominent;  colors  of  body  black  and  yellow.  .Trepobates 
DD.      Eyes    smaller,    widely    separated;  body    lead-colored,    sericeous. 

ocean  dwellers Halobates 

CC.  Fourth  segment  of  antennae  never  more  than  equal  to  the  third; 
basal  segment  of  anterior  tarsi  much  shorter  than  the  second; 
hind  femur  equal  to  or  much  shorter  than  the  hind  tibia  and  tarsus 

taken  together Rheumatobates 

BB.    First  antennal  segment  nearly  equal  to  the  remaining  three  taken  to- 
gether, much  longer  than  the  second  and  third;  antennas  almost  as 
long  as  the    entire  body;  hind  femur  twice  as  long  as  hind  tibia. 
Metrobates 

Gerris. — Of  the  twenty  species  of  water-striders  found  in  this 
country,  nine  belong  to  this  genus;  a  common  species  in  the  East  is 
Gerris  conformis  (Fig.  426). 


Fig.  426. — Gerris  conformis. 

Limndporus.- — We  have  only  a  single  species  of  this  genus,  L.  rii- 
Joscutilldtus. 

Tenagogonus. — Three  species  are  listed  from  our  fauna,  only  one 
of  which  has  been  found  in  the  North;  this  is  T.  gillettei,  which  is 
reported  from  Ohio.    The  others  are  found  in  Florida  and  California. 

Metrobates.- — Our  only  species,  M.  hesperius,  is  found  in  Ontario 
and  the  eastern  part  of  the  United  States. 


372  AN  INTRODUCTION  TO  ENTOMOLOGY 

Trepobates. — This  genus  is  represented  only  by  T.  ptctus.  This 
is  a  beautiful  vellow  and  black  species,  which  is  quite  widely  distribut- 
ed. 

Rheumatobates. — Three  species  of  this  genus  have  been  described . 
The  males  are  remarkable  for  the  strange  form  of  the  posterior  femora, 
which  are  strongly  bent,  and  the  shape  of  the  antennse,  which  are 
fitted  for  clasping. 

Halobates. — These  are  truly  pelagic  insects,  living  on  the  surface 
of  the  ocean,  often  hundreds  of  miles  from  land.  They  are  most 
abundant  in  the  region  of  calms  near  the  equator;  they  feed  on  the 
juices  of  dead  animals  floating  on  the  surface,  and  probably  attach 
their  eggs  to  floating  sea-weed  (Sargassum) .  H.  micans  is  found  off 
the  coast  of  Florida  and  H.  sericeus  off  the  coast  of  California. 

Family  MESOVELIID.'E 

The  Mesoveliids 

This  is  a  small  family  of  which  only  two  species  have  been  found 
in  North  America.    These  are  the  following. 

Mesovelia  mulsdnti. — This  is  a  small  bug,  measuring  only  4  or 
5  mm.  in  length;  it  is  of  a  pale  yellow  color  marked  with  brown. 
The  antennae  are  long,  filiform.,  and  four-jointed;  the  beak  is  three- 
jointed;  the  legs  are  moderately  long  and  slender;  and  the  tarsi  are 
three-jointed.  This  species  is  dimorphic,  the  adults  being  either  winged 
or  wingless.  In  the  winged  form,  the  membrane  of  the  hemelytra  is 
without  veins. 

This  species  lives  on  the  surface  of  quiet  waters  and  on  rafts  of 
floating  vegetation  and  is  predacious.  It  is  furnished  with  an  ovi- 
positor and  embeds  its  eggs  in  the  stems  of  aquatic  plants. 

Mesovelia  douglasensis . — This  is  a  smaller  species  than  the  pre- 
ceding; the  length  of  the  female  is  2.1  mm.,  of  the  male  1.8  mm.  It 
is  olive-brown  in  color.  It  was  recently  discovered  and  described  by 
Professor  Hungerford  ('24).  It  was  found  near  Douglas  Lake,  Michi- 
gan. 

Family  HEBRID^ 

The  Hebrids 

This  family  includes  very  small  plump-bodied  bugs,  measuring 
less  than  3  mm.  in  length.  The 
antenna  are  either  four-jointed  or  five- 
jointed;  the  beak  is  three-jointed;  and  the 
tarsi  are  two-jointed.  Ocelli  are  present. 
The  head  and  thorax  are  sulcate  beneath. 
The  clavus  of  the  hemelytra  is  similar  in 
texture  to  the  membrane,  which  is  without 

^1/S;r^^™'''^'''°"  °^     ^'^'"^  ^^'S-  427)-    Two  genera  of  this  family 
^  '^"■^'  are  found  in  the  United  States. 


HEMIPTERA  373 

Hebrus.- — In  this  genus  the  antennae  consist  of  five  segments,  not 
counting  a  minute  segment  at  the  base  of  the  third.  The 
adults  are  always  winged.  Four  species  occur  in  our  fauna.  These 
bugs  are  found  on  moist  earth  at  the  margins  of  pools  and  run  out 
upon  the  water  when  disturbed;  they  are  also  found  on  floating 
vegetation. 

Merragdta. — In  this  genus  the  antennae  are  four-jointed  not  count- 
ing the  small  segment  at  the  base  of  the  third.  The  adults  are  dimor- 
phic, short-winged  and  long-winged  forms  occcurring  in  the  same 
species.  These  insects  inhabit  still  and  stagnant  waters  and  often 
descend  beneath  the  surface;  at  such  times  the  body  is  surrounded 
by  a  film  of  air.  Only  two  species  have  been  found,  as  yet,  in  this 
country. 

Family  HYDROMETRID.-E 
The  Water-Measurers 

The  members  of  this  family  are  very  slender  insects,  with  linear 
legs  and  antennae  (Fig.  428) .  The  head  is  as  long  as  the  entire  thorax, 
although  this  region  is  long  also.  The  eyes  are 
round,  projecting,  and  placed  a  little  nearer  the 
base  than  the  tip  of  the  head.  Ocelli  are  absent. 
The  antenna  are  four-jointed;  the  beak  is  three- 
jointed;  and  the  tarsi  are  three-jointed. 

These  insects  creep  slowly  upon  the  surface  of 
the  water;  they  carry  the  body  considerably  ele- 
vated, and  are  found  mostly  where  plants  are 
growing  in  quiet  waters.  It  was  probably  their 
deliberate  gait  when  walking  on  water  that  sug- 
gested the  generic  name  Hydrometra,  or  water- 
measurer.  In  this  country  these  insects  have 
been  commonly  known  under  the  generic  name 
Limnobates,  or  marsh-treaders ;  but  Hydrometra 
is  much  the  older  name. 

Only  three  species  have  been  found  in  the 
United  States.    One  of  these,  Hydrometra  martini  Fig.  428. — Hydrome- 
(Fig.  428),  is  widely  distributed.    The  other  two,       tra  martini' 
Hydrometra  australis  and  Hydrometra  wileyi,  are 
found  in  the  South.    These  insects  are  dimorphic   both  winged  and 
wingless  forms  occurring  in  the  same  species.     Descriptions  of  the 
three  species  are  given  by  Hungerford  ('23). 

The  egg  of  Hydrometra  martini  is  remarkable  in  form ;  it  is  figured 
on  page  167. 

Family  SCHIZOPTERID^ 
The  Schizopterids 

This  family  and  the  following  one,  the  Dipsocoridae,  constitute  a 
quite  distinct  superfamily,  the  members  of  which  are  most  easily  rec- 


374 


AN  INTRODUCTION  TO  ENTOMOLOGY 


ognized  by  the  form  of  the  antennae  (Fig.  429,  b).  These  are  four- 
jointed;  the  first  two  segments  are  short  and  thick;  the  third  and 
fourth  segments  are  long,  slender,  and  clothed  with  long  hairs; 
the  third  segment  is  thickened  toward  the  base.  In  these  two  families 
ocelli  are  present;  the  beak  is  three- 
jointed;  the  legs  are  quite  slender,  and 
the  tarsi  are  three-jointed.  The  species 
are  small  or  very  minute. 

The    vSchizopteridae    is    distinguished 

from  the  following  family  by  the  shape 

of  the  head  and  the  form  of  the  cavities  in 

which  the  front  legs  are  inserted.     The 

head  when  viewed  from  above  is  wider 

than  long  and  is  strongly  defiexed;  the 

fore   coxal   cavities  are  very   prominent 

and  tumidly  formed.     The  beak  is  short. 

Fig.  429.~Glyptocombussaltator:        The  Schizopteridas  is  represented  in 

a,  dorsal  aspect;  b,  antenna,  our  fauna  by  a  single  species,  Glyptocom- 

(After  Heidemann.)  bus  saltdtor  "(Fig.  429).    This  is  a  minute 

bug,  measuring  only  1.2  mm.  in  length 

and    .6   mm.    in    width.    The    known    specimens    were   taken    on 

Plimimers    Island,     Md.    The    describer   of     this    species,    Mr.    O. 

Heidemann,  states:  "This  species  is  most  difficult  to  collect  and  is 

only  to  be  found  by  sifting  fallen  leaves,  rubbish  and  earth.    The 

collector  must    watch  patiently  until  the   minute  insect  makes    its 

presence  known  by  jumping,  and  even  then  it  takes  a  skillful  hand 

to  secure  it  in  a  vial." 


Family  DIPSOCORID^ 
The  Dipsocorids 

This  family  is  closely  allied  to  the  preceding  family;  the  dis- 
tinguishing features  common  to  the  two  families  are  indicated  in  the 
account  of  that  family. 

In  the  Dipsocoridce  the  head  is  extended  horizontally  or  slightly 
defiexed,  and  the  fore  coxal  cavities  are  not  at  all  prominent.  The 
beak  is  long. 

This  family  is  represented  in  our  fauna  by  a  single  genus,  Cera- 
tocombtis,  of  which  two  or  three  species  have  been  found  in  New 
Mexico;  and  one  of  these  is  doubtfully  reported  from  Florida.  These 
measure  less  than  2  mm.  in  length. 


Family  ISOMETOPID^ 

The  Tsometopids 

This  is  a  family  of  limited  extent,  there  being  very  few  species 
known  in  the  entire  world.  It  includes  ver\^  small  bugs,  those  found 
in  this  country  ranging  from  2  mm.  to  2.6  mm.  in  length. 


HEMIPTERA 


375 


The  Isometopickc  is  closely  allied  to  the  followinj^;  famih-,  the 
Mirida;;  by  some  writers  it  has  been  classed  as  a  subfamil\'  of  that 
family.  In  both  families  the  antennae 
are  four-jointed;  the  beak  is  four-jointed; 
the  hemelytra  are  composed  of  cla\ais, 
corium,  cuneus,  and  membrane;  at  the 
base  of  the  membrane  there  are  one  or 
two  cells;  otherwise  the  membrane  is  with 
out  veins.  The  Isometopidse  is  dis- 
tinguished from  the  following  family  by 
the  presence  of  ocelli,  two  in  number. 

Only  four  species  of  this  family  have 
been  found  in  our  fauna;  one  in  Texas, 
one  in  Arizona,  and  two  in  the  East. 
The  Eastern  species  are  Myiomma  cixii- 
formis,  which  is  dull  black  in  color  with  a 
narrow  white  band  across  the  base  of  the 
cuneus;  and  Isometopus  pulchellus,  which 
is  easily  recognizable  by  its  contrasting 
colors  of  dark  brown  and  yellowish  white 
(Pig.  430).  Both  are  exceedingly  rare  in- 
sects. 


Family  MIRID^ 
The  Leaf-Bugs 


Fig.    430.  — Isometopus    pulchel- 
lus.    (After  Heidemann.) 


This  family,  which  has  been  known  as  the  Capsidae,  is  more  large- 
h'  represented  in  this  country  than  any  other  family  of  the  Hemiptera. 
Van  Duzee  in  his  "Catalogue  of  the  Hemiptera  North  of  Mexico" 
lists  398  species,  which  represent  129  genera.  The  species  are  usually 
of  medium  or  small  size.    The  form  of  the  body  varies  greatly  in  the 

different  genera,  which  makes 
it  difficult  to  characterize  the 
family. 

The  most  available  char- 
acter for  distinguishing  these 
insects  is  the  structure  of  the 
hemelytra.  These  are  almost 
always  complete,  and  com- 
posed of  clavus,  corium,  cuneus, 
and  membrane.  At  the  base  of  the  membrane  there  are  one  or  two 
cells;  otherwise  the  membrane  is  without  veins  (Fig.  431).  Other 
characters  of  the  family  are  as  follows:  the  ocelli  are  wanting;  the 
beak  and  the  antennas  are  each  four-jointed ;  the  coxae  are  subelongate; 
and  the  tarsi  are  three-jointed. 

It  is  impracticable  to  discuss  here  the  divisions  of  this  family; 

reference  can  be  made  to  only  a  few  of  the  more  common  species. 

The  four-lined  leaf-bug,  Pcecilocapsus  lineatus. — This  is  a  bright 


Pcedlocapsus 


376  AN  INTRODUCTION  TO  ENTOMOLOGY 

yellow  bug,  marked  with  black.  It  measures  about  8  mm.  in  length. 
There  are  four  longitudinal  black  lines  which  extend  over  the 
prothoraxand  the  greater  part  of  the  hemeMra  (Fig.  432).  There  is 
in  man}^  individuals  a  black  dot  on  the  cuneus  of  each  hemelytron; 
and  the  membrane  is  also  black. 

This  insect  infests  various  plants,  but  abounds  most  on  the 
leaves  of  currant,  gooseberry,  mint,  parsnip,  Weigela,  Dahlia,  and 
rose.  It  punctures  the  young  and  tender  leaves,  causing  small 
brown  spots;  but  these  are  sometimes  so  nimierous  and  closely 
placed  that  the  leaves  become  completely  withered.  It  is  a  widely 
distributed  species,  its  range  extending  from  Canada  to  Georgia  and 
westward  to  the  Rocky  Alountains. 

There  is  only  one  generation  a  year.  The  eggs  are  laid  in  the 
terminal  twigs  of  currant  and  other  bushes  in  midsummer  and  hatch 
the  following  spring.  They  are  laid  in  clusters,  each 
containing  six  or  eight  eggs;  these  egg-clusters  are 
forced  out  of  the  stem  somewhat  by  the  growth  of  the 
surrounding  plant  tissue;  and  as  the  projecting  part  of 
the  egg  is  white,  they  can  be  easily  found. 

The  methods  of  control  are  the  pruning  and  burning 
of  twigs  containing  egg-clusters,  and,  early  in  the  season, 
^fuolat>s'  ^^^  destruction  of  the  nymphs  by  the  use  of  kerosene 
lineatus.  emulsion  or  some  one  of  the  tobacco  extracts. 

The  tarnished  plant-bug,  Lygus  pratensis. — The 
tarnished  plant-bug  is  a  very  common  species  which  is  found  through- 
out the  United  States  and  in  Canada.  It  is  smaller  than  the  preceding 
species,  measuring  5  mm.  in  length  and  2.5  mm.  in  its  greatest  width. 
It  is  exceedingly  variable  in  color  and  markings ;  its  color  varies  from  a 
dull  bark -brown  to  a  greenish  or  dirty  yellowish  brown.  In  the  more 
typical  forms  the  prothorax  has  a  yellowish  margin  and  several 
longitudinal  yellowish  lines;  there  is  a  V-shaped  yellowish  mark  on 
the  scutellum;  the  distal  end  of  the  corium  is  dark;  and  the  cuneus 
is  pale,  with  a  black  point  at  the  apex. 

This  pest  is  a  very  general  feeder;  it  has  been  recorded  as  injuring 
about  fifty  species  of  plants  of  economic  value;  its  injuries  to  the 
buds  of  Aster,  Dahlia,  and  Chrysanthemum,  and  to  the  buds  and 
blossoms  of  orchard -trees,  and  to  nursery  stock,  are  well-known. 
As  yet  no  practical  method  of  control  of  this  pest  has  been  found. 

The  apple-redbug,  Heterccordylus  malinus. — This  species  and  the 
following  one  are  sometimes  a  serious  pest  in  apple  orchards.  They 
cause  spotting  of  the  leaves;  but,  what  is  far  more  serious,  they  punc- 
ture the  young  fruit,  which  results  either  in  the  dropping  of  the 
fruit  or  in  its  becoming  badly  deformed  so  as  to  be  unmarketable. 
The  eggs  are  inserted  into  the  bark  of  the  smaller  branches  late  in 
June  or  early  in  July;  they  hatch  in  the  following  spring  soon  after 
the  opening  of  the  leaves  of  the  fruit-buds.  The  n)  mphs  are  tomato- 
red  in  color.  They  first  attack  the  tender  leaves,  but  as  soon  as  the 
fruit  sets  they  attack  it.     The  young  nymphs  can  be  killed  by  an 


IIEMIPTERA  377 

application  of  "black  leaf  40"  tobacco-extract  diluted  at  the  rate  of. 
I  pint  in  100  gallons  of  water;  the  efficiency  of  this  spray  is  increased 
by  the  addition  of  about  4  pounds  of  soap  to  each  100  gallons.  Two 
applications  of  the  spray  should  be  made:  the  first,  just  before  the 
blossoms  open;  the  second,  just  after  the  petals  fall.  The  spraying 
should  be  done  on  bright  warm  days,  for  in  cool  weather  many  of  the 
nymphs  hide  away  in  the  opening  leaves. 

The  adult  apple-redbug  is  about  6  mm.  long.  The  general  color 
varies  from  red  to  nearly  black.  Usually  the  thorax  is  black  in  front 
and  red  behind.  The  wings  are  red.  usually  black  along  the  inner 
edge  and  with  a  pointed  ovate  black  spot  near  the  outer  margin. 
The  scutellum,  legs,  and  antenn£e  are  black.  The  entire  dorsal  sur- 
face is  sparsely  covered  with  conspicuous  white,  flattened,  scale-like 
hairs. 

The  false  apple-redbug,  Lygideamendax. — This  species  resembles 
the  preceding  one  in  general  appearance  and  in  habits.  The  nymphs 
can  be  distinguished  by  their  brighter  red  color,  b^  the  absence  of 
dusky  markings  on  the  thorax,  and  by  having  the  body  clothed  with 
fine,  short,  black  hairs.  The  adult  of  this  species  is  lighter- colored  and 
lacks  the  scale-like  hairs  on  the  dorsal  surface. 

The  above  account  of  these  two  species  is  an  abstract  of  one  pub- 
lished by  Professor  C.  R.  Crosby  ('11). 

The  hop-redbug,  Paracalocoris  hawleyi. — The  leaves  of  hop  plants 
are  sometimes  perforated  and  the  stems  stunted  and  deformed  by  the 
nymphs  of  this  species,  which  are  red  with  white  markings.  The 
adult  is  6  mm.  long,  black,  with  hemelytra  hyaline  or  pale  yellowish, 
and  the  cuneus  reddish.     For  a  detailed  account  see  Hawley  ('17). 

Family  TERMATOPHYLID^ 

The  Termatophylids 

This  family  is  closely  allied  to  the  following  one,  the  Anthocorida?, 
but  differs  in  that  the  beak  is  four-jointed  and  ocelli  are  wanting. 
The  hemelytra  are  well  developed,  furnished  with  an  embolium,  and 
usually  with  a  single  large  cell  in  the  membrane.  The  tarsi  are  three- 
jointed  and  are  not  furnished  with  an  arolium. 

The  Termatophylidffi  is  a  very  small  family,  but  it  is  world-wide 
in  its  distribution.  A  single  very  rare  species  has  been  found  in  this 
country.  This  is  Hesperophylum  heidemdnni,  which  has  been  taken 
in  New  Hampshire  and  Arizona.  Only  the  female  of  this  species  has 
been  described.  It  is  dark  brown  with  the  scutellum  yellowish  white; 
the  cell  in  the  membrane  of  the  hemelytra  is  semicircular ;  the  length 
of  the  body  is  4  mm. 

Family  ANTHOCORID^ 

The  Flower-Bugs 

This  family  is  closely  allied  to  the  following  one;  but  in  the 
flower-bugs   ocelli   are   present,    though   sometimes   difficult   to  see. 


378  AN  INTRODUCTION  TO  ENTOMOLOGY 

and  the  hemelytra  are  almost  always  fully  developed  and  are  furnished 

with  an  embolium  (Fig.  433).     As  in  the  following  family,  the  beak 

consists  of  three  segments;  the 
antenna},  of  four;  and  the  tarsi, 
of  three. 

The  species  are  small.  The}^ 
are  found  in  a  great  variety  of 
situations,  often  upon  trees  and 
on  flowers,  sometimes  under  bark 
or  rubbish.  They  are  predacious. 
-Hemelytron  of  Triphelps.  Thirty-six  Species  have  been 

catalogued   in   our  fauna;  these 

represent  thirteen  genera.     The  following  species  will  serve  as  an 

example. 

The  insidious  flower-bug,  Triphelps  insididsns. — -This  is  perhaps 
the  best -known  of  our  species.  It  is  a  small  black  bug,  measuring 
only  2  mm.  in  length;  the  hemelytra  are  yellowish  white  on  the 
coritmi,  at  the  tip  of  which  is  a  large,  triangular,  blackish  spot;  the 
membrane  is  milk}'-  white.  This  species  is  widely  distributed;  it  is 
common  on  flowers,  and  is  often  found  preying  upon  the  leaf -inhabit- 
ing form  of  the  grape  Phylloxera;  it  is  also  often  found  in  company 
with  the  chinch-bug,  upon  which  it  preys  and  for  which  it  is  some- 
times mistaken. 

Family  CIMICID^ 

The  Bedbug  Family 

The  members  of  this  family  are  parasitic  bugs,  which  are  either 
wingless  or  possess  only  vestigial  hemelytra.  In  these  insects  the 
ocelli  are  absent,  the  antennae  are  four-jointed,  the  beak  is  three- 
jointed,  and  the  tarsi  are  three-jointed.  Only  four  species  belonging 
to  this  family  have  been  found  in  America  north  of  Mexico.  These 
can  be  separated  by  the  following  table,  which  is  based  on  a  more 
detailed  one  given  by  Riley  and  Johannsen  ('15). 

A.    Beak  short,  reaching  to  about  the  anterior  coxs. 

B.     Pronotum  with  the  anterior  margin  very  deeply  sinuate.  The  genus  Cimex. 
C.    Body  covered  with  very  short  hairs;  second  segment  of  the  antenna; 
shorter  than  the  third;  hemelytra  with  the  inner  margin  rounded  and 
shorter  than  the  scutellum.      The   common    bedbug.  .  .C.  lectuldrius 
CC.    Body  covered  with  longer  hairs;  second  and  third  segments  of  the  an- 
tennas of  equal  length;  hemelytra  with  the  inner  margin  straight 
and  longer  than  the  scutellum.    Species  found  on  bats.  .  .C.pilosellus 
BB.    Anterior  margin  of  the  pronotum  very  shghtly  sinuate  or  nearly  straight 
in  the  middle.     Species  found   in   swallows'    nests ..  .Qictacus  vicdrius 
AA.    Beak  long,  reaching  to  the  posterior  coxae.    Infests  poultry  in  southwest 
United  States  and  in  Mexico Hamatoslphon  inodorus 

The  common  bedbug,  Clmex  lectuldrius. — The  body  is  ovate  in 
outline  and  is  very  fiat  (Fig.  434) ;  it  is  reddish  brown  in  color,  and  is 
4-5  mm.  long  by  3  mm.  broad  when  full-grown.    This  pest  is  a  noc- 


HRMIPTERA 


379 


Fig.434.— Cme.v 
lectulanus. 


turnal  insect,  hiding  by  day  in  cracks  of  furniture  and  beneath  various 
objects.  Ordinarily  it  is  found  only  in  the  dwellings  of  man;  but  it 
has  been  known  to  infest  chicken  houses.  The  means 
commonly  employed  to  destroy  this  pest  is  to  wet 
the  cracks  of  the  bedstead  and  other  places  in  which 
it  hides  with  corrosive  sublimate  dissolved  in  alco- 
hol. This  is  sold  by  druggists  under  the  name  of 
bedbug  poison.  As  this  substance  is  a  virulent 
poison,  it  should  be  used  with  great  care.  In  case  a 
room  is  badly  infested,  it  should  be  thoroughly 
cleaned;  fumigated  with  sulphur  or  with  hydro- 
cyanic acid  gas;  the  walls  repapered,  kalsomined, 
or  whitewashed ;  and  the  woodwork  repainted.  Detailed  directions 
for  the  use  of  gases  against  household  insects  are  given  by  Herrick 
('14).  In  traveling,  where  one 
is  forced  to  lodge  at  places  in- 
fested by  this  insect  or  by  fleas, 
protection  from  them  can  be  had 
by  sprinkling  a  small  quantity 
of  pyrethrum  powder  between 
the  sheets  of  the  bed  on  retiring. 
The  other  members  of  this 
family  found  in  this  country  can 
be  distinguished  from  the  com- 
mon bedbug  by  means  of  the  table 
given  above. 

Family  POLYCTENID.-E 

The  Many-combed  Bugs 

The  Polyctenidffi  includes  a 
small  number  of  very  rare  species 
of  bugs  that  are  parasitic  upon 
bats.  Until  recently  it  was  not 
known  to  be  represented  in 
America  north  of  Mexico;  but 
Ferris  ('19)  records  the  finding 
of  one  species,  Hesperoctenes  longi- 
ceps,  on  the  bat  Eumops  calif  orni- 
cus,  near  San  Bernardino,  Cali- 
fornia. Figure  435  is  a  reduced 
copy  of  a  figure  of  this  insect  by 
Ferris.  The  left  half  of  the  figure 
represents  the  dorsal  aspect  of 
this  insect;  the  right  half,  the 
ventral  aspect.  This  carefully  made  figure  renders  a  detailed 
description  unnecessary.  The  length  of  the  body  of  the  female  is  4.5 
mm.;  of  the  male,  3.8  mm. 


Fig.  4^,5. —Hesperoctenes  longiceps:  A, 
female,  left  half  dorsal,  right  half  ven- 
tral; B,  posterior  tarsus;  C,  anterior 
tarsus;  D,  dorsal  aspect  of  second  an- 
tennal  segment,  distal  end  upward. 
(After  Ferris.) 


380 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Hemelytron  of  Nabis  ferns. 


In  this  family  the  hemelytra  are  vestigial  and  the  hind  and  middle 
tarsi  are  four-jointed.  The  name  of  the  typical  genus,  Polyctenes,  was 
probably  suggested  by  the  presence  of  several  comb-like  series  of 
spines  on  the  body. 

Family  NABIDtE 
The  Nabids 

In  this  family  the  body  is  oblong  and  somewhat  oval  behind. 
The  beak  is  long,   slender,   and  four-jointed.     The  hemelytra  are 

longer  than  the  abdomen,  or  are 
very  short .  Some  species  are  di- 
morphic, being  represented  by 
both  long-winged  and  short-wing- 
ed forms.  In  the  forms  with  long 
wings  the  membrane  is  usually 
furnished  with  four  long  veins 
bounding  three  discal  cells,  which 
are  often  open ;  from  these  discal 
cells  diverge  veins  which  form  several  marginal  cells  (Fig.  436). 
The  fore  tibiae  are  armed  with  spines  and  are  capable  of  being  closed 
tightly  upon  the  femora,  which  are  stout;  they  are  thus  fitted  for 
grasping  prey. 

Nearly  all  of  our  common  species  belong  to  the  genus  Nabts;  in 
fact  this  genus  includes  twenty-six  of  the  thirty-one  species  found  in 
this  country.  Due  to  an  error  made  long  ago,  this  genus  has  been 
commonly  known  as  Coriscus;  and  most  of  the  references  to  these 
insects  are  under  this  name. 

Nobis  ferus. — This  is  one  of  our  most  common  species.  It  measures 
about  8  mm.  in  length.     It  is  pale  yellow  with  numerous  minute 
brown  dots;  the  veins  of  the  membrane  are  also  browrlish.     This 
species  is  distributed  from  the  Atlantic  Coast  to  the 
Pacific.     It  secretes  itself  in  the  flowers  or  among  the 
foliage  of  various  herbaceous  plants,  and  captures  small 
insects  upon  which  it  feeds. 

Ndbis  subcoleoptrdtus. — The  short-winged  form  of 
this  species  is  another  very  common  insect  (Fig.  437). 
This  is  of  a  shining  jet-black  color,  with  the  edge  of 
the  abdomen  and  legs  >-ellowish.  The  hemelytra 
barely  extend  to  the  second  abdominal  segment.  The 
long-winged  form  of  this  species  is  not  common;  it  is 
much  narrower  behind,  and  the  hemelytra  and  the  ab- 
domen are  rather  dusky,  or  piceous,  instead  of  jet-black. 


Family  REDUVIID^ 
The  Assassin-Bugs 

The  Redu\didae  is  a  large  family,  including  numerous  genera  of 
diverse  forms.    AIan\'  of  the  members  of  it  are  insects  of  considerable 


HEMIPTERA  381 

size,  and  some  are  gayly  colored.  They  are  predacious,  living  on  the 
blood  of  insects.  In  some  cases  they  attack  the  higher  animals;  and, 
occasionally,  even  man  suffers  from  them. 


Fig.  438. — Arilus  cristatus.     (From  Glover.) 

In  this  family  the  beak  is  short,  three-jointed,  attached  to  the 
tip  of  the  head,  and  with  the  distal  end,  when  not  in  use,  resting  upon 
the  presternum,  which  is  grooved  to  receive  it.    Except  in  a  few  spe- 
cies, ocelli  are  present  in  the  winged  forms.    The  anten- 
nas are  four-jointed. 

More  than  one  hundred  species  occur  in  our  fauna; 
these  represent  forty-four  genera.  The  following  species 
will  serve  to  illustrate  the  great  diversity  in  form  of 
members  of  this  famHy. 

The  wheel-bug,  Arilus  cristatus. — The  wheel-bug  is 
so  called  on  account  of  the  cogwheel-like  crest  on  the 
prothorax  (Fig.  438).  It  is  a  common  insect  south  of 
New  York  City,  and  is  found  as  far  west  as  Texas  and 
New  Mexico.  The  adult,  a  cluster  of  eggs,  and  several 
nymphs,  are  represented  in  the  figure.  The  nymphs 
when  young  are  blood-red,  with  black  marks. 

The  masked  bedbug-hunter,  Rediivius  persondtus. — The  adult  of 
this  species  is  represented  by  Figure  439;  it  measures  from  15  to  20 
mm.  in  length,  and  is  black  or  ver}'  dark  brown  in  color. 


382  ^A^  INTRODUCTION  TO  ENTOMOLOGY 

There  are  two  marked  peculiarities  of  this  species  that  have  caused 
it  to  attract  much  attention:  first,  in  its  immature  instars  the  body 
is  covered  with  a  viscid  substance  which  causes  particles  of  dust  and 
fibers  to  adhere  to  it;  not  only  the  body,  but  the  legs  and  antennse 
also,  are  masked  in  this  way;  in  fact  the  nymph  resembles  a  mass  of 
lint,  and  attracts  attention  only  when  it  moves;  second,  this  species 
infests  houses  for  the  sake  of  preying  upon  the  bedbug.  It  feeds  also 
upon  flies  and  other  insects. 

The  big  bedbug,  Tridtoma  sangtiisuga. — Closely  allied  to  the 
masked  bedbug-hunter  is  a  large  bug  which  insinuates  itself  into  beds 
for  a  less  commendable  purpose  than  that  of  its  ally,  for  it  seeks 
human  blood  at  first  hand.  This  insect  measures  25  mm.  in  length; 
it  is  black  marked  with  red;  there  are  six  red  spots  on  each  side  of 
the  abdomen,  both  above  and  below.  It  inflicts  a  most  painful  wound. 
This  is  one  of  several  species  of  the  Reduviida?  that  received  the 
name  of  "kissing-bug"  as  a  result  of  sensational  newspaper  accounts 
which  were  widely  published  in  the  summer  of  1899  and  which  stated 
that  a  new  and  deadly  bug  had  made  its  appearance,  which  had  the 
habit  of  choosing  the  lips  or  cheeks  for  its  point  of  attack  on  man. 
It  is  found  from  New  Jersey  south  to  Florida  and  west  to  Illinois 
and  Texas. 

The  genus  Triatoma  was  renamed  Conorhinns  and  most  of  the 
references  to  this  species  are  under  this  generic  name. 

The  thread-legged  bug,   Emesa  hrevipennis, — This  is  our  most 

common  representative  of  one 
of  the  subfamilies  of  the  Redu- 
viidcC  in  which  the  body  is  ver}" 
slenderandthemiddle  and  hind 
legs  are  thread-like  (Fig.  440). 
The  front  legs  are  less  thread- 
like, and  are  fitted  for  grasp- 
ing ;  they  suggest  by  their  form 
the  front  legs  of  the  Mantidas; 
the  coxa  is  greatly  elongated, 
more  than  four  times  as  long  as 
Fig.  440. — Emesa  hrevipennis.  thick;  the    femur    is     spined; 

and  the  tibia  shuts  back  upon 
the  femur.  In  Figure  440  they  are  represented  beneath  the  thread- 
like antennae.  Emesa  hrevipennis  measures  about  33  mm.  in  length; 
it  is  found  upon  trees,  or  sometimes  swinging  by  its  long  legs  from  the 
roofs  of  sheds  or  barns. 

A  monograph  of  the  Reduviida?  of  North  America  has  been  pub- 
lished by  Fracker  ('12). 

Family  PHYMATID^ 

The  Ambush-  Bugs 

The  Ph^TTiatidas  is  poorly  represented  in  this  country  but  some  of 
the  species  are  very  common.     Here  we  find  the  body  extended 


IIEMIPTERA 


383 


laterally  into  angular  or  rounded  projections,  suggesting  the  name 
of  the  typical  genus.  But  the  most  striking  character  which  dis- 
tinguishes this  group  is  the  remarkable  form  of  the  front  legs.  These 
are  fitted  for  seizing  prey.  The  coxa  is  somewhat  elongated ;  the  femur 
is  greatly  thickened,  so  that  it  is  half  or  two  thirds  as  broad  as  long; 
the  tibia  is  sickle-shaped,  and  fits  closely  upon  the  broadened  and 
curved  end  of  the  femur;  both  tibia  and  femur  are  armed  with  a 
series  of  close-set  teeth,  so  that  the  unlucky  insect  that  is  grasped 
by  this  organ  is  firmly  held  between  two  saws ;  the  apparently  useless 
tarsus  is  bent  back  into  a  groove  in  the  tibia.  Another  striking 
character  is  presented  by  the  antennas,  the  terminal 
segment  being  more  or  less  enlarged  into  a  knob. 
Under  the  lateral  margin  of  the  pronottun  in  Phymata 
there  is  on  each  side  a  groove  into  which  the  antenna 
fits. 

Only  two  genera  are  represented  in  our  fauna,  each 
by  six  species.    These  are  Phymata  and  Macrocephahis. 
In  Phymata  the  scutellum  is  of  ordinary  size;  in  Macro- 
cephalus  it  is  very  large  and  extends  to  the  tip  of  the  abdomen. 
Our  most  common  species  is  Phymata  erosa  (Fig.  441).     It  is  a 
}ellow  insect,  greenish  when  fresh,  marked  with 
a  broad  black  band  across  the  expanded  part  of 
the  abdomen.     It  conceals  itself  in  the  flowers 
of  various  plants,  and  captures  the  insects  which 
come  to  sip  nectar.     It  is  remarkable  what  large 
insects   it    can   overcome   and   destroy;  cabbage 
butterflies,  honey-bees,  and  large  wasps  are  over- 
powered by  it. 

Family  ENICOCEPHALID^ 


"m 


Fig.  441. 
Phymata 
ffsa. 


The  Unique-headed  Fugs 

In  this  family  the  hemelytra  are  wholly  mem- 
branous and  provided  with  longitudinal  veins 
and  a  few  cross-veins  (Fig.  442).  The  head  is 
constricted  at  its  base  and  behind  the  eyes,  and  is 
swollen  between  these  two  constrictions.  This 
is  a  form  of  head  not  found  in  any  other  Hemip- 
tera.  Ocelli  are  present.  The  antennae  are  four- 
jointed;  the  first,  second,  and  third  segments  are 
each  followed  by  a  small  ring-joint.  The  beak  is 
four-jointed.  The  front  tarsi  are  one-jointed,  the  middle  and  hind 
tarsi  two-jointed.  The  front  legs  are  fitted  for  grasping  prey,  the 
fore  tarsi  being  capable  of  closing  upon  the  end  of  the  broad  tibiae. 

This  is  a  small  family;  but  few  species  are  known  from  the  entire 
world,  and  only  two  have  been  described  from  America  north  of 
Mexico.  These  are  Enicrcephalus  formtciua,  found  in  California, 
and  Systelloderus  biceps,  which  has  been  found  from  New  York  to  Utah. 


Fig.  442. — Systello- 
derus biceps.  (Af- 
ter    Johannsen.) 


384 


AN  INTRODUCTION  TO  ENTOMOLOGY 


But  little  has  been  published  regarding  the  habits  of  these  insects. 
It  is  evident,  from  the  structure  of  their  fore  legs,  that  they  are 
predacious.  Professor  Johannsen  ('09  b)  found  Systelloderus  biceps 
{Henicocephalus  cuUcis)  flying  in  small  swarms  near  Ithaca,  N.  Y. 
Their  manner  of  flight  resembled  that  of  chironomids.  They  were 
obser\^ed  repeatedly  from  July  5  to  the  last  week  in  August,  always  in 
the  latter  part  of  the  afternoon.  This  species  measures  4  mm.  in 
length. 

The  type  genus  of  this  family  was  first  named  Enicocephalus ;  this 
name  was  later  emended  to  Henicocephalus;  but  the  older  form  of  the 
name,  though  incorrectly  formed,  is  now  used. 

Family  TINGIDtE 


The  Lace-Bugs 

The  Tingidae  are  doubtless  the  most  easily  recognized  of  all  Hemip- 
tera.  The  reticulated  and  gauze-like  structure  of  the  hemelytra, 
usually  accompanied  by  expansions  of  the  pro- 
thorax  of  a  similar  form,  gives  these  insects  a 
characteristic  appearance  which  needs  only  to 
be  once  seen  to  be  recognized  in  the  future. 
Figure  443  represents  one  of  these  insects 
greatly  enlarged,  the  hair-line  at  the  side 
indicating  the  natural  size  of  the  insect.  They 
are  generally  verv  small  insects.  But  they 
occur  in  great  numbers  on  the  leaves  of  trees 
and  shrubs,  which  they  puncture  in  order  to 
suck  their  nourishment  from  them. 

In  this  family  the  ocelli  are  wanting;  the 

beak  and  antennas  are  four- jointed;  the  scu- 

tellum  is  usually  wanting  or  vestigial,  replaced 

by  the  angular  hind  portions  of  the  pronotiim; 

and  the  tarsi  are  two-jointed. 

About  seventv-five  species  of  lace-bugs,  representing  twenty-three 

genera,  are  now  listed  from  this  country.     There  are  two  well-marked 

subfamilies. 

Subfamily  TINGING 


Fig.  443. — Corythitcha 
arcuata. 


This  division  includes  nearly  all  of  the  known  species.  Here 
the  scutellum  is  usually  covered  by  an  angular  projection  of  the 
pronotum ;  and  the  hemelytra  have  no  distinction  between  the  clavus, 
corium,  and  membrane.  The  following  species  will  serve  as  an  il- 
lustration of  this  subfamily. 

The  hawthorn  lace-bug,  CorythUcha  arcuata. — This  is  a  widely 
distributed  species,  which  punctures  the  under  surface  of  the  leaves 
of  different  species  of  Cratcegus.  The  infested  leaves  have  a  brown 
and  sunburnt  appearance.  Eggs,  n>Tnphs,  and  adults  are  found 
together.     The  adult  is  represented,  much  enlarged,  in  Figure  443. 


HEMIPTERA 


385 


In  Figure  444  the  eggs  and  a  nymph  are  shown.    The  eggs  are  covered 
by  a  brown  substance,  which  hardens  soon  after  oviposition. 

Subfamily  PIESMIN^ 

In  this  subfamily  the  scutellum  is  not  covered;  the  hemelytra 
have  a  distinct  clavus,  with  a  well-marked  claval  suture;  the  clavus 
is  furnished  with  one,  and  the  corium  with  three, 
longitudinal  veins  which  are  much  stronger  than 
the  network  of  veins  between  them.  In  long- 
winged  individuals  the  tip  of  the  membrane  lacks 
the  network  of  veins  and  appears  like  the  mem- 
brane in  other  families.  As  yet  but  a  single 
American  species  has  been  described. 

The  ash-gray  Piesma,  Piesma  cinerea.- — This 
species  measures  about  3  mm.  in  length,  and  is  of 
an  ash-gray  color.  The  prothorax  is  deeply  pitted, 
so  that  it  presents  the  same  appearance  as  the 
base  of  the  wing-covers.  The  head  is  deeply 
bifid  at  tip,  and  there  is  a  short  robust  spine  be- 
tween the  eye  and  the  antenna  on  each  side.  This 
species  sometimes  infests  vineyards  to  an  injurious 
extent,  destroying  the  flower-buds  in  early  spring. 

Family  PYRRHOCORID^ 


Fig.  444.— Eggs  and 
nymph  of  Cory- 
ihucha  arcuata. 


The  Cotton-Stainer  Family 

In  this  family  the  antennee  are  four-jointed;  the  beak  is  also 
four-jointed;  ocelli  are  absent;  and  the  hemelytra  are  not  furnished 

with  a  cuneus.  The  members  of 
the  family  are  stout  and  heavily 
built  insects,  and  are  generally 
rather  large  and  marked  with 
strongly  contrasting  colors,  in 
which  red  and  black  play  a  con- 
spicuous part,  in  this  respect  re- 
sembling some  of  the  larger 
species  of  the  following  family. 
The  Pyrrhocoridae  can  be  dis- 
tinguished from  the  Lygasidae  by  the  absence  of  ocelli,  and  by  the 
venation  of  the  membrane  of  the  hemelytra  (Fig.  445).  At  the  base 
of  the  membrane  there  are  two  or  three  large  cells,  and  from  these 
arise  branching  veins. 

Only  twenty-two  species,  representing  five  genera,  have  been  found 
in  our  fauna,  and  these  are  restricted  to  the  Southern  and  Western 
States. 

Our  most  important  species,  from  an  economic  standpoint,  is  the 
red-bug    or  cotton-stainer,   Dysdercus  suturellus     (Fig.   446).     It  is 


Fig.  445. — Hemelytron  of  Euryopthal- 
mus  succincttis. 


386 


^.V  INTRODUCTION  TO  ENTOMOLOGY 


oblong-oval  in  form,  of  a  red  color;  the  hemeh-tra  and  an  arc  on 
the  base  of  the  prothorax,  and  also  the  scutellum,  are  pale  brown. 
The  hemeh^ra  have  the  costal  margin,  a  narrow  line  bordering  the 
base  of  the  membrane  and  continuing  diagonally  along  the  outer 
margin  of  the  clavus,  and  also  a  slender  streak  on  the  inner  margin  of 
the  clavus,  pale  yellow.  It  varies  much  in  size,  ranging  from  lo  mm. 
to  1 6  mm.  in  length.  The  young  bugs  are  bright  red 
with  black  legs  and  antennae.  From  time  immemorial 
this  has  been  one  of  the  worst  pests  with  which  the 
cotton-planters  of  Florida  and  the  West  Indies  have 
had  to  contend.  It  does  much  damage  by  piercing 
the  stems  and  bolls  with  its  beak  and  sucking  the  sap ; 
but  the  principal  injury  to  the  crop  is  from  staining 
the  cotton  in  the  opening  boll  by  its  excrement.  It 
is  also  injurious  to  oranges;  it  punctures  the  rind  of 
the  fruit  with  its  beak;  and  soon  decay  sets  in,  and 
the  fruit  drops.  These  insects  can  be  trapped  in 
cotton-fields  by  laying  chips  of  sugar-cane  upon  the 
earth  near  the  plants ;  in  orange-groves  small  heaps 
of  cotton-seed  will  be  found  useful,  as  well  as  pieces  of  sugar-cane. 
The  insects  that  collect  upon  these  traps  can  be  destroyed  with  hot 
water. 

The  species  whose  range  extends  farthest  north  is  Euryophthdlmus 
succindtus.  This  is  found  from  New  Jersey  south  to  Florida  and 
west   to    Arizona.       It    is   brownish  black,    with    the    lateral    and 


Fig.  446.  —  Dys- 
dercus  suturellus. 


hind  margins   of  the   prothorax, 
elytra,   and  the    edge    of   the 
abdomen,  margined  with  orange 
or  red.  It  measures  about    15 
mm.  in  length. 

Family  LYG^ID^ 

The  Chinch-Biig  Family 


the  costal    margin    of    the  hem- 


Fig.  447. — Hemelytron  of  Lygceus 
kalmii. 


The  Lygaeidae  is  one  of  the  larger  families  of  the  Hemiptera.  It 
includes  certain  forms  which  closely  resemble  members  of  the  pre- 
ceding family  in  size,  form,  and  strongly  contrasting  colors.  But  the 
great  majority  of  the  species  are  of  smaller  size  and  less  brightly  col- 
ored ;  and  all  differ  from  that  family  in  presenting  distinct  ocelli.  The 
membrane  of  the  hemelytra  is  furnished  with  four  or  five  simple  veins, 
which  arise  from  the  base  of  the  membrane ;  sometimes  the  two  inner 
veins  are  joined  to  a  cell  near  the  base  (Fig.  447). 

Nearly  two  hundred  species  belonging  to  this  family  have  been 
found  in  our  fauna;  these  represent  fifty-five  genera  and  seven 
subfamilies.  Although  these  insects  feed  on  vegetation,  they  have 
attracted  but  little  attention  as  pests  of  cultivated  plants  excepting 
the  following  species. 


HEMIPTERA  387 

The  chinch-bug,  BUssus  leucopterus. — This  well-known  pest  of 
grain-fields  is  a  small  bug,  which  when  fully  grown  measures  a  little 
less  than  4  mm.  in  length.  It  is  blackish  in  color,  with  conspicuous, 
snowy  white  hemelytra.  There  is  on  the  costal  margin  of  each 
hemelytron  near  the  middle  of  its  length  a  black  spot ;  from  each  of 
these  spots  there  extends  towards  the  head  a  some- 
what Y-shaped  dusky  line.  The  body  is  clothed 
with  nimierous  microscopic  hairs.  In  Figure  448 
this  insect  is  represented  natural  size  and  enlarged. 
The  species  is  dimorphic,  there  being  a  short -winged 
form. 

There  are  two  generations  of  the  chinch -bug  each  p^g  ^_^8 — BUsstis 
year.  The  insects  winter  in  the  adult  state,  hiding  leucopterus. 
beneath  rubbish  of  any  kind;  they  even  penetrate 
forests  and  creep  under  leaves,  and  into  crevices  in  bark.  In  early 
spring  they  emerge  from  their  winter  quarters  and  pair;  soon  after, 
the  females  begin  to  lay  eggs;  this  they  do  leisurely,  the  process  being 
carried  on  for  two  or  three  weeks.  The  eggs  are  yellowish ;  about  500 
are  laid  by  a  single  insect;  they  are  deposited  in  fields  of  grain,  be- 
neath the  ground  upon  the  roots,  or  on  the  stem  near  the  surface. 
The  eggs  hatch  in  about  two  weeks  after  being  laid.  The  newly 
hatched  bugs  are  red;  they  feed  at  first  on  the  roots  of  the  plant 
which  they  infest,  sucking  the  juices;  afterwards  they  attack  the 
stalks.  The  bugs  become  full-grown  in  from  forty  to  fifty  days. 
Before  the  females  of  this  brood  deposit  their  eggs,  they  leave  their 
original  quarters  and  migrate  in  search  of  a  more  abundant  supply 
of  food.  About  this  time  the  wheat  becomes  dry  and  hard;  and  the 
migration  appears  to  be  a  very  general  one.  Although  the  insects 
sometimes  go  in  different  directions,  as  a  general  rule  the  masses 
take  one  direction,  which  is  towards  the  nearest  field  of  oats,  com,  or 
some  other  cereal  or  grass  that  is  still  in  a  succulent  state.  At  this 
time  many  of  the  bugs  have  not  reached  the  adult  state ;  and  even  in 
the  case  of  the  fully  winged  individuals  the  migration  is  usually  on 
foot.  In  their  new  quarters  the  bugs  lay  the  eggs  for  the  second  or 
fall  brood. 

The  methods  of  control  of  this  pest  that  are  used  are  the  fol- 
lowing: the  burning  in  autumn  of  all  rubbish  about  fields,  in  fence 
comers,  and  in  other  places  where  the  bugs  have  congregated  to 
pass  the  winter;  the  stopping  of  the  marching  of  the  spring  brood 
into  new  fields  by  means  of  a  furrow  or  ditch  with  vertical  sides,  and 
with  holes  like  post -holes  at  intervals  of  a  few  rods  in  the  bottom  of 
the  furrow  or  ditch,  in  which  the  bugs  are  trapped;  the  use  of  a 
line  of  gas-tar  on  the  ground  to  stop  the  marching  of  the  spring 
brood ;  in  some  cases  kerosene  emulsion  has  been  used  to  advantage ; 
the  sowing  of  decoy  plots  of  attractive  grains  in  early  spring,  and  the 
later  plowing  under  of  the  bugs  and  their  food  and  harrowing  and 
rolling  the  ground  to  keep  the  bugs  from  escaping;  and  the  artificial 
dissemination  of  the  fungus  Sporotrichum  globulifenmi,  which  is  the 
QQUse  of  a  contagious  disease  of  the  chinch-bug. 


388  AN  INTRODUCTION  TO  ENTOMOLOGY 

Family  NEIDID^ 

The  Stilt-Bugs 

The  family  Neididag  consists  of  a  small  nimiber  of  species,  which 
on  account  of  their  attenuated  forms  are  very  striking  in  appearance 
(Fig.  449) .  The  body  is  long  and  narrow; 
the  legs  and  antennas  are  also  long  and 
extremely  slender.  There  is  a  transverse 
incision  in  the  vertex  in  front  of  the  ocelli. 
The  antennae  are  four-jointed,  elbowed  at 
the  base  of  the  second  segment,  and  with 

I/>\^//\,  the  tip  of  the  first  segment  enlarged.    The 

y    \J/  Y_  beak  is  four-jointed;  and  the  membrane 

r — Jh^~^       r     of  the  hemelytra  is  furnished  with  a  very 
/     /BX     1  few  veins, 

r/  /    I  \  •  W    i  Only  eight  species  of  this  family  have 

been  found  in  our  fatma ;  but  these  repre- 
sent six  genera.  Only  two  of  the  species 
are  widely  distributed  in  the  United 
States  and  Canada.  These  are  sluggish 
insects,  found  in  the  undergrowth  of 
Fig.    ^4g.~jalysus   spinosus.  woods   and   in  meadows   and   pastures. 

Jalysus  spindsus. — This  is  the  best- 
known  member  of  this  family.  It  is  distributed  from  the  Atlantic  to 
the  Pacific  in  both  the  United  States  and  Canada.  It  is  as  slender  as  a 
crane-fly  (Fig.  449)  and  of  a  pale  tawny  color.  The  front  of  the  head 
tapers  off  to  an  almost  acute,  upturned  point.  An  erect  spine  projects 
form  the  base  of  the  scutellum,  and  another  from  each  side  of  the 
mesopleura,  just  in  front  of  the  posterior  coxae.  The  body  is  about 
8  mm.  in  length. 

Jalysus  perdavatus .■ — This  is  one  of  the  southern  members  of  the 
family,  but  it  has  been  found  in  New  Jersey  and  the  District  of 
Columbia.  It  is  smaller  than  the  preceding  species;  the  length  of 
the  male  is  5  mm.,  of  the  female  6  mm.  There  is  an  erect  spine  be- 
tween the  bases  of  the  antennae ;  and  the  last  segment  of  the  antennas 
is  shorter  and  thicker  than  in  /.  spinosus. 

Neides  mUticus .—LUke  Jalysus  spinosus,  this  species  is  found  from 
the  Atlantic  to  the  Pacific  in  both  the  United  States  and  Canada. 
It  lacks  the  spines  of  the  scutellum  and  thorax;  and  the  front  of  the 
head  is  bent  down,  in  the  form  of  a  little  horn. 

The  other  representatives  of  this  family  in  our  fauna  are  found  in 
Florida,  Arizona,  New  Mexico,  and  California. 


Family  ARADID^ 

The  Flat-Bugs 

The  members  of  this  family  are  very  flat  insects;  in  fact  they 
are  the  flattest  of  all  Hemiptera.    They  live  in  the  cracks  or  beneath 


# 


HEMIPTERA  389 

the  bark  of  decaying  trees;  and  the  form  of  the  body  is  especially 
adapted  for  gliding  about  in  these  cramped  situations.     They  are 
usually  dull  brown  or  black ;  sometimes  they  are  varied  with  reddish 
or  pale  markings.     The  hemelytra    are    usually  well 
developed,    with   distinct   corium,    clavus,   and  mem- 
brane; but  they  are  reduced  in  size,   so  that  when 
folded  they  cover  only  the  disk  of  the  abdomen  (Fig. 
450).    Ocelli  are  lacking ;  the  antennae  are  four-jointed ; 
the  tarsi  are  two-jointed;  and  the  beak  is  four-jointed, 
but  often  apparently  three-jointed.  Fig.  450. — Ar- 

These  insects  are  supposed  to  feed  upon  fungi  or      adus  acutus. 
upon   the  juices   of  decaying  wood  and  bark.     The 
family  is  well  represented  in  this  country;  fifty-nine  species,  repre- 
senting nine  genera,  are  now  known,  and  doubtless  many  remain  to 
be  discovered. 

Family  COREID^ 
The  Squash-Bug  Family 

The  members  of  this  family  vary  greatly  in  form.  Some  of  the 
species  are  among  the  most  formidable  in  appearance  of  all  of  our 
Hemiptera ;  while  others  are  comparatively  weak  and  inconspicuous. 

The  family  is  characterized  as 
follows:  the  antennas  are  insert- 
ed above  an  ideal  line  extending 
from  the  eye  to  the  base  of  the 
rostrum,  and  are  four-jointed; 
the  vertex  is  not  transversely  im- 
Fig.  451.— Hemelytron  of  Leptocoris  pressed;  the  ocelli  are  present; 
trivittatus.  the    beak     is     four-jointed;  the 

scutellum  is  small  or  of  medium 
size;  the  hemelytra  are  usually  complete  and  composed  of  clavus, 
corium,  and  membrane;  the  membrane  is  furnished  with  many  veins, 
which  spring  from  a  transverse  basal  vein,  and  are  usually  forked 
(Fig.  451);  the  tarsi  are  three-jointed. 

This  is  a  large  family;  one  hundred  and  twenty- 
four  species,  representing  forty-eight  genera,  have 
been  found  in  our  fauna.  It  contains  both  vegetable 
feeders  and  carnivorous  forms ;  in  some  cases  the  same 
species  will  feed  upon  both  insects  and  plants.  The 
most  common  and  best-known  species  is  the  following. 
The  squash-bug,  Anasa  trlstis. — The  form  of  the 
body  of  the  adult  insect  is  represented  in  Figure  452. 
In  this  stage  the  insect  appears  blackish  brown  above 
and  dirty  yellow  beneath.  The  ground  color  is  really  Fig.452.— ^wa^a 
ochre-yellow,  darkened  by  numerous  minute  black  tristis. 
punctures.  Upon  the  head  are  two  longitudinal 
black  stripes;  the  lateral  margins  of  the  prothorax 
are  yellow,  owing  to  the  absence  of  the  punctures  along  a  narrow 


390 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Space;  and  the  margin  of  the  abdomen  is  spotted  with  yellow  from 
a  similar  cause;  the  membrane  of  the  hemelytra  is  black. 

This  species  winters  in  the  adult  state. 
In  early  simimer  it  lays  its  eggs  in  little 
patches  on  the  young  leaves  of  squash  and 
allied  plants.  The  young  bugs  are  short 
and  more  rounded  than  the  adult  insects. 
There    are    several    generations    of    this 

/""^■MMOii^^^  species  each  year. 

JP^k   ^\  This  is  one  of  the  most  annoying  of 

^^^|f«W  V^  the  many  pests  of  the  kitchen-garden; 
.J>  liMiim  T9  and,  unfortunately,  no  satisfactory  meth- 
od of  control  has  been  devised.  The  egg 
masses  are  conspicuous  and  can  be  col- 
lected and  destroyed ;  the  young  nymphs 
can  be  killed  by  spraying  with  io% 
kerosene  emulsion;  the  adults  can  be 
trapped  under  bits  of  boards  and  stones; 
and  many  n\Tnphs  can  be  killed  by  de- 
stroying the  vines  as  soon  as  the  crop  is 
harvested. 

Acanthocephala  femordta  (Fig.  453)  will  serve  as  an  example  of 
one  of  the  larger  members  of  this  family.  This  species  is  distribut- 
ed from  North  Carolina  to  Florida  and  Texas.  It  has  been  known 
to  destroy  the  cotton-worm,  and  is  said  to  injure  the  fruit  of  the 
cherry  by  puncturing  it  with  its  beak  and  sucking  the  juices. 


Fig.    453.- — Acanthocephala 
femorata.     (From  Glover.) 


Family  PENTATOMID^ 


The  Stink-Btig  Family 


With  the  Pentatomidas  we  reach  a  series  of  families,  three  in 
ntimber,  in  which  the  antennae  are  usually  five-jointed,  differing  in 
this  respect  from  all  of  the  preceding  families.  The 
form  of  the  body  presented  by  the  great  majority  of 
the  members  of  the  Pentatomidae  is  well  shown  by 
Figure  454.  It  is  broad,  short,  and  but  slightly  convex; 
the  head  and  prothorax  form  a  triangle.  The  scutellum 
is  narrowed  behind ;  it  is  large  and  in  a  few  forms  nearly 
covers  the  abdomen.  The  tibias  are  unarmed  or  are 
furnished  with  very  fine  short  spines. 

As  with  the  Coreidae,  the  members  of  this  family 
vary  greatly  in   their  habits;  some  are   injurious  to 
vegetation;  others  are  predacious;  while  some  species 
feed  indifferently  upon  animal  or  vegetable  matter.     Some  species 
are  often  found  on  berries  and  have  received  the  popular  name  of 


pentatomid. 


HEMIPTERA  391 

Stink-hugs  on  account  of  their  fetid  odor,  which  they  are  apt  to 
impart  to  the  berries  over  which  they  crawl.  This  nauseous  odor  is 
caused  by  a  fluid  which  is  excreted  through  two  openings,  one  on 
each  side  of  the  lower  side  of  the  body  near  the  middle  coxae. 

The  harlequin  cabbage-bug,  Murgantia  histronica. — Among  the 
species  of  the  Pentatomidae  that  feed  upon  cultivated  plants,  the 
harlequin  cabbage-bug  or  "calico-back"  is  the  most  important  pest. 
It  is  very  destructive  to  cabbage  and  other  cruciferous  plants  in  the 
Southern  States  and  on  the  Pacific  Coast.  It  is  black,  with  bands, 
stripes,  and  margins  of  red  or  orange  or  yellow.  Its  bizarre  coloring 
has  suggested  the  popular  names  given  above.  The  full-grown  bugs 
live  through  the  winter,  and  in  the  early  spring  each  female  lays  on 
the  under  surface  of  the  young  leaves  of  its  food-plants  about  twelve 
eggs  in  two  parallel  rows.  The  eggs  are  barrel-shaped  and  are  white 
banded  with  black.  The  young  bugs  are  pale  green  with  black  spots. 
They  mature  rapidly ;  and  it  is  said  that  there  are  several  generations 
in  one  season. 

This  is  an  exceedingly  difficult  species  to  contend  against.  Much 
can  be  done  by  cleaning  up  the  cabbage  stalks  and  other 
remnants  as  soon  as  the  crop  is  harvested,  and,  in  the 
following  spring,  trapping  the  bugs  that  have  hiber- 
nated by  placing  turnip  or  cabbage  leaves  in  the  in- 
fested gardens  or  fields,  or  by  planting  trap-crops  of 
mustard  or  other  cruciferous  plants.  The  bugs  that 
are  not  collected  by  these  methods  and  their  eggs 
should  be  collected  by  hand;  this  can  be  easily  done  Fig-  455 -^"J- 
as  both  the  bugs  and  their  eggs  are  conspicuous.  ^m/nWFrom 

As  if  to  atone  for  the  destruction  caused  by  their  Glover.) 
relative,  the  harlequin  cabbage-bug,  there  are  many 
members  of  this  family  that  aid  the  agriculturist  by  destroying  noxious 
insects.  The  species  of  the  genus  Podisus  have  been  reported  often  as 
destroying  the  Colorado  potato-beetle,  currant  worms,  and  other 
well-known  pests.  Figure  455.  represents  a  member  of  this  genus, 
Podisus  maculiventris. 

Family  CYDNID^ 
The  Burrower-Bugs  and  the  Negro-Bugs 

The  Cydnidas  is  the  second  of  the  series  of  families  in  which  the 
antennae  are  five-jointed.  In  this  family  the  outline  of  the  body  is 
more  generally  oval,  rounded,  or  elliptical,  and  the  form  more  convex, 
than  in  the  Pentatomidae.  The  scutellum  is  large  but  varies  greatly 
in  size  and  in  outline.  Each  lateral  margin  of  the  scutellimi  is 
furnished  with  a  furrow  into  which  the  margin  of  the  hemelytron  of 
that  side  fits.  In  this  respect  the  Cydnid^e  agrees  with  the  preceding 
family  and  differs  from  the  following  one.  The  tibiae  are  armed  with 
strong  spines. 

The  family  includes  two  well-marked  subfamilies. 


392  AN  INTRODUCTION  TO  ENTOMOLOGY 

Subfamily  CYDNIN^ 

The  Burrower-Bugs 

The  subfamily  Cydnina?  includes  the  greater  number  of  the  mem- 
bers of  the  Cydnidffi  found  in  the  United  States  and  Canada ;  of  these 
there  are  twenty-nine  species  now  listed,  representing 
nine  genera ;  most  of  these  are  restricted  to  the  South 
and  the  Far  West. 

In  this  subfamily  the  scutellum  is  either  broad 

and  bluntly  rounded,   or  triangular  with  the  apex 

pressed  down.     The  species  are  generally  black  or 

very   dark   brown.      They   are   found   burrowing   in 

sandy  places,  or  on  the  surface  of  the  ground  beneath 

sticks  and  stones,  or  at  the  roots  of  grass  and  other 

herbage.    A  European  species  is  said  to  suck  the  sap 

from  various  plants  near  the  ground.    It  is  desirable 

that  further  observations  be  made  upon  the  habits  of  this  subfamily. 

Figure  456  represents  Cyrtomenus  mirabilis,  a  species  found  in  the 

South  and  the  Southwest. 


Subfamily  THYREOCORIN^ 
The  Negro-Fugs 

The  subfamily  Thyreocorinas  is  represented  in  our  fauna  by  a 
single  genus,  Thyreocoris,  of  which  sixteen  species  have  been  found 
in  this  country.  They  are  mostly  black  and  beetle-like 
in  appearance,  some  have  a  bluish  or  greenish  tinge, 
and  all  are  very  convex.  The  body  is  short,  broad, 
and  very  convex,  in  fact  almost  hemispherical.  The 
scutellimi  is  very  convex  and  covers  nearly  the  whole 
of  the  abdomen. 

These  insects  infest  various  plants,  and  often  in-     Fig.  457-— 
jure  raspberries  and  other  fruits  by  imparting  a  dis-        ^rirZer 
agreeable,  bedbug-like  odor  to  them.     A  common  and 
widely  distributed  species  is  Thyreocoris  ater  (Fig.  457).     Another 
species  often  found  on  berries  is  T.  pulicdrius;  this  species  is  some- 
times a  serious  celery  pest.    It  is  shiny  black  and  has  a  white  stripe 
•  on  each  side  of  the  body;  it  measures  3  mm.  in  length. 


A 


Family  SCUTELLERID^ 
The  Shield-hacked  Bugs 
'The  members  of  this  family  are  turtle-shaped  bugs;  that  is,  the 


HEMIPTERA 


393 


body  is  short,  broad,  and  very  convex.  The  scutellum  is  very 
covering  nearly  the  whole  of  the  abdomen.  The 
lateral  margins  of  the  scutellum  are  not  furnished 
with  grooves  for  receiving  the  edges  of  the  hemelytra 
as  is  the  case  in  the  two  preceding  families.  The 
tibise  are  smooth  or  furnished  with  small  spines. 
Figure  458  represents  Eurygaster  alterndhis  somewhat 
enlarged,  and  serves  to  illustrate  the  typical  form  of 
members  of  this  family. 

The  family  is  represented  in  this  country  by 
fourteen  genera  including  twenty-six  species.  I  have 
met  no  account  of  any  of  our  species  occurring  in 
sufficient  numbers   to   be   of   economic  importance. 


large, 


CHAPTER  XXI 
ORDER  HOMOPTERA* 

Cicadas,  Leaf-Hoppers,  Aphids,  Scale-Bugs,  and  others 

The  winged  members  of  this  order  have  four  wings,  except  in  the 
family  Coccid<s;  the  wings  are  of  the  same  thickness  throughout,  and 
usually  are  held  sloping  at  the  sides  of  the  body  when  at  rest.  The 
mouth-parts  are  formed  for  piercing  and  sucking;  the  beak  arises  from 
the  hind  part  of  the  lower  side  of  the  head.  The  metamorphosis  is  gradual 
except  in  some  highly  specialized  forms. 

Although  the  Homoptera  is  a  well-defined  order,  the  families  of 
which  it  is  composed  differ  greatly  in  the  appearance  of  their  members. 
For  this  reason  there  is  no  popular  name  that  is  applied  to  the  order 
as  a  whole. 

The  Homoptera  was  formerly  regarded  as  a  suborder  of  the  Hemip- 
tera,  that  order  being  divided  into  two  suborders,  the  Heteroptera 
and  the  Homoptera.  But  these  two  groups  of  insects  differ  so  mark- 
edly in  structure  that  it  seems  best  to  regard  them  as  distinct  orders. 
The  Hemiptera  is,  therefore,  restricted  to  what  was  formerly  known 
as  the  suborder  Heteroptera,  and  the  suborder  Homoptera  is  raised 
to  the  rank  of  a  separate  order. 

The  wings  of  the  Homoptera  are  usually  membranous,  but  in 
some  the  front  wings  are  subcoriaceous.  In  these  cases,  however,  they 
are  of  quite  uniform  texture  throughout,  and  not  thickened  at  the 
base  as  in  the  Hemiptera. 

Many  wingless  forms  exist  in  this  order;  in  the  family  Coccidas 
the  females  are  always  wingless;  and  in  the  family  Aphididae  the 
males  may  be  either  winged  or  wingless,  while  the  sexually  perfect 
females  and  certain  generations  of  the  agamic  females  are  wingless. 
In  the  Coccidas  the  males  have  only  a  single  pair  of  wings,  the  hind 
wings  being  represented  by  a  pair  of  club-like  halteres.  Each  of 
these  is  furnished  with  a  bristle,  which  is  hooked  and  fits  in  a  pocket 
on  the  hind  margin  of  the  fore  wing  of  the  same  side. 

In  several  of  the  families  of  the  Homoptera  the  wing-venation  is 
greatly  reduced;  and  even  in  the  case  of  the  more  generalized  forms, 
if  only  the  wings  of  adults  be  studied  the  venation  of  these  wings 
appears  to  depart  widely  from  the  hypothetical  primitive  type; 
but  by  examining  the  tracheae  that  precede  the  wing-veins  in  the 
wings  of  the  nymphs,  it  is  easy  to  determine  the  homologies  of  the 
wing-veins.  This  has  now  been  done  in  the  case  of  representatives  of 
each  of  the  families.  The  most  generalized  condition  was  found  in 
the  wings  of  a  cicada,  which  will  serve  as  the  type  of  homopterous 
wing-venation . 

*Hom6ptera:  homos  (6ix6s),  same,  pteron  {irrep6v),  a  wing. 

(394) 


HOMOPTERA 


395 


Figure  459  represents  the  tracheation  of  the  fore  wing  of  a 
young  nymph  of  a  cicada.  The  dotted  hne  a-b  indicates  approximate- 
ly the  Hne  along  which 
the  hinge  of  the  wing 
of  the  adult  is  formed. 
In  this  wing  the  only 
departures  from  the 
typical  branching  of 
the  tracheae  are  the 
following:  trachea  Ri 
coalesces  with  the  ra- 
dial sector  to  a  point 
beyond  the  separation 
of  trachea  R  1+5  from 
the  sector;  the  first 
anal  trachea  coalesces 
with  trachea  Cu  for  a 
short  distance;  and 
the  second  and  third 
anal  tracheae  are  unit- 
ed at  the  base.  These 
differences  are  remark- 
ably slight  compared  with  the  great  changes  that  have  taken  place 
in  the  specialization  of  the  mouth-parts  and  other  organs  of  the 
adult  cicada. 

Figure  460  represents  the  fore  wing  of  a  mature  monph  of  a  cicada. 
In  this  wing  trachea  Ri  is  completely  aborted.     In  fact  one  of  the 


Fig.  459. — Tracheation  of  a  fore  wing  of 
nymph  of  a  cicada. 


young 


Fig.  460. — Tracheation  of  a  fore  wing  of  a  mature  nymph  of  a  cicada. 


most  characteristic  features  in  the  venation  of  the  Homoptera, 
and  of  the  Hemiptera  also,  is  the  absence  or  very  great  reduction 
of  vein  Ri  in  the  adult  wings  of  most  members  of  these  two  orders. 
In  the  stage  represented  in  this  figure  the  developing  cross-veins 
appear  as  pale  bands. 


396 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Figure  461  represents  the  wings  of  an  adult  cicada.  In  this  figure, 
where  the  veins  are  not  numbered  their  homologies  are  indicated  by 
the  numbering  of  the  cells  behind  them.  In  the  adult  wing  there 
is  a  massing  of  several  veins  along  the  costal  margin  of  the  wing, 
and  the  cross-veins  have  the  same  appearance  as  the  branches  of 
the  primary  veins. 

Further  details  regarding  the  development  of  the  wings  of  a  cicada, 
and  accounts  of  the  development  of  the  wings  of  representatives 
of  other  families  of  the  Homoptera,  are  given  in  "The  Wings  of 
Insects"  (Comstock  '18). 

In  the  Homoptera  the  front  part  of  the  head  is  bent  under  and 
back  so  that  the  beak  arises  from  the  hind  part  of  the  lower  side  of 
the  head.  There  is  no  distinct  neck;  and  so  closely  is  the  head 
applied  to  the  thorax  that  usually  the  front  coxas  are  in  contact 


Fig.  461. — The  wings  of  a  cicada. 


with  the  sides  of  the  head,  and  in  many  forms  the  beak  appears  to 
arise  from  between  the  front  legs. 

The  mouth-parts  are  formed  for  piercing  and  sucking.  The 
piercing  organs  consist  of  four  long,  bristle-like  setae,  the  mandibular 
and  maxillary  setae;  these  are  enclosed  in  a  long,  jointed  sheath, 
which  is  the  labiimi.  The  labium  and  the  enclosed  seta  constitute 
what  is  commonly  termed  the  beak. 

The  beak,  however,  corresponds  to  only  a  portion  of  the  mouth- 
parts  of  a  chewing  insect,  each  mandibular  and  maxillary  seta  being 
only  a  part  of  a  mandible  or  maxilla;  in  each  case  another  part  of 
the  organ  enters  into  the  composition  of  the  head-capsule. 

As  an  example  of  the  homopterous  type  of  head  and  mouth-parts 
those  of  a  cicada  are  probably  the  most  available,  on  account  of  the 
large  size  of  these  insects  and  the  comparative  ease  with  which  the 


HOMOPTERA  397 

parts  of  the  head  can  be  distinguished.    Figure  462  represents  a  lateral 


Pig.  463. — Head  of  a  cicada,  front  view: 
md,  mandibular  seta;  mx,  maxillary 
seta;  other  letters  as  in  Pig.  462. 
(After  Marlatt,  with  changes  in  the 
lettering.) 


Pig.  462. — Head  and  prothorax  of  a 
cicada,  lateral  aspect:  a,  antenna; 
c,  clypeus;  e,  compound  eye;  ep, 
epipharynx;  /,  labrum;  0,  ocelli;  2, 
3,  second  and  third  segments  of  the 
labium.  (After  Marlatt,  with  changes 
in  the  lettering.) 

view  of  the  head  and  prothorax  of  a  cicada,  and  Figure  463  a  front  view. 
The  corresponding  parts  are 
lettered  the  same  in  the  two 
figures. 

The  compound  eyes 
(Figs. 462  and  463, e), the  an- 
tennae (Figs.  462  and  463,  a), 
and  the  three  ocelli  (Figs. 
466  and  467,  o),can  be  easily 
recognized  and  need  not  be 
described  in  detail. 

The  front  is  a  small  scle- 
rite  near  the  summit  of  the 
head.  It  can  be  most  easily  Pig.  464.^Part  of  the  exuvias  of  the  head  of 
recognized  by  the  fact  that  a  nymph  of  a  cicada:  a,  antennae;  as, 
it  bears  the  median  ocellus.  antennal  sclerite;  c  clypeus;  e,  ^-  com- 
T      .-I  J    1.    •  .    .-L.  pound  eyes;  /,  front;  v,  v,  vertex.      (After 

In  the  adult  insect  the  su-      Berlese.) 
ture  between  it  and  the  ver- 
tex is  indistinct;  but  in  the  exuviae  of  a  nymph,  where  the  epicranial 
suture  has  been  opened  by  the  emergence  of  the  adult,  the  outline 
of  this  sclerite  is  evident  (Fig.  464).     In  many  homopterous  insects 
the  front  is  vestigial  or  wanting.  rM 

The  vertex  (Figs.  462  and  463,  v)  bears  the  paired  ocelli.  W^ 

The  clypeus  (Figs.  462  and  463,  c)  is  very  large,  occupying  the 
greater  part  of  the  anterior  surface  of  the  head.     In  several  of  the 


}<yi 


398 


AN  INTRODUCTION  TO  ENTOMOLOGY 


CO  - 


published  accounts  of  the  head  of  homopterous  insects  the  clypeus 
has  been  incorrectly  identified  as  the  front. 

The  lahnim  (Figs.  462  and  463,  /)  is  joined  to  the  lowei  end  of  the 
clypeus ;  at  its  distal  end  it  forms  a  sheath  covering  the  base  of  the 
labium  and  the  enclosed  setee.  This  part  is  described  as  the  clypeus 
by  those  who  have  incorrectly  identified  the  clypeus  as  the  front. 
The  epipharynx  (Figs.  462  and  463,  ^)  arises  at  its  normal  position 
on  the  ental  surface  of  the  labrum;  but  it  is  greatly  developed  and 
projects  beyond  the  end  of  the  labnmi.  The  projecting  part  has  been 

mistaken  for  the  labrum  by 
77^X1'  some    writers,    those    who 

l\  have  failed  to  recognize  the 

front  and  have  termed  the 
ch-peus  the  front  and  the 
labrum  the  clypeus. 

The  mandibular  sclerites 
are  easily  recognized  in  the 
cicada.  On  each  lateral  as- 
pect of  the  head  there  are 
two  quite  distinct  sclerites; 
the  one  that  is  next  to  the 
clvpeus  and  the  base  of  the 
labium  is  the  mandibular 
sclerite  (Figs.  46  2  and  463 ,  x) . 
This  sclerite  is  termed  the 
lora  by  some  writers  on  the 
Homoptera. 

The  mandibular  sclerites 
are  believed  to  be  in  each 
case  the  basal  part  of  a  man- 
dible. They  were  first  rec- 
ognized as  such  by  Profes- 
sor J.  B.  Smith  ('92);  and 
this  conclusion  has  been 
adopted  by  Marlatt  ('95), 
He\Tnons  ('99),  Meek  ('03), 
Berlese  ('09),  and  Bugnion 
and  Popofif  ('11).  On  the 
other  hand.  Muir  and  Ker- 
shaw ('12)  regard  the  lorse  as  "lateral  developments  of  the  clypeal 
region"  and  not  parts  of  mandibles. 

The  structure  of  the  mandible  as  a  whole  has  been  worked  out  by 
Meek  ('03)  and  is  shown  in  the  left  half  of  Figure  465.  Within  the 
cavity  of  the  head  the  maxillary  seta  is  enlarged,  and  to  it  are  attached 
a  retractor  muscle  (mdr)  and  a  protractor  muscle  (mdp) .  The  seta  is 
attached  to  the  dorsal  end  of  the  mandibular  sclerite  (Fig.  465.  mds) 
by  a  quadrangular  sclerite  (Fig.  465,  co). 

The  maxillary  sclerites  (Figs.  462  and  463,  y)  are  closely  parallel 
with  the  mandibular  sclerites,  but  extend  farther  down,  joining  the 


Fig.  465. — Caudal  view  of  the  head  of  a  cicada, 
with  part  of  the  head-capsule  and  muscles  re- 
moved so  as  to  show  the  left  mandible  and 
the  right  maxilla.      (From  Meek.) 


HOMOPTERA 


399 


terminal  part  of  the  labrum.  Each  maxillary  sclerite  is  a  part  of  a 
maxilla.  This  is  clearly  shown  by  the  fact  that  in  the  embryo  each 
maxilla  is  at  first  a  bilobed  appendage;  from  one  of  these  lobes  the 
maxillary  sclerite  is  developed,  and  from  the  other  the  maxillary  seta 
(see  Heymons  '99).  In  the  adult  insect  the  maxillary  sclerites  are 
not  separated  from  the  epicraninm  by  sutures  as  are  the  mandibular 
sclerites  (Figs.  462  and  463). 

The  form  and  relations  of  the  different  parts  of  a  maxilla,  as 
worked  out  by  Meek  ('03),  are  shown  in  the  right  half  of  Figure  465. 
From  the  enlarged  base  of  the  maxillary  seta  a  crescent-shaped 
sclerite  (Fig.  465,  ca)  extends  to  the  maxillary  sclerite  (Fig.  465,  mxs). 
In  this  figure  the  maxillary  retractor  muscles  {mxr),  the  maxillary 
protractor  muscles  (nixp),  and  a  tendon  (mc)  connecting  the  crescent- 
shaped  sclerite  with  the  tentoriimi,  are  also  represented. 

It  is  interesting  to  note  the  similarity  in  the  structure  of  the 
mandibles  and  the  maxillae.  Each  consists  of  a  basal  part  which  forms 
a  portion  of  the  wall  of  the  head;  a  terminal  piercing  organ,  the 
seta;  and  a  sclerite  connecting  these  two  parts. 

The  labium  forms  the  outer  wall  of  the  beak;  it  consists  of  three 
segments;  the  second  and  third  are  lettered  in  Figures  462 
and  463.  The  proximal  segment  is  probably  homologous  with  the 
submentimi  of  the  chewing  insect  mouth;  the  second  segment,  with 
the  mentiim;  and  the  third  segment,  with  the  ligula  (see  footnote, 
page  354).  The  dorsal  surface  of  the  labium,  which  is  the  lower 
surface,  is  deeply 
grooved,  forming  a 
channel  which  enclos- 
es the  mandibular  and 
maxillary  setae. 

The  labium,  which 
is  all  that  is  commonly 
seen  of  the  beak  in 
either  hemipterous  or 
homopterous  insects, 
is  not  a  piercing  or- 
gan; it  is  not  pushed 
into  the  food  sub- 
stance of  the  insect, 
but  serves  mereh^  as  a 
sheath  for  the  mandib- 
ular and  maxillary 
setae,    which    are    the 

piercing  organs  and  which  are  worked  by  the  protractor  and  retractor 
muscles  within  the  head  (Fig.  465). 

Figure  466  represents  a  cross-section  of  the  third  segment  of  the 
beak  of  a  cicada  as  figured  by  Meek  ('03),  and  shows  the  relation  of 
the  labium  to  the  mandibular  and  maxillary  setae.  Each  seta  is 
crescent-shaped  in  cross-section ;  the  mandibular  setae  lie  outside  of 
the  maxillary  setae;  the  maxillary  setae,  which  extend  side  by  side  at 


Fig.  466. — Cross-section  of  the  third  segment  of  the 
beak  of  a  cicada:  lab,  labium;  md,  mandibular 
seta;  mx,  maxillary  seta;  /,  /,  lumina  in  the  seta. 
(From  Meek.) 


400  AN  INTRODUCTION  TO  ENTOMOLOGY 

the  base  of  the  beak,  are  twisted  so  that  at  this  point  one  Hes  above 
the  other.  The  two  are  fastened  together  by  interlocking  grooves 
and  ridges ;  and  between  them  is  a  channel  for  the  passage  of  the  food. 
Within  each  of  the  four  set«,  there  is  a  lumen  (Fig.  466,  /,  /). 

The  hypopharynx  is  a  funnel-shaped,  chitinized  organ  found  near 
the  base  of  the  ental  surface  of  the  labiiun,  at  the  end  of  the  pharynx. 

The  nature  of  the  metamorphosis  differs  to  a  considerable  degree 
in  the  different  families;  in  most  cases  it  is  gradual,  but  marked 
modifications  of  this  type  have  been  developed  in  the  Aleyrodidae 
and  in  the  Coccidae. 

The  members  of  this  order  feed  on  vegetation  and  to  it  belong 
some  of  our  more  important  insect  pests. 

This  order  includes  ten  families,  which  are  designated  as  follows : 

The  Cicadas,  Family  Cicadid^,  p.  401. 

The  Spittle-insects,  Family  Cercopid^,  p.  402. 

The  Tree-hoppers,  Family  Membracid^,  p.  404. 

The  Leaf-hoppers,  Family  Cicadellid^,  p.  406. 

The  Lantern-fly  Family,  Family  Fulgorid^,  p.  408. 

The  Jimiping  Plant-lice,  Family  Chermid^,  p.  410. 

The  Typical  Aphids,  Family  Aphidid^,   p.  415. 

The  Adelgids  and  the  Phylloxerids,  Family  Phylloxerid^,  p.  428. 

The  Aleyrodids,  Family  Aleyrodid^,  p.  437. 

The  Scale-bugs,  Family  Coccid^,  p.  440. 

TABLE   FOR   DETERMINING   THE   FAMILIES    OF   THE   HOMOPTERA 

A.     Beak  evidently  arising  from  the  head;  tarsi  three-jointed;  antennae  minute, 
bristle-Hke. 

B.     With  three  ocelli,  and  the  males  with  musical  organs.     Usually  large 
insects,    with   all  the   wings   entirely   membranous,   p.  401 Cicadid^ 

BB.     Ocelli  only  two  in  number  or  wanting;  males  without  musical  organs. 
C.     Antennae  inserted  on  the  sides  of  the  cheeks  beneath  the  eyes.  p.  408 

FULGORID^ 

CC.     Antennae  inserted  in  front  of  and  between  the  eyes. 
D.    Prothorax  not  prolonged  above  the  abdomen. 

E.    Hind  tibiae  armed  with  one  or  two  stout  teeth,  and  the  tip  crowned 

with  short,  stout  spines,    p.  402 Cercopid^ 

EE.     Hind  tibiae  having  a  row  of  spines  below,     p.  406 .  CiCADELLiDiE 
DD.    Prothorax  prolonged  into  a  horn  or  point  above  the  abdomen,  p.  404 

Membracid^ 

AA.    Beak  apparently  arising  from  between  the  front  legs,  or  absent ;  tarsi  one-  or 
two- jointed;    antennae    usually    prominent    and  threadlike,   sometimes 
wanting. 
B.     Tarsi  usually  two- jointed;  wings  when  present  four  in  number. 
C.    Wings  transparent. 

D.     Hind  legs  fitted  for  leaping;  antennae  nine-  or  ten-jointed,  p.  410.  . 

Chermid^ 

DD.    Legs   long   an   slender,  not   fitted   for  leaping;  antennae   three-  to 

seven-jointed.  412 Superfamily  Aphidoidea 

CC.     Wings    opaque,  whitish;  wings  and  body  covered  with  a  whitish 
powder,    p.  437 Aleyrodids 


HOMOPTERA 


401 


BB.  Tarsi  usually  one-jointed;  adult  male  without  any  beak,  and  with  only 
two  wings;  female  wingless,  with  the  body  either  scale-like  or  gall-like  in 
form,  or  grub-like  and  clothed  with  wax.  The  waxy  covering  may  be  in  the 
form  of  powder,  of  large  tufts  or  plates,  of  a  continuous  layer,  or  of  a 
thin  scale  beneath  which  the  insect  lives,  p.  440 Coccid^ 


Family  CICADID^ 


The  Cicadas 


The  large  size  and  well-known  songs  of  the  more  common  species 
of  this  family  render  them  familiar  objects.  It  is  only  necessary  to 
refer  to  the  periodical  cicada  and  to  the  harvest- 
flies,  one  of  which  is  represented  by  Figure  467, 
to  give  an  idea  of  the  more  striking  character- 
istics of  this  family.  We  have  species  of  cicadas 
much  smaller  than  either  of  these;  but  their 
characteristic  form  is  sufficient  to  distinguish 
them  from  members  of  the  other  families  of 
this  order. 

The  species  are  generally  of  large  size,  with 
a  subconical  body.  The  head  is  wide  and  blunt, 
with  prominent  eyes  on  the  outer  angles,  and 
three  bead-like  ocelli  arranged  in  a  triangle  be- 
tween the  eyes.  The  structure  of  the  mouth- 
parts  is  described  on  an  earlier  page  and  illus- 
trated by  several  figures;  and  the  form  and 
venation  of  the  wings  are  shown  by  Figure  461. 

But  the  most  distinctive  peculiarity  is  the  form  p.  „., . 

of  the  musical  organs  of  the  males;  an  example  of    ^^j^i^  '^' 
these  is  described  and  figured  on  pages  89  to  9 1 . 

The  family  Cicadid^  is  well  represented  in  this  country ;  seventy- 
four  species,  representing  sixteen  genera,  are  now  listed  from  our 
fauna.    The  two  following  species  will  serve  as  illustrations. 

There  are  several  species  of  cicadas  that  are  commonly  known  as 
dog-day  cicadas  or  harvest -flies ;  the  most  abundant  of  these  is  the 
species  that  has  received  the  popular  name  of  the  lyreman;  this  is 
Tibtcen  limiei  (Fig.  467).  The  shrill  cry  of  this  species,  which  is  the 
most  prominent  of  the  various  insect  sounds  heard  during  the  latter 
part  of  the  summer,  has  brought  its  author  into  prominent  notice. 
This  insect  varies  both  in  size  and  colors.  It  commonly  measures  50 
mm.  to  the  tip  of  the  closed  wings;  it  is  black  and  green,  and  more  or 
less  powdered  with  white  beneath.  The  transformations  of  this 
insect  are  similar  to  those  of  the  following  species,  except  that  it 
probably  completes  its  development  in  a  much  shorter  period.     It 


402  AN  INTRODUCTION  TO  ENTOMOLOGY 

differs  also  in  seldom,  if  ever,  occurring  in  siifficient  numbers  to  be 
of  economic  importance;  but  a  brood  of  it  appears  each  year. 

The  member  of  this  family  that  has  attracted  most  attention  is 
the  periodical  cicada,  Tiblcina  septendecim.  This  species  is  commonly 
known  as  the  seventeen-year  locust;  but  the  term  locust  when  applied 
to  this  insect  is  a  misnomer,  the  true  locusts  being  members  of  the 
order  Orthoptera.  The  improper  application  of  the  term  locust  to 
this  species  was  doubtless  due  to  the  fact  that  it  appears  in  great 
swarms,  which  reminded  the  early  observers  in  this  country  of  the 
hordes  of  migratory  locusts  or  grasshoppers  of  the  Old  World.  This 
species  is  remarkable  for  the  long  time  required  for  it  to  attain  its 
maturity.  The  eggs  are  laid  in  the  twigs  of  various  trees;  the  female 
makes  a  series  of  slits  in  the  twig,  into  which  the  eggs  are  placed. 
Sometimes  this  cicada  occurs  in  such  great  numbers  that  they  seriously 
injure  small  fruit  trees,  by  ovipositing  in  the  twigs  and  smaller 
branches.  The  nymphs  hatch  in  about  six  weeks.  They  soon  volun- 
tarily drop  to  the  ground,  where  they  bury  themselves.  Here  they 
obtain  nourishment  by  sucking  the  juices  from  the  roots  of  forest  and 
fruit  trees.  And  here  they  remain  till  the  seventeenth  year  following. 
They  emerge  from  the  ground  during  the  last  half  of  May,  at  which 
time  the  empty  pupa-skins  may  be  found  in  great  numbers,  clinging 
to  the  bark  of  trees  and  other  objects.  It  is  at  this  period  that  the 
cicadas  attract  attention  by  the  shrill  cries  of  the  males.  The  insects 
soon  pair,  the  females  oviposit,  and  all  disappear  in  a  few  weeks. 

More  than  twenty  distinct  broods  of  this  species  have  been  traced 
out;  so  that  one  or  more  broods  appear  somewhere  in  the  United 
States  nearly  every  year.  In  mam^  localities,  several  broods  co-exist ; 
in  some  cases  there  are  as  many  as  seven  distinct  broods  in  the  same 
place,  each  brood  appearing  in  distinct  years.  There  is  a  variety  of 
the  species  in  which  the  period  of  development  is  only  thirteen  years. 
This  variety  is  chiefly  a  southern  form,  while  the  seventeen-year 
broods  occur  in  the  North. 


Family  CERCOPID^ 

The  Spittle-Insects  or  Frog-Hoppers 

During  the  summer  months  one  often  finds  upon  various  shrubs, 
grass,  and  other  herbs,  masses  of  white  froth.  In  the  midst  of  each  of 
these  masses  there  lives  a  young  insect,  a  member  of  this  family. 
In  some  cases  as  many  as  four  or  five  insects  inhabit  the  same  mass 
of  froth.  It  is  asserted  that  these  insects  undergo  all  their  trans- 
formations within  this  mass ;  that  when  one  is  about  to  molt  for  the 
last  time,  a  clear  space  is  formed  about  its  body  and  the  superficial 
part  of  the  froth  dries,  so  as  to  form  a  vaulted  roof  to  a  closed  chamber 
within  which  the  last  molt  is  made. 

The  adult  insects  wander  about  on  herbage,  shrubs,  and  trees. 
They  have  the  power  of  leaping  well.    The  name  frog-hoppers  has 


HOMOPTERA  403 

doubtless  grown  out  of  the  fact  that  formerly  the  froth  was  called 
"frog-spittle"  and  was  supposed  to  have  been  voided  by  tree-frogs 
from  their  mouths.  The  name  is  not,  however,  inappropriate,  for 
the  broad  and  depressed  form  of  our  more  common  species  is  somewhat 
like  that  of  a  frog. 

The  origin  and  formation  of  the  froth  of  spittle-insects  has  been 
discussed  by  many  writers.  Guilbeau  ('08)  found  by  many  experi- 
ments that  the  froth  is  derived  from  two  sources.  The  greater  part 
of  the  fluid  is  voided  from  the  anus;  to  this  fluid  is  added  a  mucilagi- 
nous substance  which  renders  it  viscous  and  causes  the  retention  of 
air  bubbles,  which  are  introduced  into  it  by  the  insect  by  means  of  its 
caudal  appendages.  The  mucilaginous  substance  is  the  excretion  of 
large  hypodermal  glands,  which  are  in  the  pleural  region  of  the 
seventh  and  eighth  abdominal  segments.  These  are  known  as  the 
glands  of  Batelli;  they  open  through  numerous  minute  pores  in  the 
cuticula. 

It  is  evident  that  the  covering  of  froth  protects  the  spittle-insects 
from  parasites  and  other  enemies. 

In  this  family  the  antennae  are  inserted  in  front  of  and  between 
the  eyes;  the  prothorax  is  not  prolonged  back  of  the  abdomen,  as  in 
the  Membracidae ;  the  tibiae  are  armed  with  one  or  two 
stout  teeth,  and  the  tip  is  crowned  with  short,   stout 
spines,  as  shown  in  Figure  468. 

The  Cercopidas  is  represented  in  our -fauna  by  six 
genera,  which  include  twenty-five  species.    The  follow-  Fig.  468. — Le- 
ing  species  will  serve  as  examples.  p  y  ro  m  a 

One  of  the  more  common  and  very  widely  distribut-  ^J^^^  '^'^nftu- 
ed  species  is  Lepyrdnia  quadranguldris  (Fig.  468).  The  ral  size,  and 
adult  of  this  species  is  a  brownish  insect,  densely  one  tibia  en- 
covered  with  microscopic  hairs,  and  black  beneath;  larged. 
the  hemelytra  are  marked  with  two  oblique  brown  bands,  which 
are  confluent  near  the  middle  of  the  costal  margin;  the  himieral 
region  is  dusky;  and  the  tip  of  each  hemelytron  is  marked  with  a 
small  blackish  curve;  the  ocelli  are  black,  but  indistinct.  This 
species  measures  from  6  mm.  to  8  mm.  in  length. 

Somewhat  resembling  the  preceding  species,  and  also  common 
and  widely  distributed,  is  Aphrophora  quadranotdta.  In  this  species 
the  body  is  pale;  the  hemelytra  are  dusky,  each  with  two  large  hya- 
line costal  spots,  margined  with  dark  brown;  the  ocelli  are  blood-red; 
and  the  head  and  pronotum  are  furnished  with  a  slightly  elevated, 
median,  longitudinal  line. 

To  the  genus  Clastopiera  belong  certain  other  common  members 
of  this  family.  In  this  genus  the  body  is  short  and  plump,  some- 
times nearly  hemispherical;  the  species  are  small,  our  common  forms 
ranging  from  3  mm.  to  6  mm.  in  length.  Clastoptera  prdteus  is  a 
conspicuous  species  on  account  of  its  bright  yellow  markings.  It 
varies  greatly  in  color  and  markings;  but  the  most  striking  forms 
are  black,  with  three  transverse  yellow  bands,  two  on  the  head  and 
one  on  the  thorax,  and  with  the  scutellum  and  a  large  oblique  band 


*\ 


404 


AN  INTRODUCTION  TO  ENTOMOLOGY 


on  each  hemelytron  yellow.  Another  common  species  is  Clastoptera 
obtusa.  This  occurs  on  black  alder  in  summer  and  autumn.  It  is  of  a 
claret-brown  color  above,  marked  with  two  pale  bands  on  the  vertex, 
two  on  the  prothorax,  and  a  wavy,  broader  band  on  the  hemelytra. 
The  membrane  is  often  whitish,  the  waved  band  is  extended  exteriorly, 
and  there  is  a  pale  V-shaped  figure  on  the  end  of  the  scutellimi. 

Family  MEMBRACID^ 
The  Tree-Hoppers 


Fig.  469. — A,  Spongophonis  hallista;  B,  Spongophoriis 
querini. 


The  most  useful  character  for  distinguishing  members  of  this 
family  is  the  prolongation  of  the  prothorax  backward  above  the 

abdomen;  some- 
times it  extends 
back  to  the  tip  of 
the  abdomen  and 
completely  cov- 
ers the  wings. 
This  develop- 
ment  of  the 
prothorax  re- 
sembles  that 
which  occurs  in 
the  pigmy  lo- 
custs, the  sub- 
family Acrv^diinae 
of  the  order  Or- 

thoptera.  In  many  of  the  Membracidffi,  however,  the  prothorax  is 
not  only  prolonged  backward  but  is  extended  sidewise  or  upwards, 
with  the  result  that  in  some  cases  the  insect  presents  a  most  bizarre 
appearance ;  this  is  especially  true  of  certain  tropical  forms ;  Figure  469 
represents  two  species  found  in  Central  America. 

Many  species  of  the  Membracidas  live  upon  bushes  or  small 
trees;  others  inhabit  grass  and  other  herbaceous  plants.  Although 
these  insects  subsist  upon  the  juices  of  plants,  they  rare- 
ly occur  in  sufhcient  numbers  to  be  of  economic  impor- 
tance. Sometimes  the  females  injure  young  trees  by  lay- 
ing their  eggs  in  the  bark  of  the  smaller  branches  and  in 
buds  and  stems.  Many  members  of  this  family  excrete 
honey-dew  and  are  attended  by  ants,  especially  in  the 
nymphal  stages,  as  are  the  aphids.  The  adults  are  good  Fig. 470.— Cer- 
leapers;  hence  the  common  name  tree-hoppers.  esabubalus. 

This  family   is    well  represented  in    this  country; 
one  hundred  eighty-five  species,  representing  forty-three  genera,  are 
now  listed.     Among  our  more  common  species  are  the  following. 

The  Buffalo  tree-hopper,  Ceresa  bubalus.- — The  popular  name  of 
this  species  refers  to  the  lateral  prolongations  of  the  prothorax, 
which  suggest  the  horns  of  a  buffalo  (Fig.  470).    The  life-history  of 


f 


HO  MO  PT ERA 


405 


this  insect  has  been  worked  out  by  Funkhouser  ('17).  The  n\Tnphs 
feed  on  succulent  herbs,  particularly  sweet  clover;  the  eggs  are  laid 
on  young  trees,  particularly  elm  and  apple,  the  stems  of  which  are 
injured  by  the  egg-punctures.  Oviposition  occurs  most  commonly 
in  early  September,  at  Ithaca,  N.  Y.  The  eggs  hatch  early  in  the 
following  May.  The  young  n>Tnphs  leave  the  trees  on  which  the 
eggs  were  deposited  and  migrate  to  succulent  weeds.  The  early  life 
of  the  adult  is  spent  on  the  weeds ;  but  later  the  females  migrate  to 
trees  for  egg-laying. 

The  two-horned  tree-hopper,  Ceresa  dtceros. — This  species  re- 
sembles the  buifalo  tree-hopper  in  size  and  form.  It  is  a  pale  dirty 
yellow,  spotted  with  brown;  the  lateral  and  caudal  aspect  of  each 
horn  is  brown;  the  caudal  tip  of  the  prothorax,  and  a  large  spot 
midway  between  the  tip  and  the  horns,  are  also  brown.  The  insect  is 
densely  clothed  with  hairs.  It  is  common  on  black  elder,  Sambucus 
canadensis.  Funkhouser  followed  the  life-history  from  the  egg  to  the 
adult  on  this  plant.  The  eggs  are  laid  about  the  middle  of  August 
in  the  second-year  stems,  and  hatch  about  the  middle  of  May. 

The  two-marked  tree-hopper,  Enchendpa  binotdta. — In  this  spe- 
cies the  pronotum  is  prolonged  in  an  upward-  and  forward- projecting 
horn  (Fig.  471).  This  insect  is  very  abundant  on  trees, 
shrubs,  and  vines.  It  is  gregarious,  and  both  adult  and 
immature  forms  are  found  clustered  together.  The 
eggs  are  usually  laid  in  frothy  masses,  which  are  very 
white  and  appear  like  wax.  Funkhouser  states  that 
a  variety  of  this  species  found  on  butternut  lays  its  eggs 
in  the  buds  and  does  not  cover  them  with  the  heavy 
froth.  The  specific  name  of  this  species  refers  to  the 
fact  there  are  two  yellow  spots  on  the  dorsal  line  of  the  pronotiim. 
Another  very  common  species,  and  one  that  is  closely  allied  to  the 
preceding,  is  Campylenchia  latipes.  This  is  brownish, 
unspotted,  and  has  a  rather  longer  horn  than  that 
of  the  two-marked  tree-hopper;  but  it  varies  much 
in  color  and  in  the  length  of  the  pronotal  horn.  This 
is  a  grass-inhabiting  species  and  is  common  in  pastures 
and  especially  on  alfalfa.  It  is  often  taken  by  sweeping. 
Telamdna. — To  this  genus  belong  our  humpback 


Fig.  471.— £«- 
chenopa  bi- 
notata. 


Fisf.    472 
amona. 


-Tel- 


406  AN  INTRODUCTION  TO  ENTOMOLOGY 

forms  (Fig.  472),  of  which  about  thirty  species  have  been  found 
in  our  fauna.  They  Hve  chiefly  on  oaks,  hickories,  basswood,  and 
other  forest  trees.  The  adults  generally  rest  singly  on  the  limbs 
and  branches  of  the  trees ;  the}'  are  strong  flyers  and  are  difficult  to 
capture.    The  immature  forms  keep  together  in  small  groups. 

Figure  473  represents  a  front  view  of  several  membracids  in  our 
collection. 

Family  CICADELLID^* 

The  Leaf-Hoppers 

This  family  is  a  very  large  one,  and  it  is  also  of  considerable 
economic  importance;  for  it  includes  a  number  of  species  that  are 
very  injurious  to  cultivated  plants.  The  members  of  it  are  of  small 
or  moderate  size.  The  antennge  are  inserted  in  front  of 
and  between  the  eyes;  the  pronotum  is  not  prolonged 
above  the  abdomen;  and  the  hind  tibiae  are  nearly 
or  quite  as  long  as  the  abdomen,  curved,  and 
armed  with  a  row  of  spines  on  each  margin.  The  form 
and  armature  of  the  hind  tibise  are  the  most  salient 
characters  of  this  family.  The  form  of  the  body  is 
commonly  long  and  slender,  often  spindle-shaped;  but 

^.  some  are  plump. 

^%elis    exiti-         These  insects  are  able  to  leap  powerfully;  and,  as 
osus.  they  are  more  often  found  on  the  leaves  of  herbage 

and  on  grass  than  elsewhere,  they  have  been  named  leaf -hoppers. 
They  infest  a  great  variety  of  plants;  some  of  them  are  important 
pests  in  gardens,  orchards,  and  vineyards;  but  they  are  most  destruc- 
tive as  pests  of  grains  and  grasses.  Although  this  is  true,  much 
less  attention  has  been  paid  to  injuries  caused  by  them  to  grains 
and  grasses  than  to  those  inflicted  upon  vineyards  and  rose  bushes. 
More  than  seven  hundred  species,  representing  about  seventy 
genera,  have  been  found  in  the  United  States  and  Canada.  Among  the 
more  important  members  of  the  family  from  an  economic  standpoint 
are  the  following. 

The  destructive  leaf-hopper,  Euscelis  exitiosus,  which  is  repre- 
sented, greatly  enlarged,  in  Figure  474,  sometimes  infests  winter 
wheat  to  a  serious  extent.  It  is  a  widety  distributed  species,  its 
range  including  nearly  the  whole  of  the  United  States.  It  is  a 
small,  active,  brownish  insect,  which  measures  with  its  wings  folded 
about  5  mm.  in  length.  It  injures  grass  or  grain  by  piercing  the 
midrib  of  the  leaf  and  sucking  the  juices  from  it. 

The  grape-vine  leaf -hopper,  Erythroneura  comes,  is  a  well-known 
pest  which  infests  the  leaves  of  grape,  in  all  parts  of  this  country 
where  this  vine  is  grown.  It  is  a  little  more  than  3  mm.  in  length, 
and  has  the  back  and  wings  marked  in  a  peculiar  manner  with  yellow 
and  red.  In  the  winter  the  darker  markings  are  a  dark  orange-red, 
but  after  feeding  has  been  restmied  for  a  short  time  in  the  spring 
they  change  to  a  light  lemon-3'ellow.     The  darker  markings  on  the 

*This  family  has  been  commonly  known  as  the  Jassidae,  but  Cicadellidae  is  the 
older  name. 


HO  MOP  T ERA 


407 


adults  vary  so  much  that  eleven  distinct  varieties  are  now  recognized ; 
two  of  these  are  represented  at  b  and  c  in  Figure  475. 

The  rose  leaf-hopper,  Empoa  roses,  is  a  well-known  pest  of  the 
rose.  Swarms  of  these  insects  may  be  found,  in  various  stages  of 
growth,  on  the  leaves  of 
the  rose-bush  through 
the  greater  part  of  the 
summer,  and  their  nu- 
merous cast  skins  may  be 
seen  adhering  to  the  low- 
er sides  of  the  leaves;  in 
fact  attention  is  most  fre- 
quently called  to  this 
pest  by  these  white  ex- 
uviae. The  adult  meas- 
ures less  than  3  mm.  in 
length.  Its  body  is  yel- 
lowish white,  its  wings 
are  white  and  transpar- 
ent, and  its  eyes,  claws, 
and  ovipositor  are  brown. 

The  apple  leaf-hop- 
per, Empodsca  mali. — Al- 
though this  species  is 
named  the  apple  leaf- 
hopper,  it  infests  to  an  in- 
jurious extent  man}'-  dif- 
ferent plants,  both  cultivated  and  wild.  Slingerland  and  Crosby  ('14) 
state  that  it  infests  apple,  currant,  gooseberry,  raspberry,  potato, 
sugar-beets,  beans,  celery,  grains,  grasses,  shade  trees,  and  .weeds. 
The  adult  insect  measures  about  3  mm.  in  length,  and  is  of  a  pale 
yellowish  green  color  with  six  or  eight  distinguishing  white  spots  on 
the  front  margin  of  the  pronotum. 

The  genus  Drceculacephala  includes  grass-green  or  pale  green, 
spindle-shaped  species,  in  which  the  head  as  seen  from  above  is  long 
and  triangular.  One  of  the  species,  D.  reticulata,  sometimes  greatly 
injures  fields  of  grain  in  the  South. 

The  genus  Oncometopia  includes  species  in  which  the  head   is 

more  blunt  than  in  the  preceding  genus  and  is  wider  across  the  eyes. 

than  the  thorax.     0.  unddta  (Fig.  476)  is  a  common. 

/~\W'  species.  Its  body,  head,  fore  part  of  the  thorax,  scutel- 
vwv  him,  and  legs  are  bright  yellow,  with  circular  lines  of 
/W\  black  on  the  head,  thorax,  and  scutellum.  The  fore 
®i  wings  are  bluish  purple,  when  fresh,  coated  with 
whitish  powder.  It  measures  12  mm.  in  length.  It  is 
said  to  lay  its  eggs  in  grape  canes,  and  to  puncture 
with  its  beak  the  stems  of  the  bunches  of  grapes, 
causing  the  stems  to  wither  and  the  bunches  to  drop  off. 
One  division  of  this  family,  the  subfamily  Gyponinas,  includes  forms 
which  resemble  certain  genera  belonging  to  the  Cercopidaeby  their 


Fig.  475. — Erythronetira  comes:  a  and  b,  female 
and  male  of  the  typical  comes  variety;  c,  the 
vitis  variety.    (From  Slingerland.) 


Fig.  476.  —On- 
cometopia 
tindata. 


408  A  N  INTROD C UTION  TO  ENTOMOLOG  Y 

pltunp  proportions.  Among  these  are  Penthima  americdna,  which  is 
a  plump,  short-bodied  insect,  resembHng  a  Clastoptera;  and  the  genus 
Gypona  includes  a  large  nimiber  of  species,  some  of  which  resemble 
very  closely  certain  species  of  Aphrophora.  A  glance  at  the  posterior 
tibiae  of  these  leaf-hoppers  will  enable  one  to  distinguish  them  from 
the  cercopids,  which  they  so  closely  resemble. 

Methods  of  combating  leaf-hoppers. — Leaf-hoppers,  being  sucking 
insects,  are  fought  with  contact  insecticides.  But  it  is  difficult  to 
destroy  the  adults,  for  they  are  so  well-protected  by  their  wings  that 
applications  strong  enough  to  kill  them  are  liable  to  injure  the  foliage 
of  the  host-plant;  and,  too,  they  are  very  active  and  fly  away  when 
approached.  The  most  effective  remedial  measures  are  those  directed 
against  the  nymphs.  These  consist  of  the  use  of  some  spray,  as  a  ten- 
per-cent.  kerosene  emulsion  or  a  soap  solution  made  by  dissolving  one 
pound  of  soap  in  six  or  eight  gallons  of  water,  or  a  solution  made  of 
one  ounce  of  "black  leaf  40"  tobacco  extract  and  six  gallons  of  water 
in  which  has  been  dissolved  a  piece  of  soap  the  size  of  a  hen's  egg. 
The  application  should  be  so  applied  as  to  wet  the  lower  surface  of 
every  leaf. 

Family  FULGORID^ 
The  Lantern-Fly  Family 

This  family  is  remarkable  for  certain  exotic  forms  which  it  includes. 
Chief  among  these  is  the  great  lantern-fly  of  Brazil,  Laterndria  pJios- 
phorea.  This  is  the  largest  species  of  the  family  and  is  one  of  the 
most  striking  in  appearance  of  all  insects  (Fig.  477).  It  has  immense 
wings,  which  expand  nearly  six  inches;  upon  each  hind  wing  there  is 


Fig.  477. — The  lantern-fly,  Latertiaria  phosphorea. 

a  large  eye-like  spot.  But  the  character  that  makes  this  insect  es- 
pecially prominent  is  the  form  of  the  head.  This  has  a  great  bladder- 
like prolongation  extending  forward,  which  has  been  aptly  compared 
to  the  pod  of  a  peanut.  Maria  Sibylla  Alerian,  a  careful  observer, 
who  wrote  more  than  two  hundred  years  ago  (1705),  stated  that  this 
prolongation  of  the  head  is  limiinescent.  This  statement  was  ac- 
cepted by  Linnseus  without  question ;  and  he  made  use  of  names  for 
this  and  some  allied  species,  such  as  laternaria,  phosphorea,  candelar- 
ia,  etc.,  to  illustrate  the  supposed  light-producing  powers  of  these 
insects.    The  common  name  lantern-fly  is  based  on  the  same  belief. 


HOMOPTERA 


409 


Fig.  478. — Antenna  of  Megamehis  notula.     (Aftei 
Hansen.) 


Fig.     479. 
Scolops. 


The  Brazilian  lantern-fly  has  been  studied  by  many  more  recent 
observers,  and  all  have  failed  to  find  that  it  is  luminescent.     It  may 
be  that  the  individuals  observed  by  Madame  Merianwere  infested 
by  Itmiinescent  bacteria, 
as  has  been  observed  to 
be  the  case  occasionally 
in  certain  other  insects. 
No  member  of  this  fam- 
ily is  known  to  be  lumi- 
nescent. 

The  Chinese  candle- 
fly,   Fulgoria  caiideldria, 
is   another   very   promi- 
nent member  of  this  family,  which  is  commonly  represented  in  col- 
lections of  exotic  insects  and  is  often  figured  by  the  Chinese.    This 
too  has  been  reputed  to  give  light. 

Certain  fulgorids  found  in  China  excrete  large 
quantities  of  a  white,  flocculent  wax,  which  is  used  by 
the  Chinese  for  candles  and  other  purposes. 

There  does  not  seem  to  be  any  typical  form  of  the 
-body  characteristic  of  this  family.  The  different  genera 
dift'er  so  greatly  that  on  superficial  examination  they 
appear  to  have  very  little  in  common.  The  most 
useful  character  for  recognizing  these  insects  is  the 
form  and  position  of  the  antennse.  These  are  situated 
on  the  side  of  the  cheeks  beneath  the  eyes;  the  two 
proximal  segments,  the  scape  and  pedicel,  are  stout  (Fig.  478) ;  the 
clavola  consists  of  a  small,  nearly  pear-shaped  basal  segment  and  a 
slender,  segmented  or  un- 
segmented,  bristle-like  ter- 
minal part.  The  pedicel  is 
provided  with  numerous 
sense-organs. 

So  far  as  numbers  are 
concerned  this  family  is 
well  represented  in  our 
fauna,  three  hundred  fifty- 
seven  species  and  seventy- 
seven  genera  having  been 
listed;  but  our  species  are 
all  small  compared  with  the 
exotics  mentioned  above.  The  following  of  our  native  genera  will 
serve  to  illustrate  some  of  the  variations  in  form  represented  in  this 
country.     The  species  all  feed  on  the  juices  of  plants. 

Scolops. — In  this  genus  the  head  is  greatly  prolonged  (Fig.  479),  as 
with  the  Chinese  candle-fly.  Our  more  common  species,  however, 
measure  only  about  8  mm.  in  length. 

Otiocerus.- — In  this  genus  the  body  is  oblong;  the  head  is  com- 
pressed, with  a  double  edge  both  above  and  below.  Otiocerus  coque- 
hertii  (Fig.  480)  is  a  gay  lemon-yellow  or  cream-colored  species,  with 


Otiocerus  coquehertii.     (From  Uh- 


410 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  481. — Ormenis  sep- 
tentrionalis. 


wavy  red  lines  on  the  fore  wings.     It  measures  about  8  mm.  to  the 
tips  of  the  wings,  and  lives  upon  the  leaves  of  grape-vmes,  oaks,  and 

hickors'. 

Ormenis. — In  our  common  representatives 
of  this  genus  the  wing -covers  are  broad,  and 
closelv  applied  to  each  other  in  a  vertical 
position;  they  are  more  or  less  truncate,  and 
give  the  insects  a  wedge-shaped  outline.  0. 
septentriondlis  (Fig.  481)  is  a  beautiful,  pale 
green  species  powdered  with  white,  which 
feeds  on  wild  grape-vines,  drawing  nourish- 
ment from  the  tender  shoots  and  midribs  of  the 
leaves,  during  its  young  stages. 

Family  CHERMID^* 

The  Jumping  Plant-Lice 

The  jumping  plant-lice  are  small  insects;  many  of  them  measure 
less  than  2  mm.  in  length ;  and  the  larger  of  our  species,  less  than  5  mm. 
They  resemble  somewhat  the  winged  aphids;  but  they 
look  more  like  miniature  cicadas  (Fig.  482).  They 
differ  from  aphids  in  the  firmer  texture  of  the  body, 
in  the  stouter  legs,  in  having  the  hind  legs  fitted  for 
jumping,  and  in  the  antennse  being  ten-jointed  or 
rarely  nine-  or  eleven-jointed.  The  terminal  segment 
of  the  antennge  bears  two  thick  setee  of  unequal  length. 
Both  sexes  are  winged  in  the  adult.  The  front 
wings  are  ample,  and,  while  often  transparent,  are  much 
thicker  than  the  hind  wings.  The  homologies  of  the 
wing-veins  of  the  fore  wings  of  Psyllia  floccosa  are  indi- 
cated in  Figure  483 . 


Tig.  483. — The  venation  of  a  fore  wing  of  Psyllia  floccosa.     (After  Patch.) 
The  beak  is  short  and  three-jointed.    The  basal  segment  of  the 
beak  is  held  rigidly  between  the  fore  coxae. 

*This  family  has  been  quite  commonly  known  as  the  Psyllidae,  a  result  of  an 
incorrect  application  of  the  name  Chermes  to  a  genus  of  the  Phylloxeridse. 


HOMOPTERA 


411 


The  jumping  plant-lice  are  very  active  little  creatures,  jumping 
and  taking  flight  when 
disturbed;  but  their 
flight  is  not  a  prolonged 
one.  They  subsist  en- 
tirely upon  the  juices  of 
plants;  some  species 
form  galls;  but  it  is  rare 
that  any  of  the  species 
appear  on  cultivated 
plants  in  sufficient  num- 
bers to  attract  attention, 
except  in  case  of  the  pear- 
tree  Psylla. 

The  family  Chermi- 
dcB  is  of  moderate  size; 
in  our  latest  list  one- 
hundred  thirty-seven 
species  representing 
twenty-four  genera,  are 
enumerated  from  our 
fauna.  The  two  fol- 
lowing species  will  serve 
to  illustrate  variations  in 
habits  of  these  insects. 

Pachypsylla  celtidis- 
ntdmma. — This  is  a  gall- 
making  species  which  in- 
fests the  leaves  of  hack- 
berry  {Celtis  occidentdlis).  Figure  484  represents  an  infested  leaf 
with  galls,  and  a  single  gall  and  a  nymph  enlarged.  The  adult  insect 
(Fig.  485)  has  a  wing  expanse  of  about  6  mm. 

The  pear-tree  psyllia,  Psyllia  pyricola. — This  is  our  most  impor- 


Fig.  484. — Gall  of  Pachypsylla  celtidis- mamma: 
a,  leaf  with  galls,  from  under-side;  b,  section!' of 
gall  enlarged  and  insect  in  cavity;  c,  nymph, 
enlarged.    (From  Riley.) 


Fig.  485. — Pachypsylla  celtidis-mamma.     (From 
Packard.) 

Fig.    486. —Psy Ilia 
pyricola. 
tant  species  from  an  economic  standpoint,  being  a  serious  enemy  of 
the  pear.     It  is  a  small  species  (Fig.  486) ;  the  summer  generations 


412  AN  INTRODUCTION  TO  ENTOMOLOGY 

measure  to  the  tips  of  the  folded  wings  from  2.1  mm.  to  2.8mm.,  the 
hibernating  form  2>-?)  mm.  to  4  mm.  The  general  color  is  light 
orange  to  reddish  brown,  with  darker  markings.  The  eggs  are  laid 
early  in  the  spring  in  the  creases  of  the  bark,  in  old  leaf-scars,  and 
about  the  base  of  the  terminal  buds.  The  }-oung  n^-mphs  migrate 
to  the  axils  of  the  leaf  petioles  and  the  stems  of  the  forming  fruit; 
later  they  spread  to  the  under  side  of  the  leaves.  They  secrete  large 
quantities  of  honey-dew,  upon  which  a  blackish  fungus  grows;  this 
is  often  the  first  indication  of  the  presence  of  the  pest.  There  are  at 
least  four  generations  each  year.  Badly  infested  trees  shed  their 
leaves  and  yoimg  fruit  in  midsimimer.  In  some  cases  orchards  have 
been  so  badly  injured  by  this  pest  that  they  have  been  cut  down  b}- 
their  owners. 

The  methods  of  control  that  are  recommended  are  the  following: 
the  scraping  off  of  the  rough  bark  from  the  trunks  and  larger  branches 
of  the  trees  and  burning  it,  in  order  to  destroy  the  hibernating  adults; 
and  thorough  spraying  of  the  trees  with  kerosene  emulsion  or  "black 
leaf  40"  tobacco  extract  when  the  petals  have  fallen  from  the 
blossoms,  in  order  to  destroy  the  newly  hatched  nvTnphs;  this  spra}^- 
ing  should  be  repeated  in  three  or  four  days;  later  sprayings  are 
not  so  effective  on  account  of  the  protection  afforded  the  insects  by 
the  expanded  leaves  and  by  their  covering  of  honey-dew. 

A  monograph  of  the  North  American  species  of  this  family  has 
been  published  by  Crawford  ('14). 

SUPERFAMILY  APHIDOIDEA 

The  Plant-Lice  or  Aphids  and  their  Allies 

The  plant-lice  or  aphids  are  well-known  insects;  they  infest 
nearly  all  kinds  of  vegetation  in  all  parts  of  the  country.  Our  most 
common  examples  are  minute,  soft -bodied, 
green  insects,  with  long  legs  and  antennas, 
which  appear  on  various  plants  in  the  house 
and  in  the  field.  Usually,  at  least,  in  each 
^.  ^^^^^/^^  species  there  are  both  winged  and  wingless 
^^^  ^^^^^^v  forms  (Fig.  487).  There  are  many  species 
^^^^  ^^^^       of  aphids,  nearly  all  of  which  are  of  small 

Fig.    487. — A    group    of     size;  some   measure   less   than    i    mm.    in 
aphids.  length;  and  our  largest  species,  only  5  or 

6  mm. 
The  body  in  most  species  is  more  or  less  pear-shaped.  The 
winged  forms  have  two  pairs  of  delicate,  transparent  wings.  These 
are  furnished  with  a  few  simple  or  branched  veins ;  but  the  venation 
is  more  extended  than  in  either  of  the  two  following  families.  The 
fore  wings  are  larger  than  the  hind  wings;  and  the  two  wings  of 
each  side  are  connected  by  a  small  group  of  hamuli.  The  wings  are 
usually  held  roof -like  when  at  rest  (Fig.  488,  ah) ,  but  are  laid  flat  on  the 
abdomen  in  some  genera.      The  beak  is  four-jointed  and  varies  greatly 


HOMOPTERA 


413 


in  length;  in  some  species  it  is  longer  than  the  body.  The  antennas 
consist  of  from  three  to  six  segments;  the  last  segment  is  usually 
provided  with  a  narrowed  prolongation  (Fig.  488,  aa).  The  first  two 
segments  of  the  antennas  are  always  short,  but  the  other  segments 
show  a  great  specific  variation  in  length  and  are  therefore  very 
useful  as  systematic  characters.  Excepting  the  first  two,  the  seg- 
ments of  the  antennee  are  usually  provided  with  sense-organs,  the 
sensoria,  which  vary  in  number  and  shape  in  different  species  and  are 


Fig.  488. — The  melon  aphis,  Aphis  gossypi:  a,  winged  agamic  female;  aa,  en- 
larged antenna  of  same;  ab,  winged  agamic  female,  with  wings  closed,  sucking 
juice  from  leaf;  b,  young  nymph;  c,  last  nymphal  instar  of  winged  form;  d, 
wingless  agamic  female.     (From  Chittenden.) 


much  used  in  the  classification  of  these  insects.  On  the  back  of  the 
sixth  abdominal  segment  there  is,  in  many  species,  a  pair  of  tubes, 
the  cornicles,  through  which  a  wax-like  material  is  excreted.  In  some 
genera  these  organs  are  merely  perforated  tubercles,  while  in  still 
other  genera  they  are  wanting.  It  was  formerly  believed  that  the 
honey -dew  excreted  by  aphids  came  from  the  cornicles;  for  this 
reason  they  are  termed  the  honey-tubes  in  many  of  the  older  books. 
The  honey-dew  of  aphids  is  excreted  from  the  posterior  end  of  the 
alimentary  canal.  It  is  sometimes  produced  in  such  quantities  that 
it  forms  a  glistening  coating  on  the  leaves  of  the  branches  below  the 
aphids,  and  stone  walks  beneath  shade-trees  are  often  densely  spotted 


414 


AN  INTRODUCTION  TO  ENTOMOLOGY 


with  it.  This  honey -dew  is  fed  upon  by  bees,  wasps,  and  ants.  The 
bees  and  wasps  take  the  food  where  they  find  it,  paying  httle  if  any 
attention  to  its  source ;  but  the  ants  recognize  in  the  plant-Hce  useful 
auxiharies,  and  often  care  for  them  as  men  care  for  their  herds. 
This  curious  relationship  is  discussed  later,  under  the  head  of  Ants. 
In  addition  to  honeydew,  many  aphids  excrete  a  white  waxy  sub- 
stance.    This  may  be  in  the  form  of  powder,  scattered   over   the 


Sc*R^M+Cu,+  lstA 


Fig.  489. — The  wings  of  Eriosoma  americana.     (From  Patch.) 

surface  of  the  bod>' ,  or  it  may  be  in  large  flocculent  or  downy  masses; 

even'  gradation  between  these  forms  exists. 

The  superfamily  Aphidoidea  includes  two  families,  the  Aphididas 

and  the  Phylloxeridas.    These  two  families  differ  in  the  life-histories 

of  their  species  and  in  the  venation  of  the  wings  of  the  winged  forms, 

as  follows: 

A.  Only  the  sexually  perfect  females  lay  eggs;  the  parthenogenetic  forms  give 
birth  to  developed  young,  which,  however,  in  some  cases,  are  each  enclosed  in  a 
pellicle.  The  radius  of  the  fore  wings  is  branched;  and  the  outer  part  of  the 
stigma   is   bounded   behind   by   vein   Ri    (Fig.   489) Aphidid^ 

^A.  Both  the  sexually  perfect  females  and  the  parthenogenetic  forms  lay  eggs. 
Vein  R,  of  the  fore  wings  is  wanting;  and  the  outer  part  of  the  stigma  is 
bounded  behind  by  the  radial  sector  (Fig.  490) Phylloxerid^ 


Se.Zl-K.Cu-'»*^ 


Sc 


Fig.  490. — The  wings  of  Adelges.     (From  Patch.) 


HOMOPTERA  415 

Family  APHIDID^ 
The  Typical  Aphids 

To  this  family  belong  the  far  greater  number  of  the  genera  and 
species  of  the  Aphidoidea.  The  distinctive  characters  of  this  family 
are  given  under  A  in  the  table  above.  For  a  detailed  discussion  of 
the  wing-venation  of  these  insects,  see  Patch  ('09). 

In  the  Aphididas  there  exists  a  remarkable  type  of  development 
known  as  heterogamy  or  cyclic  reproduction.  This  is  characterized 
by  an  alternation  of  parthenogenetic  generations  with  a  sexual 
generation .  And  within  the  series  of  parthenogenetic  generations  there 
may  be  an  alternation  of  winged  and  wingless  forms.  In  some  cases 
the  reproductive  cycle  is  an  exceedingly  complicated  one,  and  differ- 
ent parts  of  it  occur  on  different  species  of  food  plants. 

In  those  cases  where  different  parts  of  the  reproductive  cycle 
occur  on  different  food-plants,  the  plant  on  which  the  over-wintering 
fertilized  egg  is  normally  deposited  and  upon  which  the  stem-mother 
and  her  immediate  progeny  develop  is  termed  the  primary  host;  and 
that  plant  to  which  the  migrants  fly  and  from  which  a  later  form  in 
the  series  migrates  to  the  primary  host  is  known  as  the  secondary  host. 

Different  species  of  aphids  differ  greatly  in  the  details  of  their 
development;  it  is  difficult,  therefore,  to  make  generalizations  re- 
garding this  matter.  The  following  account  will  serve  to  indicate  the 
sequence  of  the  forms  occurring  in  the  reproductive  cycle  of  a  migrat- 
ing aphid,  one  in  which  the  different  parts  of  the  cycle  occur  on 
different  food-plants.  This  account  refers  to  what  occurs  in  the 
North,  where  the  winter  interrupts  the  production  of  young,  and  eggs 
are  developed  which  continue  the  life  of  the  species  through  the 
inclement  season.  In  hot  climates  also,  where  there  is  a  wet  and  a  dry 
season,  eggs  are  produced  to  carry  the  species  over  the  period  when 
succulent  food  is  lacking.  And  in  some  cases  in  the  North,  on  ex- 
hausted vegetation  the  non-migratory  species  produce  eggs  during 
the  simimer  months. 

The  stem-mother: — In  the  spring  there  hatches  from  an  over- 
wintering egg  a  parthenogenetic,  viviparous  female,  which  lives  on 
the  primary  host.  As  this  female  is  the  stock  from  which  the  summer 
generations  spring,  she  is  known  as  the  stem-mother  or  fundatrix. 
The  stem-mother  is  winged  in  some  species  of  one  of  the  tribes 
(Callipterini) ;  but  usually  she  is  wingless. 

The  wingless  agamic  form. — In  most  species  the  stem -mother  gives 
birth  to  young  which  do  not  develop  wings  and  which  are  all 
females.  These  reproduce  parthenogetically  and  are  known  as  the 
wingless  agamic  form  or  spurice  aptercB*  These  reproduce  their  kind 
for  a  variable  number  of  generations  and  then  produce  the  next  form. 
All  of  these  generations  live  on  the  primary  host.  In  a  few  species 
the  wingless  agamic  form  rarely  appears  if  at  all. 


*Spuri(Z  (New  Latin,  fern,  pi.);  Lat.  spurius,  an  illegitimate  or  spurious  child. 


416  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  winged  agamic  form.- — After  a  variable  number  of  generations 
of  the  wingless  agamic  form  have  been  developed  and  the  food-plant 
has  become  overstocked  by  them,  there  appears  a  generation  which 
becomes  winged  and  which  migrates  to  the  secondary  host.  These 
are  all  parthenogenetic,  viviparous  females.  They  are  known  as  the 
winged  agamic  form  or  spurice  alatae  or  migrants  or  migrantes.  In  some 
species,  the  second  generation,  the  offspring  of  the  stem-mother,  are 
winged  migrants. 

When  the  migrating  winged  agamic  form  becomes  etablished  on 
the  secondary  host,  it  produces  young  which  are  all  females  of  the 
wingless  agamic  form.  After  a  variable  number  of  generations  of 
this  form  have  been  developed,  there  is  produced  a  generation  of 
winged  agamic  females  which  migrate  from  the  secondary  host  to 
the  primary  host.  The  two  forms  developed  on  the  secondary  host, 
the  wingless  and  the  winged  agamic  forms,  may  closely  resemble  the 
corresponding  forms  previously  developed  on  the  primary  host  or 
may  differ  markedly  from  them. 

The  members  of  the  last  generation  of  the  series  of  partheno- 
genetic forms,  which  produce  the  males  and  the  oviparous  females, 
are  termed  the  sexuparas.  In  some  non-migrating  species  this  genera- 
tion is  wingless. 

The  males  and  the  oviparous  females. — The  winged  agamic  females 
that  have  migrated  from  the  secondary  host  to  the  primary  one, 
here  give  birth  to  true  sexual  forms,  male  and  female.  These  pair, 
and  each  female  produces  one  or  more  eggs.  These  are  sometimes 
designated  as  gamogenetic  eggs  to  distinguish  them  from  the  so-called 
pseudova  developed  in  agamic  females.    See  note  on  page  191. 

The  males  and  the  oviparous  females  are  termed  collectively  the 
sexuales;  and  some  writers  refer  to  the  oviparous  females  as  the 
ovipara.     (Note  that  ovipara  is  a  plural  noun.) 

The  sexuales  differ  greatly  in  form  and  habits  in  the  different  tribes 
of  aphids.  In  the  more  generalized  aphids  the  ovipara  of  some  species 
are  winged,  and  the  males  are  very  commonly  winged;  both  sexes 
have  beaks  and  feed  in  the  same  way  as  do  the  other  forms ;  and  each 
female  produces  several  eggs.  In  some  of  the  more  specialized  aphids 
the  sexuales  are  small,  wingless,  and  beakless;  consequently  the}'  can 
take  no  food.  Each  female  produces  a  single  egg,  which  in  some  cases 
is  not  deposited  but  remains  throughout  the  winter  within  the 
shriveled  body  of  the  female. 

In  some  cases  the  young  produced  by  the  agamic  females  are 
each  enclosed  in  a  pellicle  when  born;  this  is  soon  ruptured  and  the 
young  aphid  escapes  from  it.  The  young  thus  enclosed  are  termed 
pseudova  by  many  writers. 

The  foregoing  account,  omitting  exceptions  and  variations,  can  be 
simimarized  as  follows: 

A.       DIFFERENT    TYPES    OF    INDIVIDUALS    IN    THE    APHIDID^ 

First  type. — The  stem-mother  or  fundatrix,  which  is  hatched  from  a  fertilized 
egg,  is  usually  wingless,  and  reproduces  parthenogenetically. 

Second  type. — The   parthenogenetically   produced   wingless  agamic  females. 


HO  MOP  T ERA  417 

Third   type. — The    parthenogenetically    produced    winged    agamic    females. 
Fourth  type. — The  sexual  forms,  males  and  oviparous  females. 

B.    SEQUENCE   OF   GENERATIONS   IN   A   MIGRATING    SPECIES 

Only  the  first  of  a  series  of  similar  generations  is  counted. 

First  generation. — The  stem-mother. 

Second  generation. — Windless  agamic  females.  There  may  be  a  series  of 
generations  of  this  form  here. 

Third  generation. — Winged  agamic  females.  These  migrate  to  the  secondary 
host. 

Fourth  generation. — Wingless  agamic  females.  There  may  be  a  series  of 
generations  of  this  form  here. 

Fifth  generation. — Winged  agamic  females.  These  migrate  to  the  primary 
host  and  are  the  sexuparas. 

Sixth  generation. — Males  and  oviparous  females.  The  females  produce  the 
fertilized  eggs  from  which  the  stem-mothers  are  hatched,  thus  completing  the  life- 
cycle. 

A  remarkable  fact  that  has  been  demonstrated  by  several  ob- 
servers is  that  the  number  of  generations  of  the  wingless  agamic 
form  may  be  influenced  by  the  conditions  under  which  the  aphids 
live.  In  an  experiment  conducted  under  my  direction  by  Mr. 
Slingerland,  in  the  insectary  at  Cornell  University,  we  reared  98 
generations  of  the  wingless  agamic  form  without  the  appearance  of 
any  other  form.  The  experiment  was  carried  on  for  four  years  and 
three  months  without  any  apparent  change  in  the  fecundity  of  the 
aphids,  and  was  discontinued  owing  to  the  press  of  other  duties.  As 
the  aphids  were  kept  in  a  hothouse  throughout  the  winters,  seasonal 
influences  were  practically  eliminated ;  and  as  members  of  each  gen- 
eration were  placed  singly  on  aphid-free  plants  and  their  young  re- 
moved as  soon  as  bom,  there  was  no  crowding. 

In  order  to  determine  the  influence  of  crowding,  members  of  the 
sixtieth  generation  were  placed  on  separate  plants  and  their  young 
not  removed.  At  the  end  of  three  weeks  the  winged  agamic  form  ap- 
peared, evidently  in  response  to  need  of  migration  to  less  densely 
populated  plants ;  while  in  other  cages  where  the  young  were  removed 
promptly,  no  migrants  appeared  up  to  the  end  of  the  experiment. 

The  family  Aphididae  includes  a  very  large  nimiber  of  genera  and 
species.  The  genera  are  grouped  into  tribes  and  these  into  subfamilies 
in  various  ways  by  different  authors.  Recent  classifications  by 
American  authors  are  those  of  Oestlund  ('18)  and  Baker  ('20).  Four 
subfamilies  are  recognized  by  Baker.  The  characters  of  these  sub- 
families given  below  are  largely  compiled  from  this  author. 

Subfamily  APHIDIN^ 

To  this  subfamily  belong  most  of  the  species  of  aphids  that  are 
commonly  seen  living  free  {i.  e.,  not  in  galls)  upon  the  foliage  of 
plants.  But  while  most  of  the  species  feed  on  foliage,  some  of  them 
attack  stems  and  roots.  Their  attacks  on  foliage  in  some  cases  merely 
cause  a  weakening  of  it ;  in  other  cases,  the  leaves  become  curled  or 
otherwise  distorted;  such  distortions  are  termed  psendigalls.  True 
galls  formed  by  aphids  are  described  in  the  accounts  of  the  last  two 
subfamilies. 


418  AN  INTRODUCTION  TO  ENTOMOLOGY 

In  the  Aphidinae  the  males  and  the  oviparous  females  are  com- 
paratively generalized;  they  are  furnished  with  functioning  mouth- 
parts  and  feed  as  do  the  other  forms;  the  females  lay  several  eggs; 
in  a  few  species  the  oviparous  females  are  winged ;  and  winged  males 
are  common.  Wax-glands  are  not  abundant  in  members  of  this  sub- 
family; and  the  antennal  sensoria  are  oval  or  subcircular. 

The  following  are  a  few  of  the  more  common  representatives  of 
the  Aphidinae.  These  are  selected  to  illustrate  some  of  the  more 
striking  differences  in  habits  exhibited  by  the  different  species. 


a.      BARK-FEEDING  APHIDINv^. 

The  following  species  will  serve  as  an  example  of  the  bark-feeding 
species  belongings  to  this  subfamily,  and  also  of  the  maximum  size 
reached  by  any  aphid. 

The  giant  hickory -aphid,  Longistigma  caryce. — This  is  a  very  large 
species,  one  of  the  largest  aphids  known,  measuring  to  the  tip  of  the 
abdomen  6  mm.,  and  more  than  lo  mm.  to  the  tips 
of  the  wings  (Fig.  491).  It  can  be  distinguished  by 
the  shape  of  the  stigma  of  the  fore  wings,  which  is 
drawn  out  at  the  tip  to  an  acute  point  extending 
Fig.  491.— Longi-  aknost  to  the  tip  of  the  wing.  The  top  of  the  thorax 
sHgma  caryce.  ^^^  ^^^  veins  of  the  wings  are  black  and  there  are 
four  rows  of  little  transverse  black  spots  on  the  back.  The  body  is 
covered  with  a  bluish  white  substance  like  the  bloom  of  a  plum. 
This  is  a  bark-feeding  species;  it  is  found  clustered  on  the  under 
side  of  limbs  in  summer.  It  infests  hickory,  maple,  and  several 
other  forest  trees.  The  oviparous  female  is  wingless;  the  male, 
winged. 


0.      LEAF-FEEDING  APHIDIN^. 

Examples  of  the  leaf-feeding  species  belonging  to  this  subfamily 
can  be  found  on  a  great  variety  of  plants.  Among  those  most  easily 
observed  are  the  species  infesting  the  leaves  of  fruit  trees,  and 
especially  the  following. 

The  apple-leaf  aphis.  Aphis  pomi. — This  is  a  bright  green  species, 
the  entire  life-cycle  of  which  is  passed  on  the  apple.  The  migrants 
fly  to  other  parts  of  the  infested  tree  or  to  other  apple-trees.  As  a 
result  of  the  attacks  of  this  species  the  leaves  of  the  apple  are  often 
badly  curled  and  sometimes  drop  off  the  tree. 

The  rosy  apple-aphis,  Anuraphis  roseus. — The  common  name  of 
this  species  refers  to  the  fact  that  the  agamic  females  are  usually 
of  a  pinkish  color;  but  they  may  vary  in  color  to  a  light  brown, 
slaty  gray,  or  greenish  black,  with  the  body  covered  with  a  whitish 
coating.  This  species  is  most  common  on  apple;  but  it  infests  also 
pear,  white  thorn,  and  three  species  of  Sorbus.  It  is  a  migrating  spe- 
cies; but  its  secondary  host  is  unknown. 


HOMOPTERA  419 

The  apple-bud  aphis,  Rhopalos'iphitm  pninifdlia. — This  is  the 
species  that  most  commonly  infests  the  opening  apple-buds,  often 
nearly  covering  them.  It  also  infests  pear,  plum,  quince,  and  many 
other  plants.  It  is  a  migrating  species ;  various  species  of  grain  serve 
as  its  secondary  host. 


C.      ROOT-FEEDING  APHIDIN^. 

The  corn-root  aphis,  Anuraphts  maidi-radtcis . — This  is  a  serious 
pest  of  corn  throughout  the  principal  corn-growing  States,  sometimes 
totally  ruining  fields  of  com.  Broom-corn  and  sorghimi  are  the  only 
other  cultivated  crops  injured  by  it ;  but  it  infests  many  species  of  weeds 
that  grow  in  corn-fields.  Our  knowledge  of  this  species  is  largely  the 
result  of  investigations  of  Professor  S.  A.  Forbes,  who  has  published 
several  detailed  accounts  of  it  in  his  reports  as  State  Entomologist 
of  Illinois.  This  author  found  that  this  aphid  is  largely  dependent 
on  a  small  brown  ant,  the  corn-field  ant  {Ldsius  americdnus) ,  the 
nests  of  which  are  common  in  corn-fields.  The  ants  store  the  winter 
eggs  of  the  aphids  in  their  nests  and  care  for  them  throughout  the 
winter.  In  the  spring,  when  the  stem-mothers  hatch,  they  are  trans- 
ferred by  the  ants  to  the  roots  of  the  weeds  upon  which  they  feed. 
As  soon  as  corn-plants  are  available,  the  ants  transfer  the  aphids  to 
the  roots  of  the  corn,  the  ants  digging  burrows  along  the  roots  of  the 
com  for  this  purpose.  The  ants  in  return  for  their  labors  derive 
honey-dew  from  the  aphids. 

One  can  understand  how  these  ants  that  attend  aphids  that  are 
excreting  honey-dew  should  learn  to  drive  away  the  enemies  of  the 
aphids,  as  is  often  done ;  but  is  it  not  wonderful  that  Lasiiis  americanus 
should  recognize  the  importance  of  preserving  the  eggs  from  which 
their  herds  are  to  develop ! 

The  strawberry -root  aphid.  Aphis  forhesi. — The  winter  eggs  of  this 
species  are  found  upon  the  stems  and  along  the  midribs  of  the  green 
leaves  of  strawberry  plants.  The  stem-mothers  and  one  or  more 
generations  of  the  offspring  feed  upon  the  leaves  in  the  early  spring. 
But  "a  little  later  in  the  season  the  corn-field  ant  appears  and  transfers 
the  aphids  to  the  roots  of  the  strawberry,  where  it  cares  for  them  in 
the  same  way  that  in  corn-fields  it  cares  for  the  corn-root  aphis. 
This  ant  is  entirely  responsible  for  the  infesting  of  the  roots  by  the 
aphids;  and  it  is  here  that  the  greatest  injury  to  the  plants  is  done. 


Subfamily  MINDARIN.^ 

This  subfamily  was  established  by  Baker  ('20)  for  the  reception 
of  the  genus  Mindarus,  which  can  be  distinguished  from  all  other 
living  aphids  by  the  venation  of  the  wings.  In  this  genus  the  radial 
sector  of  the  fore  wings  separates  from  vein  Ri  at  the  base  of  the 


420 


AN  INTRODUCTION  TO  ENTOMOLOGY 


long,  narrow  stig- 
ma (Fig. 492).  In  all 
other  living  aphids 
the  origin  of  the  ra- 
dial sector  is  much 
nearer  the  tip  of  the 
wing ;  but  in  many 
of  the  fossil  aphid 
wings  it  is  as  in 
Mindarus .  The 
males  and  the 
oviparous  females 
are  small  and  wing- 
less; but  they  retain  the  beak,  at  least  in  most  individuals,  and  feed. 
The  female  lays  several  eggs. 

Only  one  species,  Mindarus  abietinus,  is  known.  This  lives  free 
upon  the  twigs  of  spruce  and  other  conifers,  which  become  somewhat 
distorted  and  are  often  killed  by  the  attack  of  the  insects.  When 
disturbed  this  insect  secretes  large  quantities  of  honeydew. 

The  life-cycle  of  this  species  usually  includes  only  three  genera- 
tions, the  stem-mother,  the  winged  agamic  females  {sexuparce),  and 
the  sexual  forms.  Sometimes  there  is  a  generation  of  wingless 
agamic  females. 

This  species  was  redescribed  by  Thomas  as  Schizoneura  pinicola. 


Fig.  492. — Wings  of  Mindarus.    (After  Patch.) 


Subfamily  ERIOSOMATIN^ 

This  subfamily  includes  those  genera  of  aphids  in  which  the  males 
and  the  oviparous  females  are  greatly  specialized  by  reduction.  They 
do  not  have  functioning  mouth -parts;  some  have  a  beak  when  born 
but  lose  it  at  the  first  molting;  in  others  the  beak  is  vestigial  at  birth. 
As  they  cannot  feed,  they  remain  small.  Both  sexes  are  wingless. 
The  oviparous  females  produce  each  a  single  sgg,  which  in  some 
species  is  not  laid  but  remains  throughout  the  winter  in  the  shriveled 
body  of  the  female. 

In  this  subfamily,  the  cornicles  are  much  reduced  or  are  wanting; 
wax-glands  are  abundantly  developed ;  and  the  antennal  sensoria  are 
prominent.    These  are  often  annular. 

The  members  of  this  subfamily  that  are  most  likely  to  attract 
attention  can  be  grouped  under  two  heads:  a,  the  woolly  aphids; 
and  6,  the  gall-making  Erisomatinge.  These  groups,  however,  do  not 
represent  natural  divisions  of  the  subfamily  and  do  not  include  all 
members  of  it.  They  are  merely  used  for  convenience  in  the  present 
discussion. 

a.     THE  WOOLLY  APHIDS 


The  woolly  aphids  are  the  most  conspicuous  members  of  the 
Aphidida;,  on  account  of  the  abundant,  white,  waxy  excretion  that 


HOMOPTERA  421 

covers  colonies  of  them.  The  three  following  species  are  widely  dis- 
tributed and  are  common. 

The  woolly  apple  aphis,  Eriosoma  lanlgera. — This  plant-louse,  on 
account  of  its  woolly  covering  and  the  fact  that  it  is  a  serious  pest  of 
the  apple,  is  known  as  the  woolly  apple  aphis,  although  the  apple  is 
its  secondary  host.  This  insect  not  only  has  a  complicated  series  of 
generations  but  the  life-cycle  is  subject  to  variations ;  its  usual  course 
is  as  follows : 

The  winter-eggs  are  deposited  in  crevices  of  the  bark  of  elm. 
From  these  eggs  stem-mothers  hatch  in  the  spring  and  pass  to  the 
young  leaves,  where  they  produce  either  the  well-known  leaf-curl  of 
the  elm  or,  when  a  group  of  terminal  leaves  are  affected,  what  has 
been  termed  a  rosette,  which  is  a  cluster  of  deformed  leaves.  Within 
these  pseudogalls  the  second  generation  is  produced;  this  consists  of 
wingless  agamic  females.  The  offspring  of  these,  the  third  generation, 
become  winged  and  migrate  from  the  elm  to  the  apple.  Here  they 
produce  the  fourth  generation,  the  members  of  which  live  on  the 
water-shoots  or  the  tender  bark  of  the  apple,  and  are  wingless.  The 
fifth  generation  also  consists  of  wingless  agamic  females.  Some  of 
these  develop  on  the  bark  of  the  branches,  which  apparently  ceases 
to  grow  at  the  point  of  attack  but  swells  into  a  large  ridge  about  the 
cluster  of  plant-lice,  leaving  them  in  a  sheltered  pit ;  the  aphids  also 
frequently  congregate  in  the  axils  of  the  leaves  and  the  forks  of  the 
branches.  Other  members  of  this  generation  pass  to  the  roots  of  the 
tree,  where  they  produce  knotty  swellings  on  the  fibrous  roots.  The 
sixth  generation  consists,  in  part,  of  winged  agamic  females  which 
migrate  from  the  apple  to  the  elm,  where  they  produce  the  seventh 
generation.  This  generation,  the  last  in  the  series,  consists  of  the 
males  and  oviparous  females,  both  of  which  are  beakless  and  wing- 
less. These  pair  and  each  female  produces  a  single  egg,  which  is 
found  in  a  crevice  of  the  bark  with  the  remains  of  the  body  of  the 
female. 

The  course  of  events  outlined  above  may  be  modified  in  two  ways : 
first,  it  is  said  that  the  sexual  forms  are  sometimes  produced  on  the 
apple;  and  second,  some  members  of  the  sixth  generation  do  not 
develop  wings  and  migrate,  but  are  wingless  and  produce  young  that 
hibernate  on  the  apple.  This  species  infests  also  mountain  ash  and 
hawthorn,  as  secondary  hosts. 

The  elm-feeding  generations  of  this  species  that  cause  the  leaf- 
curls  and  rosettes  have  been  known  as  Schizoiteura  americdna.  And 
there  are  also  found  during  the  summer  aphids  on  tender  elm  bark 
which  are  believed  to  belong  to  this  species  and  which  have  been 
described  under  the  name  Schizoneura  rileyi.  In  the  Pacific  Coast 
States  there  is  another  species  of  aphid  that  produces  leaf  curl  on  elm. 
This  is  Schizoneura  Ulnii,  a  European  species,  which  in  Europe  has 
been  found  to  migrate  to  Rihes. 

The  alder-blight,  Prociphilus  tesselldtus. — A  woolly  aphid  that  is 
found  in  dense  masses  on  the  branches  of  several  species  of  alder  is 
known  as  the  alder-blight.     Colonies  of  this  species  are  easily  found 


422  AN  INTRODUCTION  TO  ENTOMOLOGY 

in  the  regions  where  it  occurs,  as  their  covering  of  flocculent  excretion 
renders  them  very  conspicuous.  These  colonies  are  of  especial  in- 
terest, as  within  them  is  found  the  predacious  larva  of  the  wanderer 
butterfly,  Feniseca  tarquinius,  which  feeds  on  the  aphids. 

In  the  late  stmmier  or  early  autumn  the  last  generation  of  wingless 
agamic  females  bring  forth  young,  which  winter  among  the  fallen 
leaves  at  the  base  of  the  alder  and  return  to  the  branches  in  the 
spring.  From  this  there  appears  to  be  no  need  of  an  alternate  host. 
But  it  was  found  by  Dr.  Patch  that  at  the  same  time  that  the  form 
that  hibernates  at  the  base  of  the  alder  is  produced,  winged  migrants 
appear  and  fly  to  maple  trees,  where  they  give  birth,  in  the  crevices 
and  rough  places  in  the  bark,  to  males  and  oviparous  females.  Each 
of  these  females  produces  a  single  egg.  From  these  eggs  there  hatch  in 
the  spring  aphids  which  pass  to  the  lower  side  of  the  leaves  of  the 
maple,  where  they  become  conspicuous  on  account  of  their  abundant 
and  long  woolly  excretion.  In  this  period  of  its  existence  this  species 
is  the  well-known  pest  of  the  maple  that  has  long  been  known  as 
Pemphigus  acerfolii,  which  name  must  now  be  regarded  as  a  synonym 
of  Proctphilus  iesselldtus,  the  older  name.  In  July  winged  migrants 
are  developed  on  maple  which  fly  to  alder. 

The  alder-blight  excretes  honeydew  abimdantly;  the  result  is 
that  the  branches  infested  by  this  insect,  and  those  beneath  the  cluster 
of  aphids,  become  blackened  with  fungi  that  grow  upon  this  excretion. 
There  is  also  a  curious  fungus  which  grows  in  large  spongy  masses 
immediately  beneath  the  cluster  of  plant-lice;  this  is  known  to  bot- 
anists as  Scorias  spongiosa.  It  is  evidently  fed  by  the  honeydew  that 
falls  upon  it. 

The  beech-tree  blight,  Proctphilus  imbricdtor.- — This  infests  both 
twigs  and  leaves  of  beech.  Like  the  preceding  species  it  occurs  in 
clusters  of  individuals,  each  of  which  is  clothed  with  a  conspicuous 
downy  excretion.  These  clusters  often  attract  attention  by  the 
curious  habit  which  the  insects  have  of  waving  their  bodies  up  and 
down  when  disturbed.  When  an  infested  limb  is  jarred,  the  aphids 
emit  a  shower  of  honeydew.  Owing  to  the  abundance  of  this  excretion, 
the  branches  and  leaves  of  an  infested  tree  become  blackened  by 
growths  of  fungi,  as  with  the  preceding  species.  The  life-cycle  of  this 
species  has  not  been  determined. 

b.     THE  GALL-MAKING  ERIOSOMATIN^ 

Certain  members  of  this  subfamily  cause  the  growth  of  remarkable 
galls,  resembling  in  this  respect  certain  members  of  the  following 
subfamily.  Among  the  gall-making  Eriosomatinag  that  are  most  likely 
to  attract  attention  are  the  following. 

The  cockscomb  elm-gall  colopha,  Colopha  ulmtcola. — There  are 
two  species  of  aphids  that  make  similar  galls  on  the  leaves  of  elm. 
These  galls  are  commonly  known  as  cockscomb  elm-galls  on  account 
of  their  shape.  Those  made  by  the  two  species  of  aphids  are  so 
similar  that  a  description  of  one  will  apply  to  the  other.    In  each  case 


HO  MO  PT ERA 


423 


the  gall  is  an  excrescence  resembling  a  cock's  comb  in  form,  which 
rises  abruptly  from  the  upper  surface  of  the  leaf  (Fig.  493,  a).  It  is 
com'pressed,  and  has  its  sides  wrinkled  perpendicularly  and  its  siimmit 
irregularly  gashed  and  toothed.  It  opens  on  the  under  side  of  the 
leaf  by  a  long  slit-like  orifice. 

The  winter  eggs  can  be  found  during  the  winter  in  the  crevices 
of  the  bark  of  the  elm;  each  egg  is  usually  enclosed  in  the  dry  skin 
of  the  oviparous  female  (Fig.  493,  6).    In  the  spring  the  stem-mothers 


-=C:^ 


Fig.  493. — Colopha  ulmicola:  a,  leaf  showing  galls  from  above  and  beneath;  h, 
fertilized  egg  surrounded  by  the  skin  of  the  female;  c,  newly  born  young  of  the 
second  generation;  h,  its  antenna;  d,  full-grown  nymph  of  the  second  genera- 
tion; e,  adult  of  second  generation;  /,  antenna  of  migrant ;  g,  antenna  of  stem- 
mother.     (From  Riley.) 


pass  to  the  leaves  and  each  causes  by  its  attack  the  growth  of  a  gall. 
The  second  generation  is  produced  within  the  gall;  it  consists  of 
winged  agamic  females  (Fig.  493,  e).  These  migrants  can  be  dis- 
tinguished from  those  of  the  other  cockscomb  elm-gall  aphid  by  the 
fact  that  in  this  species  vein  M  of  the  fore  wings  is  forked. 

The  migrants  of  this  species  pass  from  the  elm  to  certain  grasses, 
among  them  species  of  Eragrostis  and  Panicum.  The  forms  found  on 
these  secondary  hosts  have  been  described  under  the  name  Colopha. 
eragrostidis,  but  this  is  a  much  later  name  than  Colopha  ulmtcola. 


424 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  cockscomb  elm-gall  tetraneura,  Tetraneura  gramlnis. — The 
life-cycle  of  this  species  is  quite  similar  to  that  of  the  preceding  one. 
The  prim^ary  host  is  elm.  The  stem-mothers  cause  the  growth  of 
cockscomb-like  galls;  and  the  migrants  produced  in  these  galls  pass 
to  grasses.  These  migrants  differ  from  those  of  the  preceding  species 
in  that  vein  M  of  the  fore  wings  is  not  forked.  This  species  was  first 

described  from  individu- 
als found  on  the  second- 
ary hosts  and  was  named 
Tetraneura  gramlnis.  Lat- 
er, forms  found  on  elms 
were  named  Tetraneura 
colophoides. 

For  a  detailed  ac- 
count of  the  gall-aphids 
of  the  elm,  see  Patch 
Cio). 

The  poplar-leaf  gall- 
aphid,  Thecdhius  populi- 
caulis. — This  aphid  is 
common  on  several  spe- 
cies of  poplar.  It  makes 
a  swelling  the  size  of  a 
small  marble  on  the  leaf 
at  the  junction  of  the 
petiole  with  the  blade. 
This  gall  is  of  a  reddish 
tint,  and  has  on  one  side 
a  slit-like  opening.  In  the  early  part  of  the  season  each  gall  is  occu- 
pied by  a  single  wingless  female,  probably  the  agamic  stem-mother, 
which  by  midsummer  becomes  the  mother  of  numerous  progeny. 
These  are  winged  and  probably  migrate  to  some  other  host -plant; 
but  the  life-cycle  of  this  species  has  not  been  determined. 

The  vagabond  gall-aphid,  Mordwilkdja  vagabiinda. — This  species 
infests  the  tips  of  the  twigs  of  several  species  of  poplar;  here  it  causes 
the  growth  of  large  corrugated  galls,  which  resemble  somewhat  the 
flower  of  the  double  cockscomb  of  our  gardens.  The  galls  are  at  first 
bright  green,  but  later  turn  black,  become  woody,  and  remain  on  the 
"trees  during  the  winter  (Fig.  494).  Very  little  is  known  regarding  the 
Jife-cycle  of  this  species. 


Fig.    494. — The   vagabond   poplar-gall. 
Walsh  and  Rilev.) 


(From 


Subfamily  HORMAPHIDIN^ 


The  members  of  this  subfamily  are  usually  gall-makers,  resembling 
in  this  respect  certain  members  of  the  Eriosomatinae,  and  also  re- 
sembling them  in  that  the  antennal  sensoria  are  annular.  But  in 
this  subfamily  the  sexual  forms  are  not  so  specialized  by  reduction 
:as  in  the  preceding  one.  In  the  Hormaphidinse,  although  the  males 
.and    the  oviparous  females   are   small  and  wingless,   they   possess 


HOMOPTERA 


425 


beaks,  they  feed,  and  the  oviparous  female  lays  more  than  one  egg. 
In  this  subfamily  great  specialization  of  wax-producing  organs  occurs. 
In  many  species  some  of  the  agamic  generations  become  greatly  modi- 
fied in  form  so  that  they  do  not  resemble  the  more  typical  aphids. 
In  some  species  these  modified  forms  have  the  appearance  of  an 
Aleyrodes;  in  other  species,  that  of  a  coccid. 

Our  best -known  representatives  of  this  subfamily  are  two  species 
of  gall-makers,  each  of  which  infests  alternately  witch-hazel  and 
birch.     The  life-histories  of  these  were  very  carefully  worked  out  by 


Fig.  495. — The  witch-hazel  cone-gall:  a,  natural  size;  &,  section  of  gall,  enlarged. 
(From  Pergande.) 

Pergande  ('01);  the  following  accounts  are  greatly  condensed  from 
that  author. 

The  witch-hazel  cone-gall  aphid,  Hormaphis  hamamelidis. — The 
winter- egg  is  deposited  on  the  branches  and  twigs  of  witch-hazel 
and  hatches  early  in  the  spring.  The  stem -mother,  which  hatches 
from  this  egg,  attacks  the  lower  surface  of  the  leaf,  causing  the  growth 
of  a  conical  gall  on  the  upper  surface  of  the  leaf  with  a  mouth  on 
the  lower  surface  (Fig.  495).  The  second  generation,  the  offspring 
of  the  stem-mother,  consists  of  many  individuals;  these  are  pro- 
duced within  the  gall,  which  becomes  crowded  with  them.  These 
are  agamic  females,  which  become  winged,  leave  the  gall,  and  mi- 
grate to  birches,  where  they  deposit  their  young  on  the  lower  side 
of  the  leaves.  The  first  instar  of  the  third  generation,  the  off.spring 
of  the  migrants,  is  broadly  oval,  with  the  entire  margin  of  the  body 


426 


AN  INTRODUCTION  TO  ENTOMOLOGY 


^^\,\\u,- 1,  ■^■'Ly^     ''  /~vJ2SuLs-jZII^^ 


Studded  with  short  and  stout  excretory  tubercles  (Fig.  496) ;  from 
each  of  these  there  issues  a  short,  glassy,  beautifully  iridescent,  waxy 
rod.    The  second  and  third  instars  of  this  generation  are  marked  by 

a  reduction  of  the  antennae, 
beak,  and  legs.  The  fourth 
instar,  which  is  found  about 
the  middle  of  June,  is  aley- 
rodiform  (Fig.  497).  The 
fourth  and  fifth  generations 
resemble  the  third,  there  be- 
ing three  aleyrodiform  gen- 
erations. The  members  of 
the  sixth  generation  become 
winged  and  are  the  return 
migrants.  These  fly  to 
witch-hazel,  where  they  give 
birth  to  the  seventh  genera- 
tion, which  consists  of  males 
and  oviparous  females. 
These  pair  and  the  females 
lay  the  winter  eggs;  each 
(From'  Pergande!)  female  produces  from  five 
to  ten  eggs.  The  males  and 
In  this  species  the  antennas 


Fig.  496. — Hormaphis  hamamelidis,  first  instar 
of  the  third  generation 


the  oviparous  females  are  both  wingless 
of  the  winged  forms  are  three-jointed. 

Later  experiments  by  Morgan  and  Shull  ('10)  indicate  that  this 
species  can  complete  its  life-cycle  on 
the  witch-hazel.  According  to  these 
authors  there  are  only  three  genera- 
tions: first,  the  stem-mother,  which 
causes  the  growth  of  the  cone-gall; 
second,  the  winged  forms,  which  are 
developed  in  the  gall  and  which  spread 
to  the  leaves ;  and  third,  the  males  and 
oviparous  females.  No  aleyrodiform 
individuals  were  found  on  the  witch- 
hazel. 

The  spiny  witch-hazel-gall  aphid, 
Hamameltstes  spinosus. — The  winter 
eggs  of  this  species  are  commonly  de- 
posited near  the  flower-buds  of  witch- 
hazel,  late  in  June  or  early  in  July, 
but  they  do  not  hatch  till  May  or 
June  of  the  following  year.  The 
stem-mother  attacks  the  flower-bud. 

which  becomes  transformed  into  a  large  gall  of  the  form  shown  in 
Figure  498.  Within  this  gall  the  stem-mother  produces  the  second 
generation ;  these  crowd  the  gall  and  develop  into  winged  migrants, 
which  leave  the  gall,  from  July  to  late  fall,  and  fly  to  birches.    The 


Fig.  497. — Hormaphis  hamamel- 
idis, fourth  instar  of  the  third 
generation.    (After  Pergande.) 


HOMOPTERA 


427 


young  of  the  migrants,  the  third  generation,  feed  a  short  time  and 
then  settle  close  to  the  leaf-buds,  where  they  hibernate;  the  last  in- 


Fig.  498. — The  spiny  witch-hazel  gall:  a,  mature  gall;  b,  section  of  gall.     (From 
Pergande.) 

Star  of  this  generation  resembles  a  coccid  (Fig.  499).  The  fourth 
generation  is  produced  early  in  the  spring ;  the  young  of  this  genera- 
tion move  to  the  young  and  tender  leaves  of  the  birch,  which,  as  a 


Fig.  499. — Hamamelistes  spinosus,  last  instar  of  the  third  generation,  much 
enlarged:  a,  dorsal  view;  b,  lateral  view;  c,  ventral  view;  d,  antenna;  e, 
f,  g,  legs.      (From  Pergande.) 

result  of  the  attack,  become  corrugated,  the  upper  surface  bulging 
out  between  the  veins,  and  the  folds  closing  up  below.     In  these 


428 


AN  INTRODUCTION  TO  ENTOMOLOGY 


pseudogalls  the  fifth  generation  is  produced;  the  members  of  this 
generation  become  winged  and  migrate  to  witch-hazel  in  early 
summer,  where  they  produce  the  seventh  and  last  generation  of  the 
series,  the  males  and  oviparous  females.  These  pair  and  the  females 
soon  lay  their  eggs.  Both  sexes  are  wingless.  The  winged  migrants 
of  this  species  can  be  distinguished  from  those  of  the  preceding 
species  by  their  five- jointed  antennae. 


Family  PHYLLOXERID^ 

The  Adelgids  and  the  Phylloxerids 

The  members  of  this  family  differ  from  the  typical  aphids  in  that 
both  the  sexually  perfect  females  and  the  parthenogenetic  forms  lay 
eggs,  in  lacking  vein  Ri  of  the  fore  wings,  and  in  that  the  outer  part 
of  the  stigma  is  bounded  behind  by  the  radial  sector  (Fig.   500). 


sc.n^u^Cii^^'*^ 


Fig.  500. — Wings  of  Adelges.     (From  Patch 


In  this  family  the  cornicles  are  always  wanting;  and  the  males  and 
sexualh'  perfect  females  are  dwarfed  and  wingless. 

This  family  includes  two  subfamilies,  which  can  be  separated  by 
the  following  table.  These  subfamilies  are  regarded  as  distinct 
families  bv  some  writers. 


A.  The  wingless  agamic  females  excrete  a  waxy  flocculence.  The  winged  forms 
have  five-jointed  antennae,  the  last  three  segments  of  which  bear  each  a  single 
sensorium.  The  wings  are  held  roof-like  when  at  rest.  The  free  part  of  vein 
Cu  of  the  fore  wings  is  separate  from  vein  ist  A  (Fig.  500).  The  sexual  forms 
have  a  beak.  The  alimentary'  canal  is  normal,  producing  a  fluid  excrement. 
The  species  infest  only  conifers Adelgin^e 

AA.  The  wingless  agamic  females  do  not  secrete  a  waxy  fiocculence,  but  in  the 
genus  Phylloxerina  they  excrete  a  waxy  powder.  The  winged  forms  have 
three-jointed  antennas,  the  second  segment  of  which  bears  two  sensoria.  The 
wings  when  at  rest  are  laid  fiat  upon  the  abdomen.    The  free  parts  of  veins  Cu 


HO  MOP  T ERA 


429 


and  1st  A  of  the  fore  wings  coalesce  at  base  (Fig.  501).     The  sexual  forms 

have  no  beak.    The  anus  is  closed.    The  species  do  not  infest  conifers 

Phylloxerin^ 


Sc+R+31: 


Fig.  501. — Wings  of  Phylloxera.    (From  Patch 


Subfamily  ADELGIN^ 
The  Adelgids 

This  subfamily  includes  those  insects  found  on  conifers  that  have 
been  quite  generally  known  under  the  generic  name  Chermes.  But  it 
has  been  determined  that  this  name  should  be  applied  to  certain 
jumping  plant-lice  of  the  family  Chermidae,  formerly  known  as  the 
Psyllidae.  The  necessity  of  this  change  is  very  unfortunate,  as  much 
has  been  published  regarding  members  of  the  Adelginae  and  in  most 
of  these  accounts  they  are  described  under  the  name  Chermes. 

All  the  species  of  this  subfamily  infest  conifers;  and  in  all  cases 
in  which  the  sexual  generation  is  known,  this  generation  lives  on 
spruce.    The  secondary  host  may  be  either  larch,  pine,  or  fir. 

Much  has  been  written  regarding  the  life-histories  of  these  insects. 
It  has  been  found  that  what  may  be  regarded  as  the  typical  life-cycle 
of  an  Adelges  or  ''Chermes''  is  a  very  complex  one,  including  the 
developing  of  two  parallel  series  of  forms  differing  in  habits ;  that  in 
one  of  these  series  a  single  host-plant,  spruce,  is  infested  and  the  life- 
cycle  is  completed  in  one  year;  while  in  the  other  series  the  life-cycle 
extends  over  two  years  and  is  passed  in  part  upon  spruce  and  in 
part  upon  larch  or  some  other  host-plant. 

In  this  typical  life-cycle,  beginning  with  the  individual  that 
hatches  from  a  fertilized  egg,  there  are  developed  five  generations, 
the  members  of  which  differ  in  either  form  or  habits  or  both  from 
those  of  the  other  generations,  before  the  cycle  is  completed  by  the 
production  again  of  fertilized  eggs.  The  actual  nimiber  of  generations 
may  be  greater  than  this,  owing  to  the  fact  that  in  a  part  of  the  cycle 
there  may  be  a  series  of  similar  generations  only  the  first  of  which  is 
counted  in  this  enumeration. 


430  AN  INTRODUCTION  TO  ENTOMOLOGY 

This  indicating  of  a  typical  life-cycle  is  an  effort  to  outline  as 
simply  as  possible  the  life-history  of  these  insects.  In  some  species 
it  is  much  more  complicated;  thus,  for  example,  Borner  ('08)  in  his 
account  of  the  life-history  of  Cnaphalodes  strobilobius  recognizes  seven 
parallel  series  of  forms. 

The  distinctive  characters  of  the  five  differing  generations  in  the 
typical  life-cycle  are  indicated  below .^ 

A.      GENERATIONS   ON   SPRUCE    {Piceo) 

A  one-year  cycle  or  the  first  year  of  a  two-year  cycle. 

First  generation. — This  consists  of  the  true  stem-mother  (fundatrix  vera), 
a  wingless  agamic  female.  In  the  case  of  those  supposed  parthenogenetic  species 
which  do  not  migrate  to  another  host-plant  and  which  complete  their  life-cycle  in 
one  year,  this  form  is  the  offspring  of  the  second  generation,  an  agamic  form; 
in  the  case  of  species  that  migrate  to  a  secondary  host-plant,  and  where  there  are 
two  parallel  series,  the  stem-mother  is  the  offspring  of  either  the  second  generation 
or  the  fifth  generation,  the  sexual  forms. 

The  stem-mothers  hatch  in  the  autumn ;  they  hibernate  immature  in  crevices 
at  the  bases  of  buds,  complete  their  growth  in  the  spring,  and  by  their  attack  upon 
the  buds  cause  the  beginning  of  the  growth  of  galls.  Each  stem-mother  lays  a 
large  number  of  eggs. 

Sec 0 fid  generation. — The  members  of  this  generation  hatch  from  the  eggs  laid 
by  the  stem-mothers,  and  by  their  attack  upon  the  buds  cause  the  completion  of 
the  growth  of  the  galls.  The  galls  are  formed  by  the  hypertrophy  and  coalescence 
of  the  spruce-needles.  The  members  of  this  generation  have  been  termed  the 
gallicola,  because  they  inhabit  the  galls.  They  reach  the  last  nymphal  instar 
within  the  galls.  When  this  stage  is  reached,  the  galls  open  and  the  nymphs 
emerge  and  soon  molt,  becoming  winged  agamic  females. 

As  to  their  habits,  there  are  two  types  of  gallicolae:  first,  the  non-migrants, 
which  remain  on  the  spruce  and  lay  the  eggs  from  which  the  stern-mothers  of  the 
one-year  cycle  are  hatched;  and  second,  the  migrants,  which  fly  to  a  secondary 
host-plant,  which  is  not  spruce,  and  where  they  lay  many  eggs,  but  not  so  many  as 
are  laid  by  the  stem-mothers. 

B.       GENERATIONS   ON   A   SECONDARY   HOST 

Part  of  the  second  year  of  a  two-year  cycle. 

The  secondary  host  may  be  a  species  of  either  larch  {Larix),  pine  (Pinus), 
or  fir  {A  bies) ;  but  no  galls  are  produced  on  any  of  these. 

Third  generation. — The  members  of  this  generation  hatch  from  eggs  laid  by 
migrants  of  the  second  generation  that  have  flown  from  spruce  to  larch  or  other 
secondary  host  and  laid  their  eggs  there.  The  young  that  hatch  from  these  eggs 
hibernate  in  crevices  in  the  bark  and  comolete  their  growth  in  the  spring,  becom- 
ing wingless  agamic  females.  The  members  of  this  generation  and  of  similar 
generations  which  follow  immediately  but  which  are  not  numbered  here,  are 
termed  colonici,  because  they  are  settlers  in  a  new  region,  or  exstdes,  that  is, 
exiles.  Some  writers  term  the  first  of  this  series  of  generations  false  stem-mothers 
{fimdatrices  spurice)  to  distinguish  them  from  the  true  stem-mother,  which  is  the 
beginning  of  the  two-year  cycle.  The  members  of  the  third  generation  resemble 
those  of  the  first  generation,  but  usually  lay  fewer  eggs  and  do  not  cause  the 
growth  of  galls. 

The  offspring  of  the  third  generation  are  all  wingless  agamic  females,  which 
reproduce  their  kind.  Of  these  there  may  be  a  series  of  generations,  which  are  not 
numbered  in  this  generalized  statement;  and  there  may  be  among  these  several 
parallel  series  of  generations,  differing  in  the  life-cycle  but  all  reproducing 
parthenogenetically  on  the  secondary  host.  The  secondary  host  may  be  thus 
infested  throughout  the  year;  while  the  primary  host,  if  there  is  not  an  annual 
series,  will  be  free  during  the  interval  between  the  migration  of  the  second  genera- 
tion and  the  return  migration  of  the  fourth  generation. 


HOMOPTERA  431 

Among  the  oflfspring  of  the  third  generation  two  types  are  recognized  by 
Marchal  ('13):  first,  nymphs  which  remain  undeveloped  for  a  time,  the  sislens 
type;  and  second,  nymphs  which  develop  at  once  into  wingless  agamic  females, 
the  progrediens  type.* 

Fourth  generation. — The  members  of  this  generation  are  produced  by  indi- 
viduals of  the  progrediens  type  of  the  third  generation.  They  develop  into  winged 
agamic  females.  The  adults  migrate  to  spruce  and  there  lay  a  small  number  of 
eggs.  Since  their  oflfspring  are  the  sexual  forms,  this  generation  is  known  as  the 
sexuparcB. 

C.      A   GENERATION   ON   SPRUCE 

The  completion  of  the  second  year  of  a  two-year  cycle. 

Fifth  generation. — From  eggs  laid  by  the  sexuparas  that  have  migrated  from 
the  secondary  host  to  spruce,  there  are  developed  males  and  sexually  perfect 
females,  termed  the  sexuales;  both  of  these  forms  are  wingless.  They  pair  and 
each  female  lays  a  single  egg.  These  eggs  hatch  in  the  autumn;  the  young 
hibernate  and  become  the  true  stem-mothers.  Thus  is  completed  the  two- 
year  life-cycle. 

Omitting  the  annual  series,  the  typical  two-year  life-cycle  includes  the  follow- 
ing series  of  generations,  which  are  described  above. 

First. — The  wingless  agamic  stem-mother. 

Second. — The  winged  agamic  migrants. 

Third. — The  wingless  agamic  colonici  or  exsules. 

(a)  The  sistentes,  several  generations. 

(b)  The  progredientes,   several  generations. 
Fourth. — The  winged  agamic  sexuparas. 

Fifth. — The  wingless  sexuales,  males  and  sexually  perfect  females.  Each 
female  produces  a  single  fertilized  egg,  from  which  hatches  a  stem-mother,  thus 
completing  the  life-cycle. 

In  the  case  of  some  species,  which  have  been  studied  very  carefully 
by  different  observers,  only  an  annual  series,  consisting  of  the  first 
and  second  generations  described  above,  is  knov^^n.  It  should  be 
noted  that  in  a  life-cycle  of  this  kind  there  are  no  sexual  forms  and  that 
although  a  winged  form  appears  it  is  not  known  to  migrate.  These 
facts  indicate  that  either  some  members  of  the  winged  generation 
migrate  to  a  secondary  host-plant  which  has  not  been  discovered,  or 
that  the  species  in  question  have  become,  by  adaptation,  purely  par- 
thenogenetic.  Which  of  these  alternatives  is  true  has  been  much  dis- 
cussed. 

The  following  species  are  some  of  the  more  common  of  our  repre- 
sentatives of  this  subfamily. 

The  pine-leaf  adelges,  Adelges  pinijdlics.- — Our  knowledge  of  the 
life-history  of  this  species  is  still  fragmentary.  In  one  part  of  its  life- 
cycle  it  infests  the  leaves  of  white  pine  (Ptnus  strohus).  The  genera- 
tions found  here  are  winged  agamic  females.  These  attach  them- 
selves firmly  to  the  pine-needles,  each  with  its  head  directed  towards 
the  base  of  the  needle.  Within  each  there  are  developed  about  one 
hundred  eggs,  which  are  not  extruded.  After  the  death  of  the  female, 
the  mass  of  eggs  remains  adhering  to  the  leaf,  covered   over   and 


*Sistens,  Latin  sisto,  to  stand;  progrediens,  Latin  pro,  forth,  gradior,  to  go. 


432 


AN  INTRODUCTION  TO  ENTOMOLOGY 


protected  by  the  remains  of  the  body  and  closed  wings  of  the  dead 
insect. 

It  has  been  determined  that  these  plant- 
Hce  infesting  the  pine  leaves  are  specifically 
identical  with  those  that  issue  from  a  cone- 
like gall  found  on  several  species  of  spruce 
(Fig.  502).  The  spruce-inhabiting  form  has 
been  known  as  Cherntes  abiettcolens ;  but 
pinifoUcB  is  the  older  specific  name  and 
should  be  used  for  all  forms  of  this  species. 
It  is  probable  that  this  species  has  a  two- 
year  life-cycle  and  that  spruce  is  its  primar\^ 
host  and  pine  its  secondary  host. 

The  green-winged  adelges,  Adelges  able- 
tis. — This  species  causes  the  growth  of  pine-  Fig.  502. — Gall  of  Adelges 
apple-shaped    galls    on    several    species    of      pinifoHcB  on  spruce. 
spruce  (Fig.  503).     It  is  a  European  species 

and  its  life-history  has  been  the  subject  of  much  controversy.  It  is 
held  by  Bomer  ('08)  that  it  has  a  typical  life-cycle  in  which  there  are 
two  parallel  series:  first,  an  annual  series  on  spruce  alone;  and 
second,  a  two-year  series  in  which  larch  is 
used  as  a  secondary  host.  On  the  other 
hand,  Cholodkovsky  ('15)  maintains  that  it 
is  a  parthenogenetic  species;  that  its  life- 
cycle  includes  only  two  generations,  the 
agamic  hibernating  stem-mothers  and  the 
gallicolae;  and  that  the  form  with  a  typical 
life-cycle  is  a  distinct  species  {Chermes 
vlridis).  Dr.  Patch  ('09)  has  studied  Adel- 
ges ahietis  in  Maine  and  has  found  only  the 
parthenogenetic  forms,  the  hibernating  stem- 
mothers  and  the  gallicolae ;  thus  confirming 
the  conclusion  that  it  may  have  become  a 
parthenogenetic  species. 

The  pme-bark  adelges,  Adelges  pinicorti- 
cis. — This  species  infests  several  species  of 
pine,  but  especially  white  pine.  The  trunks 
and  larger  limbs  of  the  infested  trees  often 
appear  as  if  whitewashed ;  this  is  due  to  the 
woolly  excretion  which  covers  the  bodies  of 
the  insects.  But  little  is  known  regarding  the 
life-cycle  of  the  species.  Wingless  females,  which  are  doubtless  agamic 
as  they  lay  many  eggs,  hibernate  on  the  pine  and  feed  on  the  bark 
in  the  spring.  They  lay  their  eggs  in  April ;  these  soon  hatch  and  the 
young  develop  into  winged  agamic  females  in  May.  These  soon  dis- 
appear and  the  pine  is  said  to  be  free  from  the  pest  during  the  svmimer. 
Return  migrants  to  the  pine  have  not  been  observed;  but  there 
must  be  a  generation  of  these,  the  parents  of  the  wingless  hibernating 


Fig.  503- 
abietis. 


-Gall  of  Adelges 


HOMOPTERA  433 


generation,  if,  as  stated,  the  pines  are  free  from  the  pest  during 

Riimmpr 


Subfamily  PHYLLOXERIN^ 
The  Phylloxerids 

The  distinguishing  characters  of  this  subfamily  are  given  under 
AA  in  the  table  on  page  428  and  need  not  be  repeated  here.  It  in- 
cludes two  genera.  Phylloxera  and  Phylloxerina. 

The  genus  Phylloxerina  is  distinguished  by  the  fact  that  the 
wingless  agamic  females  excrete  a  waxy  powder,  which  gives  them, 
the  appearance  of  mealy-bugs.  Species  of  this  genus  have  been  found 
in  this  country  on  poplar,  willow,  and  sour-gum. 

The  genus  Phylloxera  is  represented  by  the  grape  Phylloxera  and 
thirty  or  more  described  species  that  infest  forest-trees— hickory, 
oak,  and  cnestnut.  Most  of  these  are  found  on  hickory.  Those 
on  hickory  cause  the  growth  of  galls  either  on  the  leaves  or  on  the 
tender  twigs  and  petioles.  Other  species  produce  either  pseudogalls 
or  white  or  yellowish  circular  spots  on  the  infested  leaves. The  species 
infesting  forest-trees  were  monographed  by  Pergande  ('04). 

Although  in  this  subfamily  there  is  a  generation  of  winged  mi- 
grants in  the  life-cycle  of  each  species,  few  if  any  of  them  have  a 
secondary  host.  The  migrants  fly  to  other  parts  of  the  infested  plant 
or  to  other  plants  of  the  same  species. 

So  far  as  is  known,  the  life-cycle  of  the  species  infesting  forest -trees 
is  a  comparatively  simple  one.  The  stem-mother  hatches  in  the 
spring  from  an  over-wintering,  fertilized  egg  and  causes  the  growth  of 
a  gall;  she  develops  within  the  gall  and  produces  unfertilized  eggs. 
From  these  eggs  hatch  young  that  develop  into  winged  agamic 
females.  These  produce  eggs  of  two  sizes;  from  the  smaller  eggs 
hatch  males;  and  from  the  larger  ones,  females.  The  sexes  pair  and 
each  female  lays  a  single  fertilized  egg.  In  some  species  these  eggs 
are  laid  in  June  and  do  not  hatch  till  the  following  April. 

The  grape  Phylloxera,  Phylloxera  vastdtrix. — From  an  economic 
standpoint  this  species  is  the  most  important  member  of  the  Phyl- 
loxerina^;  millions  of  acres  of  vineyards  have  been  destroyed  by  it.* 
The  most  extensive  ravages  of  this  pest  have  occurred  in  France 
and  in  California.  This  species  is  a  native  of  the  eastern  United 
States,  where  it  infests  various  species  of  wild  grapes.  It  does  not 
injure  these  seriously;  but  when  it  was  introduced  into  France  it 
was  found  that  the  European  grape,  Vitis  vinifera,  is  extremely  sus- 
ceptible to  its  attack.  The  great  injury  to  the  vineyards  of  California 
is  due  to  the  fact  that  it  is  the  European  grape  that  is  chiefly  grown 
there. 

The  presence  of  this  insect  is  manifested  by  the  infested  vines 
in  two  ways:  first,  in  the  case  of  certain  species  of  grapes,   there 


*"The  Phylloxera  when  at  its  worst  had  destroyed  in  France  some  2,500,000 
acres  of  vineyards,  representing  an  annual  loss  in  wine  products  of  the  value  of 
$150,000,000."     (Marlatt  '98.) 


434 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  504. — Leaf  of  grapewith  galls  of  Phylloxera. 
(From  Riley.) 


appear  upon  the  lower  surface  of  the  leaves  galls,  which  are  more  or 
less  wrinkled  and  hairy  (Fig.  504),  which  open  upon  the  upper  surface 

of  the  leaf,  and  each  of 
which  contains  a  wingless, 
agamic  plant-louse  and  her 
eggs;  second,  when  the  fi- 
brous roots  of  a  sickly  vine 
are  examined,  we  find,  if  the 
disease  is  due  to  this  insect, 
that  the  minute  fibers  have 
become  swollen  and  knotty ; 
or,  if  the  disease  is  far  ad- 
vanced, they  may  be  en- 
tirely decayed  (Fig.  505,  c). 
Upon  these  root-swellings 
there  may  be  found  wing- 
less, agamic,  egg-laying 
plant-lice,  the  authors  of 
the  mischief. 

The  life-history  of  this 
species  is  a  complicated  one, 
due  to  the  fact  that  parallel 
series  of  generations  with 
different  life-cycles  may  be  developed  at  the  same  time.  While  a 
fertilized  winter  egg  may  be  considered  a  part  of  the  typical  life-cycle, 
some  of  the  agamic  females  hibernate  on  the  roots  of  the  vine  and 
form  a  part  of  a  series  of  agamic  generations  that  apparently  may 
continue  indefinitely  year  after  year. 

The  typical  life-cycle,  that  one  in  which  males  and  sexually 
perfect  females  form  a  part,  extends  over  two  years  and  includes 
four  forms  as  follows : 

The  gallicolcB. — From  an  over-wintering  fertilized  egg,  there  hatches 
in  the  spring  a  wingless  agamic  stem-mother,  which  passes  to  a  leaf 
and  by  her  attack  causes  the  growth  of  a  gall,  within  which  she  passes 
the  remainder  of  her  life.  She  reaches  maturity  in  about  fifteen 
days,  fills  the  gall  with  eggs,  and  soon  dies.  The  young  that  hatch 
from  the  eggs  laid  by  the  stem-mother  resemble  her  in  being  wingless 
agamic  females ;  they  escape  from  the  gall,  spread  over  the  leaves,  and 
in  turn  cause  the  growth  of  galls.  Six  or  seven  generations  of  this 
form  (Fig.  506)  are  developed  during  the  simimer.  They  are  termed 
the  gallicolcB. 

The  radicicolce  or  colonici. — On  the  appearance  of  cold  weather, 
young  hatched  from  eggs  laid  by  the  gall-inhabiting  form  pass  down 
the  vines  to  the  roots,  where  they  hibernate.  This  completes  the 
first  year  of  the  two-year  cycle.  In  the  following  spring  these  colonici, 
that  is,  settlers  in  a  new  region,  attack  the  fibrous  roots,  and  cause 
the  growth  of  knotty  swellings  on  them  (Fig.  505,  b,  c)  and  ultimately 
their  destruction.  This  is  the  most  serious  injury  to  the  vine  caused 
by  this  species.    There  is  a  series  of  generations  of  the  root-inhabiting 


HOMOPTERA 


435 


form  all  of  which  are  wingless  agamic  females.    This  form  (Fig.  507) 
differs  somewhat  in  appearance  from  the  gallicolfe. 

The  migrants  or  scxitparcc. —  During  the  late  summer  and  fall  there 
are  hatched  from  eggs  laid  by  some  individuals  of  the  root-inhabiting 


Fig.  505. — Phylloxera,  root-inhabiting  form:  a,  shows  a  healthy  root;  b,  one  on 
which  the  Hce  are  working,  representing  the  knots  and  swellings  caused  by 
their  punctures;  c,  a  root  that  has  been  deserted  by  them,  and  where  the  rootlets 
have  commenced  to  decay;  d,  d,  d,  show  how  the  lice  are  found  on  the  larger 
roots;  e,  agamic  female  nymph,  dorsal  view;  /,  same,  ventral  view;  g,  winged 
agamic  female,  dorsal  view;  h,  same,  ventral  view;  i,  magnified  antenna  of 
winged  insect;  j,  side  view  of  the  wingless  agamic  female,  laying  eggs  on  roots; 
k,  shows  how  the  punctures  of  the  lice  cause  the  large  roots  to  rot.  (From 
Riley.) 

form,  young  that  develop  into  winged  agamic  females  (Fig.  505,  g,  h). 
These  come  forth  from  the  ground,  fly  to  neighboring  vines,  and 
lay  eggs  in  cracks  in  the  bark  or  under  loose  bark.  They  lay  only  a 
few  eggs,  from  three  to  eight. 


436 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  506. — Phylloxera,  gall-inhabiting  form:  a,  b, 
newly  batched  nymph,  ventral  and  dorsal  views ;  c, 
egg;  d,  section  of  gall;  e,  swelling  of  tendril;  /,  g, 
h,  mother  gall-louse,  lateral,  dorsal,  and  ventral 
views;  i,  her  antenna;  j,  her  two-jointed  tarsus. 
Natural  sizes  indicated  at  sides.     (From  Riley.) 


The  sexuales. — 
The  eggs  laid  by  the 
winged  migrants  are 
of  two  sizes ;  from  the 
smaller  eggs  there 
hatch  males;  and 
from  the  larger  eggs, 
sexually  perfect  fe- 
males. These  pair 
and  each  female  pro- 
duces a  single  egg, 
which  is  laid  in  the  fall 
on  old  wood.  Here  it 
remains  over  winter, 
and  from  it  in  the  fol- 
lowing spring  a  stem- 
mother  is  hatched. 
This  completes  the 
two-year  life-cycle. 

Control.- — Owing 
to  the  great  injury 
that  this  species  has 
done  to  vineyards, 
hundreds  of  memoirs  have  been  published  regarding  it ;  but,  as  yet, 
no  satisfactory  means  of 
destroying  it  that  can  be 
generally  used  has  been 
discovered.  Where  the 
soil  conditions  are  favor- 
able it  can  be  destroyed 
by  the  use  of  carbon-bi- 
sulphide, but  this  is  an 
expensive  method ;  where 
the  vineyards  are  so  situ- 
ated that  they  can  be 
submerged  with  water  at 
certain  seasons  of  the 
year,  the  insect  can  be 
drowned ;  and  it  has  been 
found  that  vines  growing 
in  very  sandy  soil  are  less 
liable  to  be  seriously  in- 
jured by  this  pest. 

While  it  is  usually  im- 
practicable to  destroy 
this  pest  in  an  infested 
vineyard,  there  is  a  pre- 
ventative measure  that 
has  given  good  results. 


Fig.  507. — Phylloxera,  root-mhabitmg  form:  a, 
roots  of  Clinton  \me  showmg  the  relation  of 
swellings  to  leaf-galls,  and  power  of  resisting  de- 
composition; b,  nymph  as  it  appears  when 
hibernating;  c,  d,  antenna  and  leg  of  same;  e, 
f,  g,  forms  of  more  mature  lice;  h,  granulations 
of  skin;  i,  tubercle;  j,  transverse  folds  at 
border  of  joints;  k,  simple  eyes.    (From  Riley.) 


HO  MO  PT ERA 


437 


-An  aleyrodid. 


Fig.  509. — Aleurochiton  for- 
besii. 


Certain  varieties  of  American  grapes  are  not  seriously  injured  by  the 
root-form  of  the  Phylloxera.  By  growing  these  varieties,  or  by  using 
the  roots  of  them  as  stocks  on  which  to  graft  the  susceptible  European 
varieties,  the  danger  of  injury  by  this  pest  is  greatly  reduced. 

Family  ALEYRODID^ 
The  Aleyrodids  or  White  Flies 

The  members  of  this  family  are  small  or  minute  insects;  our  more 

common  species  have  a  wing-expanse  of  about  3  mm.    In  the  adult 

state  both  sexes  have  four  wings,  differing  in  this  respect  from  the 

Coccidas,  with  which  they  were  classed  by  the  early  entomologists. 

The  wings  are  transparent,  white,  clouded  or  mottled  with  spots  or 

bands.      The    wings, 

and  the  body  as  well, 

are    covered    with    a 

whitish  powder.     It  is 

this  character  that 

suggested  the  name  of 

the  typical  genus,* 

and  the  common  name 

white  flies. 

In    the    immature 

stages,    these    insects   ^'^Z-  5o8. 

are  scale-like  in  form 

and  often  resemble  somewhat  certain  species  of  the  genus  Lecanium 

of  the  family  Coccidas.    Except  during  the  first  stadium,  the  larvas 

remain  quiescent  upon  the 
leaves  of  the  infested  plant 
and  in  most  species  are  sur- 
rounded or  covered  by  a 
waxy  excretion.  In  Figure 
508  there  is  represented  one 
of  the  many  forms  of  this 
excretion.  Here  it  consists 
of  parallel  fibers,  which  ra- 
diate from  the  margin  of  the 
body,  and  its  white  color 
contrasts  strongly  with  the 
dark  color  of  the  insect.  In 
some  species  the  fringe  of 
excretion  is  wanting;  and 
in  others,  the  excretion  from 
the  margin  of  the  body,  in- 
stead of  extending  laterally 
and  forming  a  fringe,  is  di- 
rected toward  the  leaf  upon 
which  the  insect  rests,  and 


Fig.  510. — -Wings  of  Udamoselis.     (After  En- 
derlein,  with  changed  lettering.) 


*Aleyrodes  {aXevpudrjs),  like  flour. 


438  .4^  INTRODUCTION  TO  ENTOMOLOGY 

thus  the  body  is  Hfted  away  from  the  leaf  and  is  perched  upon  an 
exquisite  pahsade  of  white  wax  (Fig.  509). 

The  members  of  this  family  feed  exclusively  on  the  leaves  of  the 
host-plants.  With  few  exceptions  they  are  not  of  economic  impor- 
tance ;  and  also  with  few  exceptions,  the  injurious  species  are  not  wide- 
ly distributed  over  the  world  as  are  many  aphids  and  coccids.  This  is 
probably  due  to  the  fact  that  as  they  live  exclusively  on  leaves  they 
are  not  so  liable  to  be  transported  on  cuttings  and  nursery  stock. 
They  are  most  abundant  in  tropical  and  semi-tropical  regions. 

The  adults  present  the  following  characters :  The  compound  eyes 
are  usually  constricted  in  the  middle  and  in  some  species  each  eye 
is  completely  divided.  In  some  cases  the  facets  of  the  two  parts  of  a 
divided  eye  are  different  in  size;  it  is  probable  that  in  such  cases  one 
part  is  a  day-eye  and  the  other  part  a  night-eye  (see  page  1 44) .  The 
ocelli  are  two  in  number;  each  ocellus  is  situated  near  the  anterior 
margin  of  a  compound  eye.  The  antenna  are  usually  seven-jointed. 
The  labium  is  composed  of  three  segments.  The  fore  wings  are  larger 
than  the  hind  wings;  when  at  rest  the  wings  are  carried  nearly 
horizontally.  The  venation  of  the  wings  is  greatly  reduced;  the 
maximum  number  of  wing-veins  found  in  the  family  is  in  the  fore 
wings  of  the  genus  Udamoselis  (Fig.  510).  The  three  pairs  of  legs 
are  similar  in  form;  the  tarsi  are  two-jointed;  and  each  tarsus  is 
furnished  with  a  pair  of  claws  and  an  empodium  or  paronychiimi. 
The  anus  opens  on  the  dorsal  wall  of  the  abdomen  at  some  distance 
from  the  caudal  end  of  the  body  and  within  a  tubular  structure, 
which  is  termed  the  vasiform  orifice.  A  tongue-like  organ,  the  lingula, 
projects  from  the  vasiform  orifice;  and  at  the  base  of  the  lingula 
there  is  a  broad  plate,  the  operculum;  the  anus  opens  beneath  these 
two  organs. 

In  this  family  the  type  of  metamorphosis  corresponds  quite 
closely  with  that  known  as  complete  metamorphosis;  consequently 
the  term  larva  is  applied  to  the  immature  instars  except  the  last, 
which  is  designated  the  pupa. 

The  eggs  are  elongate-oval  in  shape  and  are  stalked.  The  larvse 
during  the  first  stadium  are  active,  after  which  they  remain  quiescent. 
There  are  four  larvil  and  one  pupal  instars.  The  wings  arise  as 
histoblasts  in  the  late  embryo,  and  the  growth  of  the  wing-buds 
during  the  larval  stadia  takes  place  inside  the  body-wall.  The 
change  to  the  pupal  instar,  in  which  the  wing-buds  are  external, 
takes  place  beneath  the  last  larval  skin,  which  is  known  as  the  pupa- 
case  or  puparium.  In  many  descriptions  of  these  insects  only  three 
larval  instars  are  recognized,  the  fourth  being  described  as  the  pupa. 
As  the  change  to  a  pupa  takes  place  beneath  the  last  larval  skin,  the 
puparium,  and  as  the  adult  emerges  through  a  T-shaped  opening  in 
the  dorsal  wall  of  the  puparium,  the  pupa  itself  is  rarely  observed. 

Parthenogenesis  occurs  in  this  family;  but  according  to  the 
observations  of  Morrill,  unfertilized  eggs  produce  only  males. 

As  with  the  adults,  the  anus  of  the  immature  forms  opens  in  a 
vasiform  orifice  on  the  dorsal  aspect  of  the  body  at  some  distance 


HOMOPTERA 


441 


from  the  caudal  end  of  the  body.     The  excrement  is  in  the  form  ot 
honey-dew,  of  which  much  is  excreted. 

Formerly  all  the  members  of  this  family  were  included  in  a  single 
genus,  Aleyrodes;  consequently,  except  in  comparatively  recent  works, 
the  various  species  are  described  under  this  generic  name.  In  later 
days,  very  extended  studies  have  been  made  of  the  family;  and  the 


Fig.  511. — Asterochiton  vaporariorum:  a,  egg;  b,  larva,  first  instar;  c,  puparium, 
dorsal  view;  d,  puparium,  lateral  view;  e,  adult.     (After  Morrill.) 

genus  Aleyrodes  has  been  divided  into  many  genera,  which  are  now 
grouped  into  three  subfamilies.  The  most  complete  systematic  works 
on  the  family  are  those  of  Quaintance  and  Baker  ('13  and  '17).  The 
following  species  are  among  our  more  common  representatives  of  the 
family. 

The  greenhouse  white  fly,  Asterochiton  vaporariorum. — One  of 
the  most  important  of  the  greenhouse  pests  is  this  insect,  which  infests 
very  many  species  of  plants  that  are  grown  under  glass;  and  some- 
times it  is  a  serious  pest  in  the  open  on  tomato  and  other  plants  that 
are  set  out  gfter  the  weather  is  warm. 

The  adult  measures  about  1.5  mm.  in  length,  and  like  other 
aleyrodids  is  covered  with  a  white,  waxy  powder.  The  eggs  are  only 
.2  mm.  in  length,  and  are  suspended  from  the  leaf  by  a  short  stalk 
(Fig.  511,  a).  In  the  first  instar  the  larva  is  flat,  oval  in  outline, 
and  with  each  margin  of  the  body  furnished  with  eighteen  spines 
(Fig.  511,  b),  of  which  the  last  is  much  the  longest.  In  the  second 
and  third  instars  there  are  only  three  pairs  of  marginal  spines,  a  very 
small  pair  near  the  cephalic  end  of  the  body  and  two  somewhat 
larger  ones  near  the  caudal  end.     The  marginal  fringe  of  wax  is 


■J  AN  INTRODUCTION  TO  ENTOMOLOGY 

narrow.  The  puparium  is  box-like,  the  body  of  the  insect  being 
elevated  on  a  palisade  of  vertical  wax  rods  (Fig.  511,  d).  There  are 
other  rods  of  wax  represented  in  the  dorsal  view  of  the  puparium 
(Fig.  511,  c). 

The  most  successful  means  of  destroying  this  pest  is  by  fumigation 
of  infested  greenhouses  with  hydrocyanic  acid  gas. 

The  strawberry  white  fly,  Asterochiton  packardi. — This  species  is 
closely  allied  to  the  greenhouse  white  fly,  but  differs  in  minute  char- 
acters presented  by  the  spines  and  wax  rods  of  the  immature  forms. 
It  infests  strawberry  plants,  and  is  a  hardy  species,  passing  the 
winter  in  the  egg  state  out  of  doors. 

The  citrus  white  fly,  Dialeurodes  cUri. — This  is  a  well-known  pest 
in  the  orange-growing  sections  of  our  country,  and  is  also  found  in 
greenhouses  in  the  North.  It  infests  all  citrus  fruits  grown  in  this 
country  and  is  found  on  several  other  plants. 

This  insect  injures  its  host  in  two  ways :  first  directly,  by  sucking 
the  sap  from  the  leaves;  and  second  indirectly,  by  furnishing  nourish- 
ment, in  the  form  of  honeydew.to  a  fungus,  the  sooty  mold  {Meliola 
camellia:),  which  forms  a  dark -brown  or  black  membranous  coating 
on  the  leaves  and  fruit,  and  thus  interfering  with  the  functioning  of 
the  leaves,  retarding  the  ripening  of  the  fruit,  and  decreasing  the 
yield  of  the  fruit.  There  are  from  two  to  six  generations  of  this 
species  in  a  year.  An  extended  account  of  it  is  given  by  Morrill  and 
Back  ('11). 

The  maple  white  fly,  Aleurochiton  forhesii. — Figure  509  represents 
this  species,  which  is  fairly  common  on  maple,  but  rarely  in  sufficient 
numbers  to  do  serious  injury. 

Family  COCCID^ 
The  Scale-Insects  or  Bark-Lice,  Mealy-Bugs,  and  others 

The  family  Coccidce  includes  the  scale-insects  or  bark-lice,  the 
mealy-bugs,  and  certain  other  insects  for  which  there  are  no  popular 
names.  To  this  family  belong  many  of  the  most  serious  pests  of 
horticulturists ;  scarcely  any  kind  of  "fruit  is  free  from  their  attacks ; 
and  certain  species  of  scale-insects  and  of  mealy-bugs  are  constant 
pests  in  greenhouses.  Most  of  the  species  live  on  the  leaves  and 
•stems  of  plants;  but  some  species  infest  the  roots  of  the  host -plants. 
The  great  majority  of  the  species  remain  fixed  upon  their  host  during 
a  part  of  their  life-cycle,  and  can  thus  be  transported  long  distances 
while  yet  alive,  on  fruit  or  on  nursery  stock ;  this  has  resulted  in  many 
species  becoming  world-wide  in  distribution.  Most  of  the  species  are 
minute  or  of  moderate  size ;  but  some  members  of  the  family  found  in 
Australia  measure  25  mm.  or  more  in  length. 

While  the  economic  importance  of  this  family  is  due  chiefly  to 
the  noxious  species  that  belong  to  it,  it  contains  several  useful  species. 
'The  most  important  useful  species  at  this  time  is  the  lac-insect, 
Tachdrdia  Idcca.     The  stick-lac  of  commerce,  from  which  shell-lac 


HOMOPTERA 


441 


or  shellac  is  prepared,  is  a  resinous  substance  excreted  by  this  species, 
which  lives  on  the  young  branches  of  many  tropical  trees,  most  of 
which  belong  to  the  genus  Ficus,  the  figs. 

In  the  past,  several  coccids  have  been  important  as  coloring  agents. 
The  bodies  of  the  lac-insects,  which  are  obtained  from  stick-lac  in  the 
manufacture  of  shellac,  are  the  source  of  lac-dye.  Another  coccid, 
Kermes  Uicis,  which  lives  on  a  species  of  oak  in  southern  Europe, 
has  been  used  as  a  dye  from  very  early  times.    And  the  well-known 


Fig.  512. — Chionaspis  furfura:  7,  scales  on  pear,  natural  size;  /a,  scale  of  male , 
lb,  adult  male,  ic,  scale  of  female,  enlarged. 


cochineal  is  composed  of  the  dried  bodies  of  a  coccid,  Coccus  cacti, 
which  lives  on  various  species  of  cactus.  Recently  these  dyes  have 
been  largely  supplanted  by  those  obtained  from  coal-tar. 

China-wax  is  also  produced  by  a  coccid.  It  is  the  excretion  of  an 
insect  known  as  pe-la,  Ericerus  pe-la,  and  was  formerly  much  used  in 
China  in  the  manufacture  of  candles,  before  the  introduction  of  paraffin. 

In  the  adult  state,  the  two  sexes  of  coccids  differ  greatly  in  form. 
The   males   are  usually   winged   (Fig.    512);    in  a  few  species  they 


442  AN  INTRODUCTION  TO  ENTOMOLOGY 

are    either    wingless    or    have    vestigial  wings.     The    fore    wings 

are  usually  large,  com- 
pared with  the  size  of  the 
body ;  the  hind  wings  are 
alwa}'s  greatl\'  reduced  in 
size;  usually  they  are  a 
pair  of  club-shaped  hal- 
teres,  but  in  a  few  forms 
they  are  more  or  less 
wing  -  like.     Each    hind 

Fig.  5I3-— Wing  of  Pseudococcus.     (From  Patch.)    ^-^^  -g  famished  with  a 

bristle,  which  is  hooked  at  the  end  and  fits  into  a  pocket  or  fold 
on  the  inner  margin  of  the  fore  wing  of  the  same  side ;  in  a  few  spe- 
cies there  are  two  or  three  or  more  of  these  hamuli. 

The  venation  of  the  fore  wings  is  greatly  reduced;  a  wing  of 
Pseudococcus  (Fig.  513)  will  serve  to  illustrate  the  usual  type  of  wing- 
venation  found  in  this  family. 

The  legs  are  wanting  in  many  adult  females,  having  been  lost 
during  the  metamorphosis.  In  adult  males  they  are  of  ordinary 
form;  except  in  a  few  species,  the  tarsi  are  one-jointed,  and  each  is 
furnished  with  a  single  claw.  Accompanying  the  tarsal  claw  there 
are  often  a  few  long,  clubbed  setcC,  the  digitules  (Fig.  514) ;  these  are 
tenent  hairs ;  some  of  the  digi- 
tules arise  from  the  tip  of  the 
tarsus,  and  some  from  the 
claw. 

The  caudal  end  of  the  ab- 
domen of  the  male  usuallv  ^.  .,,.-. 
bears  a  slender  tubular  pro-  ^ig-  ^^--Leg  of  a  female  Lecamum:  d, 
cess,  the  stylus.  In  some  spe-  ^^^  ^  ^^" 
cies  the  stylus  is  as  long  as  or  even  longer  than  the  abdomen ;  in  others 
it  is  short,  and  in  some  it  is  apparently  wanting.  The  stylus  serves 
as  a  support  for  the  penis,  which  is  protruded  from  it  and  in  some 
species  is  very  long. 

The  female  coccid  is  always  wingless,  and  the  body  is  either  scale- 
like or  gall-like  in  form,  or  grub-like  and  clothed  with  wax.  The 
waxy  covering  may  be  in  the  form  of  powder,  of  large  tufts  or  plates, 
of  a  continuous  layer,  or  of  a  thin  scale,  beneath  which  the  insect  lives. 

The  eyes  of  coccids  exhibit  varying  degrees  of  degeneration  and 
retardation  of  development.  The  extreme  of  degeneration  is  found 
in  the  females,  where  there  is  only  a  single  simple  eye  on  each  .side 
of  the  head;  this  is  probably  a  vestige  of  a  compound  eye.  In  the 
adult  males  of  the  more  generalized  forms,  compound  eyes  are  present ; 
and  in  some  of  these  forms,  there  are  also  ocelli,  two  in  some  and  three 
in  others.  When  compound  eyes  are  present  the  facets  are  usually 
large,  and  not  closely  associated.  In  the  more  specialized  forms, 
instead  of  compound  eyes  there  are  on  each  lateral  half  of  the  head 
from  two  to  eight  widely  separated  simple  eyes,  which  may  be 
scattered  vestiges  of  compound  eyes. 


HOMOPTERi 


443 


Fig.  515. — A  depigmented  "acces- 
sory eye"  of  Pseudococcus  de- 
structor: c,  cornea;  h,  corneal 
hypodermis;  i,  iris  cell;  r,  reti- 
nal cells;  n,  nerve. 


The  structure  and  develoj^ment  of  the  eyes  of  the  male  of  the  common  mealy- 
bug, Pseudococcus  (Dactylopius)  destructor,  was  studied  by  Krecker  ('09).  In 
this  insect  there  is  on  each  side  of  the  head  a  very  small  eye;  since  these  are  the 
only  eyes  posses.«ed  by  the  young  nymphs,  they  were  termed  by  Krecker  the 
primary  eyes.  In  the  adult,  in  addition  to  the  primary  eyes,  there  are  two  pairs  of 
eyes,  one  pair  on  the  dorsal  aspect  of  the  head,  and  a  second  pair  on  the  ventral 
aspect;  these  he  termed  the  accessory  eyes. 

The  so-called  primary  eyes  are  very  de- 
generate, in  the  adult  at  least.  There  is  a 
lens  below  which  there  are  a  few  retinal  cells; 
but  there  is  no  corneal  hypodermis,  no  rhab- 
doms,  and  no  iris. 

The  development  of  the  so-called  acces- 
sory eyes  is  greatly  retarded.  The  histo- 
blasts  from  which  they  are  developed  appear 
in  the  latter  part  of  the  second  nymphal 
stadium  or  in  the  beginning  of  the  third; 
these  are  thickenings  of  the  hypodermis. 
When  fully  developed  as  seen  in  the  adult, 
the  accessory  eyes  (Fig.  515)  have  a  large 
circular  cornea,  followed  by  a  comparatively 
thin  layer  of  corneal  hypodermis,  encircling 
which  is  a  single  row  of  large  iris  cells.  Below 
the  corneal  hypodermis  there  is  a  crescent- 
shaped  area  of  polygonal  rods  (rhabdoms), 
which  are  terminally  situated  upon  the  ret- 
inal cells.  From  the  proximal  end  of  the 
retinal  cells  extend  the  nerve  fibrils  which 
join  to  form  the  optic  nerve,  which  follows 

the  contour  of  the  head  to  enter  the  brain  lateral- 
ly. Reddish  brown  pigment  fills  the  retina,  the  iris, 
and  also  a  ridge  surrounding  the  eyes.  There  are 
no  cells  which  function  as  pigment  cells  alone. 

The  antennas  of  the  males  are  lon^  and 
slender,  and  consist  of  from  six  to  thirteen 
segments;  in  some  of  the  A/Targarodinc-e they 
are  branched  or  fiabellate.  The  antennae  of 
adult  females  exhibit  great  variations  in 
structure;  they  may  be  well  developed  and 
consist  of  as  many  as  eleven  segments;  or 
they  may  be  greatly  reduced  in  size  and  in 
the  number  of  segments;  in  some  species 
they  are  either  vestigial  or  entirely  wanting 
in  adult  females. 

The   mouth-parts   are   situated    on    the 

hind  part  of  the  ventral  aspect  of  the  head, 

and  often  extend  caudad  of  the  first  pair  of 

legs.    In  front  of  the  beak  there  is  a  densely 

chitinized  area,  which  includes  the  civ  pens, 

^'^-  516.— Mouth-parts  of  a  thelabrum,and  themandibularandmaxillarv 

chiSni^ed'area  m  f^oS^f  sderites.    In  cleared  specimens  there  can  be 

the  beak;  B,  the  beak;   /,  seen  withm  this  area  a  complicated  endo- 

labrum;      0,     oesophagus;  skeleton  (Fig.   Si6,  A). 

s,  loop  of  mandibular  and  'phg  labium'  (Fig.  516.  B),  which  is  com- 
Sumen?  '^(Ste^  Ber^^^o^^'  termed  the  beak  or  rostrum,  consists 
lese.)       '  of  three  segments  in  a  few  forms  found  in 


444  AN  INTRODUCTION  TO  ENTOMOLOGY 

New  Zealand,  but  usually  it  is  more  or  less  reduced,  consisting  either 
of  two  segments  or  of  only  one;  in  a  few  subfamilies  it  is  wanting 
in  the  adult.  The  mandibular  and  maxillary  setae  are  wanting  in 
the  later  nymphal  instars  of  some  forms,  in  some  adult  females, 
and  in  all  adult  males.  These  setae,  when  present,  are  usually 
long,  frequently  longer  than  the  body,  and  in  some  species  sev- 
eral times  as  long.  When  not  exserted,  they  are  coiled  within  a 
pouch,  termed  the  crumena,  only  their  united  tips  extending  to  the 
labium.  The  cnmiena  is  a  deep  invagination  of  the  body-wall,  which 
extends  far  back  into  the  body-cavity.  Its  walls  are  delicate,  and 
not  easily  observed ;  but  the  coiled  setas  within  it  can  be  easily  seen 
in  cleared  specimens  (Fig.  516,  s). 

In  the  classification  of  coccids,  the  characters  most  used  are  those 
presented  by  the  female,  although  those  of  the  male  are  used  to  some 
extent .  The  most  available  characters  of  the  female  are  the  following : 
first,  the  general  form  of  the  body;  second,  the  form  of  the  waxy 
excretions;  third,  the  structure  of  the  caudal  end  of  the  body;  and 
fourth,  the  form  and  position  of  the  pores  through  which  the  wax  is 
excreted. 

To  study  the  third  and  fourth  classes  of  characters  listed  above, 
it  is  necessary  to  remove  the  wax,  to  clarify  the  body,  and,  in  some 
cases,  to  stain  it.  The  method  most  commonly  used  for  removing  the 
wax  and  clarifying  the  body  is  to  boil  the  specimen  in  a  ten  per  cent, 
aqueous  solution  of  caustic  potash.  For  staining  the  body.  Gage  ('19) 
found  that  a  solution  of  saurefuchsin  was  most  satisfactory;  his 
formula  for  the  preparation  of  this  solution  is  as  follows : 

Saurefuchsin 0.5  gr. 

Hydrochloric  acid,  10% 25.0  c.c. 

Distilled  water 300.0  c.c. 

The  cleaned  and  stained 
specimens  are  usually  mounted 
in  Canada  balsam  for  micro- 
scopic examination. 

Within  the  family  Coccidas 
there  are  to  be  found  most  re- 
markable variations  in  struc- 
[/(   WWJfll    \  1  ture;  this  is  especially  true  of 

the  form  of  the  caudal  end  of 
the  body  and  of  the  form  of  the 
parts  through  which  the  wax 
and  other  excretions  are  exud- 
ed. These  characters  have  been 
described   by  many   authors; 
but,  unfortunately,  there  is  a 
great  lack  of  uniformity  in  the 
Fig.  517. — Caudal  end  of  female  of  Eriococ-   terminology    used    by    them. 
cus  araucaricB:  r,  anal  ring;  s,  anal-ring    j^   ^^jg    place,    only    sufficient 
setae;  /,   anal   lobe;  as,   anal   seta.      Be-  ^      „„   1  ^  j-„i,„„   4-^   /i^^^^ 

tween   the   bases   of   the   anal-ring   seta,    space  can  be  taken  to  define 
there  are  openings  of  wax-glands.  the    more     important     struc- 


HO  MO  PT ERA 


445 


tures,  using  the  terms  that  are  more  generally  applied   to   them. 

The  anal  ring. — In  the  mealy-bugs,  the  tortoise-scales,  and  the 
lac-insects,  and  in  the  nymphs  of  some  others,  the  anus  is 
surrounded  by  a  well-defined  ring,  the  anal  ring  (Fig.  517,  r). 

The  anal-ring  setce. — The  anal  ring  bears  several,  from  two  to 
thirty  but  usually  six,  long  and  stout  setse,  the  anal-ring  setcB  (Fig. 
517. -j)- 

The  anal  lobes. — -In  many  coccids,  the  caudal  end  of  the  body  is 
terminated  by  a  pair  of  lobes,  the  anal  lobes  (Fig.  517,  /). 

The  anal  setce.- — Each  anal  lobe  bears  one  or  more  prominent  setas, 
the  anal  setce  (Fig.  517,  as). 

The  anal  plates. — In  the  subfamily  Lecaniinae,  the  abdomen  of 
the  female  is  cleft  at  the  caudal  end,  and,  at  the  cephalic  end  of  the 
cleft,   there  is  a  pair  of  tri- 
angular, or  sometimes  semi-cir- 
cular plates,   the   anal  plates 
(Fig.  518,  ap). 

The  pygidium. — In  the  sub- 
family Diaspidinas,  the  abdo- 
men of  the  adult  female  is  ter- 
minated by  a  strongly  chi- 
tinizedunsegmented  region, 
which  consists  of  four  co- 
alesced segments  (Fig.  519); 
this  region  is  termed  the  pygid- 
ium by  writers  on  the  Coccidae. 
This  application  of  the  term 
pygidium  is  quite  different 
from  that  used  in  descriptions 
of  other  insects,  where  it  refers 
only  to  the  tergite  of  the  last 
abdominal  segment.  A  more 
detailed  account  of  the  charac- 
ters presented  by  the  pygidium 
of  the  Diaspidinas  is  given  later. 

The  spines  and  the  setce. — The  position  and  number  of  spines  and 
of  setae  are  often  indicated  in  specific  descriptions.  Care  should  be 
taken  to  distinguish  between  these  two  kinds  of  structures.  A  seta 
can  be  recognized  by  the  cup-like  cavity  in  the  cuticula,  the  alveolus, 
within  which  it  is  jointed  to  the  body;  while  a  spine  is  an  outgrowth 
of  the  cuticula  that  is  not  separated  from  it  by  a  joint.  See  figure  42, 
page  32.  The  writer  in  his  early  works  on  the  Coccids  ('81,  '82,  '83) 
termed  certain  spine-like  setae  spines. 

The  outlets  of  wax-glands . — In  the  Coccidse  there  are  many  minute 
openings  in  the  cuticula  through  which  wax  is  excreted;  these  vary 
greatly  in  form,  in  position  on  the  body,  and  in  the  structure  of  the 
part  of  the  cuticula  through  which  they  open.  As  the  characters 
presented  by  these  openings  are  much  used  in  the  classification  of 
coccids,  a  very  elaborate  terminology  referring  to  them  has  been 
developed.  Unfortunately  different  authors  use  quite  different  terms 


Fig.  518.  — A 
Lecanium, 
enlarged  :a^, 
anal  plates. 


Fig.  519. — Adult  female 
Lepidosaphes:  p,  py- 
gidium. 


446  AN  INTRODUCTION  TO  ENTOMOLOGY 

and,  therefore,  it  is  necessary  to  learn  the  terms  used  by  an  author  in 
order  to  understand  his  descriptions.  The  most  detailed  and  sys- 
tematic terminology  that  has  been  proposed  is  that  of  MacGillivray 
('21).  Some  of  the  many  terms  adopted  by  this  author  are  defined 
below. 

The  ceratubce. — In  the  Diaspidinae  and  in  some  species  of  several 
other  subfamilies,  the  terminal  portion  of  the  outlet  of  some  of  the 
wax-glands  is  an  invaginated  cuticular  tube.  The  inner  end  of  this 
tube  is  truncate,  and,  in  the  Diaspidinae,  bears  a  perforated  knob. 
This  invaginated  cuticular  tube  is  termed  a  ceratuba.  The  ceratubse 
vary  greatly  in  length  and  in  shape;  in  some  the  greater  part  of  the 

O^^^  _  _  tube  is  reduced  to  a  fine  thread, 

/qC3\    ^^^k    ^^?^!?\     with  a  bulb-like  inner  end.     A 
Sp<^§    V    V    t^^S::;p      few  ceratubae  are  represented  in  a 
^^      ^^    \j^j^      diagram  given  later   (Fig.   522). 
0^\.        .^"W       -^f^      .j0!!^        ^^^  openings  of  most  ceratubae 
Cj      JC^    ^^a    ^^3      ^^^  ^^^^  ^'^^^  ^^^  body-wall,  but 
Vi«^r    \/TSr    ^^m9      some  of  them  open  through  plates 
in  the  marginal  fringe.    The  dif- 
Fig.  520. — Several  types  of  openings  of  ferent  types  of  ceratubas  have  re- 
cerores.  ceived  distinguishing   names 

formed   by    combining   a   prefix  with  the  word  ceratubas. 

The  cerores. — The  various  types  of  outlets  of  the  wax-glands  in 
which  the  cuticula  is  not  invaginated  so  as  to  form  a  ceratuba  are 
termed  cerores.     The  openings  of  cerores  through  the  cuticula  vary 


Fig.  521. — Diagram  of  a  pygidium  of  a  diaspid:  a,  anus  showing  through  the 
body;  d,  densariae;  g,  genacerores;  i,  incisions;  /,  first  pair  of  lobes;  pe, 
pectinae;  pi,  plate;  s,  setag;  v,  vagina. 

greatly  in  form;  several  types  of  these  openings  are  represented  in 
Figure  520.  While  in  most  cases  the  openings  of  cerores  are  flush 
with  the  general  surface  of  the  cuticula,  in  some  coccids  (Ortheziinae) 
the  cerores  open  through  spines.  There  are  also  variations  in  the 
grouping  of  the  cerores.  Each  of  the  various  types  has  received  a 
technical  name  formed  by  combining  a  prefix  with  the  word  cerores. 


HOMOPTERA 


447 


Thus,  for  example,  the  cerores  that  occur  in  four  or  five  groups  about 
the  genital  opening  in  many  of  the  Diaspidinae  (Fig.  52 1 ,  g)  are  termed 
genacerores. 

The  features  oj  the  pygidium.- — The  pygidia  of  adult  female  diaspids 
present  characters  that  are  much  used  in  distinguishing  the  species 
of  this  subfamily;  among  these  are  the  following. 


Fig.  522. — A  composite  diagram  of  a  pygidium:  a,  anus;  b,  marginal  ceratubae, 
with  elongated  openings;  d,  ceratubas  opening  through  plates;  e,  linear 
ceratubae;  /,  /,  I,  lobes;  the  lobes  of  the  second  and  third  pairs  are  divided. 

The  position  of  the  anus,  which  opens  on  the  dorsal  aspect  of  the 
pygidium  at  varying  distances  from  the  end  of  the  body  (Fig.  522,  a). 

The  opening  of  the  vagina,  on  the  ventral  aspect  of  the  pygidium 
(Fig.  521,  ^). 

The  presence  or  absence  of  groups  of  genacerores  (Fig.  521,  g),  the 
number  of  these  groups  when  present,  and  the  number  of  cerores  in 
each  group.  The  difi^erent  groups  are  distinguished  as  the  median 
group  (mesogenacerores) ,  the  cephalo-lateral  groups,  one  on  each  side 
(pre gnacer ores),  and  the  caudo-lateral  groups,  one  on  each  side 
(postgenacerores) ,  respectively.  These  all  open  on  the  ventral  aspect 
of  the  pygidium.    Each  genaceroris  has  several  openings. 

The  position  and  number  of  openings  of  ceratubae,  and  the  types 
of  ceratubae  that  are  present  (Fig.  522). 

The  number  of  pairs  of  lobes  borne  by  the  margin,  the  shape  of 
the  lobes,  and  whether  they  are  divided  or  not  (Fig.  522,  /,  /,  /).  The 
pairs  of  lobes  are  numbered,  beginning  with  the  pair  at  the  end  of 
the  body;  in  some  species  this  pair  is  represented  by  a  single  lobe. 

The  number  of  pairs  of  incisions  {incisurce)  in  the  margin  of  the 
pygidium  (Fig.  521,  z). 

The  presence  or  absence  of  thickenings  of  the  margins  of  the 
incisions  {densaricE);  these  are  thickenings  of  the  ventral  wall  (Fig. 
521,  d). 


448 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  presence  or  absence  of  club-shaped  thickenings  of  the  dorsal 
wall  (paraphyses)  that  extend  forward  from  near  the  bases  of  the 
lobes  (Fig.  523,  ;^). 

The  presence  or  absence  of  a  thickening  of  the  lateral  margin  of 
the  pygidinm  cephalad  of  the  region  in  which  the  lobes  are  situated, 
and  resembling  the  lobes  in  structure  (Fig.  523,  m). 

The  nimiber  and  shape  of  the  thin  projections  of  the  margin, 
known  as  plates.  Two  quite  distinct  types  of  plates  can  be  dis- 
tinguished: in  one  they  are  broad  and  fringed  (Fig.  521,  pe);  the 
plates  of  this  type  have  been  termed  pectince;  in  the  other  type  they 
are  spine-like  in  form  (Fig.  521,  pi);  some  writers  restrict  the  term 
plate  to  this  type,  and  use  pectinaz  for  the  first  type.  Each  plate 
contains  the  outlet  of  a  wax-gland. 


Fig.  523. — Part  of  the  pygidium  of  Chrysomphalus  tenehricosus ,  ventral  aspect, 
with  the  paraphyses  (pp)  of  the  dorsal  wall  showing  through:  /,  /,  /,  lobes; 
m,  thickened  margin;  s,  spine-like  setas. 

The  metamorphosis  of  coccids. — In  this  family  the  two  sexes  are 
indistinguishable  during  the  first  nymphal  stadium.  Both  are  fur- 
nished with  legs,  antenncC,  and  functional  mouth-parts.  It  is  dttring 
this  period  that  the  sedentary  species  spread  over  the  plants  that  they 
infest.  In  their  subsequent  development  the  sexes  differ  greatly; 
hence  the  metamorphosis  of  each  can  be  best  discussed  separately. 

The  females  never  become  winged.  Some,  as  the  mealy-bugs  and 
Orthezia,  continue  active  throughout  their  entire  or  almost  entire  life; 
but  most  forms  become  sedentary  early  in  life  and  remain  fixed  upon 
their  host.  Many  species  lose  their  legs  and  antennae  when  they 
assume  the  quiescent  form ;  and  in  some  the  mandibular  and  maxillary 
setae  are  wanting  in  the  adult.  The  number  of  nymphal  instars  in 
females  varies  from  two  to  four;  the  smaller  number  occurs  in  the 
more  specialized  subfamilies. 

In  the  males  there  are  usually  four  nymphal  instars.  During  the 
latter  part  of  the  nymphal  life  the  male  is  quiescent,  having  formed  a 
cocoon  or  a  scale  within  or  beneath  which  it  remains  till  it  emerges 
as  an  adult.     The  stage  of  development  at  which  the  quiescent 


HOMOPTERA  449 

period  begins  varies  greatly.  Thus,  while  in  the  mealy-bugs  the 
cocoon  is  made  during  the  second  stadium,  in  Icerya  it  is  not  made  till 
near  the  end  of  the  third.  In  the  Diaspidinas  the  formation  of  the  scale 
begins  either  at  the  close  of  the  first  stadium  or  imniediately  after  the 
first  molt.  With  the  molt  at  the  beginning  of  the  quiescent  period 
the  male  loses  its  legs,  antennae,  and  mandibular  and  maxillary  setse. 
The  setae  are  not  replaced;  and,  consequently,  the  adult  males  can 
take  no  food.  The  legs  and  antennae  of  the  adult  are  developed  from 
histoblasts,  as  in  insects  with  a  complete  metamorphosis;  the  wing- 
buds  appear  in  the  last  nymphal  stadium;  but  they  are  developed 
externally,  as  in  insects  with  a  gradual  metamorphosis.  The  type  of 
metamorphosis  of  the  male  coccid  is,  therefore,  neither  strictly  com- 
plete nor  gradual.  This  illustrates  the  difficulty  of  attempting  to 
make  sharp  distinctions;  for  in  nature  all  gradations  exist  between 
the  different  types  of  structure  and  of  development. 

The  classification  of  the  Coccidce. — The  different  writers  on  the 
Coccidas  have  grouped  the  genera  into  a  variable  number  of  sub- 
families. In  the  classification  by  MacGillivray  ('21),  this  author 
recognizes  seventeen  subfamilies,  and  gives  two  tables  for  separating 
them,  one  based  on  the  characters  presented  by  the  first  nymphal 
instar,  and  one  on  those  of  adult  females.  Tables  are  also  given  for 
separating  the  genera  and  species  of  the  different  subfamilies. 

The  following  are  a  few  of  the  better-known  representatives  of 
this  family  found  in  this  country.  Several  subfamilies  not  mentioned 
here  are  represented  in  our  fauna. 


Subfamily  MONOPHLEBIN^ 

The  Giant  Coccids 

The  common  name  of  this  family 
was  suggested  by  the  large  size  of 
many  of  the  exotic  species.  The 
best-known  species  found  in  North 
America  is  of  moderate  size ;  this  is 
the  cottony-cushion  scale,  Icerya 
pUrchasi  (Fig.  524).  The  adult  fe- 
male measures  from  4  to  8  mm.  in 
length,  is  scale-like,  dark  orange- 
red,  and  has  the  dorsal  surface  more 
or  less  covered  with  a  white  or  yel- 
lowish white  powder.  It  secretes  a 
large,  longitudinally  ribbed  egg-sac, 
which  is  white  tinged  with  yellow. 
This  beautiful  insect  was  at  one  time 
the  most  dangerous  insect  pest  in 

California,  and  did  a  great  amount  of  _ 

injury.    It  is  an  introduced  Austra-   pjg.  ^^^.-Icerya  purchasi:  females, 
lian  species,  and  has  been  subdued       adults,    and    young    on    orange. 


450 


AN  INTRODUCTION  TO  ENTOMOLOGY 


to  a  great  extent  by  the  introduction  of  an   Australian    lady-bug, 
Roddlia  cardindlis. 

Subfamily  COCCIN^ 

The  Cochineal  Coccids 

This  subfamily  is  of  especial  interest  because  it  includes  the 
cochineal  insect,  Coccus  cacti.  This  is  a  native  of  Mexico,  but  occurs 
in  the  southern  United  States.  It  feeds  upon  various  species  of  the 
Cactacese.  It  has  been  extensively  cultivated  in  India,  Spain,  and 
other  countries.  The  adult  female  bears  some  resemblance  to  a 
mealy-bug,  but  differs  in  lacking  anal  lobes  and  an  anal  ring.  It 
excretes  a  mass  of  white  cottony  threads,  within  which  the  eggs  are 
laid.  The  dye-stuff  consists  of  the  female  insects,  which,  when  mature, 
are  brushed  off  the  plants,  killed,  and  dried.  The  entire  insect  is  used. 
Cochineal  is  now  being  superseded  by  aniline  dyes,  which  are  made 
from  coal-tar. 


Subfamily  ORTHEZIIN.E 


Fig.    525. — Orthezia, 
larged. 


greatly    en 


The  Ensign  Coccids 

Members  of  this  subfamily  occur 
not  uncommonly  on  various  weeds. 
They  are  remarkable  for  the  s^tti- 
metrically  arranged,  glistening,  white 
plates  of  excretion  with  which  the  body 
is  clothed.  Figure  525  represents  a 
nymph;  in  the  adult  female,  the  ex- 
cretion becomes  more  elongated  pos- 
teriorly, and  forms  a  sac  containing 
the  eggs  mixed  with  fine  down.  Later, 
when  the  young  are  bom,  they  excrete 
a  sufficient  amount  of  the  lamellar 
excretion  to  cover  them.  In  many 
species  the  egg-sac  is  held  in  a  more 
or  less  elevated  position;  this  fact 
suggested  the  common  name  ensign- 
coccids  for  these  insects.  Most  of  our 
species  belong  to  the  genus  Orthezia, 


Subfamily  ERIOCOCCIN^ 

The  Mealy-Bugs 

This  subfamily  includes  many  genera  and  species ;  the  best -known 
members  of  it  are  certain  mealy-bugs,  which  are  the  most  common 
and  noxious  of  greenhouse  pests.     These  insects  have  received  the 


HO  MO PT ERA 


451 


Fig.  527. — Pseudococciis  citri. 


Fig.    526. — Pseudococcus 
longispinosus. 


name  mealy-hugs  because  their  bodies  are  covered  with  a  fine  granular 

excretion,  appearing  as  if  they 

had  been   dusted   with   flour. 

The  females  are  active  nearly 

throughout    their   entire    life. 

The    males    make    a    cocoon 

early  in  their  nymphal  life  in 

which   they   remain   till   they 

emerge  as  adults. 

Figure  526  represents 
Pseudococcus  longispinosus,  a 
common  species  in  greenhouses; 
and  Figure  527,  Pseudococcus 

citri,   another  species  that   is       ilH^V     ^IBIf'    Mlilillliii"%  f/ 
found   in   greenhouses   in   the 
North.     The  latter  species  is 
also    a    well-known    pest    of 
orange  trees  in  the  South. 

Several  species  of  mealy- 
bugs of  the  genus  Ripersia  are 
found  in  the  nests  of  ants  of 
the  genus  Lasius. 

Subfamily  LECANIIN^ 


The  Tortoise-Scales 

The  tortoise-scales  are  so 
named  on  account  of  the  form 
of  the  body  in  many  species. 


Fig.  528. — Lecanium  hesperidum,  adult  fe- 
males, natural  size. 


452 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  most  striking  characteristic  of  this  subfamily  is  that  the  abdomen 
of  the  female  is  cleft  at  the  caudal  end,  and  at  the  cephalic  end  of  this 
cleft  there  is  a  pair  of  triangular  or  semicircular  plates,  the  anal  plates 
(Fig.  518). 

This  is  a  large  subfamily  including  many  genera  and  species. 
While  the  various  forms  agree  in  the  distinguishing  characteristics 
given  above,  there  are  great  differences  in  the  appearance  of  the  adult 
females.  Many  of  them  excrete  very  little  wax,  the  body  being 
practically  naked,  and  the  eggs,  or  the  young  in  the  viviparous  species, 


Fig.  529.    Saissetia  olece: 
enlarged. 


/,   adult   females  on  olive,  natural   size;   la,  female, 


are  deposited  beneath  the  body;  in  other  species,  although  the  body 
is  nearly  naked,  the  adult  female  excretes  a  large,  cottony  egg-sac; 
and  in  still  others  the  body  is  deeply  encased  in  wax. 

The  three  following  species  will  serve  as  examples  of  those  in 
which  the  body  is  naked  and  which  do  not  form  an  egg-sac. 

The  soft  scale,  Lecdnium  hesperidum. — This  is  the  commonest 
and  most  widely  spread  member  of  this  subfamily ;  it  infests  a  great 
variety  of  plants;  in  the  North,  it  is  very  common  in  greenhouses; 
in  the  warmer  parts  of  the  country  it  lives  out  of  doors.  The  adult 
female  is  nearly  fiat  (Fig.  528),  and  is  viviparous. 


HOMOPTERA 


453 


The  black  scale,  Saissetia  olecB. — This  is  a  well-known  pest,  es- 
pecially in  California,  where  it  infests  various  kinds  of  fruit-trees  and 
other  plants.  The  adult  fe- 
male is  dark  brown,  nearly 
black,  in  color;  nearly  hemi- 
spherical in  form  (Fig.  529), 
often,  however,  quite  a  little 
longer  than  broad.  There  is  a 
median  longitudinal  ridge  on 
the  back,  and  two  transverse 
ridges,  the  three  forming  a 
raised  surface  of  the  form  of  a 
capital  H. 

The  hemispherical  scale, 
Saissetia  hemisphcerica. — -The 
adult  female  is  nearly  hemi- 
spherical in  form,  with  the 
edges  of  the  body  flattened 
(Fig.  530).  This  species  is 
found  in  conservatories  every- 
where, and  in  the  open  air  in 
warmer  regions. 

Pulvindria. — Those  mem- 
bers of  this  subfamily  in  which 
the  adult  female  is  nearly 
naked  but  excretes  a  large 
cottony  egg-sac  beneath  or  be- 
hind the  body,  are  represented 
in  this  country  by  the  genus 
Pulvinaria,  of  which  we  have 
many  species.  Our  best -known 
species  are  the  two  following. 
The  cottony  maple-scale, 
Pulvindria  vitis. — This  species  is  common  on  maple,  osage  orange, 
grape,  and  other  plants.     Figure  531  represents  several  adult  females 

with  their  egg-sacs  on 
a  cane  of  grape. 

The  maple-leaf 
pulvinaria,  Pulvindria 
acertcola  .  —  This 
species  is  also  found 
on  maple.  It  differs 
from  the  preceding 
Fig.  531. — Pulvinaria  vitis.  species  in  that  the  egg- 

sac  is  much  longer 
than  the  body  of  the  female,  and  is  formed  on  the  leaves  instead  of 
on  the  stem  of  the  host. 

Ceroplastes. — -In  this  genus  the  body  of  the  female  is  covered  with 
thick  plates  of  wax.     More  than  sixty  species  have  been  described, 


MaTxAl 


Fig.  530. — Saissetia  hemisphcerica:  3,  adult 
females  on  orange,  natural  size;  ja, 
adult  female,  enlarged. 


454 


AN  INTRODUCTION  TO  ENTOMOLOGY 


several  of  which  are  found  in  the  southern  United  States ;  the  follow- 
ing will  serve  as  an  example  of  these  beautiful  insects. 

The  barnacle  scale,  Ceropldstes  cir- 
ripediformis. — Several  individuals  of 
this  species  are  represented  natural  size, 
and  one  enlarged,  in  Figure  532.  It 
infests  orange,  quince,  and  many  other 
plants. 

Subfamily  KERMESIIN^ 

The  Pseudogall  Coccids 

This  subfamily  includes  only  one 
genus,  Kermes.  Species  of  this  genus 
are  common  on  oaks  wherever  they 
grow.  These  insects  are  remarkable 
for  the  wonderful  gall-like  form  of  the 
adult  females.  So  striking  is  this  re- 
semblance, that  they  have  been  mis- 
taken for  galls  by  many  entomologists. 
Fig.  533  represents  a  species  of  this 
genus  upon  Quercus  agrifolia.  The  gall- 
like bodies  on  the  stem  are  adult  fe- 
males, the  smaller  scales  on  the  leaves 
are  immature  males. 

Subfamily  DIASPIDIN^ 

The  Armored  Scales 
Fig.  532.—Ceroplastes  cirripedi-  a>i,     r^-        -a-         ■      ^    a      ^u 

formis.  The  Diaspidmse  mcludes  those  coc- 

cids that  form  a  scale,  composed  in 
part  of  molted  skins  and  partly  of  an  excretion  of  the  insect,  beneath 
which  the  insect  lives.  It  is  on  account  of  this  covering  that  these 
scale-insects  are  named  the  armored  scales.  The  Diaspidinse  are  also 
characterized  by  a  coalescence  of  the  last  four  abdominal  segments 
so  as  to  form  what  is  known  as  the  pygidium;  this  peculiar  structure 
is  described  on  an  earlier  page. 

The  formation  of  the  scale  begins  immediately  after  the  close  of 
the  active  period  of  the  first  nymphal  instar.  At  this  time  the  young 
insect  settles  and  begins  to  draw  nourishment  from  its  host.  Soon 
after,  there  exude  from  the  body  fine  threads  of  wax,  the  commence- 
ment of  the  formation  of  the  scale.  At  the  close  of  the  first  stadiimi, 
the  molted  skin  is  added  to  the  scale  and  forms  a  part  of  it.  This  is 
also  true,  except  as  noted  below,  of  the  second  molted  skin  of  the 
female  (Fig.  534,  2b  and  2c).  In  the  formation  of  the  scale  of  the 
male  only  the  first  molted  skin  is  added  to  the  scale  (Fig.  534,  2d). 
The  scales  of  males  can  be  distinguished  by  this  fact,  and,  too,  they  are 
much  smaller  than  the  scales  of  females. 


HOMOPTERA 


455 


In  a  few  genera  the  female  does  not  molt  the  second  exuviae* ; 
the  body  shrinks  away  from  it,  and  transforms  within  it.  In  such 
cases  is  it  termed  a  puparium.  Figure  535  represents  the  scale  of 
Fionnia  fiormice;  here  the  pupariiim  can  be  seen  through  the  trans- 
parent scale. 


Fig-  533- — Kermes  sp.  on  Quercus  agrifolia:    adult  females  on  the  stem;  immature 
males  on  the  leaves. 


The  shape  of  the  scale,  and  the  position  of  the  exuviae  on  it,  fur- 
nish characters  that  are  very  useful  in  the  classification  of  the 
Diaspidins. 

To  this  subfamily  belong  some  of  the  most  serious  pests  of  shrubs 
and  trees,  as,  for  example,  the  San  Jose  scale  and  the  oyster-shell  scale. 
The  following  are  a  few  of  the  many  well-known  species  of  this  very 
important  subfamily. 

*The  term  exuvice  is  a  Latin  word  which  had  no  singular  form,  the  plural 
noun  being  used  as  is  in  English  the  word  clothes.  Some  recent  writers  use  the 
term  exuvia  for  a  single  molted  skin. 


456 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  purple  scale,  Lepidosaphes  pinncBjormis. — This  scale-insect  is 
well  known   in   the   orange-growing   sections   of  this   and  of  other 


JttKiS. 


Fig.  534. —  Chionaspis  pinifolicE:  2,  scales  on  Pinus  strobiis,  natural  size,  leaves 
stunted;  2a,  leaves  not  stunted  by  coccids;  2b,  scale  of  female,  usual  form, 
enlarged;  2C,  scale  of  female,  wide  form,  enlarged;  2d,  scale  of  male,  enlarged. 


countries.     It  is  one  of  the  two  most  common  scale-insects  found  on 

citrus  trees  in  Florida.    The  scales  of  this  species  are  represented  in 

Figure  536;  they  are  represented  natural  size  on  the  leaf,  and  greatly 

enlarged  in  the  other  figures.    The  scale  of  the  female 

§is  long,  more  or  less  curved,  and  widened  posteriorly 
(Fig.  536,  la  and  ih) ;  the  first  of  these  two  figures  repre- 
sents the  dorsal  scale,  and  the  second  the  ventral  scale, 
which  is  well  developed  in  this  species.  Some  eggs  can 
be  seen  through  a  gap  in  the  ventral  scale.  The  scale 
of  the  male  (Fig.  536,  ic)  is  usually  straight  or  nearly  so. 
@  At  about  one-quarter  of  the  length  of  the  scale  from  the 
posterior  extremity,  the  scale  is  thin,  forming  a  hinge 
which  allows  the  posterior  part  of  it  to  be  lifted  by  the 
male  as  he  emerges.  While  this  insect  is  chiefly  known 
as  a  pest  of  citrus  trees,  it  has  been  found  on  several 
other,  species  of  plants.  It  has  been  described  under  several  different 
names;  for  a  long  time  it  was  known  as  Mytildspis  citrlcola. 


Tig.  535— -F"*- 
orinia  fiorimcB 


HOMOPTERA 


457 


Glover's  scale,  Lepidosaphes  gloverii. — This  is  the  second  of  the 
two  most  common  species  of  scale-insects  found  on  citrus  trees  in 
Florida.  In  this  species  the  scale  of  the  female  is  much  narrower  than 
that  of  the  preceding  species.  This  species  is  widely  distributed  over 
the  warmer  parts  of  the  world. 

The  oyster-shell  scale,  Lepidosaphes  ulmi. — This  is  a  northern  rep- 
resentative of  the  genus  to  which  the  two  preceding  species  belong. 
It  is  closely  allied  to  the  purple  scale;  in  fact  Figure  536  would  serve 
to  illustrate  this  species  except  that  it  does  not  occur  on  orange  and 
that  it  is  found  chiefly  on  the  trunk  of  its  host.  The  two  species  differ 
in  the  characters  presented  by  the  pygidium.     The  oyster-shell  scale  is 


Fig-  536- — Lepidosaphes  pinnceformis :  i,  scales  on  orange,  natural  size;  la, 
scale  of  female,  dorsal  view,  enlarged;  ib,  scale  of  female  with  ventral  scale  and 
eggs,  enlarged;  ic,  scale  of  male,  enlarged. 

a  cosmopolitan  insect,  and  it  infests  very  many  species  of  shrubs  and 
trees.  In  the  North  it  is  the  commonest  and  best-known  scale-insect 
infesting  fruit-trees  and  various  ornamental  shrubs.  It  is  discussed 
in  all  of  our  manuals  of  fruit-insects ;  in  some  of  them  it  is  described 
under  the  name  Mytildspis  pomorum. 

The  scurfy  scale,  Chiondspis  furftira. — This,  like  the  preceding 
species,  is  a  very  common  pest  of  the  apple  and  various  other  trees 
and  shrubs;  but  usually  it  is  not  very  destructive.  In  this  species 
the  scale  of  the  female  is  widened  posteriorly,  and  bears  the  exuviae 
at  the  anterior  end  (Fig.  5 1 2 ,  /c) .  The  scale  of  the  male  is  very  small, 
being  only  .75  mm.  in  length,  narrow,  and  tricarinated  (Fig.  512,  la). 


458 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  pine-leaf  scale,  Chionaspis  pinifolicB: — This  is  a  very  common 
pest  of  pine,  spruce,  and  other  coniferous  trees,  throughout  the 
United  States  and  Canada.  It  infests  the  leaves  of  its  various  hosts. 
The  scale  of  the  female  is  snowy  white  in  color,  with  the  exuviae 
light  yellow;  it  is  usually  long  and  narrow,  as  represented  in  Figure 
534,  2h;  but  on  the  broader-leaved  pines  it  is  often  of  the  form  shown 


Fig.  537. — Aulacaspis  rosce:  i,  scales  on  rose,  natural  size;  la,  scale  of  female, 
enlarged;  ib,  scale  of  male,  enlarged. 


at  2c  in  the  figure ;  this  is  the  typical  form  of  the  scale  of  the  female 
in  the  genus  Chionaspis. 

The  rose-scale,  Aulacaspis  rosce. — This  species  infests  the  stems 
of  roses,  blackberry,  raspberry,  dewberry,  and  some  other  plants. 
The  infested  stems  often  become  densely  coated  with  the  scales. 
The  scale  of  the  female  is  circular,  snowy  white,  with  the  exuviae  light 
yellow  and  upon  one  side  (Fig.  537,  la).  The  scale  of  the  male  is  also 
white;  it  is  long,  tricarinated,  and  with  the  exuviae  at  one  end  (Fig. 
537,  ih);  it  measures  1.25  mm.  in  length. 

The  San  Jose  scale,  Comstockaspis  perniciosa. — The  San  Jose  scale 
was  first  described  by  the  writer  in  1881,  under  the  name  Aspidiotus 
perniciosus.  It  has  since  been  made  the  type  of  a  new  genus,  Com- 
stockaspis, by  MacGillivray  ('21).  At  the  time  it  was  described  it 
was  known  only  in  Santa  Clara  County,  California.    But  in  describing 


HOMOPTERA  459 

it,  notwithstanding  its  limited  distribution,  I  stated:  "From  what  I 
have  seen  of  it,  I  think  that  it  is  the  most  pernicious  scale-insect 
known  in  this  country."  Since  that  time  it  has  become  widely  dis- 
tributed. Slingerland  and  Crosby  write  of  it  as  follows:  "The  San 
Jose  scale  has  attained  greater  notoriety,  has  been  the  cause  of  more 
legislation,  both  foreign  and  interstate,  and  has  demonstrated  its 
capabilities  of  doing  more  injury  to  the  fruit  interests  of  the  United 
States  and  Canada  than  any  other  insect." 

This  species  infests  various  fruit-trees  and  ornamental  shrubs ;  it 
infests  the  bark,  leaves,  and  fruit  of  its  hosts,  and  usually  causes 
reddish  discolorations  of  the  bark  and  of  the  skin  of  the  fruit. 

This  species  can  be  distinguished  from  the  other  scale-insects 
that  are  important  pests  of  our  fruit-trees  by  the  form  of  the  scales. 
The  scale  of  the  female  is  circular  and  flat,  with  the  exuviae  central, 
or  nearly  so.  The  scale  is  gray,  excepting  the  central  part,  that  which 
covers  the  exuviae,  which  varies  from  a  pale  yellow  to  a  reddish  yellow. 
It  measures  2  mm.  in  diameter.  The  scale  of  the  male  is  black,  and  is 
somewhat  elongate  when  fully  formed.  The  exuviae  is  covered  with 
secretion;  its  position  is  marked  by  a  nipple-like  prominence  which 
is  between  the  center  and  the  anterior  margin  of  the  scale. 

Control  of  scale-insects. — The  extensive  damage  that  has  been  done 
by  scale-insects  to  fruit-trees  and  to  cultivated  shrubs  has  led  to  many 
experiments  in  the  destruction  of  these  insects.  The  results  have  been 
quite  satisfactory ;  with  proper  care,  it  is  now  possible  to  keep  in 
check  the  ravages  of  these  pests.  Detailed  accounts  of  the  methods 
to  be  employed  are  given  in  many  easily  available  publications,  and 
especially  in  bulletins  of  experiment  stations. 

In  the  case  of  deciduous  trees  and  shrubs,  the  best  time  to  destroy 
scale-insects  infesting  them  is  during  the  winter,  when  the  trees  are 
bare  and  in  a  dormant  state.  At  this  time  the  entire  tree  can  be 
reached  with  sprays,  without  the  interference  of  leaves;  and,  too, 
certain  sprays  can  be  safely  used  that  are  liable  to  injure  the  trees 
during  the  growing  season.  This  is  especially  true  of  the  lime-sulphur 
mixture,  which  is  very  widely  used  for  the  destruction  of  scale-insects, 
and  is  very  effective.  Among  the  other  insecticides  used  for  this 
purpose  are  kerosene  emulsion  and  dilute  miscible  oils.  For  summer 
spraying,  whale-oil  soap,  one  pound  dissolved  in  four  or  five  gallons 
of  water,  can  be  safely  used. 

In  the  case  of  trees  that  are  constantly  clothed  with  foliage,  the 
effective  use  of  sprays  is  more  difficult.  In  the  orange-growing  sections 
of  California  the  trees  are  fumigated  with  hydrocyanic  acid  gas,  the 
tree  to  be  treated  being  first  covered  with  a  large  tent. 


CHAPTER  XXII 
ORDER  DERMAPTERA* 

The  Earwigs 

The  winged  members  of  this  order  usually  have  four  wings;  but 
in  some  of  them  the  hind  wings  are  vestigial  or  wanting;  the  fore  wings 
are  leathery,  very  small,  without  veins,  and  when  at  rest  meet  in  a  straight 
line  on  the  back;  the  hind  wings,  when  well  developed,  are  large,  with 
radiating  veins,  and  when  at  rest  are  folded  both  lengthwise  and  crosswise. 
The  mouth-parts  are  formed  for  chewing.  The  caudal  end  of  the  body  is 
furnished  with  a  pair  of  appendages,  the  cerci,  which  resemble  forceps. 
The  metamorphosis  is  gradual. 

This  order  includes  only  the  earwigs.  These  are  long  and  narrow 
insects,  resembling  rove-beetles  in  the  form  of  the  body  and  in  having 
short  and  thickened  fore  wings,  which,  when 
at  rest,  meet  in  a  straight  line  on  the  back  (Fig. 
538);  but  the  earwigs  are  easily  distinguished 
from  rove-beetles  by  the  presence  of  a  pair  of 
forceps-like  appendages  at  the  caudal  end  of  the 
body. 

The  common  name,  earwig,  was  given  to 
these  insects  in  England,  and  has  reference  to  a 
widely  spread  fancy  that  these  insects  creep 
into  the  ears  of  sleeping  persons.    Other  similar 
\/        fl  ^m  I         names  are  applied   to  them  in  Europe,  Ohr- 
•*'      y  JHbLs        Wurm  in  Germany  and  perceoreille  in  France. 
^     ^/iflBi  '^■^^  earwigs  are  rare  in  the   northeastern 

"  ^H™  1         United  States  and  Canada,  but  are  more  often 
found  in  the  South  and  on  the  Pacific  Coast. 
In  Europe  they  are  common,  and  often  trouble- 
some pests,  feeding  upon  the  corollas  of  flowers, 
fruits,    and  other   vegetable  substances.      Al- 
though they  are  probably  chiefly  herbivorous, 
some  species  are  carnivorous,  feeding  on  other 
insects,  and  some  are  probably  scavengers,  as 
they  have  been  found  with  rove-beetles  about 
decaying  animal  matter.    They  are  nocturnal,  hiding  in  the  day-time 
among  leaves  and  in  all  kinds  of  crevices,  and  coming  out  by  night; 
sometimes  they  are  attracted  to  lights. 

Earwigs  are  small  or  of  moderate  size;  the  living  species  measure 
from  2.5  to  37  mm.  in  length.  The  body  is  narrow  and  flat.  The 
mouth-parts  are  fitted  for  chewing,  and  resemble  in  their  more 
general  features  those  of  the  Orthoptera ;  minute  but  distinct  parag- 
natha  are  present ;  and  the  second  maxillae  are  incompletely  fused. 

*Dermaptera:  derma  (d4pfj.a),  skin;  pteron  {Trrepdv),  a  wing. 
(460) 


Fig.    538.— An 

Labia  minor,  male. 


earwig. 


DERMAPTERA 


461 


The  compound  eyes  are  rather  large;  but  the  ocehi  are  wanting. 
The  antennas  are  slender,  and  consist  of  from  ten  to  thirty-five  seg- 
ments; the  second  segment  is  always  small.  The  fore  wings  are  leath- 
ery, very  short,  without  veins,  and  when  at  rest  meet  in  a  straight  line 
on  the  back.  This  pair  of  wings  is  commonly  termed  the  tegmina 
or  the  elytra.  The  hind  wings,  when  fully  developed,  are  large,  with 
radiating  veins,  and  when  at  rest  are  folded  both  lengthwise  and 
crosswise.  The  folded  hind  wings  project  a  short  distance  behind 
the  fore  wings  (Fig.  538).  The  radiating  veins  of  the  hind  wings  extend 
from  a  point  near  the  middle  of  the  length  of  the  wing  (Fig.  539). 
When  the  wing  is  not  in  use,  that  part  over  which  the  radiating 
veins  extend  is  folded  in  plaits  like  a  fan,  after  which  the  wing  is  folded 
twice  crosswise.    This  part  of  the  wing  is  the  greatly  expanded  anal 


Fig.  539. — Hind  wing  of  an  earwig:  nf,  nodal  furrow. 


area.  The  preanal  area  is  much  reduced  and  contains  only  two 
longitudinal  veins ;  this  area  is  quite  densely  chitinized.  The  trachea- 
tion  of  the  hind  wings  has  been  described  and  figured  by  the  writer 
(Comstock  '18).  The  wings  vary  much  in  size  and  development  even 
in  the  same  species ;  and  there  are  many  species  that  are  wingless. 
The  legs  are  similar  in  form,  and  the  tarsi  are  three-jointed. 

The  most  distinctive  feature  of  earwigs  is  the  form  of  the  cerci, 
which  are  forceps-like,  and  usually  very  prominent.  A  similar  form 
of  cerci  is  found,  however,  in  the  genus  Japyx  of  the  order  Thysanura. 
The  size  and  shape  of  the  forceps  of  earwigs  differ  in  the  different 
species  and  in  the  two  sexes  of  the  same  species;  they  are  usually 
more  highly  developed  in  the  male  than  in  the  female;  they  are  used 
as  organs  of  defense  and  offense,  in  pairing,  and  are  sometimes  used 
as  an  aid  in  folding  the  wings. 


462 


AX  INTRODUCTIOX  TO  ENTOMOLOGY 


? 


->/^- 


/ 


Fig.  541.  — Pro- 
lahia  pidchella 
hurgessi,ra2\Q. 
(From  Rehn 
and  Hebard.) 


Certain  ean\-igs  possess  stink-glands,  which  open  through  tuber- 
cles situated  one  on  each  side  near  the  hind  margins  of  the  second 
and    third  visible  abdominal   segments;   from    which,   it    is    said, 
they  can  squirt  a  foul-smelling  fluid  to 
a   distance   of  three  or    four    inches. 
These    tubercles   are    represented   in 
Figure    543. 

The  sexes  can  be  distinguished  by  .     .^_^ 

the  smaller  size  of  the  forceps  of  the    ^/^:^^\ 
female,  and  by  the  fact  that  in  the   •^'Kr^--^N 
female  there  are  distinctly  visible  only 
six    abdominal    sterna,    while  in    the 
^  .  I  |^^»  male  there  are  eight. 

/^/«rR\^  In  some  earwigs  the  two  efferent 

ducts  of  the  reproductive  organs  open^. 
separately. 

The  metamorphosis  is  gradual,  the 
yotmg  resembling  the  adult  in  form, 
and  the  wings  developing  externally. 
The  female  is  said  to  brood  over  the 
eggs,  but  to  abandon  the  young  soon  after  the}  are 
hatched. 

Fig.    540.— LoWa         The    order    Dermaptera    was    estabHshed    by 

minor,    female,   Latreille  in  1 83 1,  and  again  by  Westwood  in  1839 

and  end  of  ab-  i^^er  the  name  Euplexoptera.    This  later  name  has 

maS'^    %rom  been  used  by  many  authors,  including  the  writer;  but 

Lugger.)  the  older  name  should  be  adopted.    The  species  of 

the  world  have  been  monographed  by  Burr  ('11). 

Ear\\-igs  are  cosmopolitan  insects,  and  are  easily  transported  by 

commerce;  consequently  exotic  species  are  liable  to  be  found  near 

seaports;  and  some  such  species  have  become  established  in  this 

country. 

The  order  is  a  comparativeh"  small  one ;  only  about  four  himdred 
living  species  have  been  described,  and  these  are  mostly  tropical  or 
semi-tropical.  The  native  and  the  exotic  species  that  have  become 
established  in  America  north  of  Mexico  number  together  only  fifteen; 
among  these  are  the  following. 

Theseaside  earwig,  Anisolabis  mariiima . — In  this  species  both  pairs 
of  wings  are  wanting,  the  antennae  are  24-jointed,  and  the  length  of 
the  body  is  from  18  to  20  mm.  This  earwig  is  fotind  along  the  coast 
from  Maine  to  Texas. 

The  ring-legged  earwig,  Anisolabis  anntllipes. — This  is  also  a 
wingless  species.  It  differs  from  the  preceding  in  that  the  antennas 
are  only  15-  or  i6-jointed,  the  body  is  about  half  as  long,  and  the  legs 
are  ringed  with  fuscous.  Its  range  does  not  extend  as  far  north  as 
that  of  the  seaside  eans'ig,  but  it  extends  farther  inland. 

The  little  ean%-ig.  Labia  minor. — In  this  species  the  body  is  thickly 
clothed  with  fine  yellowish  pubescence.  It  is  a  small  species,  the  body 
measuring  only  from  4  to  5  mm.  in  length.  Figure  538  represents  the 
male,  natural  size  and  greatly  enlarged;  and  Figure  540,  the  female, 


DERMAPTERA 


463 


with  the  end  of  the  abdomen  of  the  male  below.  This  species  is  widely 
distributed  in  the  United  States  and  is  the  only  species  estabhshed  in 
Canada. 

The  handsome  earwig,  Proldbia  pulchella. — This  species  is  widely 
distributed  over  the  southern  United  States;  it  is  found  under  the 
bark  of  dead  trees.  The  body  is  dark  chestnut-brown,  shining  and 
glabrous.  It  measures  from  6  to  6.5  mm.  in  length.  This  species  is 
dimorphic;  in  one  form,  known  as  burgessi  (Fig.  541),  the  hind  wings 
are  shorter  than  the  tegmina.    This  is  one  of  our  few  native  species. 

The  spine-tailed  earwig,  Doru  aculedtum. — In  the  genus  to  which 
this  species  belongs,  the  pygidium  of  the  male  is  armed  with  a  distinct 


Fig.  ^^2.—Doni  acii- 
leatum,  male.  (From 
Blatchley.) 


Fig.  543. — Forficula  aiiricularia:  A, 
male  with  short  forceps;  B,  forceps 
of  female;  C,  long  type  of  forceps 
of  male.      (After  Morse.) 


tubercle  or  spine  (Fig.  542) .  This  species  is  dark  chestnut-brown,  with 
the  palpi,  legs,  edges  of  pronotum,  and  the  outer  two-thirds  of  the 
tegmina  yellow.  The  hind  wings  are  usually  aborted.  The  length 
of  the  body  is  7.5  to  11  mm.  The  range  of  tliis  species  extends  from 
New  Jersey  and  southern  Michigan  west  and  south  to  Nebraska, 
Georgia,  and  Louisiana. 

The  common  European  earwig,  Forficula  auriculdria. — In  this 
species  and  in  the  preceding  one  as  well,  the  second  tarsal  segment  is 
lobed  and  prolonged  beneath  the  third ;  but  the  two  species  can  be 
distinguished  by  the  shape  of  the  forceps  of  the  male  (Fig.  543). 
The  males  of  this  species  are  dimorphic;  in  one  form  the  forceps 
average  about  4  mm.  in  length,  in  the  other  about  7  mm.  This 
common  European  species  appeared  in  great  numbers  at  Newport, 
Rhode  Island,  about  191 2. 


CHAPTER  XXIII 
ORDER  COLEOPTERA* 

The  Beetles 

The  winged  members  of  this  order  have  Jour  wings;  but  the  first  pair 
of  wings  are  greatly  thickened,  forming  a  pair  of  "wing-covers''  or 
elytra,  beneath  which  the  membranous  hind  wings  are  folded  when  at  rest. 
The  elytra  meet  in  a  straight  line  along  the  middle  of  the  back  and  serve 
as  armor,  protecting  that  part  of  the  body  which  they  cover.  The  mouth- 
parts  are  formed  for  chewing.     The  metamorphosis  is  complete. 

The  order  Coleoptera  includes  only  the  beetles.  These  insects  can 
be  readily  distinguished  from  all  others  except  the  earwigs  by  the 
structure  of  the  fore  wings,  these  being  homy, 
veinless  "wing-covers"  or  el\i:ra,  which  meet 
in  a  straight  line  along  the  middle  of  the 
back  (Fig.  544);  and  they  differ  from  ear- 
wigs in  lacking  pincer-like  appendages  at 
the  caudal  end  of  the  body.  Beetles  also 
differ  from  earwigs  in  having  a  complete 
metamorphosis. 

Only  a  few  modifications  of  the  typical 
characteristics  exist  in  this  order;  among  the 
Fig.  $^.—Desmocerus  pal-     ^nore  familiar  of  these  are  the  following :  in 
liatus.  some  of  the  Meloidas  the  elytra  do  not  meet 

in  a  straight  line ;  in  many  of  the  Carabidae, 
Curculionidse,  et  al.,  the  hind  wings  are  wanting,  and  in  some  of  these 
the  elytra  are  grown  together ;  in  a  few  females  of  the  Lampyridae  and 
Phengodidae  both  pairs  of  wings  are  wanting. 

The  different  mouth-parts  are  ven^  evenly  developed;  we  do  not 
find  some  of  them  greatly  enlarged  at  the  expense  of  others,  as  in 
several  other  orders  of  insects.  The  upper  lip,  or  labrum,  is  usually 
distinct;  the  mandibles  are  powerful  jaws  fitted  either  for  seizing 
prey  or  for  gnawing;  the  maxillas  are  also  well  developed  and  are 
quite  complicated,  consisting  of  several  distinct  pieces;  the  maxillary 
palpi  are  usually  prominent;  and  the  lower  lip,  or  labium,  is  also  well 
developed  and  complicated,  consisting  of  several  parts  and  bearing 
prominent  labial  palpi.  Detailed  figures  of  the  maxillas  and  labiiim 
of  beetles  are  given  in  Chapter  II. 

In  the  classification  of  beetles  much  use  is  being  made  of  the 
variations  in  form  of  the  ventral  and  lateral  sclerites  of  the  thorax. 
Figure  545  will  serv^e  as  an  illustration  of  these  sclerites.  One  feature 
merits  special  mention:  the  coxae  of  the  hind  legs  are  flattened  and 
immovably  attached  to  the  thorax  so  that  they  appear  to  be  a  part 
of  the  thorax  instead  of  the  basal  segment  of  an  appendage. 

Coleoptera:  coleos  {hoKebs),  a  sheath;  pteron  {irrepby),  a  wing. 
(464) 


COLEOPTERA 


465 


Almost  the  only  use  that  has  been  made  of  the  characteristics  of 
the  wings  has  been  restricted  to  certain  features  of  the  elytra,  those 
that  can  be  seen  with- 
out spreading  the 
wings.  These  are  the 
shape  of  the  elytra, 
the  presence  or  ab- 
sence of  strise,  the  pres- 
ence or  absence  of 
punctures  and  their 
distribution  when 
present,  and  the  pres- 
enceor  absence  of  sets, 
pubescence,  or  scales 
on  the  surface  of  the 
elytra.  A  beginningha  s 
been  made,  however, 
to  make  use  of  the 
venation  of  the  hind 
wings;  this,  as  yet,  is 
restricted  to  an  indi- 
cation of  the  type  of 
wing-venation  charac- 
teristic in  each  case  of 
the  superfamilies. 

The  venation  of 
the  wings  of  the  Cole- 
optera  has  become 
greatly  modified,  and, 
consequently,  the  de- 
termination of  the  ho- 
mologies of  the  wing- 
veins  is  a  difficult  mat-  Fig-  545- — Ventral  aspect  of  a  beetle,  Enchroma  gigan- 
ter.  The  transforma-  /^a."  ^,  prothorax;  5,  mesothorax;  C,  metathorax; 
tion  of  the  fore  wintrc  ^'  ^'  ^'  ^°^^'  ^^'  ^^'  ^^'  epimera;  es,  es,  es,  epis- 
tion  Ol  tne  lOre  wmgs  ^^^^^.  ^_  ^_  ^^  sterna;  /,  /,  trochantins;  x,  elytrum; 
mtO  elytra  has  result-  y^  antecoxal  piece  of  metasternum. 
ed  in  a  great  reduction  of' their  venation;  and  the  foldings  of  the  hind 
wings  interrupt  the  veins  and  cause  distortions  in  their  courses. 

It  is  only  recently  that  extended  studies  of  the  wing-venation 
of  the  Coleoptera  have  been  made,  and  the  conclusions  reached  by 
the  different  investigators  are  not  fully  in  accord.  But  much  progress 
has  been  made,  and  so  much  interest  is  being  shown  in  the  subject 
that  we  can  confidently  expect  that  conclusions  will  soon  be  reached 
that  can  be  generally  accepted. 

Among  the  recent  studies  of  the  subject  is  an  extended  one  by 
Dr.  Wm.  T.  M.  Forbes  ('22  b),  in  which  the  venation  of  the  hind  wings 
of  more  than  fifty  species  of  beetles  are  figured.  The  accompanying 
figures  (Figs.  546-547),  copied  from  Dr.  Forbes'  paper,  will  serve  to 
illustrate  his  conclusions  regarding  the  homologies  of  the  wing-veins 


466 


AN  INTRODUCTION  TO  ENTOMOLOGY 


of  beetles.    Another  recent  paper  in  which  the  venation  of  the  wings 
of  many  beetles  is  figured  is  that  of  Graham  ('22). 


Fig.   546. — Tracheation  of  wing  of  imago  of   Calosoma.      (From  Forbes.) 


arc-^  *hum 


fthA,  -     -  3dA; 

Fig.  547. — Tracheation  of  wing  of  imago  of  Dysliscus  verticalis.     (From  Forbes.) 


Beetles  undergo  a  complete  metamorphosis.  The  larvag,  which 
are  commonly  called  grubs,  var}^  greatly  in  form;  some 
are  campodeiform,  others  are  scarabeiform,  and  some 
are  vermiform.  In  some  members  of  the  order  there 
is  a  hypermetamorphosis,  the  successive  larv^al  instars 
representing  different  types  of  larvae;  this  is  true  of 
members  of  the  Meloidae  and  Micromalthidffi.  Oc- 
casionally individuals  of  Tenehrio  molitor  are  found  in 
which  the  wings  are  developed  externally.  The  pupse 
are  exarate,  that  is,  the  limbs  are  free  (Fig.  548).  These 
insects  usually  transform  in  rude  cocoons  made  of 
earth  or  of  bits  of  wood  fastened  together  by  a  viscid 
substance  excreted  by  the  larvae.  Many  wood-burrowing  species 
transform  in  the  tunnels  made  bv  the  larva? ;  and  some  of  the  Dermes- 


Fig.  548.— Pu- 
pa of  a  bee- 
tle. 


COLEOPTERA  467 

tidce  as  well  as  some  of  the  Coccinellidse  transform  in  the  last  larval 
skin. 

Both  larvae  and  adults  present  a  very  wide  range  of  habits.  While 
the  majority  of  the  species  are  terrestrial,  the  members  of  several 
families  are  aquatic ;  and  while  some  feed  on  vegetable  matter,  others 
feed  upon  animal  matter.  The  vegetable  feeders  include  those  that 
eat  the  living  parts  of  plants,  those  that  bore  in  dead  wood,  and  those 
that  feed  upon  decaying  vegetable  substances.  Among  the  animal 
feeders  are  those  that  are  predacious,  those  that  feed  on  dried  parts 
of  animals,  and  those  that  act  as  scavengers,  feeding  on  decaying 
animal  matter.  Viewed  from  the  human  standpoint,  some  species 
are  very  beneficial,  others  are  extremely  noxious. 

The  Coleoptera  is  a  very  large  order;  in  the  "Catalogue  of  the 
Coleoptera  of  America,  North  of  Mexico"  by  Leng  ('20),  18,547 
species  are  listed;  these  represent  109  families.  The  order  is  divided 
into  two  suborders,  the  Adephaga  and  the  Polyphaga.  In  each  of  the 
suborders  the  families  are  grouped  into  superfamilies,  two  in  the 
Adephaga  and  twenty  in  the  Polyphaga;  and  in  the  suborder 
Polyphaga  the  superfamilies  are  grouped  into  seven  series  of 
superfamilies. 

Students  of  the  Coleoptera  are  not  fully  agreed  as  to  some  of  the 
details  of  this  classification ;  but  as  this  catalogue  will  doubtless  serve, 
for  a  long  time,  in  this  country,  as  a  guide  for  the  arrangement  of 
collections,  it  seems  best  to  follow  it  in  this  introductory  text-book. 
Some  of  the  places  where  there  is  a  lack  of  agreement  among  the 
authorities  are  indicated  in  the  conspectus  on  page  38  of  the  Catalogue. 

SYNOPSIS  OF  THE  COLEOPTERA 

{Tables  for  determining  the  families  are  given  below) 

I.  SUBORDER    ADEPHAGA 

This  suborder  includes  the  first  seven  families,  the  Cicindelidas  to  the  Gyrinidae 
inclusive,  pages  476  to  484.  The  family  Rhysodidse  (page  508)  is  also  included 
in  this  suborder  by  some  writers. 

II.  SUBORDER  POLYPHAGA 

This  suborder  includes  all  but  the  first  seven  families,  or  the  first  eight  if  the 
Rhysodidae  be  included  in  the  Adephaga. 

The  families  of  this  suborder  are  grouped  into  seven  series,  as  follows: — 

SERIES   I. — THE   PALPICORNIA 

This  series  includes  a  single  family,  the  HydrophilidjE ;  page  485. 

SERIES   II. — THE    BRACHELYTRA 

This  series  includes  fifteen  families,  the  Platypsyllidse  to  the  Histeridse,  in- 
clusive, pages  486  to  490. 

SERIES    III. — THE    POLYFORMIA 

This  series  includes  forty-three  families,  the  Lycidae  to  the  Nosodendridas, 
inclusive,  pages  491  to  508. 

SERIES    IV. — THE   CLAVICORNIA 

This  series  includes  thirty  families,  if  the  Rhysodidae  be  placed  here  instead  of 
in  the  suborder  Adephaga;  these  are  the  families  Rhysodidae  to  Cisidas,  in- 
clusive, pages  508  to  215. 


468 


AN  INTRODUCTION  TO  ENTOMOLOGY 


SERIES   V. — THE  LAMELLICORNIA 

This  series  includes  four  families,  the  Scarabaeidae,  theTrogidae,  the  Lucanidae, 
and  the  Passalidce,  pages  515  to  524. 

SERIES   VI. — THE    PHYTOPHAGA 

This  series  includes  three  families,   the  Cerambycidae,   the    Chrysomelidae , 
and  the  Mylabridae,  pages  524  to  535. 

SERIES    VII. — THE    RHYNCHOPHORA 

This  series  includes  six  families,  the  Brentidas  to  the  Scolytidae,  inclusive, 
pages  536  to  542. 

TABLES  FOR  DETERMINING  THE  FAMILIES  OF  THE  COLEOPTERA 

TABLE  I.— THE  SUBORDERS  AND  THE  SERIES  OF  SUPERFAMILIES 

A.  Ventral  part  of  the  first  segment  of  the  abdomen  divided  by  the  hind  coxal 
cavities,  so  that  the  sides  are  separated  from  the  very  small  medial  part. 
Suborder  Adephaga;  see  Table  II,  below. 

AA.  Ventral  part  of  the  first  segment  of  the  abdomen  visible  for  its  entire 
breadth.     Suborder  Polyphaga. 


Fig.  549. — Head  of  Harpalus,  ven- 
tral aspect:  a,  antenna;  g,  g, 
gula;  ga,  galea  or  outer  lobe  of 
the  maxilla;  gs,  gular  suture;  Ip, 
labial  palpus;  m,  m,  mandibles; 
mp,  maxillary  palpus;  s,  submen- 
tum. 


Fig.  550. — Prothorax  of  Harpalus, 
ventral  aspect:  c,  coxa;  em,  epi- 
merum ;  es,  episternum ;  /,  femur ; 
n,  pronotum;  s,  s,  5,  prosternum. 


B.     Head  not  prolonged  into  a  narrow  beak,  palpi  always  flexible;  two  gula 
sutures  at  least  before  and  behind  (Fig.  549) ;  sutures  between  the  prosternum 
and  the  episterna  and  epimera  distinct  (Fig.  550) ;  the  epimera  of  the  pro- 
thorax  not  meeting  on  the  middle  line  behind  the  prosternum  (Fig.  550). 
C.     Abdomen  with  at  least  three  corneous  segments  dorsally,  and  exposed 
more  or  less  by  the  short  elytra.    Hind  wings  with  simple,  straight  veins; 
antennffi  variable,  but  never  lamellate.  Series  Brachelytra,  See  Table 
III,  below. 
CC.    Abdomen  with  at  most  two  corneous  segments  dorsally,  usually  com- 
pletely covered  by  the  elytra;  hind  wings  with  veins  in  part  connected 
by  recurrent  veins. 
D.    Antennae  clubbed  or  not,  but  if  clubbed  not  lamellate. 

E.  Tarsi  usually  apparently  four-jointed,  the  real  fourth  segment 
being  reduced  in  size  so  as  to  form  an  indistinct  segment  at  the 
base  of  the  last  segment,  with  which  it  is  immovably  united  (Fig. 
551,  A);  the  first  three  segments  of  the  tarsi  dilated  and  brush-like 
beneath;  the  third  segment  bilobed.     In   two  genera,  Parandra  and 


COLEOPTERA 


469 


Spondylis,  the  fourth  segment  of  the  tarsus,  although  much  reduced 
and  immovably  united  with  the  fifth,  is  distinctly  visible,  the  first  three 


Fig-  551- — Tarsi  of  Phytophaga:  ^.typical;  B, 
Spondylis;  C,  Parandra. 


segments  are  but  slightly  dilated,  and  the  third 
is  either  bilobed,  Spondylis  (Fig.  551,  5),  or  not, 
Parandra  (Fig.  551,  C).       Series  Phytophaga. 
See  Table  VI,  below. 
EE.    Tarsi  varying  in  form  and  in  the  number  of 
the  segments,  but  when  five-jointed  not  of  the 
type  described  under  E  above,  the  joint  be- 
tween the    fourth    and    fifth    segments  being 
flexible.  Series  Palpicornia,  Polyformia,  and 
Clavicornia.      See  Table  IV,  below. 
DD.       Antennas  with  a  lamellate  club.    Series  Lam- 
ellicornia.      See  Table  V,  below. 
BB.     Head  either  prolonged  into  a  beak  or  not;  palpi 
usually  short  and  rigid;  gular  sutures  confluent  on 
the  median  line  (Fig.  552,  gs);  prosternal  sutures 
wanting;  the   epimera   of   the   prothorax   meeting 
on   the   middle   line  behind  the   prosternum    (Fig. 
552,  em).        Series  Rhynchophora.        See  Table 
VII,  below. 

TABLE     II.— THE     FAMILIES    OF    THE    SUB- 
ORDER   ADEPHAGA 


Fig.  552. — Head  and 
prothorax  of  Rhyn- 
chophorus:  gs,  con- 
fluent gular  su- 
tures; s,  proster- 
num; em,  epime- 
rum;  c,  coxa;  /,  fe- 
mur. 


.     Metasternum  with  an  antecoxal  piece,  separated  by 

a  well-marked  suture  reaching  from  one  side  to  the  other 

and  extending  in  a  triangular  process  between  the  hind 

coxag. 

B.    Antennae  eleven-jointed;  hind  coxse  mobile,  and  of  the  usual  form;  habits 

terrestrial. 

C.    Antennae  inserted  on  the  front  above  the  base  of  the  mandibles,  p.  476. 

ClCINDELID^ 


470  AN  INTRODUCTION  TO  ENTOMOLOGY 

CC.    Antenna  arising  at  the  side  of  the  head  between  the  base  of  the  mandi- 
bles and  the  eyes. 
D.     Beetles  of  a  round  convex  form  in  which  the  scutellum  is  entirely 

concealed,     p.     481 Omophronid^ 

DD.      Not    such    beetles,    p.    478 Carabid^ 

BB.  Antennce  ten- jointed;  hind  coxae  fixed  and  greatly  expanded  so  as  to 
conceal  the  basal  half  of  the  hind  femora  and  from  three  to  six  of  the  ab- 
dominal segments;  habits  aquatic,      p.  481 Haliplid^ 

AA.    Metasternum  either  with  a  very  short  antecoxal  piece,  which  is  separated 
by  an  indistinct  suture  and  which  is  not  prolonged  posteriorly  between 
the  cox£B,  or  without  an  antecoxal  piece. 
B.     Metasternum  with  a  very  short   antecoxal  piece,   p.   481  .Amphizoid^ 
BB.    Metasternum  without  an  antecoxal  piece. 
C.     Legs  fitted  for  swimming. 

D.      With   only   two   eyes.    p.      482 Dytiscid^ 

DD.     With  fotir  eyes,  two  above  and  two  below,  p.  484.   .Gyrinid^ 
CC.     Legs  fitted  for  walking,  p.     508 Rhysodid^* 

TABLE  IIL— THE  FAMILIES  OF  THE  BRACHELYTRA 

A.    Elytra  short,  leaving  the  greater  part  of  the  abdomen  exposed;  the  suture 
between  the  elytra  when  closed  straight;  wings  present,  and  when  not  in  use 
folded  beneath  the  short  elytra;  the  dorsal  part  of  the  abdominal  segments  en- 
tirely horny. 
B.    Abdomen  flexible,  and  with  seven  or  eight  segments  visible  below,  p.  488. 

Staphy-linid^ 

BB.    Abdomen  not  flexible,  and  with  only  five  or  six  ventral  segments  visible. 

C.     Antennas  with  less  than  six  joints,  p.  490 Clavigerid^ 

CC.  Antennas  eleven-jointed,  rarely  ten-jointed,  p.  489..  Pselaphid^ 
AA.  Elytra  usually  long,  covering  the  greater  part  of  the  abdomen;  when 
short  the  wings  are  wanting,  or,  if  present,  may  or  may  not  be  folded  under 
the  short  elytra  when  at  rest;  the  dorsal  part  of  the  abdominal  segments 
partly  membranous. 
B.     Hind  tarsi  five-jointed. 

C.     Antennae  elbowed,  and  clavate.  p.  490 Histerid.'E 

CC.    Antennae  rarely  elbowed,  and  then  not  clavate. 
D.    Abdomen  with  not  more  than  five  ventral  segments. 

E.    Antennae  capitate,  the  last  three  segments  forming  an  abrupt  club. 

p.  490 SPH^RITID^t 

EE.     Antennas  but  slightly  clavate  if  at  all.  p.  490..  .  .Scaphidiid^ 
DD.    Abdomen  with  six  or  more  ventral  segments. 

E.    Anterior  coxae  flat.    p.  486 Platypsyllid^ 

EE.     Anterior  coxae  either  globular  or  conical. 

F.      Anterior    coxae    globular,    p.    487 Leptinid.*; 

FF.    Anterior  coxae  conical. 

G.     Posterior  coxae  widely  separated. 

H.      Eyes    wanting    or    inconspicuous,    p.    487 Silphid^ 

HH.     With  well-developed  eyes. 

I.  Elytra    covering   the   abdomen,    p.    488 .  .  .  Scydm^nid^ 

II.  Elytra  not  covering  the  entire  abdomen,  p.  490 

SCAPHIDIIDiE 

GG.     Posterior  coxae  approximate. 

H.      Posterior    coxas    laminate,    p.    488 Clambid^ 

HH.     Posterior  coxas  not  laminate. 

*The  Rhysodidae  is  a  very  aberrant  family,  and  its  affinities  have  been  much 
discussed.  The  form  of  the  ventral  part  of  the  first  abdominal  segment  is  similar 
to  that  characteristic  of  the  Adephaga;  hence,  according  to  Table  I,  this  family 
should  be  placed  in  this  suborder.  But  other  characters  led  Leconte  and  Horn 
('83)  to  place  it  in  the  Clavicornia,  in  which  view  they  are  followed  by  recent 
writers. 

fSee  also  p.  508,  the  Nitidulidae  of  the  series  Clavicornia. 


COLEOPTERA  471 

I.  Eyes  with  large  facets,  p.  486 Brathinid/E 

II.  Eyes  with  small  facets,  p.  487 Silphid^ 

BB.  Hind  tarsi  either  only  three-jointed  or  four-jointed,  but  apparently  three- 
jointed,  the  third  segment  being  small  and  concealed  in  a  notch  at  the  end  of 
the  second  segment.     (See  also  BBB  and  BBBB.) 

C.    Abdomen  with  six  or  seven  ventral  segments. 

D.      Tarsi  four-jointed,  the  third  segment  small  and  concealed  in  a  notch 

at  the  end  of  the  second  segment,  p.  488 Corylophid^ 

DD.      Tarsi    three-jointed,    p.  490 Trichopterygid^ 

CC.      Abdomen    with    only    three    ventral    segments,    p.  490.  Sph^riid/E 
BBB.    All  tarsi  four-jointed.     (See  also  BBBB.) 

C.     Hind  coxae  contiguous  and  with  plates  covering  the  femora  entirely 

or  in  part.     p.  487 Silphid^ 

CC.    Hind  coxae  separate  and  not  covering  the  femora,  p.  488  Corylophid^ 

BBBB.    Hind  tarsi  with  only  four  segments;  the  fore  tarsi,  and  almost  always 

the  middle  tarsi  also,  with  five  segments,  p.  487 Silphid^ 

TABLE  IV.— THE  FAMILIES  OF  THE  PALPICORNIA,  POLYFORMIA 
AND  CLAVICORNIA 

It  is  impracticable  to  separate  these  three  series  of  families  in  these  tables, 
owing  to  the  fact  that  characters  sharply  separating  them  have  not  been  found. 
A.     Hind  tarsi  five-jointed. 

B.    Maxillary  palpi  as  long  as  or  longer  than  the  antennae,  p.485  Hydrophilid^ 
BB.     Maxillary  palpi  much  shorter  than  the  antennae. 

C.      Tarsal   claws   very   large;  the   first   three   abdominal  segments  grown 
together  on  the  ventral  side. 
D.     Abdomen   with   more   than   five   ventral   segments;  anterior   coxae 

with  very  large  trochantin.   p.   503 Psephenid^ 

DD.     Abdomen  with  five  ventral  segments. 

E.    Anteriorcoxae  transverse,  with  distinct  trochantin.  p.504.DRYOPiDyE. 
EE.     Anterior  coxs  rounded,   without  trochantin.  p.   504...Elmid^ 
CC.     Tarsal  claws  of  usual  size;  ventral  abdominal  segments  usually  free,, 
sometimes  (Buprestidae)  the  first  two  grown  together. 
D.    Abdomen  with  not  more  than  five  ventral  segments. 

E.     Femur  joined  to  the  apex  or  very  near  the  apex  of  the  trochanter. 

F.     Antennae  inserted  upon  the  front,  p.  514 Ptinid^ 

FF.     Antennae  inserted  before  the  eyes. 

G      Tibia;  without  spurs,  p.   514 Anobiid^ 

GO.     Tibiae  with  distinct  spurs. 

H.      First   ventral   segment   scarcely   longer   than   the   second. 

-,  P-  515. Bostrichid^ 

JrlH.     First  ventral  segment  elongated,   p.   515 Lyctid^ 

EE.    Femur  joined  to  the  side  of  the  trochanter. 

F.     Anterior   coxs   globular  or  transverse,   usually  projecting  but 
little  from  the  coxal  cavity. 
G.    Anterior  coxae  transverse,  more  or  less  cylindrical. 

H.     Posterior  coxa;  grooved  for  the  reception  of  the  femora. 

I.  Legs  stout,  retractile;  tibiae  dilated,  usually  with  a  furrow 
near  the  outer  end  for  the  reception  of  the  tarsi;  tibial 
spurs  distinct. 

J.    Antennae  inserted  at  the  side  of  the  head. 

K.  Head  prominent,  mentum  large,  p.  5o8.Nosodendrid^ 
KK.     Head  retracted,  mentum  small,  p.  5o8.Byrrhid.«; 

J  J.    Antennae  inserted  on  the  front;  head  retracted,  p.  506. 
Chelonariid^ 

II.  Tibia;  slender,  with  small  and  sometimes  obsolete  terminal 
spurs,  or  without  spurs. 

J.     Head  constricted  behind;  eyes  smooth,  p.  494.CuPESlD^. 
J  J.    Head  not  constricted  behind ;  eyes  granulated. 


472  AN  INTRODUCTION  TO  ENTOMOLOGY 

K.      Anterior  coxae  with   a   distinct   trochantin.   p.  505. 

Dascillid^ 

KK.    Anterior  coxae  without  trochantin. 

L.      Lacinia  of  the  maxillae  armed  with  a   terminal 

hook.    p.     505 EUCINETID^ 

LL.     Lacinia  not  armed  with  a  terminal  hook.  p.  505. 

Helodid.« 

HH.  Posterior  coxae  flat;  not  grooved  for  the  reception  of  the 
femora. 

I.  Tarsi  more  or  less  dilated,  first  segment  not  short. 

J.     Antennae  eleven-jointed,  terminated  by  a  three-jointed 

club.    p.     508 NlTIDULID^ 

JJ.      Antennas    ten-jointed,    club    two-jointed,    p.  508 

Rhizophagid,^ 

II.  Tarsi   slender,  first   segment   short,   p.    508 .  .  Ostomid^ 
GG.    Anterior  coxae  globular. 

H.     Presternum  with  a  process  which  extends  backward  into  a 
groove  in  the  mesosternum. 

I.  The  first  two  abdominal  segments  grown  together  on  the 
ventral  side.  p.    502 Buprestid^ 

II.  Ventral  segments  free. 

J.      Prothorax    loosely    joined    to    the    mesothorax;  front 
coxal  cavities  entirely  in  the  prosternum. 
K.    Posterior  coxae  laminate;  trochanters  small. 

L.  Antennae  somewhat  distant  from  the  eyes,  their  in- 
sertion narrowing  the  front,  p.  502 Eucnemid.'E 

LL.  Antennae  inserted  under  the  margin  of  the  front. 
M.  Antennas  arising  near  the  eyes.  p.  499.Elaterid^ 
MM.    Antennae  arising  at  a  distance  in  front  of  the 

eyes    (Perothops).    p.  502 Eucnemid.'E 

KK.    Posterior  coxae  not  laminate;  trochanters  of  middle 

and  posterior  legs  very  long.  p.  499.  .  .  .Cerophytid^ 

JJ.      Prothorax    firmly    joined    to    the    mesothorax;  front 

coxal  cavities  closed  behind  by  the  mesosternum.  p.  502 

Throscid^ 

HH.  Prosternum  without  a  process  received  by  the  mesoster- 
num, although  it  may  be  prolonged  so  as  to  meet  the  meso- 
sternum. 

I.  Posterior  coxas  contiguous,  p.  511 Phalacrid^ 

II.  Posterior  coxae  separated. 

J.     Body  depressed;  middle  coxal  cavities  not  closed  ex- 
ternally by  a   meeting  of  the  mesosternum  and  meta- 

sternum.    p.    509 CucujiD^ 

JJ.     Body  more  or  less  convex;  middle  coxal  cavities  en- 
tirely surrounded  by  the  sterna. 
K.      Prosternum     not    prolonged    behind,    p.    510.    .  . 

Mycetophagid^ 

KK.     Prosternum  prolonged,  meeting  the  mesosternum. 
L.     Anterior  coxal  cavities    open  behind,   p.   510..  .  . 

Cryptophagid.-e 

LL.      Anterior    coxal    cavities    closed   behind,  p.   509 

Erotylid^ 

T'F.     Anterior  coxae  conical,  and  projecting  prominently  from  the 
coxal  cavity. 
G.    Posterior  coxae  dilated  into  plates  partly  protecting  the  femora, 
at  least  at  their  bases. 

H.     Antennas  serrate  or  flabellate.  p.  499 Rhipicerid/E 

HH.    Antennae  with  the  last  three  segments  forming  a  large  club. 

I.  Tarsi   with   second   and   third   segments   lobed   beneath, 
p.  .SIC Byturid^ 

II.  Tarsi  simple,  p.  506 Dermestid^ 


COLEOPTERA  473 

HHH.    Antennas  with  the  last  three  segments  somewhat  larger 
than   the   preceding,  but    not    suddenly  enlarged,    p.  510. 

DERODONTID.E 

GG.     Posterior  coxse  not  dilated  into  plates  partly  protecting  the 
femora. 
H.    Posterior  coxae  flat,  not  prominent,  covered  by  the  femora  in 
repose. 

I.  Tarsi  with  the  fourth  joint  of  normal  size.  p.  493.Clerid^ 

II.  Tarsi  with  the  fourth  joint  very  small,  p.  493.Corynetid^ 
HH.    Posterior  coxas  conical  and  prominent. 

I.  Anterior  coxae  with  distinct  trochantins.  p.  493.Melyrid^ 

II.  Anterior  coxae  without  trochantins.   p.  493.Lymexylid^ 
DD.    Abdomen  with  six  or  more  ventral  segments. 

E.    Anterior  coxas  globular. 

F.     Tibial  spurs  well  developed,  p.  499 Cebrionid/E 

FF.     Tibial  spurs  very  delicate  and  short,  p.  499.  .  .  Plastocerid^ 
EE.    Anterior  coxae  conical. 

F.     Posterior  coxae  not  prominent,  flat,  covered  by  the  femora  in 
repose. 

G.     Tarsi  with  the  fourth  joint  of  normal  size.  p.  493.  .  .  .Clerid^ 
GG.     Tarsi  with  the  fourth  joint  very  small,  p.  493.  CoRYNETiDiE 
FF.     Posterior  coxae  more  or  less  conical  and  prominent  at  least  in- 
ternally, not  covered  by  the  femora  in  repose. 
G.    Anterior  coxae  long,  with  distinct  trohacntins. 
H.    Abdomen  with  seven  or  eight  ventral  segments. 

I.  Middle  coxae  contiguous;  epipleurse  distinct. 

J.      Episterna   of   metathorax   sinuate   on   inner   side,  epi- 
oleiiTce  usually  wide  at  the  base. 

K.     Head  more  or  less  covered;  antennas  approximate  or 
moderately  distant;  metathoracic  epimera  long.  p.  491. 

Lampyrid^ 

KK.       Head     exposed;  antennae     distant;  metathoracic 

epimera  wide.  o.  492 Phengodid^ 

JJ.    Episterna  of  metathorax  not  sinuate  on  the  inner  side; 
epipleurae  narrow  at  the  base.  p.  492 Cantharid^ 

II.  Middle  coxae  distant;  epipleurae  wanting,  p.  491.LYCID/E 
HH.    Abdomen  with  only  six  ventral  segments,  p.  493.MELYRiDiE 

GG.    Anterior  coxae  without  trochantins. 

H.     Elytra  entire;  length  of  body   10  mm.   or  more.   p. 493.  . 

Lymexylid^ 

HH.     Elytra  shorter  than  the  abdomen;  length  of  body  less 

than  3  mm.  p.  494 Micromalthid^ 

AA.     Hind  tarsi  either  only  three- jointed,  or  four-jointed  but  apparently  only 
three- jointed,  the  third  joint  being  small  and  concealed  in  a  notch  at  the  end  of 
the  second  joint.    (See  also  AAA  and  AAAA.) 
B.     Wings  fringed  with  long  hairs.     A  minute  aquatic  species  from  S.  Cal. 

and  Ariz.    (Hydroscapha) .    p.  485 Hydrophilid^ 

BB.     Wings  not  fringed  with  hairs. 
C.    Tarsi  with  second  segment  dilated. 

D.     Tarsal  claws  appendiculate  or  toothed;  first  ventral  abdominal  seg- 
ment with  distinct  curved  coxal  lines,    p.  51 1 .CoccinelliD/E 

DD.      Tarsal    claws   simple;  first    ventral   abdominal   segment    without 

coxal  lines,    p.  51 1 Endomychid^ 

CO.     Tarsi  with  second  segment  not  dilated. 

D.     Elytra  entirely  covering  the  abdomen;  ventral  abdominal  segments 

nearly    equal,    p.    511    Lathridiid^ 

DD.    Elytra  truncate,  the  first  and  fifth  abdominal  segments  longer  than 
the  others. 
E.     Maxillae  with  galea  distinct;  anterior  coxae  small,  rounded,  p.  509. 

MONOTOMID^ 

EE.     Galea  wanting,  anterior  coxae  subtransverse.  p.  5o8.Nitidulid^ 


474  AN  INTRODUCTION  TO  ENTOMOLOGY 

AAA.    All  tarsi  four-jointed-   (See  also  AAA  A.) 

B.     The  first  four  abdominal  segments  grown  together  on  the  ventral  side. 
C.     Tibias  dilated,  armed  with  rows  of  spines,  and  fitted  for  digging,  o.  505. 

Heterocerid^ 

CC.     Tibiae  neither  dilated  nor  fitted  for  digging. 

D.    Antennae  inserted  tmder  a  distinct  frontal  ridge;  anterior  coxae  distant 

from  the  metasternum.  p.  510 Colydiid^ 

DD.    Antennae  inserted  on  the  front ;  anterior  coxae  inclosed  behind  by  the 

metasternum.    p.    511 Murmidiid^ 

BB.     Ventral  segments  of  abdomen  not  grown  together. 

C.      Anterior   coxae   transverse,    p.    511 Mycet^id^ 

CC.    Anterior  coxae  either  globose  or  oval. 
D.    Anterior  coxae  globose. 

E.     Tarsi  slender,  p.  51 1 Endomychid^ 

EE.    Tarsi  more  or  less  dilated  and  spongy  beneath,  p.  509.  Erotylid^ 
DD.    Anterior  coxae  oval. 

E.     Anterior  coxae  separated  by  the  horny  prosternum. 

F.     Body  depressed;  head  free.   p.   510 Mycetophagid^ 

FF.      Body    cylindrical;  thorax  prolonged  over   the   head.    p.    515. 

CiSIDyE 

EE.     Anterior  coxae  contiguous ;  prosternum  semimembranous,   p.  505. 

Geory'ssid^ 

AAAA.    Hind  tarsi  with  only  four  segments;  the  fore  tarsi,  and  almost  always  the 
middle  tarsi  also,  with  five  segments. 
B.    Anterior  coxal  cavities  closed  behind. 
C.    Tarsal  claws  simple. 

D.    Abdomen  with  five  ventral  segments. 

E.    Ventral  abdominal  segments  in  part  grown  together. 

F.     Next  to  the  last  segment  of  the  tarsi  spongy  beneath,    p.  514. 

Lagriid^ 

FF.    Penultimate  segment  of  tarsi  not  spongy,  p.  513.  Tenebrionid^ 
EE.     Ventral  abdominal  segments  free. 

F.     Anterior  coxal  cavities  confluent,  p.  498 Othniid^ 

FF.     Anterior  coxal  cavities  separated  by  the  prosternum. 

G.    Elytra  truncate;  tip  of  abdomen  exposed,  p.  5o8.Rhizophagid^ 

GG.     Elytra  entire,   p.   515 Sphindid^ 

DD.     Abdomen  with  six  ventral  segments,  p.  498 Eurystethid^ 

CC.     Tarsal  claws  pectinate,  p.  512 Alleculid^ 

BB.    Anterior  coxal  cavities  open  behind. 

C.    Head  not  strongly  and  suddenly  constricted  at  base. 
D.    Middle  coxae  not  very  prominent. 

E.     Antennae  received  in  grooves,  p.  514 Monommid^ 

EE.    Antennae  free. 

F.    Prothorax  margined  at  the  sides. 

G.    Middle  coxal  cavities  entirely  surrounded  by  the  sterna,  p.  510. 

Cryptophagid^ 

GG.    Epimera  of  mesothorax  reaching  the  coxae. 

H.      Metasternum  long;  epimera  of  metathorax  visible,  p.   514. 

Melandryid^ 

HH.     Metasternum  quadrate;  epimera  of  metathorax  covered. 

p.  509 CucujiD^ 

FF.    Prothorax  not  margined  at  the  sides,   p.  498 Pythid^ 

DD.    Middle  coxae  very  prominent,    p.  494 CEdemerid^ 

CC.    Head  strongly  constricted  at  base. 

D.     Head  prolonged  behind  and  gradually  narrowed,  p.  494.Cephaloid^ 
DD.     Head  suddenly  narrowed  behind. 

E.    Prothorax  with  the  side  pieces  not  separated  from  the  pronotum  by  a 
suture. 

F.    Prothorax  at  base  narrower  than  the  elytra. 
G.    Hind  coxae  not  prominent  or  but  slightly  so. 

H.     Anterior  coxae  globular,  not  prominent,    p.  509.CucujiD^ 


COLEOPTERA  475 

HH.     Anterior  coxce  conical,  prominent. 

I.  Abdomen  composed  of  five  free  segments;  tarsi  with  the 
penultimate  joint  lobed  beneath. 

J.      Neck   wide;  eyes   large,    finely   faceted,  and   generally 
emarginate.      p.     498 " Pedilid^ 

JJ.    Neck  narrow,  eyes  not  emarginate. 

K.    Eyes  large,  oval,  rather  finely  faceted,  p.  498.Pedilid^ 

KK.  Eyes  small,  rounded,  generally  coarsely  faceted,  p.498. 

Anthicid^ 

II.  Abdomen  composed  of  four  free  segments,  the  first  formed 
of  two  united,  with  the  suture  sometimes  indicated;  tarsi 
with   the   antepenultimate  joint   lobed   beneath,    p.   499.. 

EuGLENID^ 

GG.    Hind  coxse  large,  prominent. 

H.     Tarsal  claws  simple;  head  horizontal.  p.498.PYROCHROiDyE 

HH.      Claws  cleft   or  toothed,   front   vertical,   p.  495.Meloid^ 

FF.    Prothorax  at  base  as  wide  as  the  elytra,  p.  494.  .Rhipiphorid^ 

EE.    Lateral  suture  of  prothorax  distinct;  base  of  prothorax  as  wide  as 

the  elytra. 

F.     Antennas  filiform. 

G.     Hind  coxae  plate-like.  p.  494 Mordellid^ 

GG.     Hind  coxae  not  plate-like.  p.  514 Melandryid^ 

FF.    Antennae  flabellate  in  the  male,  subserrate  in  the  female,  p.  494. 
Rhipiphorid^ 

TABLE    v.— THE    FAMILIES    OF    THE    LAMELLICORNIA 

A.     Plates  composing  the  club  of  the  antennae  flattened  and  capable  of  close 
apposition. 

B.     Abdomen  with  six  visible  ventral  segments,  p.  515 Scarab^id^ 

BB.    Abdomen  with  five  visible  ventral  segments. 

C.     Epimera  of  mesothorax  attaining  the  oblique  coxae,  p.  5I5.Scarab^iD/E 

CC.     Epimera  of  mesothorax  not  attaining  the  coxae,  p.   522 .  .  Trogid^ 

AA.     Plates  composing  the  club  of  the  antennae  not  capable  of  close  apposition, 

and  usually  not  flattened. 

B.      Mentum   deeply   emarginate,   ligula   filling   the   emargination.   p.    524.. 

■.••••. Passalid^ 

BB.     Mentum  entire,  ligula  covered  by  the  mentum  or  at  its  apex.  p.  523. 

LUCANID^ 

TABLE  VI.— FAMILIES    OF    THE   PHYTOPHAGA 

This  series  includes  three  families,  which  are  so  connected  by  intermediate 
forms  that  it  is  not  easy  to  separate  them.    The  following  table  will  aid  the  student 
in  separating  the  more  typical  forms. 
A.     Body  elongate;  antennas  almost  always  long,  often  as  long  as  the  body  or 

longer.    The  larvae  are  borers,  p.  524 Cerambycid^ 

AA.    Body  short  and  more  or  less  oval;  antennae  short. 

B.  Front  prolonged  into  a  broad  quadrate  beak;  elytra  rather  short  so  that 
the  tip  of  the  abdomen  is  always  exposed.     The  larvas  live  in  seeds,  p.  535. 

Mylabrid^ 

BB.  Front  not  prolonged  into  a  beak;  usually  the  tip  of  the  abdomen  is 
covered  by  the  elytra.  Both  larvae  and  adults  feed  on  the  leaves  of  plants, 
p.  530 Chrysomelid^ 

TABLE  VII.— THE  FAMILIES  OF  THE  RHYNCHOPHORA 

{Compiled  from  Blatchley  and  Leng) 

A.    Beak  rarely  absent,  usually  longer  than  broad;  tibiae  never  with  a  series  of 
teeth  externally. 


476 


AN  INTRODUCTION  TO  ENTOMOLOGY 


B.    Antennas  straight  without  a  distinct  club,  though  with  the  outer  joints  often 
more  or  less  thickened;  beak  present  at  least  in  the  female  and  pointing 
directly  forward ;  form  usually  very  slender  and  elongate,  p.  536..Brentid^ 
BB.    Antennae  straight  or  elbowed,  always  with  a  distinct  club. 

C.     Palpi  flexible;  antennal  club  rarely  compact;  beak  always  short  and 
broad;  labrum  present;  thorax  with   a  transverse  raised  line  which  is 

either  ante-basal  or  basal,  p.   536.  .  . Platystomid^ 

CC.    Palpi  rigid  and  labrum  wanting  except  in  the  subfamilyRhinomacerinae 
antennal  club  usually  compact;  beak  variable  in  length,  often  long  and 

ctirved    downwards,    p.    537 Curculionid^* 

AA.  Beak  absent  or  extremely  short  and  broad ;  tibiae  with  a  series  of  teeth  ex- 
ternally, or,  if  these  are  wanting,  with  a  prominent  curved  spine  at  apex;  an- 
tennae short,  but  little  longer  than  the  head,  always  elbowed,  and  with  a  com- 
pact club  except  in  Phthorophcelus  where  the  club  is  lamellate;  palpi  rigid; 
body  short,  subcylindrical  or  rarely  oval. 
B.    Anterior  tarsi  with  the  first  segment  longer  than  the  second,  third  and 

fourth  together,    p.  541 — Platypodid^ 

BB.     Anterior  tarsi  with  the  first  segment  shorter  than  the  second,  third,  and 
fom-th  together,     p.  542 Scolytid^ 


Suborder  ADEPHAGAf 

The  name  of  this  suborder,  Adephaga,  was  suggested  by  the  pre- 
dacious habits  of  its  members.  These  beetles  are  distinguished  from 
other  Coleoptera  by  the  presence  of  a  suture  on  each  side  of  the  pro- 
thorax  separating  the  pleurtim  from  the  notum,  and  by  the  fact  that 

the  ventral  part  of  the  first  segment 
of  the  abdomen  is  divided  by  the 
hind  coxal  cavities  so  that  the  sides 
are  separated  from  the  very  small 
medial  part  (Fig.  553). 

The  Adephaga  differ  from  other 
Coleoptera  in  that  the  nutritive  cells 
of  the  ovaries  alternate  with  the  egg- 
chambers. 

The  larvae  are  campodeiform, 
and  differ  from  all  other  beetle 
larvae  in  that  their  legs  are  six- 
jointed  except  in  a  single  exotic 
species;  this  is  one  more  segment 
than  is  found  in  the  legs  of  other 
beetle  larvae.  The  legs  are  usually 
whereas  the  legs  of  other  coleopterous 


/si  A 


Fig.  553. — Ventral  aspect  of  part  of 
thorax  and  abdomen  of  Galerita 
janus:  ist  A,  first  abdominal  seg- 
ment ;  2d  A,  second  abdominal  seg- 
ment. 


furnished  with  two  claws, 
larvae  are  one-clawed. 

f-This  suborder  is  represented  in  North  America  by  seven  families 
these  can  be  separated  by  Table  II,  page  469. 


Family  CICINDELID^ 

The  Tiger-Beetles 

The  graceful  forms  and  beautiful  colors  of  the  greater  number 
of  the  tiger-beetles,  those  of  the  genus  Cicindela,  have  made  the 

*Since  this  table  was  published  by  Blatchley  and  Leng,  the  family  Belidae  has 
been  separated  from  the  Curculionidae.    See  page  537. 
fAdephaga:  adephagous  {dd-ncpdyoi) ,  voracious. 


COLEOPTERA 


477 


Fig.  555- 


Fig-  554- 


family  one  of  the  favorites  of  students  of 
Coleoptera.     Their  popular  name  is  sug- 
gestive of  their  predacious  habits,  and  of 
the  stripes  with  which  many  are  marked. 
They   are   usually    a   metallic    green   or 
bronze,  banded  or  spotted  with  yellow. 
Some  are  black;  and  some  that  live  on 
white  sand  are  grayish  white,  being  ex- 
actly like  the  sand  in  color.     Figure  554 
represents  a  common  species  of  Cicindela. 
A  useful  character  for  distinguishing  the  members  of  this  family 
is  the  fact  that  the  terminal  hook  of  the  maxilla  (the  digitus)  is 
united  to  this  organ  by  a  movable  joint  (Fig.  555,  h). 

The  sexes  of  the  tiger-beetles  can  be  distinguished,  except  in 
Amhlycheila,  by  the  sixth  abdominal  segment  of  the  males  being 
notched  .so  as  to  expose  a  small  seventh  segment;  while  in  the 
females  only  six  segments  are  visible.  In  the  males,  the  first  three 
segments  of  the  anterior  tarsi  are  usually  dilated  and  densely  clothed 
with  hair  beneath. 

The  tiger-beetle  larvae  (Fig.  556)  are  as  ugly  and  ungraceful  as 
the  adults  are  beautiful.  The  two  have  only  one  habit  in  common — 
their  eagerness  for  prey.  The  larvae  live  in  vertical 
burrows  in  sandy  places  or  in  beaten  paths.  These 
burrows  occur  also  in  ploughed  fields  that  have  become 
dry  and  hard .  They  often  extend  a  foot  or  more  in  depth . 
The  larva  takes  a  position  of  watchfulness  at  the 
mouth  of  its  burrow.  Its  dirt-colored  head  is  bent  at 
right  angles  to  its  lighter-colored  body  and  makes  a 
neat  plug  to  the  opening  of  the  hole.  Its  rapacious  jaws 
extend  upward,  wide  open,  ready  to  seize  the  first  un- 
wary insect  that  walks  over  this  living  trap,  or  near  it; 
for  a  larva  will  throw  its  body  forward  some  distance 
in  order  to  seize  its  prey.  On  the  fifth  segment  of  the 
abdomen  there  is  a  hump,  and  on  this  hump  are  two  hooks  curved 
forward.  This  is  an  arrangement  by  which  the  little  rascal  can  hold 
back  and  keep  from  being  jerked  out  of  its  hole  when  it  gets  some 
large  insect  by  the  leg,  and  by  which  it  can  drag  its  struggling  prey 
down  into  its  lair,  where  it  may  eat  it  at  leisure.  It  is  interesting 
to  thrust  a  straw  down  into  one  of  these  burrows,  and  then  dig  it 
out  with  a  trowel.  The  chances  are  that  you  will  find  the  indignant 
inhabitant  at  the  remote  end  of  the  burrow,  chewing  savagely  at  the 
end  of  the  intruding  straw. 

One  hundred  and  fourteen  species  of  tiger-beetles  are  now  listed  in 
our  fauna;  these  represent  four  genera,  which  can  be  separated  as 
follows : 

A.     Posterior  coxae  contiguous;  eyes  large,  prominent. 

B.     Third  joint  of  the  maxillary  palpi  shorter  than  the  fourth. .  .Cicindela 
BB.     Third  joint  of  the  maxillary  palpi  longer  than  the  fourth Tetracha 

AA.    Posterior  coxas  separated;    eyes  small. 


Fig.  556. 


478  AN  INTRODUCTION  TO  ENTOMOLOGY 

B.    Sides  of  the  elytra  widely  inflexed ;  thorax  scarcely  margined.  Amblycheila 
BB.    Sides  of  the  elytra  narrowly  inflexed;  thorax  distinctly  margined.  ..Omus 
Cicindela. — To  this  genus  belong  the  greater  number  of  our  tiger- 
beetles;  seventy-six  species  and  many  varieties  occur  in  our  fauna; 
excepting  the  two  species  of  Tetracha,  all  of  the  tiger-beetles  found  in 
the  East  belong  to  the  genus  Cicindela. 

The  members  of  this  genus,  unlike  most  other  members  of  the 
family,  are  diurnal  in  habit.  They  are  found  on  bright,  hot  days  in 
dusty  roads,  in  beaten  paths,  and  on  the  shores  of  streams.  They  are 
the  most  agile  of  all  beetles;  and  they  are  not  merely  swift  of  foot, 
but  are  also  able  to  fly  well.  When  approached,  they  remain  still 
until  we  can  see  them  well  but  are  still  out  of  reach ;  then  like  a  flash 
they  fly  up  and  away,  alighting  several  rods  ahead  of  us.  Before 
alighting  they  usually  turn  so  that  they  face  us,  and  can  thus  watch 
our  movements.  They  hide  by  night  and  in  cloudy  or  rainy  weather 
in  holes  in  the  ground  or  beneath  stones  or  rubbish.  The  beetles 
have  been  found  hibernating,  each  in  a  separate  burrow  extending 
under  a  stone.  I  have  seen  them  in  September  digging  burrows  in  a 
hillside;  these  descended  slightly  and  were  about  five  inches  deep. 
The  beetles  kicked  the  dirt  out  behind  them  as  they  dug,  so  that  it 
lay  in  a  heap  at  the  opening  of  the  hole. 

Tetracha. — Two  species  of  this  genus  are  widely 
distributed  in  the  United  vStates.  They  are  rather 
large,  metallic-green  beetles.  Figure  557  represents 
Tetracha  Carolina,  which  can  be  distinguished  by  the 
apical  portion  of  the  elytra  being  yellow.  Our  only 
other  species  is  Tetracha  virgmica.  These  beetles  are 
nocturnal,  hiding  during  the  day  and  hunting  by 
night. 

Amblycheila.— The   best-known    representative 

of  this  genus  is  Amblycheila  cylindriformis,  which  is 

ig-557-  found   in    Kansas,    Colorado,    Arizona,    and    New 

Mexico.    It  is  a  very  large  species,  measuring  3 5  mm. 

in  length.    It  is  nocturnal,  hiding  in  holes  during  the  day  and  coming 

forth  at  night  to  capture  its  prey.     Two  other  species  of  this  genus 

have  been  described  from  Arizona  and  Utah. 

Omus. — Thirty-three  species  of  this  genus  have  been  found  on  the 
Pacific  Coast,  nearly  all  of  them  in  California.  They  are  nocturnal 
insects,  hiding  under  rubbish  during  the  daytime. 

Family  CARABID^ 

The  Ground-Beetles 

The  ground-beetles  are  so  called  because  they  are  very  common 
on  the  surface  of  the  ground,  lurking  under  stones  or  rubbish,  where 
they  hide  by  day.  At  night  they  roam  about  in  search  of  their  prey. 
Our  more  common  species  are  easily  recognized  by  their  shining  black 
color  and  long  legs.  On  the  Pacific  Coast,  however,  the  darkling 
beetles  (Family  Tenebrionidae) ,  which  are  also  black  and  have  long 
legs,  abound  under  stones  and  fragments  of  wood  on  the  ground. 


COLEOPTERA  479 

But  the  two  families  can  be  easily  distinguished  by  the  fact  that  in 
the  ground-beetles  all  the  tarsi  are  five-jointed,  while  in  the  darkling 
beetles  the  hind  tarsi  are  only  four-jointed;  and  the  darkling 
beetles  do  not  run  rapidly  as  do  the  ground-beetles. 

With  the  ground-beetles,  the  antennse  are  thread-like,  tapering 
gradually  towards  the  tip,  and  each  segment  is  of  nearly  uniform 
thickness  throughout  its  length ;  the  legs  are  fitted  for  running,  and 
the  antenna  are  inserted  between  the  base  of  the  mandibles  and  the 
eyes.  Although  most  of  the  species  are  black,  there  are  those  that 
are  blue,  green,  or  brown,  and  a  few  that  are  spotted.  The  wing- 
covers  are  almost  always  ornamented  with  longitudinal  ridges  and 
rows  of  punctures. 

Most  members  of  this  family  are  predacious,  feeding  upon  other 
insects,  which  they  spring  upon  or  capture  by  chase.  A  few  species 
use  vegetable  food;  but  their  depredations  are  rarely  of  economic 
importance.  As  there  are  more  than  two  thousand  described  North 
American  species,  and  as  many  of  the  species  are  very  common,  this 
family  may  be  considered  the  most  important  family  of  the  pre- 
dacious insects. 

The  larvae  of  ground-beetles  are  generally  long,  with  the  body  of 
nearly  equal  breadth  throughout  (Fig.   558). 
They  have   sharp   projecting  mandibles;  and 
the  caudal  end  of  the  body  is  usually  furnished 
with  a  pair  of  conical  bristly  appendages.  They  pjg    erg. 

live  in  the  same  obscure  situations  as  the  adult 

insects,  but  are  more  shy,  and  are  consequently  less  frequently  seen. 
Like  the  adults,  they  are  predacious. 

Among  the  more  common  ground-beetles  are  the  following. 
The  searcher,  Calosdma  scrutator. — This  is  one  of  the  larger  and 
more  beautiful  of  our  ground -beetles ;  it  has 
green  or  violet  wing-covers  margined  with 
reddish,  and  the  rest  of  the  body  is  marked 
with  violet-blue,  gold,  green,  and  copper 
(Fig.  559).  This  beetle  and  the  two  follow- 
ing have  been  known  to  climb  trees  in  search 
of  caterpillars. 

Calosdma  sycophanta,  a  common  species 
in  Europe,  has  been  introduced  and  success- 
fully colonized  in  New  England,  as  a  means 
of  combating  the  gipsy-moth  and  the 
brown-tail  moth.  This  species  is  somewhat 
smaller  than  the  preceding,  and  lacks  the 
reddish  band  on  the  margins  of  the  elytra. 
The  fiery  hunter,  Calosdma  cdlidum,  is 
easily  recognized  by  the  rows  of  reddish  or 
Fig.  559.  copper-colored  pits  on  the  wing-covers  (Fig. 

560). 
The  bombardier-beetles,  Brachlnus. — There  are  many  species  of 
beetles  that  have  at  the  hind  end  of  the  bodv  little  sacs  in  which 


480 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  560. 


is  secreted  a  bad-smelling  fluid,  which  is  used 
as  a  means  of  defence.  These  beetles  spurt  this 
fluid  out  onto  their  enemies  when  attacked. 
But  in  the  case  of  the  bombardier-beetles  this 
fluid  changes  to  a  gas,  which  looks  like  smoke 
as  soon  as  it  comes  in  contact  with  the  air,  and 
is  ejected  with  a  sound  like  that  of  a  tiny  pop- 
gun. When  some  larger  insect  tries  to  capture 
one  of  these  insect-soldiers,  and  gets  very 
near  it,  the  latter  fires  its  little  gun  into  the  face 
of  its  enemy.  The  noise  astonishes  the  pursuer, 
and  the  smoke  blinds  him.  By  the  time  he 
has  recovered  from  his  amazement,  the  little  bombardier  is  at  a  safe 
distance.  These  beetles  have  quite  a  store  of  ammunition;  for  we 
have  often  had  one  pop  at  us  four  or  five  times  in  succession,  while  we 
were  taking  it  prisoner.  The  bombardier-beetles  belong  to  the  genus 
Brachinus,  of  which  we  have  in  this  country  twenty-seven  species. 
They  are  ver>^  similar  in  appearance;  the  head,  prothorax,  and  legs 
are  reddish  yellow,  and  the  wing-covers  are  dark  blue,  blackish,  or 
greenish  blue  (Fig.  561). 

There  is  a  common  beetle  which  resembles  the  bom- 
bardier-beetles quite  closely  in  size  and  color,  but  whi 
may  be  distinguished  by  the  comb-like  form  of  the  tarsal 
claws;  this  is  Lehia  grandis  (Fig.  562).  It  has  been 
reported  more  often  than  any  other  insect  as  destroying 
the  Colorado  potato-beetle. 

Galerlta  jdnus  is  still  another  species  that  bears  some         Fig.  561. 
resemblance  to  the  bombardier-beetles.    But  it  is  much 
larger,  measuring  16  mm.  in  length,  and  has  only  the  prothorax  and 
legs  reddish  yellow,  the  head  being  black;  the  prothorax  is  only  about 

*half  as  wide  as  the  wing-covers. 
What  is  perhaps  the  most  com- 
mon type  of  ground -beetle  is  illus- 
trated by  Hdrpalus  caliginosus, 
which  is  represented  natural  size 
in  Figure  563.  It  is  of  a  pitchy 
black  color,  and  is  one  of  the  most 
commonof  our  larger  species.  There 
are  one  hundred  and  thirty -six  de- 
scribed species  of  Harpalus  in  this 
country.  Most  of  them  are  smaller 
than  this  one,  are  flattened,  and  have 
the  prothorax  nearly  square. 

The  beetles  of  the  genus  Die celus 
are  quite  common;  and  some  of  the 
larger  species  resemble  Harpalus 
caliginosus  quite  closely.  They  can 
be  distinguished  by  a  prominent  keel- 
shaped  ridge  which  extends  back  upon  each  wing- 
cover  from  near  the  comer  of  the  prothorax.  Fig.  564. 


Dm-  \     /^ 

lich  vVy 

rsal  y^kT 

leen  />^^C\ 


Fig.  563- 


Fig.  562. — Lebia 
grandis,  natu- 
ral size  and 
enlarged. 


COLEOPTERA  481 

The  most  common  of  all  ground-beetles,  in  the  Northeastern  States 
at  least,  is  Pcecihis  lucublandus.  In  this  species  (Fig.  564)  the  nar- 
row, flat  margin  on  each  side  of  the  prothorax  is  widened  near  the 
hind  angle  of  this  segment. 

The  family  AMPHIZOID^  is  represented  in  our  fauna  by  two 
species  of  Aniphizoa,  which  occur  in  California,  Vancouver,  and 
Alaska,  clinging  to  logs  or  stones  under  the  surface  of  streams.  In 
these  beetles  the  metasternum  is  truncate  behind,  not  reaching  the 
abdomen,  and  has  a  very  short  antecoxal  piece. 

The  familv  OMOPHRONID^  consists  of  a  single  genus, 
Oiuophron,  the  members  of  which  are  remarkable  for  their  round  form 
and  the  fact  that  the  scutellum  is  entirely  concealed.  They  measure 
about  6  mm.  in  length,  and  are  found  in  holes  in  wet  sand  near  the 
margins  of  streams  and  ponds.  They  are  found  from  the  Atlantic  to 
the  Pacific;  fourteen  species   have   been   described. 

Family  HALIPLID^ 
The  Crawling  Water-Beetles 

This  family  includes  a  few  species  of  small  aquatic  beetles,  which 
are  oval,  more  or  less  pointed  at  each  end,  and  very  convex;  our 
larger  species  measure  from  3.5mm.  to  5  mm.  in  length,  but  some 
are  much  smaller.  The  wing-covers  have  rows  of  punctures,  and  the 
hind  cox«  are  greatly  expanded  so  as  to  conceal  the  basal  half  of  the 
hind  femora  and  from  three  to  six  of  the  abdominal  segments.  The 
anterior  and  middle  tibiae  and  the  tarsi  of  all  of  the  legs  are  fur- 
nished with  long,  swimming  hairs. 

These  beetles  are  found  in  ponds  and  streams,  but  most  frequently 
in  spring-fed  pools  that  do  not  dry  up  during  the  summer,  and 
contain  filamentous  algse  and  other  aquatic  plants.  They  swim 
poorly  but  crawl  over  the  stems  of  aquatic  plants.  Little  is  known 
regarding  the  feeding  habits  of  the  adults.  Matheson  ('12)  found  that 
several  species  feed  on  the  contents  of  the  cells  of  A^ite//a  and  the  softer 
portions  of  Chara  and  other  filamentous  algae.  He  observed  also  that 
two  species  of  Peltodytes  attach  their  eggs  to  aquatic 
plants,  mainly  Nitella  and  Chara,  while  Haliplus 
ruficollis  places  its  eggs  within  the  dead  cells  of  Nitella. 

The  larvae  are  aquatic,  living  in  the  same  pools  as 
the  adults.    The  body  is  slender;  each  segment  except 
the  head  is  furnished  on  the  back  with  fleshy  lobes 
with  spiny  tips  (Fig.  565),  which  vary  greatly  in  size 
in  different  species;  in  the  larv£e  of  Peltodytes  each  of 
these  spines  bears  a  long,  jointed  filament,  which  is  a 
tracheal  gill.    The  larvffi  of  this  genus  have  no  spiracles ; 
but  the  larvae  of  Haliplus  possess  both  thoracic  and        Fig.  565. 
abdominal  spiracles.    The  larvae  of  the  Haliplidae  feed  on  filamentous 
algae;  when  mature,  they  leave  the  water  and  each  makes  a  cell  in 
the  damp  earth  in  which  the  pupa  state  is  passed. 

About  forty  species  of  the  Haliplidae  have  been  found  in  our 
fauna;  these  represent  three  genera.    In  Brychius,  which  is  represented 


482  AN  INTRODUCTION  TO  ENTOMOLOGY 

by  two  species  in  California,  the  prothorax  is  quadrate;  in  the  other 
genera  it  is  narrowed  in  front.  In  Haliplus  the  last  segment  of  the 
palpi  is  small  and  awl-shaped ;  in  Peltodytes  it  is  longer  than  the 
third  segment,  and  conical.  The  last  two  genera  are  widely  distribu- 
ted. 

Family  DYTISCID^ 

The  Predacious  Diving-Beetles 

If  one  will  approach  quietly  a  pool  of  standing  water,  there  may 
be  seen  oval,  flattened  beetles  hanging  head  downward,  with  the  tip 
of  the  abdomen  at  the  surface  of  the  water.  Such  beetles  belong  to 
this  family. 

The  predacious  diving-beetles  are  usually  brownish  black  and 
shining,  but  are  often  marked  indefinitely  with  dull  yellow  They 
can  be  distinguished  from  the  water  scavenger-beetles,  which  they 
resemble  in  general  appearance,  by  the  thread-like  form  of  the  antennae. 
The  hind  legs  are  the  longest  and  are  fitted  for  swimming,  being 
flattened  and  fringed  with  hair.  The  middle  and  the  hind  pair  of 
legs  are  widely  separated.  This  is  due  to  the  very  large  hind  coxae 
which  cover  the  greater  part  of  the  lower  surface  of  the  thorax. 
In  the  males  of  certain  genera  the  first 
three  segments  of  the  fore  tarsi  are  di- 
lated and  form  a  circular  disk,  upon 
the  under  side  of  which  are  little  cup- 
like suckers  (Fig.  566);  these  serve  as 
clasping  organs.  In  a  few  cases  the 
middle  tarsi  are  dilated  also.  The  fe- 
males of  some  species  exhibit  an  inter- 
Fig.  566.  Fig.  567.      esting      dimorphism     in     that  some 

of  the  individuals  have  the  elytra  fur- 
nished with  a  number  of  deep  furrows  (Fig  567 j,  while  others  of  the 
same  species  have  them  smooth. 

The  diving-beetles  abound  in  our  streams  and  ponds,  but  they 
are  more  often  found  in  standing  water  than  in  streams.  When  at 
rest  they  float  in  an  inclined  position,  head  downward,  with  the  tip 
of  the  hind  end  of  the  body  projecting  from  the  water.  The  spiracles 
open  on  the  dorsal  side  of  the  abdomen  beneath  the  elytra.  By 
lifting  the  elytra  slightly  a  reservoir  is  formed  for  air,  which  the 
beetle  can  breathe  as  it  swims  through  the  water.  When  the  air 
becomes  impure  the  beetle  rises  to  the  surface,  forces  it  out,  and 
takes  a  fresh  supply. 

These  beetles  are  very  voracious.  They  destroy  not  only  other 
insects,  but  some  of  them  will  attack  larger  animals,  as  small  fish. 
When  kept  in  aquaria  they  can  be  fed  upon  any  kind  of  meat,  raw 
or  cooked.  They  fly  from  pond  to  pond,  and  are  often  attracted  to 
light  at  night.  Many  of  the  species  make  sounds,  both  under  the 
water  and  in  the  air.  In  some  cases  this  is  done  by  rubbing  the 
abdominal  segments  upon  the  elytra;  in  others,  by  rubbing  the  hind 
legs  upon  a  rough  spot  on  the  lower  side  of  the  abdomen. 


COLEOPTERA  483 

The  females  deposit  their  eggs  singly  in  punctures  in  the  tissues 
of  living  plants.  The 
larvae  are  known  as 
water-tigers,  because 
of  their  blood-thirsti- 
ness. They  are  elon- 
gated, spindle-form  Fig.  568. 
grubs  (Fig.  568).   The                 . 

head  is  large,  oval  or  rounded,  and  flattened;  the  mandibles  are  large 
and  sickle-shaped;  in  each  there  is  a  slit-like  opening  near  the  tip; 
from  this  opening  a  canal  leads  along  the  inner  surface  to  a  basal 
opening  on  the  upper  surface,  which  communicates  with  the  corner 
of  the  mouth  when  the  mandible  is  closed.  The  central  part  of  the 
mouth,  between  the  mandibles,  is  closed,  the  upper  and  lower  lips 
being  locked  together  by  a  dovetail  joint.  The  mandibles  are  ad- 
mirably fitted  for  holding  prey  and  at  the  same  time  sucking  juices 
from  its  body.  The  thorax  is  furnished  with  six  well-developed  legs. 
The  abdomen  is  teiTninated  by  a  pair  of  processes;  at  the  tip  of  the 
abdomen  there  is  a  pair  of  large  spiracles,  which  the  larva  protrudes 
into  the  air  at  intervals,  in  order  to  breathe. 

When  a  larva  is  fully  grown  it  leaves  the  water,  burrows  into  the 
ground,  and  makes  a  round  cell,  within  which  it  undergoes  its  trans- 
formations. The  pupa  state  lasts  about  three  weeks  in  summer; 
but  the  larvse  that  transform  in  autumn  remain  in  the  pupa  state 
all  winter. 

This  is  the  largest  of  the  families  of  water-beetles;  more  than 
three  hundred  North  American  species  are  known. 

Thebest  way  to  obtain  specimens  is  to  sweep  the  vegetation  grow- 
ing on  the  bottom  of  a  quiet  pool  with  a  dip-net. 

The  larger  of  our  common  species  belong  to  CyMster,  Dytlscus, 
and  allied  genera.  In  Cybister  the  little  cups  on 
the  vmder  side  of  the  tarsal  disks  of  the  male  are 
similar,  and  arranged  in  four  rows.  In  Dytiscus 
and  its  allies  the  cups  of  the  tarsal  disks  vary  in 
size.  Figure  569  represents  a  common  species  of 
Dytiscus. 

The  most  common  of  the  diving-beetles  which 
are  of  medium  size  belong  to  the  genus  Acllius.    In 
this  genus  the  elytra  are  densely  pimctured  with 
very  fine  punctures,  and  the  females  usually  have 
Fig-  569-  four  furrows  in  each  wing-cover  (Fig.  567). 

There  are  also  common  di  v^ing-beetles  which  are 
of  about  the  same  size  as  the  preceding,  but  which  have  the  wing- 
covers  marked  with  numerous  very  fine  transverse  striae;  these  be- 
long to  the  genus  Colymbetes. 

Of  the  smaller  diving-beetles,  measuring  less  than  6  mm.  in  length, 
many  species  can  be  foimd  in  almost  any  pond.  These  represent 
many  genera. 


484  AN  INTRODUCTION  TO  ENTOMOLOGY 

Family  GYRINID^ 

The  Whirligig-Beetles 

As  familiar  to  the  country  rover  as  the  gurgling  of  the  brook  or 
the  flecks  of  foam  on  its  "golden -braided  centre,"  or  the  trailing  ferns 
and  the  rustling  rushes  on  its  banks,  are  these  whirligigs  on  its 
pools.  Around  and  around  each  other  they  dart,  tracing  graceful 
curves  on  the  water,  which  vanish  almost  as  soon  as  made.  They 
are  social  fellows,  and  are  almost  always  fotmd  in  large  numbers, 
either  swimming  or  resting  motionless  near  together.  They  rareh^ 
dive,  except  when  pursued;  but  are  so  agile  that  it  is  extremely 
difficult  to  catch  them  without  a  net.  Man}^  of  them  when  caught 
exhale  a  milky  fluid  having  a  very  disagreeable  odor.  They  feed 
upon  small  flies,  beetles,  and  other  insects  that  fall  into  the  water, 
and  are  furnished  with  well-developed  wings,  with  which  they  fly 
from  one  body  of  water  to  another. 

This  is  one  of  the  most  easily-recognized  families  of  the  whole 
order  Coleoptera.  The  members  of  it  are  oval  or  elliptical  in  form 
(Fig.  570),  more  or  less  flattened,  and  usually  of  a  very 
brilliant  bluish  black  color  above,  with  a  bronze  metallic 
lustre.  The  fore  legs  are  very  long  and  rather  slender;  the 
middle  and  hind  legs  are  short,  broad,  and  very  much 
flattened.  These  insects  are  remarkable  for  having  the  eyes 
completely  divided  b}  the  margin  of  the  head,  so  that  they 
appear  to  have  four  eyes — a  pair  upon  the  upper  surface  of 
the  head  with  which  to  look  into  the  air,  and  a  pair  upon 
the  under  side  for  looking  into  the  water.  The  antennae  are  very  short 
and  peculiar  in  form.  The  third  segment  is  enlarged,  so  as  to  resemble 
an  ear-like  appendage,  and  the  following  ones  form  a  short  spindle- 
shaped  mass.    They  are  inserted  in  little  cavities  in  front  of  the  eyes. 

The  eggs  of  these  insects  are  small,  of  cylindrical 
form,  and  are  placed  end  to  end  in  parallel  rows  upon 
the  leaves  of  aquatic  plants.  The  larvae  (Fig.  571) 
are  long,  narrow,  and  much  flattened.  Each  abdominal 
segment  is  furnished  with  a  pair  of  tracheal  gills,  and 
there  is  an  additional  pair  at  the  caudal  end  of  the 
body.  The  elongated  form  of  the  body  and  the  con- 
spicuous tracheal  gills  cause  these  larv^se  to  resemble 
small  centipedes.  When  a  larva  is  full-grown  it  leaves 
the  water  and  spins  a  gray,  paper-like  cocoon  attached 
to  some  object  near  the  water.  The  pupa  state  of  those 
species  in  which  it  has  been  observed  lasts  about  a 
month.  Fig.  571. 

The  family  is  a  small  one.  At  present  only  forty-one 
North  American  species  are  known.  These  represent  three  genera. 
The  genus  Gyretes  is  distinguished  by  having  the  last  ventral  segment 
of  the  abdomen  elongated  and  conical.  It  is  represented  by  two 
species.  In  the  other  two  genera  the  last  ventral  segment  is  flattened 
and  roimded  at  the  tip.  In  DineHtus  the  scutellum  is  invisible;  there 
are  thirteen  species  of  this  genus.  In  Gyrlnus  the  scutellum  is  visible; 
of  this  genus  we  have  twenty-six  species. 


COLEOPTERA 


485 


Family  HYDROPHILID^ 
The  Water -Scavenger  Beetles 
The  water-scavenger  beetles  are  common  in  quiet  pools,  where 
they  may  be  found  swimming  through  the  water,  or  crawling  among 
the  plants  growing  on  the  bottom.    They  can  be  easily  taken  by  sweep- 
ing such  plants  with  a  dip-net. 

They  are  elongated,  elliptical,  black  beetles,  resembling  the  pre- 
dacious diving  beetles  in  appearance;  but  they  are  usually  more 
convex,  and  differ  also  in  having  club-shaped  antenna  and  very  long 
palpi.  As  the  antennae  are  usually  concealed  beneath  the  head,  it 
often  happens  that  the  inexperienced  student  mistakes  the  long 
palpi  for  antenna?. 

These  beetles  are  supposed  to  live  chiefly  upon  the  decaying  vege- 
tation in  the  water ;  but  a  number  of  species  have  been  known  to  catch 
and  eat  living  insects.  They  breathe  by  carrying  a 
film  of  air  on  the  lower  surface  of  the  body.  This 
film  gives  them  a  silvery  appearance  when  seen 
from  below.  They  obtain  the  air  by  bringing  the  head 
to  the  surface  of  the  water  and  projecting  the  an- 
tennae, which  they  again  fold  back  with  a  bubble  of  air 
when  they  descend.  The  female  makes  a  case  for  her 
eggs  out  of  a  hardened  silk-like  secretion.  Some 
species  deposit  as  many  as  a  hundred  eggs  in  one  of 
these  water-proof  packages  (Fig.  572).  The  egg- 
cases  in  some  instances  are  fastened  beneath  the 
leaves  of  aquatic  plants ;  in  others  they  are  provided 
with  floats  and  let  loose  in  the  water;  and  in  still  other  species  the 
cases  are  carried  by  the  mother  underneath  her  body  and  steadied 
with  her  hind  legs.  Frequently  some  of  the 
young  larva  devour  their  companions;  in  this 
way  the  size  of  the  family  is  decreased  before 
it  escapes  from  the  egg-case.  Later  they  live 
upon  insects  that  fall  into  the  water,  and  upon 
snails.  These  larvae  resemble  somewhat  those 
of  the  Dytiscida;  but  the  body  is  much  more 
plimip,  and  the  mandibles  are  of  moderate  size. 
The  family  Hydrophilidae  is  represented  in 
North  America  by  one  hundred  and  ninety 
species.  The  largest  of  our  common  species  is 
Hydrous  triangularis  (Fig.  573).  In  the  genus 
Hydrous  the  metasternum  is  prolonged  back- 
ward into  a  spine  between  the  hind  legs,  and 
the  sternum  of  the  prothorax  bears  a  deep 
furrow. 

The  beetles  of  the  genus  Tropisternus  agree 
with  Hydrous  in  the  form  of  the  prostemum  and  metasternum,  but 
differ  in  size,  our  species  measuring  less  than  12  mm.  in  length.  The 
most  common  species  in  the  East  is  Tropisternus  glabra,  and  on  the 
Pacific  Coast  T.  calif ornicus . 


Fig-  572. 


Fig-  573- 


486  AN  INTRODUCTION  TO  ENTOMOLOGY 

Next  in  size  to  Hydrous  are  several  species  of  Hydrophilus.  In 
this  genus  the  metasternum  is  prolonged  somewhat,  but  does  not 
form  a  long,  sharp  spine  as  in  Hydrous  and  Tropisternus,  and  the 
sternum  of  the  prothorax  bears  a  keel-shaped  projection.  Our  most 
conunon  species  is  Hydrophilus  obtusdhts;  this  measures  about  1 5  mm. 
in  length. 

Some  of  the  sm.aller  species  of  this  family  are  not  aquatic,  but 
live  in  moist  earth  and  in  the  dung  of  cattle,  where,  it  is  said,  they 
feed  on  dipterous  larvae. 

Suborder  POLYPHAGA* 

In  the  suborder  Polyphaga  the  ventral  part  of  the  first  segment 
of  the  abdomen  is  visible  for  its  entire  breadth  (Fig.  574);  the  first 

three  ventral  segments  are  immov- 
ably united  (except  in  the  Cupesidas), 
and  the  notum  of  the  prothorax  is 
not  separated  from  the  pleura  by 
distinct  sutures. 

So  far  as  known,  the  nutritive 
cells  of  the  ovaries  are  massed  to- 
gether in  the  terminal  chamber  of 
each  ovarian  tube  in  all  members  of 
this  suborder. 

The  larvse  vary  greatly  in  form; 
Fig.  574.-Ventral  aspect  of  part  of  some  are  campodeiform, "  some  are 
thorax  and  abdomen  of  Enchro-  scarabeiform,  and  others  are  vermi- 
ma  gigantea:  ist  .4,  first  abdom-  form;  in  none  are  the  legs  more  than 
mal  segment.  five-jointed,  and  in  none  are  the  legs 

two-clawed. 
This  suborder  includes  all  but  the  seven  preceding  families  of  the 
Coleoptera ;  the  families  included  in  it  are  grouped  into  seven  series ; 
see  synopsis,  page,  467. 

Family  PLATYPSYLLID^ 
The  Beaver-Parasite 

Only  a  single  representative  of  this  family  is  known;  this  is 
Platypsylla  castoris,  which  lives  parasitically  on  the  beaver.  This 
beetle  is  about  2.5  mm.  in  length;  the  body  is  ovate,  elongate,  and 
much  flattened;  the  wing-covers  are  short,  about  as  long  as  the 
prothorax,  and  leave  five  abdominal  segments  exposed;  the  eyes  and 
wings  are  wanting. 

Specimens  of  this  remarkable  insect  are  most  easily  obtained  by 
beating  over  a  sheet  of  paper  the  dried  skins  of  beavers,  which  can 
be  found  in  fur-stores. 

The  family  BRATHINID^  is  composed  of  the  genus  Brathinus, 
of  which  three  species  are  described,  two  from  the  East  and  one  from 
California.      These  beetles  are  somewhat  elongate,  with  the  outline 

*Polyphaga:  polyphagus,  eating  many  kinds  of  food. 


COLEOPTERA  487 

of  the  prothorax  and  of  the  elytra  elliptical;  they  measure  from 
3.6  mm.  to  5  mm.  in  length.  The  Cahfomian  species  was  found  living 
in  wet  moss,  darkly  overshadowed  by  bushes,  at  the  margin  of  a 
mountain  stream. 

Family  LEPTINID^ 
The  Mammal-Nest  Beetles 

This  family  is  represented  by  only  three  species  in  North  America. 
One  of  these,  Lepthms  testdceus,  is  a  European  species,  but  is  widely 
distributed  in  this  country.  It  lives  in  the  nests  of  mice  and  other 
small  rodents  and  insectivora,  and  also  in  the  nests  of  bumble-bees. 
Whether  it  is  a  parasite  or  merely  a  guest  has  not  been  definitely  de- 
termined ;  but  it  seems  probable  that  it  feeds  upon  the  eggs  and  young  of 
mites  and  other  small  creatures  found  in  these  nests.  This  beetle  is 
oblong-oval  and  much  depressed  in  form,  and  pale  yellow  in  color; 
it  measures  from  2  mm.  to  2.5  mm.  in  length.  Specimens  can  be 
obtained  by  shaking  a  nest  of  a  mouse  over  a  sheet  of  paper. 

The  other  two  species  are  LeptinUlus  vdlidus,  found  in  Hudson 
Bay  territory,  and  LeptinUlus  aplodonttce,  found  in  California  on  a 
rodent  (Aplodontia) . 

Family  SILPHID^ 
The  Carrion-Beetles 

The  carrion-beetles  are  mostly  of  medium  or  large  size,  many 
species  attaining  the  length  of  35  mm.  while  the  smaller  species  of  the 
more  typical  genera  are  nearly  12  mm.  in 
length;  some  members  of  the  family,  how- 
ever, are  minute.  The  segments  near  the  tip 
of  the  antennae  are  usually  enlarged  so  as  to 
form  a  compact  club,  which  is  neither  comb- 
like nor  composed  of  thin  movable  plates; 
sometimes  the  antennae  are  nearly  filiform. 

These  insects  usually  feed  upon  decaying 
animal  matter;  some,  however,  feed  upon 
fungi ;  some  on  vegetables ;  and  a  few  species 
have  been  known  to  be  predacious  when 
pressed  by  hunger,  destroying  living  snails 
and  insects,  even  members  of  their  own  spe- 
cies ;  while  a  few  occur  only  in  the  nests  of  ants . 

It  is  easy  to  obtain  specimens  of  these  in- 
sects by  placing  pieces  of  meat  or  small  dead  pjg   ^^^ 
animals  in  the  fields  and  examining  them 

daily.  There  are  several  other  families  of  beetles  the  members  of 
which  can  be  attracted  in  this  way. 

The  larvae  also  live  upon  decaying  flesh  and  are  found  in  the  same 
situations  as  the  adults. 

We  have  in  this  country  more  than  one  hundred  species  of  this 
family.  Our  larger  and  more  familiar  species  represent  two  genera, 
Necrophorus  and  Silpha. 

The  burying-beetles,  Necrophorus. — To  this  genus  belong  the 
larger  members  of  the  family.  The  body  is  very  stout,  almost  cylin- 
drical (Fig.  575).    Our  common  species  have  a  reddish  spot  on  each 


i88  AN  INTRODUCTION  TO  ENTOMOLOGY 

end  of  each  wing-cover;  these  spots  are  often  so  large  that  they 
appear  as  two  transverse  bands.  In  some  species  the  prothorax  and 
the  head  are  also  marked  with  red. 

These  insects  are  called  burying-beetles  because  they  bury  carrion. 
When  a  pair  of  these  beetles  discover  a  dead  bird,  mouse,  or  other 
small  animal,  they  dig  beneath  it,  removing  the  earth  so  as  to  allow 
the  carrion  to  settle  into  the  ground.  This  they  will  continue  until 
the  object  is  below  the  surface  of  the  groimd.  Then  they  cover  it 
with  earth,  and  finally  the  female  digs  down  to  it  and  lays  her  eggs 
upon  it.  The  larvae  that  hatch  from  these  eggs  feed  upon  the  food 
thus  provided  for  them.  There  are  many  accoimts  of  exhibitions  of 
remarkable  strength  and  sagacity  by  burying-beetles.  A  pair  of 
these  insects  have  been  known  to  roll  a  large  dead  rat  several  feet  in 
order  to  get  it  upon  a  suitable  spot  for  burying. 

The  members  of  the  genus  SUpha  are  very  much 

«f         flattened  (Fig.  576).    The  prothorax  is  round  in  outline, 
with  very  thin  edges  which  overlap  the  wing-covers 
\       somewhat.    The  body  is  not  nearly  as  stout  as  that  of 
\         a    burying    beetle,    being   fitted    for    creeping    under 
{         dead  animals  instead  of  for  performing  deeds  requiring 
great  strength.     SUpha  bituberosa,  which  is  known  as 
Fig-  576.        -thg  spinach  carrion-beetle,  feeds  on  spinach,  beets,  and 
other  plants,  in  the  West. 
In  some  of  the  minute  members  of  this  family  the  body  is  nearly 
hemispherical. 

The  family  CLAMBID^  consists  of  very  minute  species,  measur- 
ing about  I  mm.  in  length.  They  live  in  decomposing  vegetable 
matter.  The  edge  of  the  hind  wings  is  fringed  with  long  hairs.  For 
other  characters,  see  table,  page  470.  Only  six  species,  representing 
three  genera,  occur  in  our  fauna. 

The  family  SCYDM^NID^  includes  very  small  insects  found 
under  bark  or  stones,  in  ants'  nests,  or  near  water.  They  are  small, 
shining,  usually  ovate  but  sometimes  slender  insects,  of  a  brown  color, 
and  more  or  less  clothed  with  erect  hairs.  Other  characters  are  given 
in  the  preceding  table  of  families.  About  one  hundred  seventy-five 
North  American  species  are  known. 

The  family  CORYLOPHID^  includes  minute  beetles  found  under 
damp  bark  and  in  decaying  fungi  and  other  vegetable  matter.  The 
body  is  oval  or  rounded,  and  in  many  species  is  clothed  with  a  grayish 
pubescence.  The  wings  are  wide,  and  fringed  with  long  hairs.  Some 
of  our  common  species  measure  less  than  i  mm.  in  length.  Fifty- 
seven  North  American  species  have  been  described. 

Family  STAPHYLINID/E 

The  Rove-Beetles 

The  rove-beetles  are  very  common  about  decaying  animal  matter, 
and  are  often  found  upon  the  groimd,  imder  stones  or  other  objects. 


COLEOPTERA  4  89 

They  are  mostly  very  small  insects;  a  few  species,  however,  are  of 
larger  size,  measuring  12  mm.  or  more  in  length.  Their  appearance 
is  very  characteristic,  the  body  being  long  and  slender, 
and  the  wing-covers  very  short  (Fig.  577).  The  wings, 
however,  are  fully  developed,  often  exceeding  the  ab- 
domen in  length;  when  not  in  use  the  wings  are  folded 
beneath  the  short  wing-covers.  The  abdominal  seg- 
ments are  freely  movable. 

It  is  interesting  to  watch  one  of  these  insects  fold 
its  wings;  frequently  they  find  it  necessary  to  make 
use  of  the  tip  of  the  abdomen  or  of  one  of  the  legs  in 
order  to  get  the  wings  folded  beneath  the  wing-covers.         Fig.  577. 

The  rove-beetles  can  run  quite  swiftly;  and  they 
have  the  curious  habit,  when  disturbed,  of  raising  the  tip  of  the 
abdomen  in  a  threatening  manner,  as  ii  they  could  sting.  As  some 
of  the  larger  species  resemble  wasps  somewhat  in  the  form  of  the  body, 
these  threatening  motions  are  often  as  effective  as  if  the  creatures 
really  had  a  sting.  William  Beebe  states  {Atlantic  Monthly,  October 
19 1 9)  that  when  some  rove-beetles  were  attacked  by  ants  they  raised 
their  tails  and  ejected  a  drop  or  two  of  a  repellent  fluid  which  drove 
the  ants  away.  This  observation  indicates  the  probable  explanation 
of  the  actions  of  these  beetles  when  disturbed. 

As  these  insects  feed  upon  decaying  animal  and  vegetable  matter, 
they  should  be  classed  as  beneficial.  The  larvae  resemble  the  adults 
in  the  form  of  the  body  and  are  found  in  similar  situations,  about 
decaying  animal  and  vegetable  matter,  beneath  bark  and  in  fungi. 
Some  species  are  guests  in  the  nests  of  ants,  and  others  in  the  nests 
of  termites. 

Nearly  three  thousand  North  American  species  of  rove-beetles 
have  been  described.  The  great  majority  are  small  and  exceedingly 
difficult  to  determine.  Among  the  large  species  that  are  common  are 
the  following. 

Creophilus  maxillosus. —  This  species  varies  from  12  mm.  to  nearly 
25  mm.  in  length.  It  is  of  a  shining  black  color,  spotted  with  patches 
of  fine  gray  hairs.  There  is  a  conspicuous  band  of  these  across  the 
middle  of  the  wing-covers,  and  another  on  the  second  and  third 
abominal  segments;  this  abdominal  band  is  best  marked  on  the  lower 
side  of  the  body. 

Staphyllnus  maculosus  is  a  larger  species,  which  often  measures 
fully  25  mm.  in  length.  It  is  densely  punctured,  and  of  a  dull  brown 
color,  with  the  scutellimi  black,  and  a  row  of  obscure,  square,  blackish 
spots  along  the  middle  of  the  abdomen. 

Staphylhius  vulplnus  resembles  the  preceding  somewhat,^  but  it 
has  a  pair  of  bright  yellow  spots  at  the  base  of  each  abdominal  segment. 

Ontholestes  cinguldtus  is  of  about  the  same  size  as  the  preceding. 
It  is  brown,  speckled  with  brownish  black  spots,  and  the  tip  of  its 
abdomen  is  clothed  with  golden  hairs. 

The  family  PSELAPHID^  includes  certain  very  small  beetles, 
the  larger  ones  not  exceeding  3  mm.  in  length.     They  resemble  rove- 


490  AN  INTRODUCTION  TO  ENTOMOLOGY 

beetles  in  the  shortness  of  the  wing-covers  and  in  having  the  dorsal 
part  of  the  abdominal  segments  entirely  hom}^;  but  they  differ 
from  them  in  that  the  abdomen  is  not  flexible,  and  in  having  fewer 
abdominal  segments,  there  being  only  five  or  six  on  the  ventral  side. 
The  species  are  chestnut -brown,  dull  yellow,  or  piceous,  and  are 
usually  slightly  pubescent.  The  antennae  are  usually  eleven-jointed, 
rarely  ten-jointed.  The  elytra  and  abdom.en  are  convex  and  usually 
wider  than  the  head  and  prothorax.  These  beetles  are  usually  found 
imder  stone  and  bark,  or  flying  in  the  twilight;  a  few  species  have 
been  found  in  the  nests  of  ants.  There  are  three  hundred  and  fifty- 
five  described  North  American  species. 

The  family  CLAVIGERID^,  or  the  ant-loving  beetles,  includes 
a  small  number  of  beetles  that  resemble  the  Pselaphids  in  the  char- 
acters given  above  except  that  the  antennae  are  only  two-jointed. 
These  beetles  live  in  the  nests  of  ants.  They  excrete  from  small 
tufts  of  hairs,  on  the  three  basal  abdominal  segments,  a  fluid  of 
which  the  ants  are  very  fond.  The  ants  caress  the  tufts  of  hairs  with 
their  antennae,  causing  the  exudation  of  the  fluid,  which  they  greedily 
swallow.  The  ants  are  said  to  feed  the  beetles  and  to  allow  them  to 
ride  about  on  their  backs,  when  the  beetles  wish  to  do  so.  Only 
seven  North  American  species  are  described. 

The  family  TRICHOPTERYGID^,  or  the  feather-wing  beetles, 
includes  the  smallest  beetles  that  are  known;  most  of  our  species  are 
less  than  i  mm.  in  length.  The  most  striking  feature  of  the  typical 
forms  is  the  shape  of  the  wings,  which  are  long,  narrow,  and  fringed 
with  long  hairs,  being  feather-like  in  appearance;  but  in  some  species 
the  wings  are  wanting.  Some  species  live  in  rotten  wood,  muck, 
manure,  and  other  decaying  organic  matter;  few  have  been  found  in 
ants'  nests.     There  are  about  eighty  described  species  in  our  fauna. 

The  family  SCAPHIDIID^E,  or  shining  fungus-beetles,  includes 
small,  oval,  very  shining  beetles,  found  in  fungi,  rotten  wood,  dead 
leaves,  and  beneath  the  bark  of  logs.  The  elytra  are  broadly  tnuicate 
behind,  not  covering  the  tip  of  the  conical  abdomen.  But  little  is 
known  regarding  their  life-history.  There  are  fifty  described  North 
American  species. 

The  family  SPH^RITID^  is  represented  in  our  fauna  by  a 
single  species,  Sphcerltes  glabrdtus,  which  has  been  found  in  Alaska  and 
California.  This  beetle  is  very  similar  in  appearance  to  those  of  the 
genus  Hister.    For  distinguishing  characters,  see  table,  page  470. 

The  family  SPH^RIID^  includes  a  single  genus,  SphcErius, 
which  is  represented  in  North  America  by  only  three  known  species. 
They  are  very  minute  beetles,  measuring  about  .5  mm.  in  length; 
they  are  very  convex,  and  may  be  found  walking  on  mud  or  under 
stones  near  water. 

The  family  HISTERID^  includes  certain  easily  recognized 
beetles  which  are  foimd  about  carrion  and  other  decomposing  sub- 
stances. They  are  mostly  small,  short,  rounded  or  somewhat  square- 
shaped  beetles,  of  a  shining  black  color,  with  the  wing  covers  marked 


COLEOPTERA  491 

by  lines  of  fine  punctures  and  truncate  behind,  leaving  two  segments 

of  the  abdomen  exposed  (Fig.  578).    In  some  species  the  wing-covers 

are  marked  with  red.    There  are  nearly  four 

\u       /      hundred  described  North  American  species. 

)^l  The  family  LYCID^  includes  certain 

'Hl\      beetles  that  were  formerly  classed  in  the 

^  ^        fire-fly    family;  but    they    differ    from    the 

Fig.  578.     Lampyridae    in    having    the    middle    coxae 

distant,   and   in   that   the   elytra  lack   epi- 

pleurae.    The  elytra  are  usually  furnished  with  several 

longitudinal  ribs  and  a  network  of  fine  elevated  lines. 

The  members  of  this  family  are  diurnal  in  habits ;  they 

are  found  on  the  leaves  of  plants,  where  they  seek  and  feed  upon 

other  insects.    A  common  species  is  Calopteron  reticuldtum  (Fig.  579). 

Family  LAMPYRID^ 
The  Firefly  Family 

During  some  warm,  moist  evening  early  in  our  northern  June  we 
are  startled  to  see  here  and  there  a  tiny  meteor  shoot  out  of  the 
darkness  near  at  hand,  and  we  suddenly  realize  that  summer  is  close 
upon  us,  heralded  by  her  mysterious  messengers,  the  fireflies.  A 
week  or  two  later  these  little  torch-bearers  appear  in  full  force,  and 
the  gloom  that  overhangs  marshes  and  wet  meadows,  the  dusk  that 
shrouds  the  banks  of  streams  and  ponds,  the  darkness  that  haunts 
the  borders  of  forests,  are  illumined  with  myriads  of  flashes  as  these 
silent,  winged  hosts  move  hither  and  thither  under  the  cover  of  the 
night. 

The  fireflies  are  soft -bodied  beetles  of  medium  or  small  size,  with 
slender,  usually  eleven-jointed,  saw -like  antennae.  The  prothorax  is 
expanded  into  a  thin  projecting  margin,  which  in  most  cases  com- 
pletely covers  the  head  (Fig.  580).  The  wing-covers  are  rather  soft, 
and  never  strongly  embrace  the  sides  of  the  abdomen,  as 
with  most  other  beetles. 

The  fireflies  are  nocturnal  insects  and  are  sluggish  by 
day.  The  property  of  emitting  light  is  possessed  by  adults 
of  both  sexes  and  by  larvae.  The  latter  and  the  wingless 
females  of  certain  species  are  known  as  glow-worms.  The 
light-organs  of  the  winged  adults  are  situated  on  the  lower  . 
side  of  one  or  more  of  the  abdominal  segments;  but  they  ^^' 
are  lacking  in  some  genera. 

There  have  been  many  speculations  as  to  the  usefulness  of  the 
light-producing  power  of  various  organisms  to  the  organisms  them- 
selves; and  as  regards  many  of  these  photogenic  creatures  no  definite 
conclusions  have  been  reached.  But  there  is  considerable  evidence  to 
show  that  in  the  case  of  adult  lampyrids  it  serves  to  enable  these 
insects  to  find  their  mates.  It  has  been  found  that  females  enclosed 
in  a  perforated  opaque  box  do  not  attract  males,  while  those  enclosed 


# 


492  ^A^  INTRODUCTION  TO  ENTOMOLOGY 

in  a  glass  vial  do;  thus  showing  that  it  is  the  light  emitted  by  the 
female,  and  not  its  odor,  that  attracts  the  male.  It  has  also  been  shown 
that  in  some  cases  at  least  there  are  specific  differences  in  the  method 
of  flashing  which  enables  the  insects  to  distinguish  at  a  distance  their 
proper  mates. 

More  than  fifty  species  of  the  Lampyridas  have  been  found  in 
this  country. 

The  family  PHENGODID^  includes  a  small  number  of  species 
that  were  formerly  included  in  the  firefly  family.  In  this  family 
theprothorax,  though  rounded  in  front,  does  not  cover  the  head,  which 
is  exposed.  The  antennas  are  usually  pltimose  or  flabellate  in  the 
males.  The  females  of  some  species,  at  least,  are  glow-worms,  re- 
sembling the  larv£e  in  form,  and  are  photogenic.  Only  twenty -three 
American  species  have  been  described ;  most  of  these  are  found  in 
California,  Texas,  and  Arizona,  but  some  occur  in  the  East. 

Family  CANTHARID^ 

The  Soldier-Beetles  and  others 

The  family  Cantharidae  includes  those  genera  that  were  formerly 
included  in  the  family  Lampyridse  as  the  subfamily  Telephorinas. 
For  the  distinctive  characters  separating  this  from  the  allied  families, 
see  the  table,  page  473. 

The  application  of  the  name  Cantharidge  to  this  family  is  the 
result  of  one  of  those  unfortunate  changes  in  generic  names  rendered 
necessary  by  our  code  of  nomenclature.  In  this  case  the  change  is 
especially  unfortunate,  as  the  generic  name  Cantharis  has  been  com- 
monly applied  to  certain  blister-beetles  and  is  used  in  that  sense  in 
many  medical  works  and  in  most  text-books  of  entomology.  The 
change  is  sure  to  result  in  much  confusion. 

The  most  common  members  of  this  family  are  the  soldier-beetles, 
Chauliopnathus.    These  are  very  abundant  in  late  summer  and  autumn 
on  various  flowers,  but  especially  on 
\  y      those  of  goldenrod.     The  most  com- 

mon species  in  the  East  are  the  Penn- 
sylvania soldier-beetle,  Chauliognathus 
pennsylvanicus,  which  is  yellow,  with  a 
black  spot  in  the  middle  of  the  pro- 
thorax  and  one  near  the  tip  of  each 
wing-cover  (Fig.  581);  and  the  mar- 
gined  soldier-beetle,  C.  margindtus. 
ig-  5  I-  'pj^^g  species  (Fig.  582)  can  be  dis- 
tinguished from  the  former  by  the  head  and  lower  parts  of  the  femora 
being  orange.  The  beetles  of  this  genus  are  remarkable  for  having 
an  extensible,  fleshy  filament  attached  to  each  maxilla.  These  fila- 
ments are  probably  used  in  collecting  pollen  and  nectar  from  flowers. 
This  family  is  represented  in  our  fauna  by  nine  genera  which  in- 
clude more  than  one  hundred  and  fifty  species. 


COLEOPTERA  493 

The  family  MELYRID^  is  composed  chiefly  of  small  or  very 
small  beetles,  some  of  which  are  found  on  flowers,  and  others  on  the 
groimd  in  low,  moist  places.  They  are  said  to  be  carnivorous.  They 
var\'  greatly  in  form,  but  bear  a  general  resemblance  in  structure  to 
the  preceding  four  families,  from  which  they  can  be  distinguished 
by  the  presence  of  only  six  ventral  abdominal  segments.  Some 
members  of  the  family  are  furnished  with  soft,  orange- 
colored  vesicles,  which  they  protrude  from  the  sides  of 
the  body  and  which  are  supposed  to  be  scent  organs  for 
defence.  One  of  our  most  common  representatives  is 
Collops  quadrimaculdtus ,  which  is  yellow -orange,  with  Fig.  583. 
the  top  of  the  head  and  four  spots  on  the  elytra  bluish 
black  (Fig.  583).  This  species  is  found  on  grasses  in  damp  localities. 
The  family  is  represented  in  our  fauna  by  more  than  three  hundred 
species. 

The  family  CLERID^,  or  the  checkered  beetles,  includes  a  con- 
siderable ntmiber  of  predacious  species  which  are  foimd  on  flowers 
and  on  the  trunks  of  trees.  Many  of  them  are  beautifully  marked 
with  strongly  contrasting  colors;  this  has  suggested  the  common 
name  checkered  beetles  for  them.  Frequently  they  are  more  or  less 
ant-like  in  form,  the  prothorax  being  in  these  cases  narrower  than 
the  wing-covers,  and  slightly  narrower  than  the  head.  The  abdomen 
has  either  five  or  six  ventral"  segments;  the  anterior  coxae  are  conical, 
prominent,  and  contiguous,  or  very  slightly  separated;  the  hind 
coxae  are  transverse,  not  prominent,  and  covered  by  the  femora  in 
repose;  the  legs  are  slender ;  and  the  tarsi  are  five-jointed. 
In  the  larval  state  these  insects  are  usually  camivo- 

trous,  living  imder  bark  and  in  the  burrows  of  wood-boring 
insects,  upon  which  they  prey;  some  are  found  in  the 
nests  of  bees;  and  still  others  feed  on  dead  animal  matter. 
The  family  is  represented  in  our  fauna  b}^  nearly  two 
p.  „  hundred  species.  Figure  584  represents  one  of  our  more 
common  species,  Trichodes  nutialli. 

The  family  CORYNETID^  has  recently  been  sep- 
arated from  the  Cleridae,  which  they  closely  resemble.  In  this  family 
the  fourth  joint  of  the  tarsi  is  atrophied;  this  character  distinguishes 
these  beetles  from  the  Clerids.  About  forty  American  species  have 
been  described. 

To  this  family  belongs  the  red-legged  ham-beetle,  Necrohia  riifipes. 
This  is  a  small  steel-blue  beetle  with  reddish  legs;  it  measures  from 
3.5  mm.  to  6  mm.  in  length.  It  is  foimd  about  dead  animal  matter 
in  fields  and  in  other  situations.  It  sometimes  invades  storehouses 
and  seriously  infests  hams. 

The  family  LYMEXYLID^  includes  elongated,  narrow  beetles, 
with  short  serrate  antennae.  Only  two  species  have  been  foimd  in 
this  country  and  these  are  rare.  To  this  family  belongs  the  ship- 
timber  beetle,  Lymexylon  navdle,  of  northern  Europe.  The  larv^a  of 
this  species  was  at  one  time  a  very  serious  pest  in  ship-yards,  on 
account  of  its  habit  of  drilling  cylindrical  holes  in  the  timber.     The 


494  AN  INTRODUCTION  TO  ENTOMOLOGY 

method  of  control  by  immersing  the  timber  during  the  time  of  o\'i- 
position  of  the  beetle  was  suggested  bv  Linnaeus. 

The  family  MICROMALTHID^  includes  a  single  species, 
Micromalthus  dehilis.  This  is  a  small  beetle,  measuring  only  2.2  mm. 
in  length.  It  is  elongate,  piceous,  shining,  with  the  antennas  and  legs 
yellow.  This  species  is  of  great  interest  on  account  of  its  remarkable 
life-history,  only  a  part  of  which  is  yet  known.  Two  papers  on  this 
subject  have  been  published  by  Mr.  H.  S.  Barber  ('13a,  '13b). 
Briefl3^  this  author's  observations  indicate  that  eggs  are  produced  by 
larvae  as  well  as  by  the  adult  females ;  that  there  are  seven  or  eight 
forms  of  larvae;  that  the  two  sexes  of  adults  are  developed  through  two 
distinct  lines  of  larv^s;  and  that  viviparous  as  well  as  oviparous 
paedogenesis  occurs  in  the  life-cycle.  The  larA'^e  are  foimd  in  decaying 
oak,  chestnut,  and  pine  logs,  where  they  make  burrows  in  the  decay- 
ing wood,  on  which  they  feed. 

The  family  CUPESID^E  includes  only  four  American  species. 
These  are  foiind  imder  the  bark  of  decaying  trees,  and  sometimes  in 
houses.  The  body  is  covered  with  small  scales ;  other  characteristics 
are  given  in  the  table  of  families,  page  471. 

The  family  CEPHALOID^  is  a  small  family  of  which  only  eight 
American  species  have  been  described.  See  table,  page  474,  for  dis- 
tinctive characters. 

The  family  CEDEMERID^  is  composed  of  beetles  of  moderate 

size,  with  elongate,  narrow  bodies.     The  head  and  prothorax  are 

somewhat  narrower  than  the  wing-covers;  the  antennae  are  long, 

nearly  filiform,   sometimes  serrate;  the  anterior  coxal  cavities  are 

open  behind,  and  the  middle  coxae  are  very  prominent.     Less  than 

fifty  North  American  species  have  been  described.    They  are  generally 

foimd  on  plants,  but  some  live  on  the  ground  near  water.    The  lar\^ae 

live  for  the  most  part  in  decaying  wood. 

^^  The  family  MORDELLID^  includes  a  large  number 

>4H^       of  small  beetles  which  are  easily  recognized  by  their  pe- 

f^—^         cuhar  form   (Fig.   5S5).     The  body  is  arched,   the  head 

Fio-.   585.      being  bent  do\^m;  and  the  abdomen  is  usually  prolonged 

into  a  slender  point.    Our  most  common  species  are  black; 

but  many  are  variegated,  and  all  are  pubescent.     The 

adults  are  usualh'  found  on  flowers ;  the  larv^ae  live  in  rotten  wood  and  in 

the  pith  of  various  plants,  upon  which  they  are  supposed  to  feed.  Nearly 

one  hundred  fiftv  American  species  have  been  described. 

The  family  RHIPIPHORID^  includes  a  small  num- 
ber of  beetles,  which  are  very  remarkable  in  structure  and 
habits.    The  wing-covers  are  usually  shorter  than  the  ab- 
domen, and  narrowed  behind  (Fig.  586);  sometimes  they 
are  ver>^  small,  and  in  one  exotic  genus  they  are  wanting      p-      .gg 
in  the  female,  which  lacks  the  wings  also  and  resembles  a 
larva  in  form.    The  antennae  are  pectinate  or  flabellate  in 
the  males,  and  frequently  serrate  in  the  females.    The  adult  insects 
are  foimd  on  flowers.    The  larv^se  that  are  known  are  parasites,  sorne 
in  the  nests  of  wasps,  and  some  on  cockroaches. 


COLEOPTERA  495 

Family  MELOID^ 
The  Blister -Beetles 

The  blister-beetles  are  of  medium  or  large  size.  The  body  is  com- 
paratively soft;  the  head  is  broad,  vertical,  and  abruptly  narrowed 
into  a  neck;  the  prothorax  is  narrower  than  the  wing-covers,  which 
are  soft  and  flexible ;  the  legs  are  long  and  slender ;  the  hind  tarsi  are 
four-jointed,  and  the  fore  and  middle  tarsi  are  five-jointed. 

These  beetles  are  found  on  foliage  and  on  flowers,  on  which  they 
feed  in  the  adult  state;  some  of  the  species  are  very  common  on 
goldenrod  in  the  autumn;  and  several  species  feed  on  the  leaves  of 
potato. 

The  blister-beetles  are  so  called  because  they  are  used  for  making 
blister-plasters.  The  beetles  are  killed,  dried,  and  pulverized,  and 
the  powder  thus  obtained  is  made  into  a  paste,  which  when  applied 
to  the  skin  produces  a  blister.  The  species  most  commonly  used  is  a 
European  one,  commonly  known  as  the  Spanish-fl}';  but  our  Ameri- 
can species  possess  the  same  blistering  property. 

The  postembryonic  development  of  those  blister-beetles  of  which 
the  complete  life-history  is  laiown  is  a  very  remarkable  one;  for  it 
has  been  found  that  in  each  of  these  cases  there  is  a  complicated 
hypermetamorphosis.  The  food  of  the  larva  consists,  in  some  species, 
of  the  eggs  of  short-horned  grasshoppers,  in  others  of  the  egg  and  the 
food  stored  in  the  cell  of  some  solitary  bee.  The  female  blister-beetle 
lays  her  eggs  in  the  ground;  a  large  number  of  eggs  are  laid  by  a 
single  female ;  this  fact  is  doubtless  correlated  with  the  difficulties  to 
be  overcome  by  the  larvee  in  their  search  for  their  proper  food,  in 
which  comparatively  few  are  successful.  The  newly  hatched  larva  is 
campodeiform  (Fig.  587,  A),  and  is  known  as  the  triungulin,  a  term 
applied  to  the  first  instar  of  blister-beetle  larvae.  This  term  was  sug- 
gested by  the  fact  that  in  this  instar  the  tarsi  appear  to  be  three- 
clawed;  but  in  reality  each  tarsus  is  armed  with  a  single  claw,  on  each 
side  of  which  there  is  a  claw-like  seta. 

The  triungulins  are  very  active.  In  the  case  of  those  that  feed 
on  the  eggs  of  short -homed  grasshoppers,  they  run  over  the  groiuid 
seeking  a  place  where  one  of  these  insects  has  deposited  its  egg-pod; 
if  a  triungulin  is  successful  in  this  search  it  bores  its  way  into  the  egg- 
pod;  if  more  than  one  find  the  same  egg-pod,  battles  occur  till  only 
one  is  left.  In  the  case  of  those  species  that  develop  in  the  nests  of 
bees,  the  triiuigulin,  instead  of  hunting  for  a  nest,  merely  climbs  a 
plant,  and  remains  near  a  flower  till  it  has  a  chance  to  seize  hold  of 
a  bee  visiting  the  flower;  it  then  clings  to  the  bee  until  she  goes  to 
her  nest,  then,  letting  go  of  the  bee,  it  remains  in  the  cell  and  is  shut 
up  there  with  the  egg  of  the  bee  and  the  store  of  food  which  she 
provides  for  her  young.  The  triungulin  first  devours  the  egg;  after 
which  it  molts  and  undergoes  a  change  of  form,  becoming  a  clumsy 
creature,  which  feeds  upon  the  food  stored  in  the  cell.  Several  other 
changes  in  form  occur  before  the  beetle  reaches  the  adult  stage ;  these 
changes  are  quite  similar  to  those  undergone  by  the  larva  of  £/?i'caM^a. 
described  below. 


496 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  wonderful  instinct  by  which  the  triunguHns  of  these  bHster- 
beetles  find  their  way  to  the  nests  of  soHtary  bees  has  not  yet  reached 
perfection ;  for  many  of  them  attach  themselves  to  flies,  wasps,  honey- 
bees, and  other  flower-visiting  insects,  and  merely  gain  useless  trans- 
portation thereby. 

The  life-history  of  Epicauta  vittdta,  which  was  worked  out  by 
Mr.  C.  V.  Riley  ('77),  will  serve  to  illustrate  the  hypermetamorphosis 
of  blister-beetles.  The  adult  beetle  is  yellowish  or  reddish  above, 
with  the  head  and  prothorax  marked  with  black  and  with  two  black 
stripes  on  each  wing-cover  (Fig.  587,  F).  It  feeds  on  the  leaves  of 
potato,  and  is  sometimes  a  serious  pest.    The  female  lays  her  eggs  in 


Fig.  587. — Hypermetamorphosis  of  Epicauta  vittata.     (From  Sharp,  after  Riley.) 


the  ground  in  loose,  irregular  masses  of  about  130  each;  several  such 
masses  are  laid  by  a  single  female.  She  prefers  for  purposes  of  ovi- 
position  the  very  same  warm,  sunny  locations  chosen  by  the  locusts 
for  laying  their  eggs.  The  triungulins  that  hatch  from  the  blister- 
beetle  eggs  (Fig.  587,  A)  are  very  active;  when  one  of  them  finds  an 
egg-pod  of  a  locust  it  penetrates  it,  and  in  the  course  of  several  days 
devours  two  of  the  eggs;  a  period  of  rest  follows  during  which  it 
molts.  The  second  instar  (Fig.  587,  B)  differs  greatly  in  form  from 
the  triungulin,  and  is  known  as  the  caraboid  larva.  A  second  molt 
takes  place  after  about  a  week,  but  it  is  not  accompanied  by  any 
very  great  change  of  form,  though  the  larva  is  now  curved,  less 
active,  and  in  form  like  the  larva  of  a  scarabasid  beetle.  About  a  week 
later,  the  third  molt  occurs;  the  change  in  form  at  this  molt  is  not 
great,  the  fourth  instar  (Fig.  587,  D)  like  the  third  being  scarabaeoid 
in  form ;  these  two  instars  can  be  distinguished  as  the  first  scarabceoid 
/art)a  and  the  second  scarabceoid  larva  respectively.    The  second  scara- 


COLEOPTERA 


497 


baeoid  larva  grows  apace,  its  head  being  constantly  bathed  in  the  rich 
juices  of  the  locust  eggs,  which  it  rapidly  sucks  or  more  or  less  com- 
pletely devours.  In  another  week  it  forsakes  the  remnants  of  the 
locust  egg-mass  and  forms  a  smooth  cavity  in  the  soil  a  short  distance 
from  it.  The  larva  then  molts;  the  skin  is  not  shed  entirely,  but 
remains  attached  to  the  caudal  end  of  the  body  (Fig.  587,  C).  The 
new  skin  of  the  larva  becomes  rigid  and  of  a  deeper  yellow  color, 
reminding  one  of  a  puparium  of  a  dipterous  insect;  this  instar,  the 
fifth,  is  termed  the  coarctate  larva.  The  insect  has  the  power  of  re- 
maining in  this  coarctate  larval  condition  for  a  long  time,  and  gen- 
erally thus  hibernates.  At  the  fifth  molt  the  larva  becomes  active 
again,  and  burrows  about  in  the  ground;  it  now  resembles  in  form 
the  second  scarabaeoid  larva  except  that  it  is  smaller  and  whiter;  this, 
the  sixth  instar,  was  termed  by  Riley  the  scolytoid  larva.  In  the  cases 
observed  by  Riley,  the  scolytoid  larvae  did  not  feed  but  transformed 
to  pupae  (Fig.  587,  E)  in  the  course  of  a  few  days.  The  pupa  state 
lasted  five  or  six  days. 

More  than  two  hundred  species  of  blister-beetles  have  been 
found  in  this  country;  but  by  far  the  greater  number  of  these  are 
confined  to  the  western  half  of  this  region.  Our  most  com- 
mon species  in  the  East  belong  to  the  genus  Epicauta. 
These  insects  feed  in  the  adult  state  on  the  leaves  of 
various  plants,  but  especially  those  of  potato,  and  upon 
the  pollen  of  goldenrod;  the  larvee,  so  far  as  is  known, 
are  parasitic  in  the  egg-pods  of  locusts  (Melanoplus).  In 
addition  to  Epiciuta  vittdta,  discussed  above,  our  more 
corrmion  species  are  the  Pennsylvania  blister-beetle,  Epi- 
cauta pennsylvdnica,  which  is  of  a  uniform  black  color 
(Fig.  588) ;  and  Epicauta  cinerea,  which  is  sometimes 
clothed  throughout  with  an  ash-colored  pubescence,  and  sometimes  the 
wing-covers  are  black,  except  a  narrow  gray  margin;  the  two  varieties 
were  formerly  considered  distinct  species ; 
the  first  is  commonly  known  as  the  gray 
blister-beetle,  the  last  as  the  margined 
blister-beetle. 

Closely  allied  to  the  beetles  mentioned 
above  are  those  of  the  genus  Macrobasis. 
The  most  common  species  of  this  genus 
found  in  the  East  is  Macrobasis  unlcolor. 
This  beetle  measures  from  8  mm.  to  15 
mm.  in  length ;  it  is  represented,  enlarged, 
in  Figure  589;  it  is  black,  but  rather 
densely  clothed  with  grayish  hairs,  which 
give  an  ashen  hue  to  the  upper  surface; 
it  is  known  as  the  ashy-gray  blister-beetle. 
The  beetles  of  the  genus  Meloe  present 
an  exception  to  the  characters  of  the 
Coleoptera  in  that  the  wing-covers,  instead  of  meeting  in  a  straight 


Fig.  5«8. 


498  AN  INTRODUCTION  TO  ENTOMOLOGY 

line  down  the  back,  overlap  at  the  base  (Fig.  590).  These  wing- 
covers  are  short,  and  the  hind  wings  are  lacking.  These  beetles  are 
called  oil-beetles  in  England,  on  account  of  the  yel- 
lowish liquid  which  oozes  from  their  joints  when  they 
are  handled.  Our  most  common  species  is  the  butter- 
cup oil-beetle,  Meloe  angusticollis .  It  is  found  in 
meadows  and  pastures  feeding  on  the  leaves  of  vari- 
ous species  of  buttercups. 

The  species  of  the  genus  Nemognatha  and  some 
allied  forms  are  remarkable  for  having  the  maxillse 
developed  into  a  long  sucking-tube,  which  is  some- 
times as  long  as  the  body,  and  which  resembles  some- 
what the  sucking-tube  of  a  butterfly. 
The  family  EURYSTETHID^  includes  only  "three    American 
species,  one  found  in  Alaska  and  two  found  in  California.     One  of  the 
latter,  Eurystethus  subopdcus,  was  found  by  Professor  VanDyke  on  the 
seashore,  in  crevices  of  inter-tidal  rocks. 

The  farnily  OTHNIIDyE  is  represented  in  our  territory  by  five 
species  of  Othnius,  one  from  the  East  and  four  from  the  Far  West. 
They  are  small  beetles,  which  are  found  running  actively  on  the  leaves 
of  trees,  and  are  probably  predacious.  In  this  family  the  anterior 
coxal  cavities  are  closed  behind,  and  none  of  the  abdominal  segments 
are  grown  together  on  the  ventral  side. 

The  family  PYTHID^  includes  less  than  a  score  of  North 
American  species.  Some  of  these  live  under  bark,  and  are  said  to 
prey  on  bark-beetles ;  others  are  found  under  stones.  See  table,  p.  474, 
for  distinctive  characters. 

The  family  PYROCHROID^  includes  a  small  number  of  beetles, 
which  are  from  8  mm.  to  18  mm.  in  length.  The  body  is  elongate; 
the  head  and  prothorax  are  narrower  than  the  wing- 
covers;  the  antennae  are  serrate  or  subpectinate  in  the 
females  and  usually  fiabellate  in  the  males  (Fig.  591). 
The  beetles  are  found  about  decaying  trees,  beneath 
the  bark  of  which  the  larvae  live. 

The  family  PEDILID^.— In  this  and  in  the  fol- 
lowing family  the  abdomen  is  composed  of  five  free 
segments,  and  the  tarsi  have  the  penultimate  joint 
lobed  beneath.  In  this  family  the  eyes  are  large,  finely  ^^§'  59i- 
faceted,  and  usually  emarginate.  These  beetles  are 
arboreal  in  habits.  There  are  about  fifty  described  species  in  our 
fauna. 

The  family  ANTHICID^. — In  this  family,  as  in  the  preceding 
one,  the  abdomen  consists  of  five  free  segments,  and  the  penultimate 
joint  of  the  tarsi  is  bilobed.  But  in  this  family  the  eyes  are  small, 
rounded,  usually  coarsely  faceted,  and  emarginate.  These  are 
active  ground  beetles  of  predacious  habits.  Among  our  more  com- 
mon species  are  those  of  the  genus  Notoxus,  in  which  the  prothorax  is 
prolonged  over  the  head  into  a  horn.  There  are  nearly  two  hundred 
described  species  of  this  family  in  our  fauna. 


\^ 


COLEOPTERA  499 

The  family  EUGLENID^E  is  composed  of  small  or  minute  beetles, 
found  on  leaves  and  flowers;  many  of  them  are  less  than  2  mm.  in 
length.  They  resemble  the  members  of  the  two  preceding  families; 
but  differ  in  having  the  antepenultimate  segment  of  the  tarsi  bilobed, 
instead  of  the  penultimate,  and  in  having  the  abdomen  composed  of 
only  four  free  ventral  segments,  of  which  the  first  is  formed  of  two, 
firmly  united  but  with  the  suture  sometimes  evident.  There  are 
about  forty  described  North  American  species. 

The  family  CEROPHYTID^  includes  only  two  rare  species  of 
Cerophytum,  one  found  in  California  and  one  in  Pennsylvania.  These 
were  formerly  included  in  the  Elateridas;  but  they  differ  from  that 
family  in  that  the  posterior  coxee  are  not  laminated,  and  the 
trochanters  of  the  middle  and  posterior  legs  are  very  long. 

The  family  CEBRIONID^  includes  a  few  species  foimd  in  the 
South.  They  were  formerly  included  in  the  Elaterid^;  but  they 
differ  from  that  family  in  that  the  abdomen  consists  of  six  or  more 
ventral  segments.  This  family  dift'ers  from  the  following  one  in  hav- 
ing the  tibial  spurs  well  developed. 

The  family  PLASTOCERID^  includes  about  a  score  of  species 
found  in  the  South  and  in  California.  It  is  closely  allied  to  the  pre- 
ceding family,  but  differs  in  having  the  tibial  spurs  short  and  very 
delicate. 

The  family  RHIPICERID^,  or  cedar-beetles,  is  represented  in 
this  country  by  a  very  small  number  of  species,  which  are  most  com- 
monly found  on  cedars.  The  antennse  are  serrate  in  the  females, 
frequently  flabellate  in  the  males.  The  anterior  and  middle  coxse 
are  conical  and  prominent,  the  former  with  large  trochantins;  the 
posterior  coxae  are  transverse,  and  dilated  into  a  small  plate  partly 
covering  the  femora. 


Family  ELATERID^ 
The  Click-Beetles  or  Elators 

There  is  hardly  a  coimtry  child  that  has  not  been  entertained  by 
the  acrobatic  performances  of  the  long,  tidy-appearing  beetles  called 
snapping-bugs,  click-beetles,  or  skip-jacks  (Fig.  592). 
Touch  one  of  them  and  it  at  once  curls  up  its  legs,  and 
drops  as  if  shot;  it  usually  lands  on  its  back,  and  lies  there 
for  a  time  as  if  dead.  Suddenly  there  is  a  click,  and  the 
insect  pops  up  into  the  air  several  inches.  If  it  comes 
down  on  its  back,  it  tries  again  and  again  until  it  succeeds 
in  striking  on  its  feet,  and  then  it  runs  oft\ 

Our  common  species  of  click-beetles  are  mostly  small 
or  of  medium  size,  ranging  from  2.5  mm.  to  18  mm.  in  length.  A 
few  species  are  larger,  some  reaching  the  length  of  nearly  50  mm. 
The  majority  of  the  species  are  of  a  uniform  brownish  color; 
some  are  black  or  grayish,   and   some  are   conspicuously   spotted 


500  AN  INTRODUCTION  TO  ENTOMOLOGY 


^^^ 

^A 


(Fig.  593).  The  body  is  elongated,  somewhat  flattened,  and  tapers 
more  or  less  toward  each  end ;  the  antennae  are  moderately  elongated 
and  more  or  less  serrate;  the  first  and  second  ab- 
dominal segments  are  not  grown  together  on  the 
ventral  side;  and  the  hind  coxae  are  each  furnished 
with  a  groove  for  the  reception  of  the  femur. 

The  ability  to  leap  into  the  air  when  placed  on 
their  back,  which  is  possessed  by  most  members  of 
this  family  and  by  a  few  members  of  the  following 
^i  g.-    5  93  ---A  family,  is  due  to  two  facts:  first,  the  prostemum  is 
4  ^Id       r'   prolonged  into  a  process  which  extends  into  a  groove 
natural  size  and  ^^  ^he  mesosternum;  and  second,  the  prothorax  is 
enlarged.  loosely  joined  to  the  mesothorax,  so  that  it  can  be 

freely  moved  up  and  down.  When  preparing  to 
leap,  the  beetle  bends  its  body  so  as  to  bring  the  prosternal  process 
nearly  out  of  the  groove  in  the  mesosternum;  then  it  suddenly 
straightens  its  body,  with  the  result  that  the  prosternal  process 
descends  violently  into  the  groove ;  the  blow  thus  given  to  the  meso- 
thorax causes  the  base  of  the  elytra  to  strike  the  supporting  surface, 
and  by  their  elasticity  the  whole  body  is  propelled  upward. 

Adult  elaters  are  found  on  leaves  and  flowers,  and  are  exclusively 
phytophagous;  the  larvas  live  in  various  situations;  most  of  them 
are  phytophagous,  but  some  species 
are  carnivorous. 

The  larvae  are  long,  narrow, 
worm-like  creatures,  very  even  in 
width,  with  a  very  hard  cuticula, 

and  are  brownish  or  yellowish  in  

color  (Figs.  594  and  595).  They  are  Fig.  ^g^. 

commonly  known  as  wire-worms,  a 

name  suggested  by  the  form  and  hardness  of  the  body. 

Some  wire-worms  live  under  the  bark  of  trees  and  in  rotten  wood ; 
but  many  of  them  live  in  the  ground,  and  feed  on  seeds  and  the  roots 
of  grass  and  grain.  In  fact  there  is  hardly  a  cultivated  plant  that  they 
do  not  infest,  and,  working  as  they  do  beneath  thesurface  of  the  ground, 
it  is  extremely  difficult  to  destroy  them.  Not  only  do  they  infest 
a  great  variety  of  plants,  but  they  are  very  apt  to  attack  them  at  the 
most  susceptible  period  of  their  growth,  before  they  have  attained 
sufficient  size  and  strength  to  withstand  the  attack;  and  often  seed 
is  destroyed  before  it  is  germinated.  Thus  fields  of  com  or  other 
grain  are  ruined  at  the  outset.  The  appearance  of  these  insects  when 
in  the  grormd,  as  seen  through  the  glass  side  of  one  of  our  root-cages, 
is  shown  in  Fig.  596. 

There  is  a  vast  number  of  species  of  click-beetles ;  more  than  five 
hundred  have  been  described  from  North  America  alone.  It  is  quite 
difficult  to  separate  the  closely  allied  species,  as  there  is  but  little 
variation  in  shape  and  color. 

The  larvas  also  show  comparatively  little  variation  in  the  general 
form ;  but  in  this  stage  the  shape  of  the  parts  of  the  head  and  its  ap- 


COLEOPTERA 


501 


pendages,  and  the  structure  of  the  caudal  end  of  the  body,  afford  useful 
characters.  The  value  of  these  characters  in  indicating  the  principal 
divisions  of  the  family  is  pointed  out  by  Hyslop  ('17). 

An  extended 
series  of  experi- 
ments were  con- 
ducted by  Com- 
stock   and  Slin- 
gerland    ('91)  in 
an  ciiort  to  discover  a  practicable 
method  of  preventing  the  ravages 
of  wire-worms.   In  those  species  that 
we  bred,  it  required  several  years 
for  the  larva  to  complete  its  growth. 
In  these  species  the  full-grown  larva 
changes  to  a  pupa  in  the  latter  part 
of  the  summer,  in  a  little  cell  in  the 
ground;  the  pupa  soon  afterwards 
changes  to  an  adult ;  but  the  adult 
remains  in  the  cell  formed  by  the 
larva  till  the  following  spring. 

Although  we  tried  an  extensive 
series  of  experiments,  extending  over 
several  years,  we  were  unable  to  find 
any  satisfactory  way  of  destroying 
the  larvae  infesting  field  crops.  But 
we  foimd  that  if  the  cells  containing 
pupfe  or  recently-transformed  adults 
were  broken,  the  insects  perished. 
We  conclude,  therefore,  that  much 
can  be  done  towards  keeping  these 
insects  in  check  by  fall-ploughing; 
for  in  this  way  many  of  the  cells 
containing  pupse 
or  young  adults 
would  be  broken. 
The  eyed  el- 
ater,  Alaus  ocu- 
/aiM5.- Although 
most  of  our  click- 
beetles  are  of 
moderate  size, 
we  have  a  few  species  that  are  large.  The  most 
common  of  these  is  the  eyed  elater.  This  is  the 
great  pepper-and-salt-colored  fellow  that  has  two 
large,  black,  velvety,  eye-like  spots  on  the  pro- 
thorax  (Fig.  597).  These  are  not  its  eyes,  how- 
ever. The  true  eyes  are  situated  one  on  each  side 
of  the  head  near  the  base  of  the  antenna.     This 


Fig.  596. — ^A  corn-plant  growing  in  a 
root-cage  infested  by  wire-worms 
and  click-beetles.  (From  a  speci- 
men   in    the    Cornell    Insectary.) 


502  A  N  INTROD  UCTION  TO  ENTOMOLOG  Y 

insect  varies  greatly  in  size,  some  individuals  being  not  more  than 
half  as  large  as  others. 

The  larvse  live  in  decaying  wood,  and  are  often  found  in  the 
trunks  of  old  apple  trees.  It  was  formerly  believed  that  they  fed  on 
the  decaying  wood;  but  they  have  been  found  to  be  carnivorous. 
The  larger  larvae  are  about  60  mm.  in  length. 

There  is  an  elater  quite  similar  to  the  preceding  that  differs  in 
having  the  eye-like  spots  less  distinctly  marked;  this  is  Alaus  myops. 
This  species  is  not  as  common  as  the  preceding  one. 

The  family  EUCNEMID^  was  formerly  regarded  as  a  subfamily 
of  the  Elaterida?.  It  differs  from  the  Elateridas,  as  now  restricted, 
in  having  the  labrum  concealed,  and  in  that  the  antennse  are  some- 
what distant  from  the  eyes,  and  their  insertion  narrowing  the  front. 
The  adults  are  found  under  bark  or  on  the  leaves  of  plants ;  most  of 
the  species  are  rare.  "The  larvae  have  a  striking  resemblance  to  those 
of  the  family  Buprestidae,  both  in  form  and  habits,  being  abruptly 
enlarged  in  front,  and  usually  occurring  in  wood  which  has  just  begun 
to  decay."     (Blatchley  '10.) 

The  family  THROSCID^  includes  a  few  small  species  which 
resemble  the  elaters  and  buprestids  in  having  the  prostermun  pro- 
longed behind  into  a  process,  w^hich  is  received  in  the  mesosternum. 
They  differ  from  the  elaters  in  having  the  prothorax  firmly  joined  to 
themesothorax,  and  the  front  coxal  cavities  closed  behind  by  the  meso- 
sternum instead  of  by  the  prosternum;  and  from  the  buprestids  in 
having  the  ventral  abdominal  segments  all  free.  The  adult  beetles 
are  found  on  flowers. 

Family  BUPRESTIDS 
The  Metallic  Wood-Eorers  or  Buprestids 

The  buprestids  resemble  the  click-beetles  somewhat  in  form,  being 
rather  long  and  narrow;  but  they  are  easily  recognized  by  their 
metallic  coloring.  Their  bodies  are  hard  and  inflexible,  and  usually 
appear  as  if  made  of  bronze ;  but  some  species  exhibit  the  brightest 
of  metallic  colors.  The  antennae  are  serrate;  the  first  and  second 
abdominal  segments  are  grown  together  on  the  ventral  side ;  and  these 
beetles  do  not  have  the  power  of  springing  when  placed  on  the  back. 

The  adults  are  found  upon  flowers  and  upon  the  bark  of  trees, 
basking  in  the  hot  sunshine.  Some  of  them  fly  ver\^  rapidly,  with  a 
loud  buzzing  noise;  and  some  drop  to  the  ground  when  disturbed, 
and  feign  death. 

Most  of  the  larvae  are  borers,  feeding  beneath  bark  or  within 
solid  wood.  In  such  species  the  body  is  of  a  ver\^  characteristic 
form,  which  is  commonly  designated  as  "flat -headed."  The  flattened 
portion,  however,  is  composed  largely  of  the  segments  immediately 
following  the  head.  The  first  thoracic  segment  is  very  wide  and  flat; 
the  next  two  or  three  segments  are  also  flattened,  but  are  successively 
smaller;  while  the  rest  of  the  body  is  quite  narrow  and  cylindrical. 


COLEOPTERA  503 

These  "flat -headed"  larvas  are  legless,  and  have  been  compared  to 
tadpoles  on  account  of  their  form.  Their  burrows  are  flattened, 
corresponding  with  the  shape  of  the  larger  part  of  the  body.  In  some 
of  the  smaller  species  the  larvte  are  cylindrical,  and  are  furnished  with 
three  pairs  of  legs.  These  are  leaf -miners;  and  in  the  adult  state  the 
body  is  much  shorter  than  in  the  more  typical  species. 

This  family  is  represented  in  our  fauna  b\^  nearly  three  hundred 
species;  among  the  more  important  of  those  that  infest  cultivated 
plants  are  the  following. 

The  Virginian  buprestid,  Chalcophora  virginica. — -This  is  the  larg- 
est of  our  common  buprestids  (Fig.  598).     It  is  copper-colored,  often 
almost  black,   and  has  its  upper  surface  roughened  by  irregular, 
lengthwise  furrows.  This  bee- 
tle appears  late  in   spring   in 
the  vicinity  of  pine-trees.    The 
larvffi  bore  in  the  wood  of  pine, 
and  are  often  very   injurious. 
Dicer  ca  divaricdta  is  18  mm. 
or    more    in    length,    copper- 
colored  or  brassy  above,  with 
the  wing-covers  marked  with 
square,  elevated,  black  spots. 
The  wing-covers    taper    very 

much  behind,   and  are  separated  at  the  tips  (Fig.   599). 
va  bores  in  peach,  cherry,  beech,  and  maple. 

The  flat-headed  apple-tree  borer,  Chrysohothris  femordta. — This  is 
one  of  the  most  injurious  of  all  buprestids.  The  adult  (Fig.  600)  is 
about  12  mm.  long,  and  is  very  dark  green  above,  with  bronze  re- 
flections, especially  in  the  furrows  of  the  wing-covers.  It  appears 
during  June  and  July,  and  lays  its  eggs  upon  the  trunk  and  limbs  of 
apple,  peach,  oak,  and  other  trees.  The  larvae  at  first  bore  into  the 
bark  and  sap-wood,  and  later  into  the  solid  wood.  The  transforma- 
tions are  completed  in  one  year. 

To  prevent  the  ravages  of  this  pest,  the  trees  are  rubbed  with 
soap  during  June  or  July,  or  cakes  of  soap  are  placed  in  the  forks  of 
the  trees,  so  that  the  rains  will  dissolve  the  soap  and  wash  it  down 
over  the  trunks.  This  is  supposed  to  prevent  the  beetles  from  deposit- 
ing their  eggs  on  the  trees.  After  a  tree  is  once  infested,  the  larvas 
should  be  cut  out  with  a  gouge  or  a  knife.  Nursery  stock 
that  is  infested  should  be  promptly  burned. 

The  red-necked  agrilus,  Agrilus  ruficolHs. — This  beetle 
(Fig.  601)  is  about  7.5  mm.  long.    Its  body  is  narrow  and 
nearly  cylindrical.    The  head  is  of  a  dark  bronze  color,  the 
prothorax  of  a  beautiful  coppery  bronze,  and  the  wing- 
covers  black.     The  larva  bores  in  the  stems  of  raspberry 
and  blackberry,  causing  a  large  swelling,  known  as  the 
Fig.  601.      raspberry  gouty-gall.    These  galls  should  be  collected  and 
burned  in  early  spring. 
The  family  PSEPHENID^  includes  only  the  genus  Psephenus, 
of  which  we  have  four  species,  one  found  in  the  East  and  three  in 


•504 


AN  INTRODUCTION  TO  ENTOMOLOGY 


California.    This  genus  was  formerly  included  in  the  following  family ; 
but  it  differs  from  the  Dryopidas  in  having  more  than  five  ventral  ab- 
dominal segments.    Our  eastern  species  is  Psephenus  lecontei.    These 
beetles  are  found  in  the  vicinity  of  running  water,  and  often,  in  the 
heat  of  the  day-,  collect  on  stones  that  project  from  the  water;  they 
fly  swiftly  when  disturbed.     The  body  is  oval,  subdepressed,  nar- 
rowed in  front,  and  clothed  with  fine,  silken  hairs,  which  retain  a  film 
of  air  when  the  insect  goes  beneath  water.    The  females  deposit  their 
eggs  in  a  layer  on  the  under  side  of  submerged  stones  in  shallow 
brooks.     The  beetles  measure  from  4.5  mm.  to  6  mm.  in  length. 
The  larva  is  found  clinging  to  the  lower  surface 
of  stones  in  rapid  streams,  and  I  have  found  it  in 
muck  near  a  spring.     It  is  very  fiat,  circular  in  out- 
line   (Fig.    602),    and  measures   about    7    mm.    in 
length .    It  breathes  by  five  pairs  of  branched  tracheal 
gills  on  the  ventral  side  of  the  abdomen.    It  is  rarely 
recognized  as  an  insect  by  the  young  collector;  in 
fact  it  was  originally  described  as  a  crustacean  under 
the  generic  name  Fluvicola.    I  have  suggested  the 
common  name  water-penny   for   the   larva.     When 
mature   the  larva  leaves   the  water,   and    pupates 
under  the  last  larval  skin,  beneath  a  stone  or  other 
object  in  a  damp  situation. 

The  family  DRYOPID^  as  now  restricted  includes  only  the  sub- 
family Paminas  of  the  old  family  Parnidce,  in  which  were  included 
the  preceding  family  and  the  following  family.  The 
Dryopidae  differ  from  the  Psephenidae  in  that  the 
members  of  it  have  only  five  ventral  abdominal  seg- 
ments, and  from  the  Elmidae  in  that  in  the  Dryopidae 
the  anterior  coxge  are  transverse,  with  a  distinct  tro- 
chantin. 

This  family  includes  small  water-beetles  in  which 
the  legs  are  not  fitted  for  swimming.  They  are 
found  most  often  in  swift-running  water,  where  they 
cling  to  stones,  logs,  or  aquatic  plants.  The  body  is 
clothed  with  fine,  silken  hairs,  which  retain  a  film  of 
air  when  the  insect  is  beneath  the  water.  They  feed 
on  decaying  matter  in  the  water. 

The    larvae    are    also    aquatic 


Fig.   602. 


Fig.  603. 


The  larva  of 
Helichus  lithophilus  (Fig.  603)  resembles  somewhat 
the  water-penny  {Psephenus),  except  that  the  body 
is  more  elongate  and  is  deeply  notched  between  the 
segments. 

Seventeen  species  of  this  family  have  been  found  in  our  fauna . 

The  family  ELMID^  includes  beetles  that  are  closely  allied  to 
the  preceding  family  in  structure  and  in  habits;  but  in  this  family 
the  anterior  coxae  are  rounded  and  without  a  trochantin,  and  the  body 
is  less  densely  pubescent  than  in  the  Dryopidas. 


COLEOPTERA 


505 


Fig.  604. 


The  larvae  of  some  exotic  species  are  said  to  live  in  damp  earth; 
but   the   larva   of  Stenelmis   bicarindtus ,   which   was   described   by 
Professor  Matheson  ('14)  is  aquatic.  This  larva  (Fig.  604) 
differs  greath^  in  form  from  the  representatives  of  the  two 
preceding  families  figured  above,  being  long  and  slender. 

The  family  HETEROCERID^,  or  the  variegated 
mud-loving  beetles,  includes  only  the  genus  Heterocerus, 
of  which  eleven  species  have  been  found  in  our  fauna.  In 
this  family  all  of  the  tarsi  are  four-jointed;  the  first  four  ab- 
dominal segments  are  grown  together  on  the  ventral  side ; 
and  the  tibias  are  dilated,  armed  with  rows  of  spines,  and 
fitted  for  digging.  These  beetles  are  oblong  or  sub-elon- 
gate, oval,  densely  clothed  with  short,  silky  pubescence, 
very  finely  punctate,  and  of  a  brown  color,  with  the  elytra 
usually  variegated  with  undulated  bands  or  spots  of  yellow 
color.  They  live  in  galleries  which  they  excavate  in  sand 
or  mud  at  the  margins  of  bodies  of  water,  and,  when  dis- 
turbed, run  from  their  galleries  and  take  flight. 

The  family  GEORYSSID^,  or  the  minute  mud-loving 
beetles,  includes  only  the  genus  Georyssus,  of  which  only 
two  species  have  been  found  in  the  United  States.    They 
are  very  minute,  rounded,  convex,  roughly  sculptured,  black  insects, 
found  at  the  margin  of  streams,  on  wet  sand;  they  cover  themselves 
with  a  coating  of  mud  or  fine  sand,  so  that  they  can  be  detected  only 
when  they  move. 

The  family  DAvSCILLID^  includes  certain  beetles  that  live  on 
plants,  usually  near  water.  The  legs  are  short,  with  slender  tibias; 
The  tarsi  are  five-jointed;  the  anterior  coxse  bear  a  distinct  trochan- 
tin;  the  posterior  coxae  are  transverse,  and  dilated  into  a  plate  partly 
covering  the  femora ;  and  the  abdomen  has  five  free,  ventral  segments, 
the  fifth  rounded  at  the  tip. 

Sharp  ('99)  states  that  the  larva  of  Z)a5c^//M5  cervlnus  is  subterra- 
nean, and  is  believed  to  live  on  roots;  in  form  it  is  somewhat  like  a 
lamellicom  larva,  but  is  straight,  and  has  a  large  head. 

Only  twenty-one  species  of  this  family  have  been  described  from 
our  fauna;  but  these  represent  fifteen  genera. 

The  family  EUCINETID^  has  recently  been  separated  from  the 
Dascyllidse.  In  the  Eucinetidae  the  anterior  coxae  do  not  bear  a 
trochantin;  the  posterior  coxse  are  dilated  into  immense  oblique 
plates,  concealing  the  hind  legs  in  repose;  and  the  internal  lobe  of 
the  maxillae  is  armed  with  a  terminal  hook.  Only  eight  species  of 
this  family  occur  in  our  fauna;  seven  of  these  belong  to  the  genus 
Eucinetus. 

The  larva  of  a  European  species  of  Eticinetus  lives  on  fungoid 
matter  on  wood. 

The  family  HELODID^E  includes  small  beetles,  less  than  6  mm. 
in  length,  found  on  plants  near  water.  As  in  the  preceding  family, 
the  anterior  cox«  are  without  a  trochantin;  but  the  lacinia  of  the 
maxillae  is  not  armed  with  a  terminal  hook;  and  the  cuticula  of  the 


506  AN  INTRODUCTION  TO  ENTOMOLOGY 

body  is  usually  soft  and  thin.  Sharp  ('99)  states  that  the  larvee  are 
aquatic,  and  are  remarkable  for  possessing  antennae  consisting  of  a 
great  many  joints.  Our  fauna  includes  thirty-two  described  species 
of  this  family. 

The  fami"ly  CHELONARIID^E  is  represented  in  our  fauna  by  a 
single  species,  Chelondrium  lecontei,  found  in  Florida.  See  table,  page 
471,  for  distinguishing  characters. 

Family  DERMESTID^ 
The  Dermestids 

There  are  several  families  of  small  beetles  that  feed  on  decaying 
matter,  or  on  skins,  furs,  and  dried  animal  substances.  The  most 
important  of  these  is  the  Dermestidas,  as  several  species  belonging  to 
this  family  destroy  household  stores  or  goods. 

The  dermestids  can  be  distinguished  from  most  of  the  other  beetles 
with  similar  habits  by  the  fact  that  the  wing-covers  completely  cover 
the  abdomen.  They  are  chiefly  small  beetles,  although  one  of  the 
common  species  measures  8  mm.  in  length.  They  are  usually  oval, 
plump  beetles,  with  pale  gray  or  brown  markings,  which  are  formed 
of  minute  scales,  which  can  be  rubbed  off.  These  beetles  have  the 
habit  of  pretending  that  they  are  dead  when  they  are  disturbed; 
they  will  roll  over  on  their  backs  with  their  legs  meekly  folded  and 
lie  still  for  a  long  period. 

The  larvae  do  much  more  damage  than  the  adults.  They  are  ac- 
tive, and  are  clothed  with  long  hairs.  These  hairs  are  covered 
throughout  their  entire  length  with  microscopic  barbs. 

This  family  is  represented  in  our  fauna  by  about  one  hundred  thirty 
species;  the  following  are  some  of  the  more  important  of  these. 

The  larder-beetle,  Dermestes  lardarius. — This  pest  of  the  larder  is 

the  most  common  of  the  larger  members  of  this  family.    It  measures 

from  6  mm.  to  7.5  mm.  in  length,  and  is  black  except  the 

basal  half  of  its  wing-covers,  which  are  pale  buff  or  brown- 

*ish  yellow.  This  lighter  portion  is  usually  crossed  by  a 
band  of  black  spots,  three  on  each  wing-cover  (Fig.  605). 
The  larva  feeds  on  dead  animal  matter,  as  meat,  skins, 
feathers,  and  cheese.  It  is  often  a  serious  pest  where  bacon 
Fig-  605.  Qj.  i^^j^  -g  s^Qj.g(j_  When  full-grown  it  is  about  12  mm.  in 
length,  dark  brown  above,  whitish  below,  and  rather 
thickly  covered  with  long,  brown  hairs.  It  is  said  that  these  insects 
can  be  attracted  by  baits  of  old  cheese,  from  which  they  may  be 
gathered  and  destroyed. 

The  carpet -beetle,  Anthrenus  scrophuldrim. — This  is  a  well-known 
household  pest.  It  is  an  introduced  European  insect,  which  was  first 
recognized  as  a  serious  joest  in  this  country  about  1874.  It  feeds  in 
its  larval  state  on  carpets,  woollens,  furs,  and  feathers;  and  for  a 
considerable  period  was  exceedingly  destructive.  In  recent  years  its 
ravages  have  been  greatly  reduced  by  the  more  general  use  of  rugs 
instead  of  carpets.    As  rugs  are  taken  up  and  cleaned  frequently,  the 


COLEOPTERA  507 

insect  does  not  have  a  chance  to  breed  as  it  does  under  carpets  which 
are  tacked  to  the  floor  and  taken  up  only  once  or  twice  a  year.  The 
larva  is  well  known  to  many  housekeepers  as  the  buffalo-moth.  It 
is  a  short,  fat  grub,  about  5  mm.  in  length  when  full-grown,  and 
densely  clothed  with  dark  brown  hairs.  It  lives  in  the  cracks  of 
floors,  near  the  edges  of  rooms,  and  beneath  furniture,  where  it  eats 
holes  in  the  carpet.  It  also  enters  wardrobes  and  destroys  clothing. 
The  adult  is  a  pretty  little  beetle  which  may  be  found  in  infested 
houses,  in  the  spring,  on  the  ceilings  and  windows.  It  measures  from 
2.2  mm.  to  3.5  mm.  in  length  and  is  clothed  with  black,  white,  and 
brick-red  scales.  There  is  a  whitish  spot  on  each  side  of  the  prothorax, 
and  three  irregular,  whitish  spots  on  the  outer  margia  of  each  wing- 
cover;  along  the  suture  where  the  two  wing-covers  meet,  there  is  a 
band  of  brick-red  scales,  which  is  widened  in  several  places.  It  is 
worth  while  to  learn  to  know  this  beetle ;  for  a  lady-bug  which  often 
winters  in  our  houses  is  frequently  mistaken  for  it.  The  carpet-beetle 
in  its  adult  state  feeds  on  the  pollen  of  flowers.  Sometimes  it  abounds 
on  the  blossoms  of  currant,  cherry,  and  other  fruits.  The  best  way 
to  avoid  the  ravages  of  this  pest  is  to  use  rugs  instead  of  carpets,  and 
to  trap  the  larvae  by  placing  woollen  cloths  on  the  floors  of  closets. 
By  shaking  such  cloths  over  a  paper  once  a  week,  the  larvae  can  be 
captured. 

The  change  from  carpets  to  rugs  is  a  very  desirable  one;  for 
carpets  that  are  tacked  to  the  floor  and  taken  up  only  once  or  twice 
a  year  are  unwholesome.  The  change  need  not  be  a  very  expensive 
one.  As  carpets  wear  out  they  may  be  replaced  with  rugs;  and 
good  carpets  can  be  made  over  into  rugs.  If  the  floors  are  not  polished, 
as  is  usually  the  case  where  it  was  planned  to  cover  them  with  carpets, 
they  can  be  made  presentable  by  filling  the  cracks  with  putty  and 
painting  the  boards  where  they  are  to  be  exposed. 

The  museum  pests,  Anthrenus  verhdsci  and  Anthrenus  nntseomm. — 
There  are  two  minute  species  of  this  family  that  are  a  constant  source 
of  annoyance  to  those  having  collections  of  insects.  The  adult 
beetles  measure  from  2  mm.  to  3  mm.  in  length,  and  are  very  convex. 
They  deposit  their  eggs  on  specimens  in  our  collections;  and  the 
larvae  feed  upon  the  specimens,  often  destroying  them.  In  order  to 
preserve  a  collection  of  insects  it  is  necessary  that  they  should  be 
kept  in  tight  cases,  so  that  these  pests  cannot  gain  access  to  them. 
Specimens  should  not  be  left  exposed  except  when  in  use.  And  the 
entire  collection  should  be  carefully  examined  at  least  once  a  month. 
The  injury  is  done  by  the  larvae,  which  are  small,  plump,  hairy  grubs. 
Their  presence  is  indicated  by  a  fine  dust  that  falls  on  to  the  bottom 
of  the  case  from  the  infested  specimens.  These  larvcC  can  be  destroyed 
by  pouring  a  small  quantity  of  carbon  disulphide  into  the  case,  and 
keeping  it  tightly  closed  for  a  day  or  two.  Benzine  poured  on  a  bit 
of  cotton  in  the  box  will  cause  the  pests  to  leave  the  specimens,  when 
they  may  be  taken  from  the  box  and  destroyed.  But  we  have  found 
carbon  bisulphide  the  better  agent  for  the  destruction  of  these  pests. 


508  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  family  BYRRHID^,  or  the  pill-beetles,  are  short,  very  con- 
vex beetles  of  small  or  moderate  size;  some,  however,  are  12  mm.  in 
length.  The  body  is  clothed  with  hair  or  minute  scales.  The  legs  can 
be  folded  up  verv^  compactly,  the  tibia  usually  having  a  furrow  for 
the  reception  of  the  tarsus.  These  beetles  are  found  upon  walks  and 
at  the  roots  of  trees  and  grass;  a  few  live  under  the  bark  of  trees. 
Nearlv  one  hundred  species  hoxe  been  found  in  this  countrv. 

The  family  NOvSODENDRID^  includes  two  species  of  Noso- 
dendron,  one  found  in  the  East  and  one  in  California.  They  were 
formerly  included  in  the  Byrrhidffi,  but  differ  from  that  family  in 
having  the  head  prominent  and  the  mentum  large.  These  beetles  live 
under  the  bark  of  trees. 

The  family  RHYSODID^  includes  only  four  species,  two  from 
each  side  of  the  continent.  They  are  elongate,  somewhat  flattened 
beetles,  with  the  head  and  prothorax  deeply  furrowed  with  longi- 
tudinal grooves;  and  the  abdomen  with  six  ventral  segments,  the 
first  broadly  triangular,  widely  separating  the  coxte.  They  are  found 
under  bark.    See  footnote,  page  470. 

The  family  OSTOMID^  includes  oblong,  somewhat  flattened 
beetles,  of  a  black  or  reddish  black  color.  Most  of  them  live  under 
bark;  but  some  are  found  in  granaries,  and  have  been  widely  dis- 
tributed by  commerce.  The  larva  of  a  species  found  under  bark  has 
been  observed  to  feed  on  the  larva  of  the  codlin-moth. 

One  well-known  species,  Tenebroides  mauritanicus,  infests  gran- 
aries. It  is  a  shining  brown  beetle  measuring  about  8  mm.  in  length; 
it  is  commonly  known  as  the  cadelle.  Both  adult  beetles  and  larvae 
feed  on  grain,  but  are  also  predacious,  feeding  on  other  insects  infest- 
ing grain.  The  larvae  when  full-grown  burrow  into  the  sides  of  the 
bins,  where  they  transform. 

The  family  NITIDULID^  comprises  small,  somewhat  flattened 
beetles.  With  many  species  the  prothorax  has  wide,  thin  margins, 
and  the  wing-covers  are  more  or  less  truncate,  so  as  to  leave  the  tip 
of  the  abdomen  exposed;  but  sometimes  the  elytra  are  entire.  The 
tarsi  are  usually  fi\^e-jointed,  with  the  fourth  segment  very  small; 
they  are  more  or  less  dilated;  the  posterior  coxae  are  flat, not  sulcate; 
the  anterior  coxae  are  transverse;  and  the  abdomen  has  five  free 
ventral  segments. 

Most  species  of  this  family  feed  on  the  juices  of  fruits  and  ferment- 
ing sap  that  exudes  from  trees ;  a  few  are  found  on  flowers,  and  others 
on  fungi  or  carrion.    About  one  hundred  thirty  species  are  known 

tfrom  North  America.      One  of  the  most  common  species  is 
Glischrochms  dps)  fascidtus  (Fig.  606).     This  is  a  shining 
black  species,  with  two  conspicuous,  interrupted,  reddish 
bands  across  the  wing-covers, 
p.     ^^^  The  family  RHIZOPH  AGIDyE  includes  only  the  genus 

^^'  ■  i?/iZ2;o^/mgM5,  of  which  there  are  fourteen  North  American 
species.  These  are  small,  slender,  elongate  species,  which  live 
beneath  bark.  This  genus  was  formerly  included  in  the  preceding 
family;  it  differs  from  that  family  in  that  the  antennae  are  only 
ten-jointed,  and  the  club  of  the  antennae  is  two-jointed. 


COLEOPTERA 


509 


The  family  AIONOTOMID^  is  composed  of  small,  depressed 
beetles,  found  mostly  under  the  bark  of  trees,  but  some  species  live 
in  the  nests  of  ants.  The  wing-covers  are  truncate  behind,  leaving 
the  last  abdominal  segment  exposed.  There  are  nearly  forty  described 
North  American  species. 

Family  CUCUJIDtE 
The  Cucujids 

The  insects  of  this  family  are  very  fiat  and  usually  of  an  elongate 
form;  most  of  the  species  are  brown,  but  some  are  of  a  bright  red 
color.  As  a  rule  they  are  found  under  bark  and  are  believed  to  be 
carnivorous  both  in  the  larval  and  adult  states;  but  some 
feed  in  grain.  There  are  nearly  one  hundred  species  in  our 
fauna. 

The  most  conspicuous  of  our  common  species  is 
Cucujus  cldvipes  (Fig.  607).  This  insect  is  about  12  mm. 
in  length  and  of  a  bright  red  color,  with  the  eyes  and  an- 
tennae black  and  the  tibiae  and  tarsi  dark. 

The  most  important  member  of  this  family  is  the  corn  Fig-  607. 
silvanus,  Silvamis  surinamensis,  which  is  one  of  the  small 
beetles  that  infest  stored  grain.  This  species  is  readily  distinguished 
from  other  small  beetles  with  similar  habits  by  its  flattened  form  and 
the  saw-like  edges  of  the  prothorax.  Besides  grain  it  often  infests 
dried  fruits  and  other  stores.  It  measures  from  2.5  mm.  to  3  mm.  in 
length.  The  larva  as  well  as  the  adult  feeds  on  grain.  It  differs  from 
the  larva  of  the  granary -weevil  (Calendra)  in  the  more  elongate  form 
of  its  body  and  in  the  possession  of  three  pairs  of  legs. 

Family  EROTYLID^ 
The  Erotylids 
The  members  of  this  family  are  usually  of  moderate  or  small  size; 
but  some  species  are  quite    large,  measuring    18   mm.  or  more  in 


^ 


Fig.  608. 


Fig.    609. 


length.     Some    of    our    more    common    species   are    conspicuously 
marked  with  shining  black  and  red. 

To  the  genus  Megalodachne  belong  two  common,  large  species, 
which   are   black,    with   two    dull  red   bands  extending  across  the 


510  AN  INTRODUCTION  TO  ENTOMOLOGY 

wing-covers.    M.  heros    (Fig.   608)    is   16  mm.  or  more  in    length. 
M.  fascidta  is  about  12  mm.  in  length. 

The  genus  Languria  includes  long,  narrow  species,  which  resemble 
click -beetles  in  form.  Figure  609  represents  Languria  mozdrdi. 
greatly  enlarged.  This  is  a  reddish  species  with  dark  blue  wing- 
covers;  the  larva  bores  in  the  stalks  of  clover.  It  has  not  become 
a  serious  pest  as  the  larvse  are  destroyed  whenever  clover  is  cut  at 
the  proper  time. 

The  larvae  of  some  species  of  this  family  feed  on  fungi. 

The  family DERODONTID^  includes  only  five  American  species, 
two  found  in  the  East  and  three  in  the  Far  West.  They  are 
small  brown  or  dull  brownish  yellow  beetles,  having  the  head  deeply 
impressed,  with  a  small,  smooth  tubercle  on  each  side  inside  the 
eye.     These  beetles  are  found  on  fungi. 

The  family  CRYPTOPHAGID^  includes  insects  of  small  size, 
usually  less  than  2.5  mm.  in  length,  and  of  variable  form  but  never 
very  flat.  The  thorax  is  nearly  or  quite  as  wide  as  the  wing-covers, 
and  the  first  ventral  abdominal  segment  is  somewhat  longer  than 
the  others.  They  are  generally  of  a  light  yellowish  brown  color, 
and   live  on   fungi   and  decomposing  vegetable  matter. 

The  family  BYTURID^  includes  only  the  genus  Bytilrus,  of 
which  there  are  five  species  in  our  fauna.  This  genus  was  formerly 
.  included  in  the  Dermestidae,  but  it  differs  from  that  family  in  having 
the  second  and  third  segments  of  the  tarsi  lobed  beneath,  the  front 
coxal  cavities  closed  behind,  and  the  tarsal  claws  armed  with  a  large 
basal  tooth.    The  following  is  a  well-known  species. 

The  raspberry  fruit -worm,  Byturus  unicolor. — The  fruit  of  the  red 
raspberry  is  often  infested  by  a  small  white  worm,  which  clings  to 
the  inside  of  the  berry  after  it  is  picked.  This  is  the  larva 
of  an  oval,  pale,  dull  yellow  beetle,  which  is  densely 
clothed  with  short,  fine,  gray  hairs.  The  beetle  is  repre- 
sented enlarged  in  Figure  610;  it  measures  from  3.7  to  t, 
4.5  mm.  in  length.  This  insect  is  also  injurious  in  the 
adult  state,  as  it  feeds  on  the  buds  and  tender  leaves  of  the 
raspberry  and  later  attacks  the  blossoms.  Fig.  610. 

The    family    MYCETOPHAGID^,     or    the    hairy 
fungus-beetles,  is  composed  of  small,  oval,  rarely  elongate,  moderately 
convex  beetles.     They  are  densely  punctured  and  hairy,  and  are 
usually  prettily  marked  insects.    They  live  on  fungi  and  under  bark. 
There  are  about  thirty  species  in  our  fauna. 

The  family  COLYDIID^  is  composed  of  small  insects  which  are 
usually  of  an  elongate  or  cylindrical  form,  and  are  found  under  bark, 
in  fungi,  and  in  earth.  Some  of  the  species  are  known  to  be  carniv- 
orous, feeding  on  the  larvae  of  wood-boring  beetles.  The  tarsi  are 
four-jointed;  the  tibiae  are  not  fitted  for  digging,  and  the  first  four 
abdominal  segments  are  grown  together  on  the  ventral  side.  More 
than  eighty  North  American  species  are  known. 


i 


COLEOPTERA  511 

The  family  MURMIDIID^  includes  five  introduced  species 
representing  five  genera.  They  are  very  small,  oval  beetles,  differing 
from  the  Colydiids  in  having  the  antennas  inserted  on  the  front,  and 
in  having  the  anterior  coxae  inclosed  behind  by  the  metasternum. 

The  family  LATHRIDIID^  includes  very  small  beetles  which 
are  found  chiefly  under  bark  and  stones  or  in  vegetable  debris,  es- 
pecially decaying  leaves.  They  are  oblong;  the  wing-covers  are  usu- 
ally wider  than  the  prothorax  and  entirely  cover  the  abdomen.  There 
are  about  one  hundred  species  in  our  fauna. 

The  family  MYCET^ID^  includes  only  four  American  species, 
which  have  recently  been  separated  from  the  following  family;  they 
differ  from  the  Endomychidse  in  having  the  tarsi  distinctly  four- 
jointed. 

The  family  ENDOMYCHID^  includes  a  small  number  of 
species,  whch  are  found  chiefly  in  fungus,  in  decaying  wood,  or  be- 
neath logs  and  bark.  They  are  small,  oval  or  oblong  beetles.  The 
antennae  are  about  half  as  long  as  the  body;  the  prothorax  is  nearly 
square,  and  usually  has  a  w^ide,  thin  margin,  which  is  slightly  turned 
upwards  at  the  sides. 

The  family  PHALACRID^,  or  the  shining  flower-beetles,  in- 
cludes very  small,  convex,  shining  black  beetles;  they  are  found  on 
flowers  and  sometimes  under  bark.  The  larvae  live  in  the  heads  of 
flowers,  especially  in  those  of  the  Compositas.  More  than  one  hundred 
North  American  species  have  been  described. 

Family  COCCINELLID^ 

The  Lady-Eugs 

These  insects  are  well-known  to  nearly^  every^  child  under  the 
popular  name  given  above.  They  are  more  or  less  nearly  hemi- 
spherical, generally  red  or  yellow,  with  black  spots,  or  black,  with 
white,  red,  or  y^ellow  spots. 

The  larvae  occur  running  about  on  foliage ;  they  are  often  spotted 
with  bright  colors  and  clothed  with  warts  or  with  spines  (Fig.  6ii). 
When  ready-  to  change  to  a  pupa  the  larva  fastens 
itself  by  its  tail  to  any  convenient  object,  and  the 
skin  splits  open  on  the  back.  Sometimes  the  pupa 
state  is  passed  within  this  split  skin,  and  some- 
times the  skin  is  forced  back  and  remains  in  a  little 
wad  about  the  tail  (Fig.  612). 

With  very  few  exceptions,  the  lady-bugs  are  Fig.  611.  Fig.  612. 
predacious,  both  in  the  larval  and  adult  states. 
They  feed  upon  small  insects  and  upon  the  eggs  of  larger  species. 
The  larvae  of  certain  species  are  known  as  "niggers"  by  hop-growers, 
and  are  greatly  prized  by^  them ;  for  they-  are  very  destructive  to  the 
hop-louse.  On  the  Pacific  Coast  lady-bugs  are  well  known  as  the  most 
beneficial  of  all  insects  to  the  fruit-growers.  In  addition  to  the  native 
species  found  there,  several  species  have  been  introduced  as  a  means 
of  combating  scale-insects.     One  of  these,  Rodolia  cardindlis,  which 


ft 


a2 


AN  INTRODUCTION  TO  ENTOMOLOGY 


has  been  incorrectly  known  as  Veddlia  cardtndhs,  has  proved  of  very 
great  value  in  subduing  the  cottony-cushion  scale  (Icerya  purchasi). 
This  lady-bug  was  introduced  from  Australia. 

The  larva  of  Brachyacautha  is  found  in  the  nests  of  ants.  It  is 
covered  with  dense  tufts  of  delicate  white  wax;  its  food  probably 
consists  of  the  eggs  of  coccids  living  in  the  nests. 

A  very  common  lady-bug  in  the  East  is  Addlia  hipunctdta.  This 
species  is  reddish  yellow  above,  with  the  middle  of  the  prothorax 
black,  and  with  a  black  spot  on  each  w4ng-cover.  It  frequently 
passes  the  winter  in  our  dwellings,  and  is  found  on  the  walls  and 
windows  in  early  spring.  Under  such  circumstances  it  is  often  mis- 
taken for  the  carpet -beetle,  and,  unfortunately,  destroyed. 

The  nine-spotted  lady-bug,  Coccinella  novemnotdta,  has  yellowish 
wing-covers,  with  four  black  spots  on  each,  in  addition 
to  a  common  spot  just  back  of  the  scutellvim  (Fig.  613). 
Although  almost  all  of  the  Coccinellidae  are  predacious, 
there  are  some  that  are  herbivorous.     One    of    these   is      -p-     f. 
found  in  the  East.    This  is  the  squash -ladybird,  Epildchna        ^^'    ^^' 
boredlis.     This  beetle  and  its  larva  (Fig.  614)  feed  on  the  foliage  of 
various  cucurbitaceous  plants,  but  prefer  that  of  the  squash.     The 

adult  is  yellow- 
^  \    "* 'T  f]  ^sh'    with    large, 

,W:n  '  ^'/  black  spots.  The 

larva  is  yellow 
and  is  clothed 
with  forked 
spines.  A  pupa 
is  shown  in  the 
figure  near  the 
upper  right-hand 
corner. 

The  bean- 
ladybug,  Epi- 
Idchfia  corrupta, 
which  is  found  in 
the  South  and 
Southwest,  is  an- 
other herbivo- 
rous species. 

The  familv 
ALLECULI- 
DJE  ,    or    the 

comb-clawed  bark-beetles,  includes  brownish  beetles,  without  spots, 
which  are  found  on  leaves  and  flowers  and  under  bark.  The  body  is 
usually  elongate,  elliptical,  quite  convex,  and  clothed  above  with 
minute  hairs,  which  give  a  silken  gloss  to  the  surface.  They  are  most 
easily  distinguished  from  allied  families  by  the  tarsal  claws  being 
pectinate,  and  the  anterior  coxal  cavities  closed  behind.  The  larvae 
of  some  of  our  species  at  least  live  in  rotten  wood  and  resemble  wire- 


COLEOPTERA  513 

worms  in  appearance.     There  are  more  than  one  hundred  described 
North  American  species. 

Family  TENEBRIONID^ 

The  Darkling  Beetles 

The  darkhng  beetles  are  nearly  all  of  a  uniform  black  color, 
although  some  are  gray,  and  a  few  are  marked  with  bright  colors. 
The  different  species  vary  greatly  in  size  and  in  the  form  of  the  body. 
The  hind  tarsi  are  four-jointed,  and  the  fore  and  middle  tarsi  are 
five-jointed.    For  other  characters,  see  table,  p.  474. 

These  insects  occur  chiefly  in  dry  and  warm  regions.  Thus  while 
we  have  comparatively  few  species  in  the  northeastern  United  States, 
there  are  many  in  the  Southwest.  Most  of  the  species  feed  on  dry 
vegetable  matter,  and  often  on  that  which  is  partially  decomposed; 
some  live  in  dung,  some  in  dead  animal  matter,  others  in  fungi,  and 
a  few  prey  upon  larvae.  More  than  eleven  hundred  species  occur  in 
this  country.  The  three  following  will  serve  to  ilhistrate  the  variations 
in  form  and  habits. 

The  meal-worm,  Tenebno  molitor.- — This  is  a  well-known  pest  in 
granaries  and  mills.  The  larva  is  a  hard,  waxy  yellow,  cylindrical 
worm,  which  measures  when  full-grown  25  mm.  or 
more  in  length,  and  closely  resembles  a  wire-worm ; 
it  feeds  on  flour  and  meal.  The  beetle  is  black  and 
about  15  mm.  in  length,  (Fig.  615).  The  larvse 
and  pupae  are  used  for  bird-food  and  are  grown  in 
quantity  by  bird-supply  houses. 

TheiovkQ6.hxng\xs-heet\e,Boletotheruscornutus, 
is  common  in  the  northeastern  United  States  and       ^'S-  Fig- 

in  Canada  about  the  large  toadstools  {Poly poms)         '^' 
which  grow  on  the  sides  of  trees.    The  surface  of  the  body  and  wing- 
covers  is  very  rough,  and  the  prothorax  bears  two  prominent  horns 
(Fig.  616).    The  larva  lives  within  the  fungi  referred 
to  above. 

The  pinacate-bugs. — Several  species  of  Eleddes 
are  abundant  on  the  Pacific  Coast,  where  they  are 
found  under  stones  and  pieces  of  wood  lying  on  the 
ground.  They  are  apt  to  congregate  in  large  numbers 
under  a  single  shelter,  and  are  clumsy  in  their  move- 
ments. They  defend  themselves  when  disturbed  by 
elevating  the  hinder  part  of  the  body  and  discharging 
an  oily  fluid  from  it.  They  present  an  absurb  appear- 
ance, walking  off  clumsily,  and  carrying  the  hind  end 
of  the  body  as  high  as  possible.  The  most  common 
Fig.  617.  species  are  large,  smooth,  club-shaped  beetles  (Fig. 

617),  and  are  commonly  known  as  pinacate-bugs. 
These  beetles  and  those  belonging  to  several  closely  allied  genera  lack 
hind  wings. 


yellow,  cylmdrical 

m 


514  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  family  LAGRIIDy^,  or  the  lagriid  bark-beetles,  includes 
elongate  beetles,  with  a  narrow,  subcylindrical  prothorax,  and  a  more 
or  less  brassy  color.  They  are  closely  allied  to  the  preceding  family, 
but  differ  in  having  the  next  to  the  last  segment  of  the  tarsi 
spongy  beneath.  They  are  found  under  bark  and  on 
leaves.  The  larva  feed  freely  on  foliage  and  are  much  less 
retiring  in  habits  than  those  of  the  darkling  beetles. 
Seventeen  species  are  listed  from  the  United  States ;  most 
of  these  are  found  in  the  South  and  Far  West.  Our  most 
common  species  in  the  East  is  Arthromdcra  cenea  (Fig.  6i8) ; 
this  species  measures  from  9.5  mm.  to  13.5  mm.  in  length.       Fig.  618. 

The  family  MONOMMID^  is  represented  in  this 
country  by  only  six  species,  found  chiefly  in  the  Far  West  and  in 
Florida.  They  are  small,  black,  oval  beetles,  in  which  the  anterior 
coxal  cavities  are  open  behind,  the  hind  tarsi  four-jointed,  and  the 
other  tarsi  five-jointed;  and  in  which  the  antennae  are  received  in 
grooves  on  the  under  side  of  the  prothorax.  Except  one  species  found 
in  Florida,  our  species  belong  to  the  genus  Hyporhdgus. 

The  family   MELANDRYID^   includes  about   eighty   North 
American  species.    These  are  found  under  bark  and  in  fungi.    They 
are  usually  of  elongate  form,  although  some,  like  the  one 
figured  here,  are  not  so.     The  maxillary  palpi  are  fre- 
quently very  long  and  much  dilated ;  and  the  first  seg- 
ment of  the  hind  tarsi  is  always  much  elongated .    Among 
our  more  common  species  are  two  belonging  to  the 
genus  Penthe.    These  are  rather  large,  oval,  depressed 
beetles,  upwards  of   12  mm.  in   length,  and  of  a  deep 
Fig.  619.        black  color.    Penthe  obliqudta  is  distingmshedhy  having 
the  scutellimi  clothed  with  rust-red  hairs  (Fig.  619). 
Penthe  pimelia  closely  resembles  this  species,  except  that  the  scutelltun 
is  black. 

The  family  PTINIDyE  has  been  restricted  recently  to  one  of  the 
subfamilies  of  the  old  family  Ptinidse,  which  included,  in  addition  to 
the  insects  now  retained  in  it,  those  classed  in  the  three  following 
families.  In  the  Ptinidae,  as  now  restricted,  the  antennae  are  inserted 
upon  the  front  of  the  head  and  rather  close  together,  and  the  thorax 
is  not  margined  at  the  sides.  Only  thirty-seven  of  our  listed  species  are 
retained  in  this  famih'.  They  are  all  small  beetles  and  some  of  them 
are  household  pests,  infesting  stored  provisions,  clothing,  and  books. 
The  best -known  species  is  P^zwM^/wr.  This  is  a  reddish  brown  beetle;  in 
the  female  the  elytra  are  marked  with  two  patches  of  white  hairs. 
It  measures  from  2.8  mm.  to  3.5  mm. 

The  family  ANOBIIDyE,  or  the  death-watch  family,  includes  a 
large  part  of  the  old  family  Ptinidae,  there  being  more  than  two 
hundred  species  in  our  fauna.  In  this  family  the  antennas  are  inserted 
on  the  sides  of  the  head  in  front  of  the  eyes;  the  thorax  is  usually 
margined  at  the  sides;  and  the  tibiae  are  without  spurs.  These 
beetles  are  small,  and  are  generally  of  a  cylindrical  form,  though 
some  are  broadly  oval  or  nearly  globular.     They  live  chiefly  on  dry 


H 


COLEOPTERA  515 

vegetable  matter  and  are  often  found  boring  in  the  woodwork  of 
buildings.  Some  are  pests  in  drug-stores  and  groceries,  where  they 
infest  a  great  variety  of  substances  both  vegetable  and  animal. 
Among  the  better -known  species  are  the  drug-store  beetle,  Sitodrepa 
pamcea,  which  not  only  infests  many  kinds  of  drugs  but  is  also  some- 
times a  pest  in  groceries  where  it  infests  cereals;  and  the  cigarette- 
beetle,  Lasioderma  serricorne ^vhich.  infests  dried  tobacco  and  destroys 
cigarettes  and  cigars  by  boring  holes  through  them. 

To  this  family  belongs  the  death-watch,  Xestohimn  rufovillosum, 
which  bores  in  the  timbers  of  buildings  and  makes  a  ticking  sound  by 
striking  its  head  or  jaws  against  the  walls  of  its  burrows.  This 
sound  heard  in  the  night  h\  superstitious  watchers  by  sick-beds  has 
been  supposed  to  portend  death. 

The  family  BOSTRICHID^,  or  the  powder-post  beetles,  includes 
beetles  which  are  elongate  in  form;  the  head  is  usually  deflexed,  and 
protected  by  the  thorax,  which  is  then  hood-like  in  form;  and  the 
first  ventral  segment  of  the  abdomen  is  scarcely  longer  than  the 
second.  These  beetles  live  almost  exclusively  in  dry  wood  either  in 
c>-lindrical  burrows  or  beneath  the  bark.  Sometimes  they  infest 
timbers  to  such  an  extent  that  the  wood  is  largely  reduced  to  pow^der, 
hence  the  common  name,  powder-post  beetles.  The  adult  of  one 
species,  Amphicerus  bicauddtus,  bores  into  the  living  twigs  of  fruit- 
trees  and  grape-vines  for  food,  but  it  breeds  in  dying  wood,  such  as 
prunings  and  dying  branches.  This  species  is  known  as  the  apple-twig 
borer  and  also  as  the  grape-cane  borer. 

The  family  LYCTID^  is  composed  of  a  small  number  of  beetles 
which  resemble  the  powder-post  beetles  in  habits.  In  this  family  the 
head  is  prominent  and  not  covered  by  the  prothorax;  and  the  first 
ventral  segment  of  the  abdomen  is  much  longer  than  the  second. 
Most  of  our  species  belong  to  the  genus  Lyctus. 

The  family  SPHINDID^  is  represented  in  North  America  only 
by  six  small  species,  which  are  found  in  dry  fungi  which  grow  on  the 
trunks  of  trees  and  on  logs. 

The  family  CISID^  includes  very  small  beetles,  rarely  exceeding 
3  mm.  in  length,  found  under  the  bark  of  trees  and  in  the  dry  and 
woody  species  of  fungi.  The  body  is  cylindrical;  the  prothorax  is 
prolonged  over  the  head;  the  abdomen  has  five  ventral  segments,  of 
which  the  first  is  longer  than  the  others;  and  the  tarsi  are  all  four- 
jointed.    There  are  nearly  one  hundred  species  in  our  fauna. 

Family  SCARAByEID^ 

The  ScarahcBids  or  Lamellicorn  Beetles 

This  very  large  family  is  represented  in  our  fauna  by  nearly  one 
thousand  species,  and  includes  beetles  that  exhibit  a  wide  range  of 
variation  in  size,  form,  and  habits.  They  are  mostly  short,  stout-bodied 
beetles,  of  which  the  well-known  June-bugs  or  May-beetles  represent 
the  most  familiar  type.    The  most  useful  character  for  distinguishing 


516  AN  INTRODUCTION  TO  ENTOMOLOGY 

these  insects  is  the  lamellate  form  of  the  club  of  the  antennas,  the 
segments  constituting  it  being  greatly  flattened,  and  capable  of  being 
brought  close  together.  It  is  this  character  that  suggests  the  name 
lamellicorn  beetles.  In  the  next  family,  the  Trogidae,  which  has 
recently  been  separated  from  this  family,  the  antennas  are  lamellate. 
The  two  families  can  be  separated  by  the  fact  that  in  the  Scarabaeidas 
the  epimera  of  the  mesothorax  extend  to  the  coxae,  while  in  the 
Trogidee  they  do  not. 

According  to  their  habits,  the  members  of  this  family  can  be 
separated  into  two  well-marked  groups — the  scavengers  and  the  leaf- 
chafers. 

THE  LAMELLICORN  SCAVENGERS 

The  lamellicorn  scavengers  in  both  the  larval  and  adult  states  feed 
upon  decaying  vegetable  matter.  Nearly  all  the  species  live  in  dung, 
chiefly  that  of  horses  and  cows;  but  a  few  species  feed  upon  fungi. 
The  following  are  the  more  common  representatives  of  this  division. 

I.  The  tumble-bugs. — These  are  the  most  familiar  of  all  dung- 
beetles,  for  their  peculiar  habits  have  attracted  much  attention  from 
the  earliest  times.  They  are  of  rounded  form,  and  the  wing-covers 
are  shortened  so  as  to  expose  the  tip  of  the  abdomen.  They  are 
generally  black,  but  some  are  colored  with  rich  metallic  hues.  They 
vary  greatly  in  size. 

The  name  tumble-bug  refers  to  the  habit  which  many  species 
exhibit  of  forming  round  balls  of  dung,  which  they  roll  long  distances 
and  then  bury.  They  often  work  in  pairs  and  it  was  formerly  be- 
lieved that  such  a  pair  was  a  male  and  a  female  working  together  to 
make  provision  for  their  progeny ;  but  Fabre  found  by  dissecting  the 
beetles  that  the  two  members  of  a  pair  often  proved  to  belong  to  the 
same  sex;  and  concluded  that  the  eager  fellow-worker,  under  the 
deceitful  pretense  of  lending  a  helping  hand,  nurses  the  scheme  of 
purloining  the  ball  at  the  first  opportunity. 

According  to  the  observations  of  Fabre  ('79  and  '11),  the  balls 
made  early  in  the  year  are  devoured  by  the  beetles,  which  bury  them- 
selves with  them  and  feed  upon  them.  Later  other  balls  are  made  and 
buried,  upon  each  of  which  an  egg  is  laid.  The  larva  hatching  from 
this  egg  feeds  upon  the  ball  of  dung,  and  when  full-grown  transforms 
within  the  cavity  in  which  the  ball  was  placed. 

This  strange  habit  of  rolling  these  balls  has  occasioned  much 
speculation  as  to  its  object,  and  has  been  the  source  of  many  super- 
stitions, especially  in  ancient  times.  The  only  reasonable  theory  that 
we  have  met  is  that,  as  many  predacious  insects  frequent  the  masses 
of  dung  from  which  the  balls  are  obtained,  in  order  to  prey  upon  the 
larvae  which  live  there,  the  more  intelligent  timible-bugs  remove  the 
food  for  their  larvae  to  a  safe  distance. 

The  most  noted  member  of  this  group  of  genera  is  the  sacred 
beetle  of  the  Egyptians,  Ateuchus  sdcer.     This  insect  was  held  in 


on   Liitj  iiiiuuit 


COLEOPTERA  517 

high  veneration  by  this  ancient  people.  It  was  placed  by  them  in 
the  tombs  with  their  dead;  its  picture  was  painted  on  sarcophagi, 
and  its  image  was  carved  in  stone  and  precious  gems.  These  sculp- 
tured beetles  can  be  found  in  almost  any  collection  of  Egyptian  an- 
tiquities. 

From  the  habits  and  structure  of  this  scarabaeid  the  Egyptians 
evolved  a  remarkable  symbolism.  The  ball,  which  the  beetles  were 
supposed  to  roll  from  sunrise  to  sunset,  represented  the  earth;  the 
beetle  itself  personified  the  sun,  because  of  the  sharp  projections  on 
its  head,  which  extend  out  like  rays  of  light ;  while  the  thirty  segments 
of  its  six  tarsi  represented  the  days  of  the  month.  All  individuals  of 
this  species  were  thought  to  be  males,  and  a  race  of  males  symbolized 
a  race  of  warriors.  This  latter  superstition  was  carried  over  to  Rome 
and  the  Roman  soldiers  wore  images  of  the  sacred  beetle  set  in  rings. 
Our  common  tiimble-bugs  are  distributed  among  three  genera: 
Cdnthon,  Copris,  and  Phanceus.  In  the  genus  Canthon  the  middle 
and  posterior  tibiae  are  slender,  and  scarcely  enlarged 
at  the  extremity.  Canthon  Icevis  is  our  most  common 
species  (Fig.  620).  In  Copris  and  Phanceus  the 
middle  and  posterior  tibi®  are  dilated  at  the  ex- 
tremity. In  PhancBus  the  fore  tarsi  are  wanting,  and 
the  others  are  not  furnished  with  claws;  the  species 
are  brilliantly  colored.  PhancBus  carnifex,  with  its 
rough  copper-colored  thorax  and  green  elytra,  is  one  pjg  520 

of  our  most  beautiful  beetles,  and  is  our  best -known 
species.     It  is  about  16  mm.  in  length,  and  the  head  of  the  male  is 
furnished  with  a  prominent  horn.    In  Copris  all  the  tarsi  are  present 
and  furnished  with  claws.  Copris  Carolina  is  a  large,  well-known  species, 
which  measures  more  than  25  mm.  in  length. 

II.    The  aphodian  dung-beetles . — These  are  small  insects,  our  com- 
mon species  measuring  from  4  mm.  to  8  mm.  in  length.    The  body  is 
oblong,  convex,  or  cylindrical  in  form,  and,  except  in  one  small  genus, 
the  clypeus  is  expanded  so  as  to  cover  the  mouth-parts  entirely. 
These  insects  are  very  abundant  in  pastures  in  the  dung  of  horses  and 
cattle,  and  immense  nvunbers  of  them  are  often  seen  flying  through 
the  air  during  warm  autumn  afternoons.     More  than  one  hundred 
and  fifty  North  American  species  have  been  described;  of  these,  one 
hundred  belong  to  the  genus  Aphodius.     One  of  the  more  common 
species  is  Aphodius  fimetdrius,  which  is  about  8  mm.  in 
\  ^^^  /      length,  and  is  easily  recognized  by  its  red  wing-covers. 
^^Ukr  III.      The  earth-boring  dung-beetles. — -These  beetles 

>2j^^bw  are  of  a  rounded  convex  form  (Fig.  621).  They  differ 
JQU^^^L  from  all  other  dung-beetles  in  having  the  antennae 
W^BHf  eleven-jointed,  and  in  the  lab  rum  and  mandibles 
r^^'^A  being  visible  from  above.  This  is  a  small  group,  only 
p-     ^  twenty-two  North  American  species  having  been  de- 

scribed. The  popular  name  is  deiived  from  that  of  the 
typical  genus,  Geotriipes,  which  signifies  earth-boring.  Those  species 
the  habits  of  which  are  known,  live  in  excrement.    The  females  bore 


518  AN  INTRODUCTION  TO  ENTOMOLOGY 

holes  into  the  earth  either  beneath  the  dung  or  near  it;  into  these 
holes  they  convey  a  quantity  of  the  dung ;  this  is  to  serve  as  food  for 
the  larvae,  an  egg  being  laid  in  each  hole.  This  is  an  approach  to  the 
peculiar  habits  of  the  tvimble-bugs. 

THE  LAMELLICORN  LEAF-CHAFERS 

The  leaf-chafers  are  herbivorous  insects  which  in  the  adult  state 
usually  feed  upon  the  leaves  of  trees,  but  many  of  the  species  devour 
the  pollen  and  petals  of  flowers.  In 
the  larval  state  some  of  these  insects 
are  found  in  rotten  wood;  others  live 
in  the  ground,  where  they  feed  upon 
the  roots  of  grass  and  other  plants. 
These  larvae  are  thick,  fleshy  grubs, 
with  well-developed  legs  (Fig.  622). 
The  caudal  segments  of  the  abdomen 
are  very  large,  and  appear  black  on  ac- 
count of  the  large  amount  of  dirt  in  the 
intestine.  The  body  is  strongly  curved, 
so  that  the  larvae  can  crawl  only  with 
Pig  522.  great  difficulty;  when  in  the  ground 

they  usually  lie  on  their  backs. 
The  following  groups  include  the  more  important  representatives 
of  this  division. 

I.  The  May-beetles  or  June-hugs. — During  the  warm  evenings  of 
May  and  June  we  throw  open  our  windows  so  that  we  may  feel  the 
refreshing  coolness  of  the  night  air  and  the  inspiration  of  the  new 
simimer.  Suddenly,  as  we  sit  working  or  reading,  our  peace  is  dis- 
turbed by  a  buzzing  object  which  whirls  above  us.  Then  comes  a 
sharp  thud  and  silence.  A  little  later  the  scratching  of  six  pairs  of 
tiny  claws  tells  us  the  whereabouts  of  the  intruder.  But  so  familiar 
are  we  with  his  kind  that  we  need  not  look  to  know  how  he  appears, 
the  mahogany-brown  blunderer,  with  yellowish  wings  sticking  out 
untidily  from  under  his  pohshed  wing-covers. 

Although  these  insects  are  beetles,  and  attract 
our  attention  each  year  in  May,  they  have  received 
the  infelicitous  title  of  June-bugs.  They  are  more 
properly  termed  May-beetles. 

The  May-beetles  belong  to  the  genus  Phylloph- 
aga,  of  which  we  have  nearly  one  hundred  species. 
The  adults  frequently  do  much  injur}''  by  eating  the 
foliage  of  trees.  In  the  case  of  large  trees  this  injury 
usually  passes  unnoticed;  but  small  trees  are  often 
completely  defoliated  by  them.  When  troublesome, 
they  can  be  easily  gathered  by  shaking  them  from 
trees  upon  sheets.    Figure  623  represents  a  common  ^'§-  ^-^■ 

species. 

The  larvae  of  the  different  species  of  May-beetles  are  commonly 
classed  together  imder  the  name  "white-grubs."  They  are  often  great 


COLEOPTERA  519 

pests  in  meadows  and  in  cultivated  fields.  We  have  known  large 
strawberry  plantations  to  be  destroyed  by  them,  and  have  seen  large 
patches  of  ground  in  pastures  from  which  the  dead  sod  could  be 
rolled  as  one  would  roll  a  carpet  from  a  floor,  the  roots  having  been 
all  destroyed  and  the  ground  just  beneath  the  surface  finely  pulver- 
ized by  these  larvae.  No  satisfactory  method  of  fighting  this  pest  has 
been  discovered  as  yet.  If  swine  be  turned  into  fields  infested  by  white- 
grubs  they  will  root  them  up  and  feed  upon  them.  We  have  destroyed 
great  numbers  of  the  beetles  by  the  use  of  trap-lanterns,  but  many 
beneficial  insects  were  destroyed  at  the  same  time. 

II.  The  rose-bugs. — The  common  rose-bug,  Macroddctylus  suh- 
spinosus,  is  a  well-known  pest.  It  is  a  slender  beetle,  tapering  before 
and  behind,  and  measuring  9  mm.  in  length  (Fig.  624). 

It  is  thickly  clothed  with  fine,  yellow,  scale-hke  hairs,  which 

give  it  a  yellow  color;  the  legs  are  long,  slender,  and  of  a        ^JtJ 

pale  red  color.    These  beetles  appear  in  early  summer,       (wk 

and  often  do  great    injury    to  roses   and  other   flowers,      /W^VS 

and  to  the  foliage  of  various  fruit-trees  and  shrubs.    This      /      \ 

is  a  very  difficult  pest  to  control.    The  best  method  now 

known  is  to  use  Paris  green  when  safe  to  do  so;  in  other        ^^'    ""*■ 

cases  the  beetles  should  be  collected  by  jarring  them  into 

a  large  funnel  which  is  fitted  into  a  can.    The  larvae  of  rose-bugs  feed 

on  the  roots  of  plants. 

III.  The  shining  leaf -chafers . — These  insects  resemble  the  May- 
beetles  in  form,  but  can  be  distinguished  from  them  by  the  position 
of  the  hind  pair  of  spiracles,  which  are  visible  on  the  sides  below  the 
edges  of  the  wing-covers ;  and  they  differ  from  the  other  leaf-chafers 
in  which  the  spiracles  are  in  this  position  in  that  the  tarsal  claws  are 
of  unequal  size,  one  claw  of  each  pair  being  larger  than  the  other. 
These  beetles  are  usually  polished,  and  many  of  them  are  of  brilliant 
colors.  To  this  family  belong  the  most  beautiful  beetles  known, 
many  appearing  as  if  made  of  burnished  gold  or  silver,  or  other  metal. 

The  goldsmith-beetle,  Cotalpa  lanigera. — This  is 
one  of  our  most  beautiful  species.  It  measures  from 
20  mm.  to  26  mm.  in  length,  and  is  a  broad  oval  in 
shape.  It  is  of  a  lemon-yellow  color  above,  glittering 
like  burnished  gold  on  the  top  of  the  head  and 
thorax ;  the  under  side  of  the  body  is  copper-colored 
and  thickly  covered  with  whitish  wool. 

The  spotted  pelidnota,  Pelidnota  punctata. — -This 
beetle  is  reddish  brown  above,  with  three  black  spots 
on  each  wing-cover  and  one  on  each  side  of  the  pro- 
Fig.  625.  thorax  (Fig.  625).    The  scutellum,  base  of  the  head, 
and   entire   body  beneath,  are  of  a  deep,  bronzed- 
green  color.     The  adult  is  commonly  found  feeding  on  the  leaves  of 
grape.     The  larva  feeds  upon  decaying  roots  and  stumps  of  various 
trees. 

The  Japanese  beetle,  Popillia  japonica. — This  is  a  very  serious 
pest  which  feeds  in  the  adult  state  on  the  foliage  of  many  cultivated 


520  AN  INTRODUCTION  TO  ENTOMOLOGY 

and  wild  plants,  being  practically  omnivorous,  and  in  the  larval  state 
feeds  on  the  roots  of  grasses.  It  was  first  observed  in  this  country  in 
a  limited  area  in  Burlington  County,  New  Jersey,  in  191 6,  and  has 
since  spread  over  other  counties  of  this  state  and  into  Pennsylvania. 
The  adult  insect  is  about  the  size  of  the  Colorado  potato-beetle,  but 
slightly  longer.  The  head  and  thorax  are  shining  bronze-green  in 
color,  with  the  wing-covers  tan  or  brownish, tinged  with  green  on  the 
edges.  Along  the  sides  of  the  abdomen  are  white  spots,  and  two  very 
distinct  white  spots  at  the  tip  of  the  abdomen  below  the  wing-covers. 
The  larva  resembles  the  larvse  of  May  beetles. 

This  pest  is  regarded  as  of  so  great  importance  that  a  special 
laboratory,  "The  Japanese  Beetle  Laboratory,"  has  been  established 
for  investigations  regarding  it  at  Riverton,  N.  J. 

IV.  The  rhinoceros-beetles.- — -The  name  rhinoceros-beetles  was 
suggested  for  this  group  by  the  fact  that  in  many  species  the  male 
bears  a  horn  on  the  middle  of  the  head.  In  addition  to  this  horn 
there  may  be  one  or  more  horns  on  the  thorax.    These  beetles  are 

of  medium  or  large  size ;  in 
fact,  the  largest  beetles 
known  belong  to  this  group. 
As  with  the  flower-beetles, 
the  claws  of  the  tarsi  are  of 
equal  size,  but  the  fore  coxae 
are  transverse,  and  not 
prominent. 

One  of  the  largest  of  our 
rhinoceros-beetles  is  Dynds- 
Fig-  626.  ^^^    tUyrus.      This    is    of   a 

greenish  gray  color,  with 
scattered  black  spots  on  the  wing-covers,  or,  if  only  recently  trans- 
formed, of  a  uniform  dark  brown.  The  male  (Fig.  626)  bears  a 
prominent  horn  on  the  top  of  the  head,  and  a  large  one  and  two 
small  ones  on  the  prothorax.  The  female  has  only  a  tubercle  on  the 
head.  This  insect  is  found  in  the  Southern  States;  the  larva  lives  in 
rotten  wood.  In  the  Far  West  there  is  a  closely  allied  species,  Dynastes 
grantii,  in  which  the  large  horn  on  the  thorax  is  twice  as  long  as  in 
JD.  tityrus.  In  the  West  Indies  there  occurs  a  species,  Dynastes 
..hercules,  which  measures  150  mm.  in  length. 

Several  other  genera  occur  in  this  coimtry,  in  some  of  which  the 
■males  have  prominent  horns;  in  others  the  horns  are  represented 
^,by  tubercles,  or  are  wanting.  The  following  species  represents  the 
Jatter  type. 

The  sugar-cane  beetle,  Euctheola  riigiceps . —  This  beetle  is  a  serious 
-pest  in  the  cane-fields  of  Louisiana,  and  it  sometimes  injures  corn. 
Figure  627  represents  the  adult,  and  its  method  of  attacking  a  plant. 

V.  The  flower-beetles . — The  flower-beetles  are  so  called  because 
many  of  them  are  often  seen  feeding  upon  pollen  and  flying  from 
flower  to  flower.  These  beetles  are  somewhat  flattened,  or  nearly 
level  on  the  back;  the  claws  of  the  tarsi  are  of  equal  size  and  the 


COLEOPTERA 


521 


fore  coxae  are  conical  and  prominent 
occur  in  this  country. 

The  hermit  flower-beetle,  Os- 
moderma  eremicola.- — This  is  one 
of  the  larger  of  our  flower-beetles 
(Fig.  628).  It  is  of  a  deep  mahog- 
any-brown color,  nearly  smooth, 
and  highly  polished.  It  is 
supposed  that  the  larva  lives  on 
decaying  wood  in  forest-trees. 

The  rough  flower-beetle,  Os- 
moderma  scdbra,  is  closely  allied 
to  the  preceding.  It  is  not  quite 
as  large,  measuring  about  25  mm. 
in  length.  It  is  purplish  black, 
and  the  wing-covers  are  rough- 
ened with  irregular,  coarsely 
punctured  strice.  It  is  nocturnal, 
concealing  itself  during  the  day  in 
the  crevices  and  hollows  of  trees. 
The  larva  lives  in  the  decaying 
wood  of  apple  and  cherry,  con- 
siuning  the  wood  and  inducing 
more  rapid  decay. 

The  genus  Euphoria  repre- 
sents well  the  form  of  the  more 
typical  flower-beetles,  which  are 
distinguished  by  the  margin  of 
each  wing-cover  having  a  large, 
wavy  indentation  near  its  base, 
which  renders 
the  side  pieces 
of  the  meso- 
thorax  visible 
from  above. 
This  indenta- 
tion makes  it 
unnecessarv 


More  than  one  hundred  species 


V\.H.UVCiHO\_S» 


Fig.  627. — The  sugar-cane  beetle. 


for  these  insects  to  raise  or  expand  their  wing- 
covers  when  flying,  as  most  beetles  do,  as  they 
are  able  to  pass  the  wings  out  from  the  sides. 
The  bumble  flower-beetle.  Euphoria  tnda. — 
The  most  common  of  our  flower-beetles,  at  least 
in  the  North,  is  a  yellowish  brown  one,  with  the 
wing-covers  sprinkled  all  over  with  small,  irregular. 
Fig.  628.  black  spots  (Fig.  629) .    It  is  one  of  the  first  insects 

to  appear  in  the  spring.  It  flies  near  the  surface  of 
the  ground  with  a  loud  humming  sound,  like  that  of  a  bumble-bee,  for 
which  It  is  often  mistaken.    During  the  summer  months  it  is  not  seen ; 


522  AN  INTRODUCTION  TO  ENTOMOLOGY 

but  a  new  brood  appears  about  the  middle  of  September.  The  adult 
is  a  general  feeder  occurring  upon  flowers,  eating  the  pollen,  upon 
corn-stalks  and  green  com  in  the  milk,  sucking  the 
juices,  and  upon  peaches,  grapes,  and  apples.  Oc- 
casionally the  ravages  are  very  serious. 

The  green  June-beetle  or  fig-eater,  Cotinus  mtida. — 
This  species  extends  over  the  Atlantic  slope,  and  is  very 
common  in  the  South.  It  is  a  green,  velvety  insect, 
measuring  from  i6  mm.  to  25  mm.  in  length.  It  is 
somewhat  pointed  in  front,  and  usually  has  the  sides 
of  the  thorax  and  elytra  brownish  yellow.  These  beetles 
often  fly  in  great  numbers  at  night,  making  a  loud 
buzzing  noise  similar  to  that  of  the  May-beetles.  In  fact,  in  the 
South  the  term  June-bug  is  often  applied  to  this  insect.  The  larvae 
feed  upon  the  vegetable  mold  of  rich  soils;  sometimes  they  injure 
growing  vegetables  by  severing  the  roots  and  growing  stalks ;  but  the 
chief  injury  is  due  to  the  upheaval  of  the  soil  around  the  plants, 
which  disturbs  the  roots;  the  larvse  are  also  often  troublesom.e  on 
lawns  and  golf  greens  by  making  little  mounds  of  earth  on  the  surface. 
Sometimes  they  leave  the  ground  and  crawl  from  one  place  to  another. 
When  they  do  so,  they,  strangely  enough,  crawl  upon  their  backs, 
making  no  use  of  their  short  legs.  On  one  occasion  we  saw  them  crawl- 
ing over  the  pavements  on  the  Capitol  grounds  at  Washington  in 
such  numbers  that  bushels  of  them  were  swept  up  and  carted  away. 
The  adults  frequently  attack  fruit,  especially  figs,  grapes,  and  peaches. 


Family  TROGID^ 

The  Skin-Beetles 

This  is  a  small  family,  which  is  represented  in  this  country  by 
twenty-five  species.  Until  recently  these  insects  were  included  in  the 
preceding  family;  they  can  be  distinguished  from  scarabasids  by  the 
fact  that  the  epimera  of  the  mesothorax  do  not  extend  to  the  coxae 
as  they  do  in  the  Scarabasidas.  The  members  of  this  family  are 
oblong,  convex  species,  in  which  the  surface  of  the  body  and  wing- 
covers  is  usually  very  rough,  and  covered  with  a  crust  of  dirt,  which 
is  removed  with  great  difficulty.  They  are  small  or  of 
medium  size;  our  most  common  species  measure  from 
8  mm.  to  12  mm.  in  length.  The  abdomen  is  covered 
by  the  elytra ;  the  feet  are  hardly  fitted  for  digging,  but 
the  femora  of  the  front  legs  are  greatly  dilated. 

These  beetles  feed  upon  dried,  decomposing  animal 
matter;  many  species  are  found  about  the  refuse  of 
tanneries,    and  upon  the  hoofs  and  hair  of   decaying         ^^^-  ^•5°- 
animals. 

Except  a  few  species  found  in  the  Far  West,    all  of  our  species 
belong  to  the  genus  Trox  (Fig.  630). 


^ 


COLEOPTERA  523 

Family  LUCANID^ 

The  Stag-Beetles 

The  stag-beetles  are  so  called  on  account  of  their  large  mandibles 
which  in  the  males  of  some  species  are  branched  like  the  antlers  of 
a  stag.  They  and  the  members  of  the  following  family  are  dis- 
tinguished by  the  form  of  the  club  of  the  antenna?,  which  is  composed 
of  flattened  plates ;  but  these  plates  are  not  capable  of  close  appo- 
sition, as  in  the  antennae  of  the  lamellicorn  beetles.  In  the  stag-beetles 
the  mentum  is  not  emarginate  and  the  ligula  is  covered  by  the 
mentum  or  is  at  its  apex. 

The  adult  beetles  are  found  in  or  beneath  decaying  logs  and 
stumps.  Some  of  them  are  attracted,  at  night,  to  lights.  They  are 
said  to  live  on  honeydew  and  the  exudations 
of  the  leaves  and  bark  of  trees,  for  procur- 
ing which  the  brushes  of  their  jaws  and  lips 
seem  to  be  designed;  but  it  seems  probable 
that  some  species,  at  least,  feed  upon  de- 
composing wood.  They  lay  their  eggs  in 
crevices  of  the  bark  of  trees,  especially  near 
the  roots.  The  larv«  feed  upon  juices  of 
wood  in  various  stages  of  decay.  They  re- 
semble the  well-known  larvae  of  May -beetles. 
The  family  is  a  small  one;  only  thirty 
North  American  species  are  now  known. 
The  common  stag-beetle,  Lucdnus  dama. 
— The  most  common  of  our  stag-beetles  is 
this  species  (Fig.  631).  It  flies  by  night 
with   a   loud  buzzing   sound,   and  is  often  -^^S-  631. 

attracted  to  lights  in  houses.  The  larva  is  a  large,  whitish  grub  re- 
sembling the  larvae  of  the  lamellicorn  beetles.  It  is  found  in  the 
trunks  and  roots  of  old,  partially  decayed  trees,  especially  apple, 
cherry,  willow,  and  oak.  The  specimen  flgured  here  is  a  male;  in 
the  female  the  mandibles  afe  shorter. 

The  giant  stag-beetle,  Lucdnus  elaphus,  is  a  large 
species  found  in  the  South.  It  measures  from  35  mm. 
to  50  mm.  in  length,  not  including  the  mandibles, 
which  in  the  case  of  the  male  are  more  than  half  as  long 
as  the  body,  and  branched  like  the  antlers  of  a  stag. 
The  antelope-beetle,  Dorcus  parallelus. — This  beetle 
is  somewhat  smaller  than  the  species  of  Lucanus,  and 
differs  in  having  the  wing-covers  marked  with  longi- 
Fig-  632.        tudinal  striae  and  the  teeth  on  the  outside  of  the  fore 

tibiae  much  smaller  (Fig.  632). 
Several  species  of  stag-beetles  that  are  much  smaller  than  Dorcus 
are  found  in  this  country. 


524 


AN  INTRODUCTION  TO  ENTOMOLOGY 
Family  PASvSALID^ 


The  members  of  this  family  resemble  the  stag-beetles  in  the  form 
of  the  antennas,  but  differ  in  that  the  mentum  is  deeply  emarginate, 
with  the  ligula  filling  the  emargination. 

A  single,  widely  distributed  species  is  found  in 
the  United  States;  this  is  the  homed  passalus, 
Pdssalus  cornutus  (Fig.  633).  It  is  a  large,  shining, 
black  beetle,  with  a  short  horn,  bent  forwards,  on 
the  top  of  the  head.  This  beetle  and  its  larva  are 
found  in  decaying  wood.  The  larva  appears  to 
have  only  four  legs,  the  hind  legs  being  shortened 
and  modified  so  as  to  form  part  of  a  stridulating 
organ.    See  Figure  loi,  page  89. 

The  beetles  of  this  genus  are  common  through- 
out the  tropics  of  both  hemispheres.     According 
to  the  observations  of  Ohaus,  which  have  been 
Fig-  633.  confirmed  by  Professor  Wheeler  ('23),  these  beetles 

are  social.  They  form  colonies,  consisting  of  a  male  and  female  and 
their  progeny,  and  make  large,  rough  galleries  in  rather  damp,  rotten 
logs.  The  parent  beetles  triturate  the  rotten  wood  and  apparently 
treat  it  with  some  digestive  secretion  which  makes  it  a  proper  food 
for  the  larvse,  since  their  mouth-parts  are  too  feebly  developed  to 
enable  them  to  attack  the  wood  directly.  All  members  of  the  colony 
are  kept  together  by 
stridulatory  signals.  The 
stridulatory  organ  of  the 
adult  consists  of  patches 
of  minute  denticles  on 
the  dorsal  surface  of  the 
abdomen,  which  may  be 
rubbed  against  similar 
structures  on  the  lower 
surface    of    the    wings. 


Family 
CERAMBYCID^ 

The  Long-horned  Beetles 
or  Cerambycids 

This  is  a  very  large 
family,  there  being  more 
than  eleven  hundred  de- 
scribed species  in  North 
America  alone.  As  a  rule 
the  beetles  are  of  medium 

or  large  size,  and  graceful  in  form ;  many  species  are  beautiful  in  color. 
The  body  is  oblong,  often  cylindrical.     The  antennas  are  long,  often 


ABC 
Fig.  634. — Tarsi  of  Phytophaga:  A,  typical; 
Spondylis;  C,  Parandra. 


B, 


COLEOPTERA  525 

longer  than  the  whole  body;  but  except  in  one  genus,  Prionus,  they 
are  only  eleven-jointed,  as  with  most  beetles.  The  legs  are  also  long, 
and  the  tarsi  are  apparently  four-jointed,  the  fourth  segment  being 
very  small  and  hidden;  the  third  segment  of  the  tarsi  is  strongly 
bilobed  (Fig.  634.). 

They  are  strong  flyers  and  swift  runners;  but  many  of  them 
have  the  habit  of  remaining  motionless  on  the  limbs  of  trees  for 
long  intervals,  and  when  in  this  apparent  trance  they  suffer 
themselves  to  be  picked  up.  But,  when  once  caught,  many  species 
make  an  indignant  squeaking  by  rubbing  the  prothorax  and  meso- 
thorax  together. 

The  larva?  are  borers,  living  within  the  solid  parts  of 
trees  or  shrubs,  or  beneath  bark.    They  are  white  or  yel- 
lowish grubs.    The  body  is  soft,  and  tapers  slightly  from 
head  to  tail  (Fig.  635);  the  jaws  are  powerful,  enabling 
these  insects  to  bore  into  the  hardest  wood.     The  larval 
state  usually  lasts  two  or  three  years.    The  pupa  state  is 
passed  within  the  burrow  made  by  the  larva;  frequently 
a  chamber  is  made  by  partitioning  off  a  section  of  the       ^^'  ^^' 
burrow  with  a  plug  of  chips;  but  sometimes  the  larva  builds  a  ring 
of  chips  around  itself  just  beneath  the  bark    before    changing   to 
a  pupa.    The  pupal  state  is  comparatively  short,  lasting  only  a  few 
days  or  weeks. 

This  family  comprises  three  subfamilies,  which  are  separated  by 
LeConte  and  Horn  as  follows: 

A.     Sides  of  the  prothorax  with  a  sharp  margin,    p.  525 PRiONiNiE 

AA.    Prothorax  not  margined. 

B.    Front  tibiae  not  grooved ;  palpi  never  acute  at  tip.     p.  526 .  CERAMBYCiNyE 

BB.    Front  tibiae  obliquely  grooved  on  the  inner  side;  palpi  with  the  last 
segment  cylindrical  and  pointed,     p.  528 Lamiin^e 

Subfamily  PRIONIN^ 
The  Prionids 

The  larger  of  the  long-homed  beetles  constitute  this  subfamily. 
They  are  distinguished  from  other  cerambycids  by  having  the  sides 
of  the  prothorax  prolonged  outwards  into  a  thin  margin,  which  is 
more  or  less  toothed.  The  wing-covers  are  usually  leathery  in  ap- 
pearance, and  of  a  brownish  or  black  color.  The  following  are  our 
best-known  species. 

The  aberrant  long-horned  beetles. — The  beetles  of  the  genus  Pa- 
randra  exhibit  some  strikingdifferences  from  the  more  typical  ceramby- 
cids, and  were  formerly  placed  in  a  separate  family,  the  Spondylidcs; 
but  they  are  now  included  in  the  Cerambycidae.  There  are  only  four 
North  American  species  of  this  genus.  These  live  under  bark  of  pine 
trees.  The  fourth  segment  of  the  tarsus,  although  much  reduced  in 
size,  is  distinctly  visible ;  the  first  three  segments  are  but  slightly  di- 


526 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  636. 


Fig.  637 


lated,  and  the  third  is  either  bilobed  or  not  (Fig.  634,  C).    The  seg- 
ments of  the  antennae  have  deep  impressions,  in  which  are  situated 
the  organs   of  special   sense    (Fig.    636).     The 
most  common  species  is  Parandra  brunnea  (Fig. 
637);  this  insect  is  of  a  mahogany-brown  color, 
and  measures  from  9  mm.  to  18  mm.  in  length. 
The  broad-necked  prionus,  Prionus  laticdllis. 
— This  is  the  largest  of  our  common  species; 
but  the  individuals  vary  from  22  mm.  to  50  mm. 
in  length.     It  is  of  a  pitchy-black  color,  and  of 
the  form  shown  in  Figure  638.     The  antennae 
are  twelve-jointed  in  both  sexes.     The  larva  is 
a  large,  fleshy  grub,  and  infests  the  roots  of  grape, 
apple,  poplar,  and  other  trees. 
The  tile-homed  prionus,  Prionus  imbricdrms,  is  very  similar  to 
the  preceding  species  but  can  be  distinguished  at  a  glance  by  the 
form  of  the  antennae.    In  the  antennse  of 
the    male    the    nimiber    of  segments 
varies  from  eighteen  to  twenty,  while  in 
the  female  the  number  varies  from  sixteen 
to  seventeen.     The  popular  name  refers 
to  the  fact  that  the  segments  of  the  an- 
tennae of  the  male  overlap  one  another 
like  the  tiles  on  a  roof.    The  larva  infests 
the  roots  of  grape  and  pear,  and  also  feeds 
upon  the  roots  of  herbaceous  plants. 

The    straight-bodied    prionid,    Dero- 
brachus  brunneus,  is  also  a  common  spe- 
cies.   The  body  is  long,  narrow,  and  some- 
what flattened;  it  measures  from  25  mrii. 
to  35  mm.  in  length,  and  is  of  a   light 
brown  color.    The  prothorax  is  short,  and 
is  armed  on  each  side  with  three  sharp 
spines.    The  sides  of  the  wing-covers  are 
very  nearly  parallel ;  this  suggests  the  common  name.    The  adult  flies 
by  night,  and  is  often  attracted  to  lights;  the  larva  is  supposed  to 
infest  pine. 


Fig.  63 8. 


Subfamily  CERAMBYCINyE 

The  Typical  Cerambycids 

In  this  subfamily  the  prothorax  is  rounded  on  the  sides,  the  tibiae 
of  the  fore  legs  are  not  grooved,  and  the  palpi  are  never  acute  at  the  tip. 
There  are  nearly  four  hundred  American  species,  representing  more 
than  one  hundred  genera.  The  few  species  mentioned  below  are  those 
that  the  beginning  student  is  most  likely  to  meet. 

The  ribbed  pine-borer,  Rhdgium  linedtum. — This  is  a  gray  beetle 
mottled  with  black,  and  has  a  narrow  thorax,  with  a  spine  on  each 


COLEOPTERA 


527 


Fig.  639. 


side  (Fig.  639).  It  received  its  name  because  of  the  three  ridges 
extending  lengthwise  on  each  wing-cover.  Its  larva  bores  in  the 
wood  of  pine-trees.  On  one  occasion  the  writer  found 
many  of  them  in  a  pine-tree  eight  inches  in  diameter, 
which  they  had  bored  through  and  through.  When  the 
larva  is  full-grown  it  makes  a  hole  nearly  through  the 
thick  bark  of  the  tree,  so  that  it  may  easily  push  its 
way  out  after  its  transformations;  it  then  retreats  a 
short  distance  and  makes  a  little  ring  of  chips  around 
itself,  between  the  bark  and  the  wood,  and  changes  to  a 
pupa  within  this  rude  cocoon.  The  adult  beetle  re- 
mains in  this  pupal  cell  through  the  winter. 

The  cloaked  knotty-horn,  Desmocerus  pallidtus. — This  beautiful 
insect  is  of  a  dark  blue  color,  with  greenish  reflections.     The  basal 
part   of  the  wing-covers   is   orange-yellow, 
giving  the  insect  the  appearance  of  having 
a   yellow   cape   thrown   over   its   shoulders 
(Fig.  640).     The  segments  in  the  middle  of 
the  antennae  are  thickened  at  the  outer  end, 
so  that  they  look  like  a  series    of    knots. 
The  adult  is  quite  common  in  June  and  July 
on  elder,  in  the  pith  of  which  the  larva  bores. 
The    beautiful    maple-borer,     Glycohius 
speciosus. — This     is     a     handsome     insect, 
marked  with  black  and  yellow,  as  indicated 
in  Figure  641.     It  lays  its  eggs  in  midsum- 
mer on  the  trunks  of  sugar-maples,  in  the  wood  of  which  the  larvae 
bore.     If  an  infested  tree  be  examined  in  the  spring  the  presence  of 
these  borers  can  be  detected  by 
the  dust  that  falls  from  the  bur- 
rows.     The   larvae    can    be  de- 
stroyed at  this  time  by  the  use  of 
a  knife  and  a  stiff  wire. 

The  locust-borer,  Cyllene  ro- 
hincB. — To  the  enthusiastic  ento- 
mologist the  goldenrod  is  a  rich 
mine,  yielding  to  the  collector 
more  treasures  than  any  other 
flower.  It  gives  up  its  gold-dust 
pollen  to  every  insect-seeker;  and 
because  of  this  generous  attitude  to  all  comers 
it  is  truly  emblematic  of  the  country  that  has 
chosen  it  as  its  national  flower. 

Among  the  insects  that  revel  in  this  golden 
mine  in  the  autumn  is  a  black  beetle  with  numerous  transverse  or 
wavy  yellow  bands  (Fig.  642).  This  beetle  is  also  found  on  locust- 
trees,  where  it  lays  its  eggs.  The  larvse  bore  under  the  bark  and  into 
the  hard  wood;  they  attain  their  growth  in  a  little  less  than  a  year. 
The  locust-trees  have  been  completely  destroyed  in  some  localities 
by  the  depredations  of  these  larvae. 


Fig.  640. 


Fig.  642. 


Fig.  641 


528  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  painted  hickor>^-borer,  Cyllene  cdryce. — This  beetle  resembles 
the  preceding  so  closely  that  the  same  figure  will  represent  either. 
But  the  hickory-borer  not  only  infests  a  different  kind  of  tree,  but 
appears  in  the  spring  instead  of  the  autiunn.  In  this  species  the 
second  segment  of  the  hind  tarsus  is  densely  pubescent  beneath, 
while  it  is  glabrous  in  the  locust-borer. 

The  oak-pruner,  Hypermallus  villosus. — The  work  of  this  insect 
is  much  more  likely  to  attract  attention  than  the  insect  itself.  Fre- 
quently, in  the  autumn,  the  ground  beneath  oak-trees,  and  sometimes 
beneath  apple-trees  also,  is  strewn  with  small  branches  that  have 
been  neatly  severed  from  the  trees  as  if  with  a  saw.  These  branches 
are  sometimes  nearly  25  mm.  in  diameter,  and  have  been  cut  off  by 
the  larva  of  a  beetle,  which  on  account  of  this  habit  is  called  the  oak- 
pruner.  The  beetle  lays  each  of  its  eggs  in  a  small  twig.  The  larva 
eats  out  the  inside  of  this  twig,  and  works  down  into  a  larger  branch, 
following  the  center  of  it  towards  the  trunk  of  the  tree.  When  full- 
grown  the  larva  enlarges  the  burrow  suddenly,  so  as  nearly  to  sever 
the  branch  from  the  tree,  leaving  only  the  bark  and  a  few  fibers  of 
wood.  It  then  retreats  up  its  burrow  a  short  distance,  and  builds  a 
plug  of  chips  below  it.  The  autimm  winds  break  the  branch  from 
the  tree.  The  larva  remains  in  its  burrow  through  the  winter,  and 
undergoes  its  transformations  in  the  spring.  No  one  has  explained 
its  object  in  severing  the  branch.  The  adult  is  a  plain,  brownish  gray 
beetle.  Whenever  it  becomes  abundant  its  increase  can  be  checked 
by  gathering  the  fallen  branches  in  the  autiimn  and  burning  them 
before  the  beetles  have  escaped. 

Subfamily  LAMIIN^ 

The  Lamiids 

As  in  the  preceding  subfamily,  the  prothorax  is  rounded  with  these 

beetles;  but  the  lamiids 
are  distinguished  by  hav- 
ing the  fore  tibiae  oblique- 
ly grooved  on  the  inner 
side,  and  the  last  segment 
of  the  palpi  cylindrical 
and  pointed.  The  follow- 
ing are  some  of  the  more 
important  species. 

The    sawyer,    Mono- 

chamus  notdtus. — This 

beautiful  brown  and  ray. 

beetle   is   about  30gmm 

long,with  antenna  aslong 

as  the  body  in  the  case  of 

the  female  and  twice  as 

p.     ,  long  in  the  case  of  the 

^^-  ^^-  male    (Fig.    643).      The 

larva  bores  in  the  sound  wood  of  pine  and  of  fir,  making,  when  full- 


COLEOPTERA 


529 


grown,  a  hole  12  mm.  in  diameter.  The  pupa  state  is  passed  within 
the  burrow.  It  sometimes  occurs  in  such  numbers  as  to  kill  the 
infested  trees. 

The  rounded-headed  apple-tree  borer,  Saperda  Candida. — Except- 
ing the  codlin-moth,  which  infests  the  fruit,  this  is  the  worst  enemy  of 
the  apple  that  we  have.  Its  common  name  is  used  to  distinguish  it  from 
the  fiat-headed  apple-tree  borer,  already  described,  the  larva  of  this 
species  being  nearly  cylindrical  in  form  "(Fig.  635).  The  eggs  are  laid 
on  the  bark  at  the  base  of  the  tree  late  in  June  or  July.  The  larva 
at  first  bores  in  the  soft  sap-wood,  making  a  disk-shaped  mine; 
after  this  it  works  in  an  upward  direction 
in  the  harder  wood,  and  at  the  close  of  its 
larval  existence  comes  to  the  surface  sev- 
eral inches  above  the  place  it  entered. 
Itrequires  nearly  three  years  for  this  larva 
to  attain  its  growth ;  it  changes  to  a  pupa, 
near  the  upper  end  of  its  burrow,  about 
the  middle  of  May,  and  emerges  as  a 
beetle  in  June.  The  beetle  (Fig.  644)  is 
of  a  pale  brown  color  above,  with  two 
broad  white  stripes  extending  the  whole 
length  of  the  body.  Although  the  larva 
is  found  chiefly  in  apple,  it  infests  many 
other  trees.  The  presence  of  the  borers  can  be  detected  by  the  saw- 
dust-like castings  which  the  larvae  throw  out  at  the  entrances  of  their 
burrows. 

The  two-spotted  oberea,  Oberea  himacidata,  is  sometimes  a  serious 
pest,  boring  in  the  canes  of  blackberry  and  raspberry.     The  larva 

resembles    that    of    the    preceding 
species.     The  adult    (Fig.    645)    is 

T_ _^    about   12  mm.  in  length  and  of  a 

\^^^^       deep  black  color,  except  the  protho- 
jpll  rax,  which  is  yellow.    There  are  usu- 

vBI^  ally  two  or  three  black  spots  on  the 

/l!^'^  pronotum,  but  frequently  these  are 

wanting. 

By  cutting  and  burning  all  the 
picked,  the  borers  in  them  can  be 


Fig.  644. 


Fig.  645. 


Fig.  646. 


canes   after  the  crop  has  been 
destroyed. 

The  red  milkweed-beetles,  Tetraopes. — There  are  several  species 
of  bright  red  beetles  that  are  common  on  milkweeds  {Asclepias). 
These  belong  to  the  genus  Tetraopes.  Our  most  common  species 
(Fig.  646)  is  T.  tetraophthdlmus.  In  this  species  there  are  four  black 
spots  on  each  wing-cover,  and  the  antenncC  are  black  and  not  ringed 
with  a  lighter  color.  The  larva  bores  in  the  roots  and  the  lower  parts 
of  the  stems  of  milkweeds. 


530  AN  INTRODUCTION  TO  ENTOMOLOGY 

Family  CHRYSOMELID^ 
The  Leaf -Beetles  or  Chrysomelids 

The  leaf -beetles  are  so  called  because  they  feed  upon  the  leaves  of 
plants  both  as  larvee  and  adults.  They  are  usually  short -bodied,  and 
more  or  less  oval  in  outline;  the  antennae  are  usually  of  moderate 
length ;  and  the  front  is  not  prolonged  into  a  beak.  The  legs  are  usu- 
ally short,  and  are  furnished  with  tarsi  of  the  same  type  as  those  of 
the  preceding  family  (see  Fig.  634,  p.  524). 

Although  we  are  unable  to  cite  any  characteristic  that  will  in- 
variably distinguish  these  beetles  from  the  preceding  family,  the 
student  will  rarely  have  any  difficulty  in  making  the  distinction. 
The  beetles  of  the  genus  Dondcta,  described  below,  are  the  only 
common  ones  that  are  liable  to  be  misplaced.  In  other  cases  the  more 
or  less  oval  form  of  the  body,  and  the  comparatively  short  antennse, 
and  the  leaf -feeding  habits,  will  serve  to  distinguish  the  chrysomelids. 

The  leaf-beetles  are  nearly  all  comparatively  small,  the  Colorado 
potato-beetle  being  one  of  our  larger  species. 

The  eggs  are  usually  elongated  and  yellowish,  and  are  laid  upon 
the  leaves  or  stems  of  the  plants  upon  which  the  larvae  feed.  Many 
of  the  larvae  live  exposed  on  the  leaves  of  plants;  others  that  live  in 
similar  situations  cover  themselves  with  their  excrement;  some  are 
leaf -miners;  and  a  few,  as  the  striped  squash -beetle,  bore  in  the  roots 
or  stems  of  plants. 

This  is  a  large  family,  of  which  nearly  one  thousand  North  Ameri- 
can species  are  known.  The  following  illustrations  will  serve  to  show 
the  variations  in  form  and  habits. 

The  long-horned  leaf-beetles,  Dondcia. — These  are  the  common 

leaf -beetles  that  are  liable  to  be  mistaken  for  cerambycids.    They  are  of 

elongated  form,  with  slender  antennae  (Fig.  647).     They  measure- 

from  6  mm.  to  1 2  mm.  in  length,  and  are  of  a  metallic  color 

f- — either  greenish,  bronze,  or  purplish.     The  lower  side  of 
the  body  is  paler  and  is  clothed  with  very  fine  hair  which 
serves  as  a  water-proof  coat  when  the  insect  is  submerged. 
The  larvffi  feed  upon  the  roots  or  in  the  stems  of  aquatic 
plants ;  and  the  adults  are  found  on  the  leaves  of  the  same 
Fig- 647-    plants.     We  have  many  species,  but  they  resemble   one 
another  so  closely  that  it  is  difficult  to  separate  them. 
The  three-lined  lema,  Lema  trilinedta. — This  insect  is  common, 
feeding  on  the  leaves  of  potato.    The  beetle  is  6  mm.  long,  yellow,  with 
three  black  stripes  on  the  wing-covers.    The  eggs  are  usually  laid  in 
rows  along  the  midrib  on  the  lower  side  of  the  leaves.     The  larvae 
feed  on  the  leaves,  and  can  be  easily  recognized  by  a  habit  they  have 
of  covering  their  backs  with  their  own  excrement.    They  transform 
in  the  ground  in  earthen  cells.     There  are  two  broods  each  year; 
the  second  hibernates  in  the  ground  as  pupae. 

The  asparagus-beetle,  Crioceris  aspdragi. — This  is  a  small  red, 
yellow,  and  black  beetle,  that  gnaws  holes  into  the  heads  of  young 


COLEOPTERA 


531 


asparagus,  and  lays  oval,  black  eggs  upon  them.    The  larvas,  which 

are  small,  brown,  slug-like  grubs,  also  feed  upon  the  young  heads  in 

the  spring,  and  later  in  the  season  a  second 

brood  feed  upon  the  full-grown  plant.     Figure 

648  represents  a  head  of  asparagus  bearing  the 

eggs  of  this  beetle,  also  a  beetle  and  a  larva 

enlarged.     The  beetle  measures  about  6  mm. 

in  length.     When  this  pest  occurs,  care  should 

be  taken  to  destroy  all  wild  asparagus.    This 

will  force  the  beetles  to  lay  their  eggs  upon  the 

shoots  that  are  cut  for  market.     The  larvas 

hatching  from  such  eggs  will  not  have  a  chance 

to  mature. 

The  grape  root-worm,  Fldia  longipes. — This 
insect  is  the  most  destructive  enemy  of  the 
grape  occurring  east  of  the  Rocky  Mountains. 
The  adult  is  a  small,  grayish  brown  beetle, 
measuring  about  6  mm.  in  length.  It  feeds  on 
the  leaves  in  July,  eating  out  characteristic 
chain-like  holes.  The  eggs  are  laid  beneath  the 
loose  bark  of  the  vines.  On  hatching,  the  larvee 
drop  to  the  ground  and  burrow  down  to  the 

roots,  which  they  destroy,  causing  the  death  of  the  vine.  Most  of 
the  larvce  do  not  transform  till  the  following  spring.  The  best  means 
of  fighting  this  pest  is  to  poison  the  beetles  while  they  are  feeding  on 
the  leaves,  and  before  they  lay  their  eggs,  by  the  use  of  a  spray  made 
by  dissolving  six  pounds  of  arsenate  of  lead  in  100  gallons  of  water. 
The  Colorado  potato-beetle,  Leptinotarsa  decemlinedta. — -A  good 
many  insect  tramps  have  come  to  us  from  Europe  and  from  Australia, 
and  appropriated  whatever  pleased  them  of  our  grow- 
ing crops  or  stored  grain.  But  two  of  our  worst  insect 
pests  have  swarmed  out  on  us  in  hordes  from  their 
strongholds  in  the  region  of  the  Rocky  Mountains. 
These  are  the  Rocky  Mountain  locust  and  the  Colorado 
potato-beetle  (Fig.  649).  The  latter  insect  dwelt  near 
the  base  of  the  Rocky  Mountains,  feeding  upon  the 
sand-burr  {Solanuni  rostratum),  until  about  the  year 
1859.  At  that  time  it  began  to  be  a  pest  in  the  potato-fields  of  the 
settlers  in  that  region.  Having  acquired  the  habit  of  feeding  upon 
the  cultivated  potato,  it  began  its  eastward  march  across  the  conti- 
nent, spreading  from  potato  patch  to  potato  patch.  At  first  the 
migration  took  place  at  about  the  rate  of  fifty  miles  a  year,  but  later 
it  was  more  rapid;  and  in  1874  the  insect  reached  the  Atlantic  Coast. 
The  adult  beetles  hibernate  in  the  groimd;  they  emerge  early  in 
April  or  May,  and  lay  their  eggs  on  the  young  potato  plants  as  soon 
as  they  appear;  both  larvae  and  adult  beetles  feed  on  the  foliage  of 
the  potato.  The  larvae  enter  the  ground  to  transform.  This  pest  is 
usually  controlled  by  the  use  of  Paris  green. 

Labidomera  clivicollis. — This  species  is  closely  allied  to  the  Colorado 
potato-beetle  and  resembles  it  in  size  and  form.    It  is  of  a  deep  blue 


Fig.  649. 


532  AN  INTRODUCTION  TO  ENTOMOLOGY 


M 


color,  except  the  wing-covers,  which  are  orange,  with  three  dark -blue 
spots  on  each  (Fig.  650).  There  is  considerable  variation 
in  the  size  and  shape  of  these  spots;  frequently  the  two 
near  the  base  of  the  wing-covers  are  joined  so  as  to  make 
a  continuous  band  extending  across  both  wing-covers. 
The  larva  feeds  on  milkweed  {Asclepias) . 

Fig.  650.  The  diabroticas. — Several  very  important  pests  belong 

to  the  genus  Diabrotica.  In  the  East  they  are  known  as 
cucumber-beetles;  but  on  the  Pacific  Coast,  where  they  are  more 
feared  on  account  of  their  injuries  to  fruit  and  fruit-trees,  they  are 
commonly  called  the  diabroticas.  They  are  chiefly  greenish  yellow 
beetles,  marked  with  black  stripes  or  spots.  The  striped  diabrotica, 
D.  vttdta,  has  two  black  stripes  on  each  wing-cover.  The  adult  feeds 
on  the  leaves  of  cucumber,  squash,  and  melon;  and  the  lar\'a,  which 
is  a  slender,  worm -like  creature,  bores  in  the  stems  and  roots  of  the 
same  plants.  The  twelve-spotted  diabrotica,  D.  duodecimpttnctdta, 
and  Diabrotica  soror,  agree  in  having  six  black  spots  on  each  wing- 
cover.  The  former  is  verv'  common  in  the  East ;  the  latter  occurs  on 
the  Pacific  Coast,  and  is  the  most  destructive  of  all  of  the  diabroticas. 
Diabrotica  longicornis  is  a  green  species,  which  feeds  on  the  pollen 
and  silk  of  corn  and  on  the  pollen  of  other  plants.  Its  larva  is  known 
as  the  com  root -worm ;  it  is  very  destructive  to  com  in  the  Mississippi 
Valley.  Its  injuries  are  greatest  where  corn  is  grown  on  the  same 
land  year  after  year;  hence  a  rotation  of  crops  should  be  practised 
where  this  pest  is  troublesome.  The  other  species  of  Diabrotica 
mentioned  above  are  difficult  to  combat,  as  the  leaves  of  cucumber, 
melon,  and  squash  are  very  apt  to  be  injured  by  the  use  of  arsenical 
poisons.  The  most  practicable  way  of  protecting  these  vines  is  to 
cover  them  while  young  with  frames  covered  with  netting.  Where 
they  infest  fruit-trees  they  can  be  fought  with  Paris  green;  but  this 
poison  must  be  used  with  great  care  on  such  trees  as  pnme  and 
apricot.  Squashes  should  not  be  grown  in  orchards,  as  is  sometimes 
done  in  California. 

'     The  flea-beetles. — There  is  a  group  of  leaf-beetles,  of  which  we 
have  many  species,  in  which  the  hind  legs  are  fitted  for  leaping,  the 
thighs  being  very  large.    These  are  commonly  called  the 
fiea-beetles. 

The  striped  flea-beetle,  Phyllotreta  vittdta,  is  exceed- 
ingly common  on  cabbage,  turnip,  radish,  mustard,  and 
allied  plants.    It  is  a  small,  black,  shining  beetle,  with  a 
broad,  wavy,  pale,  dull  yellow  stripe  upon  each  wing- 
cover  (Fig.  651);  it  measures  about  2.5  mm.  in  length. 
These  beetles  eat  numerous  little  pits  in  the  thicker       ^^^-  ^^^' 
leaves  that  they  infest,  and  minute  perforations  in  the 
thinner-leaved  plants.     The  larva  is  a  slender,  white  worm,  about  8 
mm.  in  length ;  it  feeds  on  the  roots  of  the  plants  infested  by  the  adult. 
The  adult  beetles  can  be  destroved  with  kerosene  emulsion. 


COLEOPTERA 


533 


The  cucumber  flea-beetle,  Epitrix  cucwneris,  is  a  common  pest 
of   melon    and    cucumber    vines;    it    also    attacks    the    leaves    of 

potatoes, 
raspberry, 
t  u  r  n  i  ]j  , 
cabbage, 
and  other 
I?  1  a  n  t  s  . 
This  is  a 
minute 
black  spe- 
cies, meas- 

in    length.     The    body    is     finely 
punctured     and    clothed     with     a 
whitish  pubescence ;  there  is  a  deep 
transverse    furrow  across  the  hind 
part  of  the  prothorax;   the   antennas   are 
dull  yellow,  and  the  legs  are  of  the  same 
hue,  except  the  posterior  femora,  which  are 
brown.  The  adult  beetles  feed  on  the  leaves 
of  plants  in  the  same  manner  as  the  preced- 
ing species;  and  the  larvse  on  the  roots  of 
the  infested  plants. 

The  grape  flea-beetle,  Hdltica  chalybea. 
■ — This  is  a  larger  species  than  the  two  pre- 
ceding, measuring  from  4  mm.  to  5  mm.  in  length, 
and  is  of  a  dark,  steel-blue  color.  It  is  a  great  pest 
in  vineyards,  eating  into  the  buds  of  grape  in  early 
spring,  and  later  gnawing  holes  in  the  leaves  (Fig. 
652).  In  May  and  June  the  brown,  sluggish  larvae 
may  also  be  found  feeding  upon  the  surface  of  the 
leaves.  The  full-grown  larva  is  chestnut  brown 
marked  with  black  spots  (Fig.  653).  It  drops  to  the 
ground  and  makes  a  cell  in  the  earth  in  which  it 
transforms.  The  most  important  injury  caused  by 
this  pest  is  the  destruction  of  buds  in  early  spring, 
which  causes  a  great  loss  of  foliage  and  fruit.  This 
pest  is  most  easily  controlled  by  spraying  the  vines  with  an  arsenical 
poison  between  the  middle  of  June  and  the  middle  of  July,  while  the 
larvae  are  feeding  on  the  leaves. 

The  wedge-shaped  leaf -beetles . — These  insects  are  characterized  by 
the  peculiar  form  of  the  body,  which  is  narrow  in  front  and  broad 
behind.  In  most  of  the  species  the  body  is  much  roughened  by  deep 
pits,  and  usually  the  pits  on  the  wing-covers  are  in  regular  rows. 
These  insects  and  the  tortoise-beetles  differ  from  other  leaf -beetles 
in  having  the  fore  part  of  the  head  prominent,  so  that  the  mouth 
is  confined  to  the  under  surface.  Some  of  the  larvae  feed  externally 
upon  the  leaves  and  bear  a  parasol  composed  of  their  excrement; 


Fig.  652. 


534  AN  INTRODUCTION  TO  ENTOMOLOGY 

other  species  are  leaf -miners.    Baliosus  rubra  is  a  good  representative 

of  this  group3(Fig.  654).     It  varies  in  length  from  3  mm.  to  5  mm. 

It  is  of  a  reddish  color,  with  the  elevated  portions  of 

•\^\  I  ^  the  elytra  more  or  less  spotted  with  black.    The  larva 

IV  J  mines  in  the  leaves  of  apple,  forming  a  blotch-mine; 

^mC.  the  transformations  are  undergone  within  the  mine. 

JfwBSa\,    *^     We  have  also  found  this  species  mining  the  leaves  of 
jflf&y    JjSk  basswood  in  great  numbers. 

IJPiP  The  tortoise-beetles. — Among  the  more  beautiful 

Fig.  654.  Coleoptera  are  certain  bright  golden,  green,  or  irides- 

cent beetles  found  on  the  leaves  of  sweet  potato, 
moming-glor_y,  nettle,  and  other  plants.  In  these  beetles  the  body  is 
flattened  below  and  convex  above ;  the  head  is  nearly  or  quite  con- 
cealed beneath  the  prothorax;  and  the  margins  of  the  prothorax  and 
elytra  are  broadly  expanded,  forming  an  approximate- 
ly circular  or  oval  outline,  and  suggesting  a  resem- 
blance to  the  shell  of  a  tortoise  (Fig.  655).  Not  all 
of  the  species  are  iridescent ;  and  in  the  case  of  those 
that  are,  the  brightness  of  the  colors  is  said  to  de- 
pend on  the  emotions  of  the  insect.  What  a  beautiful 
way  to  express  one's  feelings — to  be  able  to  glow  like  pjg  5^^ 

melted  gold  when  one  is  happy !    Unfortimately  for 
the  beauty  of  our  collections,  these  bright  colors  disappear  after  the 
death  of  the  insect. 

The  larvae  of  the  tortoise-beetles  are  flattened,  and  have  the  margin 
of  the  body  fringed  with  spines.  At  the  caudal  end  of  the  body  there  is  a 
forked  appendage  which  serves  a  vers^  strange  purpose.  This  fork 
is  bent  forward  over  the  back,  and  to  it  are  attached  the  cast-off 
skins  of  the  larva  and  its  excrement;  these  constitute  a  parasol. 
When  about  to  change  to  the  pupa  state  these  larvae  fasten  the  caudal 
end  of  the  body  to  the  under  side  of  a  leaf;  the  skin  then  splits  open, 
and  is  forced  back  to  this  end  of  the  body,  where  it  remains. 

The  one-dotted  or  five-dotted  tortoise,  Physonota  unipunctata. — 
The  largest  of  our  bright-colored  tortoise-beetles  is  common  in  mid- 
summer, feeding  on  the  leaves  of  wild  sunflower.  It  measures  from 
9  to  12  mm.  in  length,  and  is  yellow,  with  the  margins  whitish. 
On  the  prothorax  there  are  flve  black  dots — two  close  together  in 
front,  and  three  more  widely  separated  behind.  Sometimes  all  but 
one  of  these  dots  are  wanting.  It  was  this  form  that  was  first  de- 
scribed, hence  the  name  unipunctata.  We  have  found  the  larv^ae  abun- 
dant in  July  on  the  same  plant  with  the  adults. 

The  milkweed-tortoise,  Chelymorpha  cassldea,  is  a  large,  brick 
red  species,  which  measures  from  9  mm.  to  12  mm.  in  length,  and  has 
the  prothorax  and  wing-covers  marked  with  many  black  spots.  This 
species  feeds  on  milkweed  (Asdepias)  and  various  other  plants. 


* 


COLEOPTERA  535 

Family  MYLABRID^ 
The  Pea-Weevil  Family 

These  are  small  beetles,  the  larva;  of  which  live  in  the  seeds  of 
legttminous  plants.  The  head  of  the  adult  is  prolonged  into  a  broad 
beak;  and  the  wing-covers  are  rather  short,  so  that  the  tip  of  the 
abdomen  is  always  exposed  (Fig.  656).  This  is  a  compara- 
tively small  family;  ninety-three  species  are  listed  in  our 
fauna,  of  which  eightv-one  belong  to  the  genus  Mylabris. 

The  pea-weevil,  Mylabris  pisorum. — "Buggy  peas"  are  /M^^  T 
well  known  in  most  sections  of  our  country;  but  just  how  /^Hl\l 
the  "bugs"  find  their  way  into  the  peas  is  not  so  generally 
understood.  The  eggs  of  the  pea-weevil  are  laid  upon  the 
pod  while  the  peas  are  quite  small;  when  the  larv^  hatch  p^„  g^g^ 
they  bore  through  the  pod  into  the  young  peas.  Here  they 
feed  upon  the  substance  of  the  seed,  which  ripens,  however, 
and  in  some  cases  will  germinate  when  planted.  The  larva  before 
transforming  eats  a  circular  hole  on  one  side  of  the  seed,  leaving  only 
a  thin  scale,  which  is  easily  pushed  away  by  the  mature  beetle.  The 
adult  is  about  5  mm.  in  length;  it  is  dark  brown,  with  a  few  white 
spots  on  the  wing-covers,  and  one  on  the  prothorax  near  the  middle. 
Sometimes  the  beetles  leave  the  peas  during  the  autumn  or  winter; 
but  as  a  rule  they  remain  in  the  seed  till  spring,  and  are  often  planted 
with  it.  Seed  peas  should  be  placed  in  water,  and  the  infested  ones, 
which  will  float,  should  be  picked  out  and  destroyed.  This  species 
is  not  known  to  oviposit  on  dry  peas. 

This  and  other  grain-infesting  insects  can  be  destroyed  by  placing 
the  grain  in  a  closed  receptacle  with  a  small  quantity  of  bisulphide 
of  carbon. 

The  bean-weevil,  Mylabris  obtectiis. — This  species  resembles  the 
preceding  quite  closely;  but  it  is  a  little  smaller  (Fig.  656),  and  lacks 
the  white  markings  characteristic  of  M.  pisorum.  It  infests  beans,  and 
often  several  individuals  inhabit  a  single  bean.  The  eggs  are  laid  within 
the  pod,  being  pushed  through  a  slit  which  the  female  gnaws  through 
the  pod.  This  species  will  oviposit  on  dry  beans,  peas,  and  other 
grain,  and  will  continue  to  breed  for  many  generations  in  stored  beans 
and  peas. 

SERIES  VII.— THE  RHYNCHOPHORA* 

The  six  families  included  in  this  series  constitute  a  well-marked 
division  of  the  order,  which  has  long  been  known  as  the  Rhynchophora 
or  snout-beetles.  These  names  were  suggested  by  the  fact  that  in 
many  of  these  insects  the  head  is  prolonged  so  as  to  form  a  snout  or 
beak;  but  it  should  be  remembered  that,  while  these  names  are  very 
appropriate  for  a  large  part  of  this  series,  in  some  members  of  it  the 
head  is  not  thus  prolonged.    This  is  especially  true  of  the  last  twa 

*Rhynch6phora:  rhynchos  (New  Latin),  snout;  phoros  {<p6pos),  bearing. 


536 


AN  INTRODUCTION  TO  ENTOMOLOGY 


families,  the  bark-beetles  and  timber-beetles,  in  which  the  beak  is 

either  wanting  or  extremely  short  and  broad. 

The  most  distinctive  features  characterizing  this  series  of  families 

are  the  following:  the  suppression  of  the  gula,  the  gular  sutures  being 
confluent  (Fig.  657,  gs);  the  absence  of  sutures 
between  the  prostemum  and  the  epistema  and 
epimera;  the  meeting  of  the  epimera  of  the  pro- 
thorax  on  the  middle  line  behind  the  prosternum 
(Fig.  657,  em);  and  the  palpi  being  usually  short 
and  rigid. 

A  volume  entitled  "Rhynchophora  or  Weevils 
of  North  Eastern  America"  was  published  by 
W.  S.  BlatchleyandC.  W.  Lengin  1916.  This  work 
includes  descriptions  of  the  then  known  species 
found  in  this  region,  with  analytical  keys,  and 
many  figures. 

Family  BRENTID^ 

The  Primitive  Weevils 
Fig-  657. 

This  family  is  confined  chiefly  to  tropical  re- 
gions; only  six  species  are  found  in  the  United  States,  and  but  one  of 
these  in  the  North. 

The  northern  brentid,  Eilpsalis  minuta. — In  the  female  the  head 
is  prolonged  into  a  slender  snout ;  but  in  the  male  the  snout  is  broad 
and  flat,  and  is  armed  with  a  pair  of  powerful  jaws 
(Fig.  658).  These  are  weapons  of  offence,  for  the  males 
fight  desperately  for  their  mates;  and  too,  the  males 
are  generally  larger  than  the  females.  In  these  respects 
these  insects  resemble  the  stag-beetles,  the  males  of 
which  also  fight  for  their  mates. 

The  northern  brentid  is  found  beneath  the  bark 
of  recently  felled  or  dying  oak,  poplar,  and  beech  trees 
in  the  solid  wood  of  which  the  larvae  bore;  and  is 
widely  distributed  over  the  United  States  and  Canada. 


Fig.  658. 


Family  PLATYSTOMID^^ 


The  Fungus  Weevils 

This  family  includes  a  small  number  of  snout-beetles  in  which  the 
beak  is  short  and  broad,  and  the  lab  rum  is  present;  the  antennae 
are  not  elbowed,  and  the  terminal  segments  rarely  form  a  compact 
club;  the  palpi  are  flexible;  and  the  prothorax  bears  a  transverse 
elevated  ridge  at  or  near  its  base. 

The  larvae  of  many  species  infest  woody  fungi,  others  breed  in  the 
smut  of  corn  and  wheat,  and  still  others  bore  in  dead  wood.     The 

*This  family  is  the  Anthribidas  of  many  authors. 


COLEOPTERA  537 

larvae  of  one  cosmopolitan  species,  known  as  the  coffee-bean  weevil, 
ArcBocerus  Jasciculdtus ,  attack  seeds  of  various  plants. 

Sixty-two  species  of  this  family  are  known  to  occur  in  America 
north  of  Mexico. 

Family  BELID^E 
The  New  York  Weevil 

The  family  Belid^e  is  represented  in  our  fauna  by  a  single  species, 
the  New  York  weevil,  Ithycerus  novehoracensis.  This  is  a  large  species, 
measuring  from  1 2  mm.  to  1 8  mm.  in  length .  It  is  black,  rather  sparse- 
h'  clothed  with  a  mixture  of  ash-gray  and  pale  brown  prostrate  hairs 
which  give  it  a  black-spotted  appearance.  The  beak  is  short  and  broad. 
The  mandibles  are  prominent,  not  very  stout,  and  emarginate  at  the 
tip,  with  an  inferior  cusp.  The  antennee  are  not  elbowed;  the  first 
segment  is  longer  than  the  second;  and  the  terminal  segments  form 
a  small,  oval  club. 

This  species  breeds  in  the  twigs  and  tender  branches  of  oak,  hick- 
ory, and  possibly  other  forest  trees.  The  adult  beetles  appear  in  early 
spring,  and  sometimes  do  much  damage  to  fruit-trees  by  eating  into 
buds,  and  gnawing  the  tender  bark  on  new  growth.  They  can  be 
caught  by  jarring  them  on  to  sheets  or  by  the  use  of  a  plum-curculio 
catcher. 

Family  CURCULIONID/E 

The  Curculios  or  Typical  Snout-Beetles 

The  CurculionidcB  is  a  very  large  family;  it  is  represented  in 
America  north  of  Mexico  by  more  than  eighteen  hundred  species; 
to  it  belong  four-fifths  of  all  our  Rhynchophora.  This  family  includes 
the  typical  snout-beetles,  the  head  being  prolonged  into  a  well-defined 
beak,  which  is  usually  long  and  curved  downward. 

The  family  Curculionidae  is  divided  into  thirteen  subfamilies; 
but  several  of  these  are  very  small.  The  seven  subfamilies  mentioned 
below  will  serve  to  illustrate  the  more  important  variations  in 
structure  and  in  habits,  and  they  include  the  more  important  species 
from  an  economic  standpoint. 

The  subfamily  Rhinomacerin^.,  or  pine-flower  snout-beetles,  in- 
cludes a  small  number  of  snout-beetles  in  which  the  elytra  have  no  fold 
on  the  lower  surface  near  the  outer  edge,  and  in  which  the  labnmi  is 
distinct.  The  head  is  prominent,  not  deflexed;  the  snout  is  as  long 
as  the  prothorax,  rather  flat,  narrowest  about  the  middle,  wider  at 
base  and  tip;  the  elytra  are  rounded  at  the  tip,  and  entirely  cover 
the  abdomen.  These  beetles  infest  the  staminate  flowers  of  coniferous 
trees,  in  which  the  eggs  are  laid.    Six  species  are  found  in  our  fauna. 

The  subfamily  Rhynchitin^,  or  toothed-nose  snout-beetles,  in- 
cludes snout-beetles  in  which  the  elytral  fold  is  feeble,  the  labnmi 
is  wanting,  and  the  mandibles  are  toothed  on  both  the  outer  and 
the  inner  side.  The  mandibles  can  be  spread  widely,  and  when  closed 
the  outer  tooth  at  the  end  of  each  projects  forward  so  that  two  small, 
acute  teeth  seem  to  project  from  the  mouth. 


I 


538  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  most  common  member  of  the  family  is  Rhynchltes  hlcolor 
(Fig.  659).     This  is  red  above  except  the  snout,  and  black  below; 

the  body,  not  including  the  snout,  is  about  6  mm.  long, 
^^M^  the  snout  is  half  that  length.  The  adults  are  often  abun- 
.^^7^      *^^i^t  on  wild  roses,  and  less  frequently  on  cultivated  roses. 

The  larvae  infest  the  hips  of  roses. 
Fig.   659. 

The  subfamily  Attelabin^.,  or  leaf-rolling  weevils,  is 
composed  of  beetles  which  have  neither  an  elytral  fold  nor  a  labrum, 
and  in  which  the  mandibles  are  flat,  pincer-shaped,  and  toothed  on  the 
inner  side.  The  el>i:ra  do  not  entirely  cover  the  abdomen,  and  each  is 
separately  rounded  at  the  tip.  Only  five  species  are  known  from  this 
country;  all  of  these  belong  to  \he  germs  Attelabus .  The  females  pro- 
vide for  their  young  in  a  very  remarkable  way.  They  make 
compact  thimble-shaped  rolls  from  the  leaves  of  trees 
(Fig.  660),  and  lay  a  single  egg  in  each.  The  larvae  feed 
on  the  inner  parts  of  these  rolls,  and  when  full-grown  enter 
the  ground  to  transform.  Sometimes  these  rolls  are  found 
hanging  by  a  narrow  piece  to  the  leaf  from  which  they 
were  made,  and  sometimes  they  are  found  lying  on  the  Fig.  660. 
ground  separated  from  the  leaf. 

The  subfamily  Cyladin^  is  represented  in  Florida,  Louisiana,  and 
Texas  by  a  single  species,  the  sweet-potato  root-borer,  Cylas  formicd- 
rius.  This  beetle  is  somewhat  ant-like  in  form;  this  fact  suggested 
the  specific  name.  It  is  about  6  mm.  long;  the  color  of  the  eltyra, 
head,  and  snout  is  bluish  black,  that  of  the  prothorax  reddish  brown. 
Both  larvae  and  adults  bore  into  the  stems  and  tubers  of  the  sweet 
potato,  and  sometimes  do  very  serious  damage.  This  species  was 
formerly  included  in  the  Brentidee. 

The  subfamily  Otiorhynchin^,  or  scarred  snout-beetles,  is  one 
of  the  larger  of  the  subfamilies  of  the  Curculionidae ;    it  is  repre- 
sented in  our  fauna  by  more  than  two  hundred  species.     The  most 
distinctive  characteristic  of  these  insects  is  the  presence  in  the  pupa 
state,  and  sometimes  also  in  recently  matured  adults,  of  an  ap- 
pendage on  each  mandible,  and  in  the  adult  state  of  a  scar  indicating 
the  place  from  which  the  appendage  has  fallen.    This  scar  is  on  the 
anterior  face  of  the  mandible,  and  frequently  at  the  tip  of  a  slight 
process.    Many  species  of  this  family  are  beautifully 
ornamented  with  scales  which  resemble  in  a  striking 
manner  the  scales  on  the  wings  of  butterflies.    Among 
\  f         the  more  important  species  are  the  following. 

^TA^  The   imbricated    snout -beetle,    Epiccerus   imhri- 

^fiT^  cdtMS,  is  usually  a  dull,  silvery  white  beetle  with 

/^^^\  brown  markings;  but  the  species  is  quite  variable 

. /^HH^\  in  color.     It  is  represented,  somewhat  enlarged,  in 

^^^pnV  Figure  661.    It  is  omnivorous,  gnawing  holes  in  va- 

/^^A  rious  garden  vegetables,  strawberry  plants,  and  other 

.  fruits.    The  greater  part  of  the  insect  is  clothed  with 

^^'      ^'  imbricated  scales,  which  suggested  the  specific  name. 


COLEOPTERA  539 

Fuller's  rose-beetle,  Pantomorus  fulleri.- — This  is  an  oval,  black 
snout-beetle,  lightly  covered  with  dark  brown  scales,  and  about  6mm. 
in  length.  It  attacks  roses  and  many  other  greenhouse  plants.  The 
adults  feed  on  the  foliage,  flowers,  and  buds,  the  larvae  on  the  roots, 
of  its  food  plants. 

The  strawberry  crown-girdler,  Brachyrhlrms  ovdtus. — This  is  a 
dark  brown,  almost  black,  snout-beetle,  about  5  mm.  in  length,  which 
often  invades  dwellings  in  search  of  shelter,  in  the  Northern  States 
and  Canada.  The  larva?  feed  on  the  roots  of  the  strawberry,  cutting 
them  off  near  the  crown.  The  adults  feed  on  the  foliage.  In  the 
adult,  the  hind  wings  are  wanting  and  the  elytra  are  grown  together. 

The  black  vine-weevil,  Brachyrhinus  sulcdtus.- — This  beetle  is 
larger  than  the  preceding  species,  measuring  9  mm.  in  length;  it  is 
black,  with  small  patches  of  yellowish  hairs  on  the  elytra.  The 
larvae  destroy  the  roots  of  strawberries;  and  both  larvffi  and  adults 
infest  various  greenhouse  plants. 

The  subfamily  Curculionin^,  is  represented  in  our  fauna  by 
more  than  one  thousand  species,  among  which  are  some  very  destruc- 
tive pests.  In  this  family  there  is  on  the  lower  side  of  each  wing-cover 
a  strong  fold  near  the  outer  margin,  which  limits  a  deep  groove  in 
which  the  upper  edge  of  the  abdomen  fits;  the  mandibles  have  no  scar; 
the  antenna?  are  usually  elbowed,  and  have  a  ringed  or  solid  club; 
the  tarsi  are  usually  dilated,  with  the  third  segment  bilobed  and 
spongy  beneath ;  in  a  few  cases  the  tarsi  are  narrow,  but  not  spinose 
beneath. 

The  larvcB  are  soft,  white,  maggot-like  grubs  destitute  of  feet. 
They  feed  chiefly  on  fruits,  seeds,  and  nuts,  but  all  parts  of  plants  are 
subject  to  their  attacks. 

In  laying  her  eggs,  the  female  first  bores  a  hole  with  her  snout, 
then  drops  an  egg  into  this  hole,  and  finally  pushes  the  egg  to  the 
bottom  of  the  hole  with  her  snout.     In  many  species  the  snout  is 
highly  developed  for  this  purpose;  sometimes  it  is 
twice  as  long  as  the  remainder  of  the  body.    This  is 
well  shown  in  the  acorn-weevils  and  the  nut-weevils, 
which  belong  to  the  genus  Balaninus.     Figure  662 
represents  Balaninus  rectus  resting  on  an  acorn;  the 
specimen  figured,  when  found,  had  her  snout  inserted 
in  the  acorn  up  to  the  antennae.    Of  the  closely  allied 
species  Balaninus  nasicus  breeds  in  hickory-nuts, 
and  Balaninus  prohoscldeus  in  chestnuts. 

The  following  are  some  of  the  more  important  Fig-  662. 

pests  belonging  to  this  subfamily: 

The  plum-curculio,  Conotrachelus  nenuphar. — ^This  is  the  insect 
that  stings  plums,  often  destroying  a  large  portion  of  the  fruit;  the 
larva  is  also  the  well-known  "worm"  of  "wormy"  cherries.  This 
species  is  the  most  destructive  insect  that  infests  plums,  cherries,  and 
other  stone  fruits;  it  also  breeds  in  apple.  Its  presence  in  an  orchard 
can  be  determined  early  in  the  season  by  a  peculiar  mark  it  makes 
when  laying  its  eggs  in  the  young  fruit.    The  female  beetle  makes  an 


540  ^A^  INTRODUCTION  TO  ENTOMOLOGY 

incision,  with  her  snout,  through  the  skin  of  the  fruit.  In  this  incision 
she  lays  a  single  egg,  which  she  pushes  with  her  snout  to  the  bottom 
of  the  cavity  that  she  has  prepared.  She  then  makes  a  crescent-shaped 
incision  in  front  of  the  one  containing  the  egg.  This  last  cut  under- 
mines the  egg,  leaving  it  in  a  little  flap.  The  larvse  feed  within  the 
fruit.  In  the  case  of  the  plums  the  infested  fruit  falls  to  the  ground; 
but  not  so  with  cherries.  When  full-grown  the  larvae  go  into  the  ground 
to  transform.  This  species  infests  nectarines,  apricots,  and  peaches, 
as  well  as  plums  and  cherries.  This  insect  is  fought  in  two  ways: 
the  beetles  are  jarred  from  the  trees  upon  sheets  in  early  spring,  and 
destroyed  before  they  have  laid  their  eggs ;  they  are  also  poisoned  by 
spraying  the  trees  with  arsenate  of  lead,  either  alone  or  combined 
with  a  fungicide  before  the  fruit  is  large  enough  for  them  to  oviposit 
in  it.  The  adult  beetle  feeds  upon  the  foliage,  and  can  thus  be  poisoned. 

The  apple-curculio,  Anthonomus  quadriglbhus,  infests  the  fruit  of 
apple,  often  in  company  w4th  the  pliim-curculio.  The  specific  name 
was  suggested  by  the  fact  that  there  are  two  wart-like  projections 
near  the  hind  end  of  each  wing-cover. 

The  strawberry-weevil,  Anthonomus  signdtus,  infests 

strawberry,  blackberr}',  raspberry,  and  dewberry.     The 
female  beetle  (Fig.  663)  after  laying  an  egg  in  the  flower- 
p.     ,,        bud  causes  it  to  fall  by  cutting  the  pedicel;  the  larva  de- 
^^'     ^'     velops  within  the  fallen  bud. 

The  cotton-boll  weevil,  Anthonomus  grdndis,  is  one  of  the  most 
serious  insect  pests  known  in  the  United  States.  •  It  infests  only  cotton. 
The  egg  is  deposited  in  a  young  boll,  which  the  larva  destroys.  The 
adults  also  feed  upon  the  young  bolls  and  upon  the  leaves,  doing  as 
much  or  more  damage  than  that  done  by  the  larvae.  This  species  is 
a  native  of  Central  America.  It  spread  through  Mexico,  and  entered 
Texas  about  1890.  Since  that  time  it  has  spread  over  a  large  part 
of  the  cotton-belt.  Ver\^  extensive  investigations  of  this  pest  have 
been  made  by  the  Federal  Government  and  by  several  state  govern- 
ments ;  and  much  literature  regarding  it  is  available  to  those  interested. 

The  subfamily  Calendrin.^.  includes  the  bill-bugs  and  the  grain- 
weevils,  some  of  which  are  among  our  more  common  snout-beetles. 
The  larvae  of  the  larger  species  feed  upon  the  roots  and  bore  in  the 
stems  of  plants,  especially  grass  and  corn,  while  those  of 
the  smaller  species  infest  grains  and  seeds. 

Most  of  our  larger  species  belong  to  the  genus  Sphenoph- 
orus;  one  of  these  is    represented  in  Figure  664.    These 
are  of  medium  or  rather  large  size,  and  are  often  marked 
in  a  very  characteristic  manner  by  longitudinal  elevated 
bands  of  darker  color;  frequently,  when  collected,  they 
arecoveredwithacoat  of  clay.    Tliey  are  commonly  known 
as  the  bill-bugs.  One  species,  Sphenophorus  maidis,  is  an    ^^S-  664. 
important  pest  of  com  in  the  South ;  it  bores  in  the  tap- 
root and  lower  part  of  the  stalk.    Most  of  the  beetles  hibernate  in  the 
corn-stubble,  and  can  be  destroyed  by  pulling  out  and  burning  the 
stubble. 


I 


COLEOPTERA 


541 


Among  the  smaller  members  of  this  subfamily  are  two  exceedingly 
important  pests  of  stored  grains;  these  are  the  granar>'-weevil, 
Calandra  grandria,  and  the  rice-weevil,  Calandra  oryzcB.  The  rice- 
weevil  is  so  called  because  it  was  first  found  in  rice  in  India;  but  it 
infests  various  kinds  of  stored  grain;  and  in  the  South  it  is  fully  as 
important  a  granary-pest  as  is  the  granary -weevil. 

The  two  species  are  quite  similar  in  appearance;  but  the  granary- 
weevil  is  the  larger,  measuring  from  3  mm.  to  4  mm.  in  length; 
while  the  rice-weevil  measures  less  than  3  mm.  in  length,  and  differs 
from  the  granary-weevil  in  having  the  elytra  marked  with  four 
reddish  spots.  The  thorax  of  the  rice-weevil  is  closely  pitted  with  round 
punctures;  that  of  the  granary -weevil,  with  sparse  elongate  punc- 
tures. 

The  adult  female  of  both  of  these  species  gnaws  a  tiny  hole  in  a 
kernel  of  grain  and  then  deposits  an  egg  in  it.  The  larva  feeds  on 
the  grain,  becomes  full-grown,  and  transforms  within  the  kernel.  The 
adult  continues  the  injury  begun  by  the  larva,  eating  out  the  inside 
of  the  kernel. 

The  most  effective  method  of  destroying  grain-weevils  is  by  the 
use  of  carbon  bisulphide.  The  grain  is  placed  in  a  tight  bin  or  other 
receptacle,  and  the  carbon  bisulphide  is  poured  into  a  shallow  tin 
pan  placed  on  top  of  the  grain,  and  then  covered  with  blankets  to 
keep  in  the  fumes.  Two  or  three  pounds  of  carbon  bisulphide  should 
be  used  for  each  1000  cubic  feet  of  space.  Care  should  be  taken 
not  to  go  near  the  bin  with  a  lighted  lantern  or  fire  of  any  kind  until 
after  the  blankets  have  been  removed  and  the  gas  has  been  dissipated. 


Family  PLATYPODID^ 

This  is  a  small  family,  which  is  represented  in 
our  fauna  by  a  single  genus.  Platypus,  of  which 
only  five  species  have  been  found  in  America 
north  of  Mexico;  these  are  found  chiefly  in  the 
vSouth  and  the  Far  West. 

Formerly  this  group  was  classed  as  a  subfamily 
of  the  Scolytidse.  It  is  distinguished  from  the 
Scolytidae  by  the  fact  that  the  first  segment  of  the 
anterior  tarsi  is  longer  than  the  second,  third,  and 
fourth  together.  The  form  of  the  body  is  cylindri- 
cal (Fig.  665) ;  and  the  head  is  large,  wider  than  the 
prothorax. 

The  species  of  this  genus  attack  many  kinds 
of  conifers  and  deciduous  trees.  They  bore  deeply 
into  the  heart -wood,  making  "pin-holes"  that 
often  render  limiber  useless.  The  eggs  are  de- 
posited in  the  galleries;  and  the  larvae  feed  on  a 
fungus,  which  is  cultivated  by  the  beetles  and  is 
known  as  ambrosia.  In  this  respect  Platypus  resembles  several  genera 
of  the  Scolytidae,  which  also  bore  in  solid  wood  and  feed  on  ambrosia; 


Fi?.  665. — Platypus 
wilsoni,  female. 
(After  Swaine.) 


542 


AN  INTRODUCTION  TO  ENTOMOLOGY 


all  of  these  are  known  as  ambrosia-beetles.  The  galleries  of  ambrosia- 
beetles  are  usually  blackened  by  the  fungus.  See  further  account  of 
the  ambrosia-beetles  in  the  discussion  of  the  next  family. 

Family  SCOLYTID^ 


Fig.  666.— Phthoro- 
phlceus  liminaris. 


The  Engraver-Beetles  and  the  Ambrosia-Beetles 

The  members  of  the  family  Scolytidas  are  mostly  of  cylindrical 
form  (Fig.  666)  and  of  small  or  moderate  size;  some  species  measure 
only  I  mm.  in  length,  but 
others  are  much  larger,  at- 
taining a  length  of  6  mm. 
or  more.  They  are  usually 
brown,  sometimes  black.and 
with  many  the  hind  end  of 
the  body  is  very  blunt,  as 
if  cut  off.  The  antennas  are 
elbowed  or  bent  in  the  mid- 
dle, and  are  clubbed  at  the 
tip;  the  tibise  are  usually 
serrate;  and  the  first  seg- 
ment of  the  anterior  tarsi  is 
shorter  than  the  second, 
third,  and  fourth  together. 

A  few  members  of  this  family  infest  herba- 
ceous plants ;  our  most  important  one  of  these  is 
the  following. 

The  clover-root  borer,  Hyldstinus  ohscurus. 
— This  pest  was  introduced  from  Europe  and 
has  become  the  most  serious  enemy  of  clover, 
especially  red  clover  and  mammoth  clover,  in 
New  York  State  and  in  other  sections  of  the 
North.  It  bores  in  the  roots  of  plants  beginning 
their  second  year  of  growth  and  destroys  them 
(Fig.  667) .  Where  it  is  common  it  is  practically 
impossible  to  keep  fields  in  clover  longer  than 
the  second  simimer  after  seeding.  In  these 
regions  it  is  the  common  practice  to  seed  with 
i^   ''/^ll^li^H'  clover   and   timothy  mixed;  after  the   clover 

iV  B  Al^H  disappears  the  field  becomes  a  timothy  meadow. 

/^  'J  fl  W  No  practical  method  of  control  of  this  pest  has 

been  found. 
Fig.  667. — Work  of  do-         Most  scolytid  beetles  infest  woody  plants; 
ver-root   borer.    (After  among  them  are  some  of  the  most  destructive 
Webster.)  enemies  of  forest -trees,  and  a  few  attack  fruit- 

trees.    As  a  rule  they  are  more  liable  to  attack  sickly  trees,  but  their 
injuries  are  not  confined  to  these. 


COLEOPTERA  543 

The  scolytid  beetles  exhibit  two  radically  different  types  of 
habits;  and  from  this  point  of  view  they  can  be  grouped  into  two 
groups:  first,  the  engraver-beetles  or  bark-beetles;  and  second,  the 
ambrosia-beetles  or  timber-beetles.  These  two  groups,  however,  do 
not  represent  a  natural  division  of  the  family  based  on  structural 
characters.  The  peculiar  habits  of  the  ambrosia-beetles  are  believed 
to  have  arisen  independently  in  different  parts  of  the  series  of  scolytid 
beetles,  and  in  the  family  Platypodidae  as  well. 

The  Engraver-Beetles  or  Bark-Beetles 

If  the  bark  be  pulled  from  dead  branches  or  trunks  of  trees,  the 
inner  layer  and  the  sap-wood  will  be  found,  in  many  cases,  to  be 
ornamented  with  burrows  of  more  or  less  regular  form.  The  smoothly 
cut  figures  are  the  mines  of  engraver-beetles,  which  are  also  known  as 
bark -beetles.  Many  kinds  of  these  engravings  can  be  found,  each 
characteristic  of  a  particular  species  of  engraver  beetles.  A  common 
pattern  is  shown  in  Figure  668. 

Many  figures  and  detailed  descriptions  of  the  burrows  of  engraver- 
beetles  have  been  published  by  writers  on  forest-insects;  among  the 
more  important  papers  on  this  subject  published  in  America  are  those 
by  Hopkins  ('09)  and  Swaine  ('18),  in  which  can  be  found  references 
to  many  other  papers. 

The  different  species  of  engraver-beetles  vary  so  greatly  in  the 
details  of  their  habits  that  it  is  difficult  to  make  generalizations  re- 


Fig.  668. 

garding  them  in  the  space  available  here.  In  a  common  type,  the 
adult  beetle,  after  penetrating  the  bark,  makes  a  tunnel  in  the  inner 
layer  of  the  bark  or  in  the  sap-wood  or  in  both ;  this  is  known  as  the 
egg-tunnel,  and  may  be  either  simple  or  branched.  In  the  sides  of 
the  tunnel,  most  species  make  niches,  the  egg-niches,  in  which  the 
eggs  are  laid.  The  larva  when  hatched  feeds  on  the  bark  or  sap-wood 
or  both  and  thus  makes  a  lateral  tunnel.  These  lateral  tunnels  made 
by  the  larvas  often  extend  parallel  in  a  more  or  less  regular  manner, 
as  shown  in  Figure  668. 

While  most  of  the  engraver-beetles  infest  forest-trees,  the  two 
following  species  are  well-known  pests  of  fruit-trees. 


544 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  fruit-tree  bark -beetle,  Scolytus  rugtddsus. — This  species  in- 
fests apple,  quince,  plum,  peach,  and  other  stone-fruits.  It  is  some- 
times called  the  shot-hole  borer  by  fruit-growers  on  account  of  the 
small  entrance  holes  of  its  burrows.  The  adult  beetle  measures  from 
2  mm.  to  2.5  mm.  in  length,  and  is  dark  brown  or  nearly  black.  It 
infests  chiefly  sickly  trees. 

The  peach-tree  bark-beetle,  Phthorophlceus  limindris. — This  spe- 
cies resembles  the  preceding  in  size  and  habits,  except  that  its  injuries 
are  confined  chiefly  to  peach  and  cherr^^  It  can  be  distinguished  from 
the  fruit-tree  bark -beetle  by  the  fact  that  the  club  of  the  antennae  is 
lamellate,  an  unusual  feature  in  this  family  (Fig.  666). 

The  Ambrosia-Beetles  or  Timber-Beetles 

Certain  members  of  the  family  Scolytidse  differ  in  habits  from  the 
engraver-beetles  or  bark-beetles  in  a  remarkable  manner;  these  are 
those  known  as  ambrosia-beetles  or  timber-beetles.    Thev  are  termed 


Fig.  669. — Gallery  of  Monarthrum  mail  in  maple.     (From  Hubbard.) 

ambrosia-beetles  because  they  cultivate  fungi,  commonly  called  am- 
brosia, upon  which  they  feed;  and  timber-beetles,  because  they 
burrow  in  the  solid  wood. 

The  galleries  of  the  ambrosia-beetles  can  be  distinguished  from 
those  of  other  wood-boring  insects  by  the  fact  that  in  all  of  their 
ramifications  they  are  of  uniform  size  and  free  from  wood-dust  and 
other  refuse,  and  their  walls  are  stained  black  or  brown  by  the  fungus 
that  is  grown  upon  them. 

The  galleries  of  different  species  differ  in  form ;  but  usually  there 
is  a  main  gallery,  which  extends  deeply  into  the  solid  wood  and  is 
often  branched ;  and  extending  from  the  sides  of  the  main  gallery 
there  are  short  chambers,  termed  cradles,  in  each  of  which  an  egg  is 
laid  and  a  larva  reared  (Fig.  669).  In  some  species,  the  female  de- 
posits her  eggs  loosely  in  the  galleries,  and  the  young  and  old  live 
together  in  the  same  quarters. 


COLEOPTERA  545 

The  galleries  are  excavated  by  the  adult  beetles.  In  some  species 
the  gallery  is  started  by  a  single  female,  in  others  the  males  assist  the 
females  in  this  work.  The  entrances  through  the  bark  to  the  galleries 
are  similar  to  those  made  by  the  bark-beetles  and  like  them  are  known 
as  "shot-holes."  Under  favorable  conditions  colonies  may  continue 
their  excavations  during  two  or  three  generations. 

The  fungi  upon  which  these  beetles  feed  are  carefully  cultivated 
by  them.  So  far  as  is  known,  each  species  of  ambrosia-beetle  culti- 
vates only  a  single  species  of  fungus,  and  only  the  most  closely  allied 
species  have  the  same  food-fungus.  The  fungus  is  started  by  the  moth- 
er-beetle upon  a  carefully  packed  bed  or  layer  of  chips.  It  is  probable 
that  some  conidia  are  brought  for  this  purpose  from  the  gallery  in 
which  the  female  w^as  developed.  The  excrement  of  the  larvae  is 
used  in  some  and  probably  in  all  the  species  to  form  new  beds  for  the 
propagation  of  the  fungus. 

In  those  species  in  which  the  larvae  are  reared  in  separate  cradles, 
"the  mother-beetle  is  constantly  in  attendance  upon  her  young  during 
the  period  of  their  development,  and  guards  them  with  jealous  care. 
The  mouth  of  each  cradle  is  closed  with  a  plug  of  the  food-fungus,  and 
as  fast  as  this  is  consumed  it  is  renewed  with  fresh  material.  The 
larvce  from  time  to  time  perforate  this  plug  and  clean  out  their  cells, 
pushing  out  the  pellets  of  excrement  through  the  opening.  This  debris 
is  promptly  removed  by  the  mother  and  the  opening  again  sealed  with 
ambrosia.  The  young  transform  to  perfect  beetles  before  leaving 
their  cradles  and  emerging  into  the  galleries." 

A  detailed  account  of  the  ambrosia-beetles  of  the  United  States 
was  published  by  Hubbard  ('97),  from  which  I  have  drawn  largely 
in  the  preparation  of  the  account  given  here. 

While  the  ambrosia-beetles  are  chiefly  injurious  to  forest-trees, 
there  are  certain  species  that  injure  wine  and  beer  casks;  and  one 
species,  the  pear-blight  beetle,  Anisandrus  pyri,  sometimes  infests 
the  tips  of  pear  and  apple  branches,  causing  an  injury  that  is  often 
mistaken  for  the  bacterial  disease  known  as  pear-blight. 

Nearly  four  hundred  species  of  scolytid  beetles,  representing 
many  genera,  have  been  described  from  America  north  of  Mexico. 


CHAPTER  XXIV 
ORDER  STREPSIPTERA* 

The  Stylopids  or  Twisted-winged  Insects 

The  members  of  this  order  are  small,  endoparasitic  insects,  which  prey 
on  other  insects.  Only  the  males  are  winged;  in  this  sex,  the  fore  wings 
are  reduced  to  club-shaped  appendages ;  the  hind  wings  are  large  com- 
pared with  the  size  of  the  tiny  body ,  fan-shaped,  furnished  with  radiating 
wing-veins,  and  folded  longitudinally  when  at  rest.  The  adult  female  is 
larviform  and  legless.  The  mouth-parts  are  vestigial  or  wanting;  the 
alimentation  is  probably  by  osmosis.  Both  sexes  undergo  a  hyper- 
metamorphosis. 

The  order  Strepsiptera  comprises  insects  that  were  formerly 
classed  as  a  family  of  the  Coleoptera,  the  Stylopidse;  for  this  reason, 
these  insects  have  been  known  as  the  stylopids.  Recently  since  the 
establishment  of  the  order  Strepsiptera,  the  name  the  twisted-winged 
insects,  derived  from  the  technical  name  of  the  order,  has  been  pro- 
posed for  them;  but  the  old  name  is  less  cumbersome,  and  will  prob- 
ably continue  to  be  used. 

The  stylopids  are  small  insects  which  live  parasitically  within  the 
bodies  of  other  insects,  chiefly  bees,  wasps,  digger  wasps,  and  certain 
Homoptera.  Their  small  size  and  the  fact  that  nearly  their  entire 
existence  is  passed  within  the  bodies  of  their  hosts  result  in  their 
being  rarely  seen  except  by  those  who  are  searching  for  them.  During 
the  first  stadium  the  young  larvse  of  both  sexes  are  free,  and  the  adult 
winged  male  leads  a  free  existence  for  a  brief  period;  but  only  the 
most  skilled  collectors  are  likely  to  observe  these  minute  creatures 
during  these  periods,  the  only  free  stages  of  their 
existence. 

The  stvlopids  are  most  easily  found  by  examin- 
ing adult  individuals  of  the  species  of  insects  that 
they  infest,  in  which  may  be  found  adult  females 
and  male  pupae  of  the  parasites.  The  presence  of  a 
stylopid  is  indicated  by  the  projecting  of  the  head 
end  of  the  body  from  between  two  of  the  abdominal 
segments  of  the  host  (Fig.  670).  Frequently  a  single 
host  will  contain  several  parasites.  A  female  Polistes 
with  eleven  male  stylopids  has  been  recorded.  If 
this  projecting  part  of  the  parasite  is  a  flat  disk-like 
plate,  it  is  the  head  end  of  a  female ;  but  if  it  is  the 
rounded  and  tuberculate  end  of  a  cdindrical  body.  Fig.  670.— Abdo- 
it  is  the  head  end  of  the  puparium  of  a  male.  Adult  men  of  stylo- 
male  stvlopids  can  be  bred  bv  keeping  alive  stvlo-       pized  insect:  s, 

J  ■  "      \  ,    •    •  1     -  i      o  -  5   stylopids. 

pized  msects  contammg  male  pupae. 

*Strepsiptera:  strepsis  {ffTpi^Ls),  a  turning;  pteron  {TTTtpdv),  a  wing. 

(546) 


STREPSIPTERA 


547 


Fig.  671. — Opthalmochliis  duryi.     (After  Pierce. 


Figure  671  will  serve  to  illustrate  the  appearance  of  an  adult  male 
stylopid.  The  more  striking  features  are  the  flabellate  antenna; 
the  large, 
stalked,  com- 
pound eyes ; 
the  shortness 
of  the  pro- 
thorax  and 
the  mesotho- 
rax,  and  the 
great  length 
of  the  meta- 
thorax;  the  re- 
duction of  the 
fore-wings  to 
club-shaped 
appendages ; 
and  the  large 
size  of  the 
hind  wings. 

The  an- 
tennae of  adult 
males  differ 

greatly  in  form  in  the  different  families  of  this  order.  The  number  of 
antennal  segments  varies  from  four  to  seven;  the  third  segment  is 

always  furnished 
with  a  lateral  pro- 
longation, a  fiabel- 
lum,  and  one  or 
more  of  the  follow- 
ing segments  may 
or  may  not  be  fla- 
bellate. 

The  compound 
eyes  of  adult  males 
are  large  and  more 
or  less  stalked.  The 
facets  are  separated 
by  densely  ciliate 
walls. 
The  mouth-parts  are  greatly  reduced;  those  of  two  adult  males 
are  represented  in  Figure  672.  The  mouth  opening  is  small.  The 
labrum  and  labium  are  wanting  as  distinct  parts.  In  Acroschlsmus 
bruesi  (Fig.  672,0)  the  mandibles  are  slender,  curved,  and  scimitar- 
like; beneath  the  mandibles  are  the  maxillae;  these  are  two-jointed; 
the  second  segment  is  believed  to  be  the  reduced  palpus.  In  Pento- 
zocera  austrdlensis  (Fig.  672,  b)  the  mandibles  are  greatly  reduced, 
but  the  maxilllary  palpi  are  quite  large. 

The  three  pairs  of  legs  are  similar  in  form.     The  tarsi  are  five- 
jointed  in  one  family  (Mengeidce),  and  furnished  with  two  claws; 


Fig.  672. — Mouth-parts  of  male  stylopids:  a,  Acros- 
chismus  bruesi.  (After  Pierce.)  b,  Pentozocera  aiistral- 
ensis.      (After   Perkins.) 


548 


AN  INTRODUCTION  TO  ENTOMOLOGY 


2d  A 


Fig-    673. — Wing  of  Paraxenos  eberi. 
(From    Pierce,    after     Saunders.) 


in  the  other  families  they  are  two-  to  four-jointed  and  without  claws. 
The  venation  of  the  hind  wings  is  degenerate.    There  is  a  variable 

nirmber  of  radiating  veins,  which  in  the  most  generalized  wings  are 

eight  in  number.  These  are  sup- 
posed, by  Pierce  ('09),  to  be  the 
eight  principal  veins  of  the  typi- 
cal wing,  the  costa,  subcosta,  ra- 
dius, media,  cubitus,  and  the  three 
anal  veins,  respectively  (Fig.  673). 
The  abdomen  is  composed  of 
ten  segments. 

The  adult  female  is  very  de- 
generate in  form.  That  part  of 
the  body  which  projects  from  the 
body  of  the  host  is  the  cephalo- 
thorax,  the  head  and  thorax  being 
consolidated  into  a  single  disk- 
like region.  The  abdomen,  which 
is  within  the  body  of  the  host,  is 
a  great  sac  filled  with  eggs.  The 
body  of  the  adult  female  is  in- 
closed in  the  skin  of  the  last  larval 

instar,  which  is  termed  the  puparium;  but  there  is  no  pupal  stage  in 

this  sex. 

The  postembryonic  development  of  the  stylopids  is  very  peculiar. 
In  the  adult  female  the  eggs  are  free  in  the  body  cavity,  where  they 
hatch.  The  young  larvce  are  campodeiform  and  active.  As  they 
bear  some  resemblance  to  the  triungulins  of  the  parasitic  blister-beetles, 
they  are  termed  triungulins  by  some  writers ;  but  as  they  do  not  possess 
three  tarsal  claws,  this  term  is  inappropriate  when  applied  to  them. 
For  this  reason  the  first  instar  of  a  stylopid  larva  is  termed  a  triun- 
gulinid. 

The  stylopids  are  very  prolific;  more  than  2000  triungulinids  pro- 
duced by  a  single  female  have  been  counted.  This  fecundity  is 
doubtless  correlated  with  the  uncertainty  of  any  individual  triun- 
gulinid  being  able  to  find  its  proper  host. 

The  triungulinids  escape  from  the  body  of  the  female  through 
unpaired  median  genital  apertures  on  the  second  to  fifth  abdominal 
segments.  These  apertures  open  into  the  space  between  the  venter 
of  the  female  and  the  puparium,  which  is  termed  the  brood  chamber. 
The  triungulinids  escape  from  this  space  through  a  slit  in  the  cephalo- 
thorax  of  the  puparium,  between  the  head  and  the  prothorax,  and  then 
crawl  over  the  body  of  the  host.  This  is  the  beginning  of  the  most 
critical  period  in  the  life  of  the  stylopids.  For  the  continued  existence 
of  any  individual  of  the  brood  it  must  find  a  larva  or  a  nymph  of  the 
particular  species  that  is  its  proper  host.  This  is  doubtless  accom- 
plished in  different  ways  in  the  different  species.  Those  that  infest 
Homoptera  and  other  insects  that  do  not  build  nests  must  wander 


STREPSIPTERA  549 

over  the  plants  on  which  these  insects  Hve  till  they  find  a  nymph  of 
their  host  species.  In  the  case  of  stylopids  that  infest  social  insects 
the  problem  is  obviously  not  so  difficult,  especially  if  the  triunj^linids 
leave  their  host  while  it  is  in  or  near  the  nest.  But  those  stylopids 
that  infest  solitary  nest-building  species  are  beset  with  more  serious 
difficulties.  It  is  believed  that  parasitized  female  bees  and  wasps 
are  so  weakened  that  they  do  not  build  nests;  hence  the  triungulinids 
issuing  from  them,  and  from  males  as  well,  must  attach  themselves 
to  other  females  of  the  same  species  in  order  to  be  carried  to  a  nest 
where  they  can  find  their  appropriate  victims.  This  transfer  is 
probably  made  in  the  flowers  visited  by  these  insects. 

When  a  triungulinid  finds  a  larva  or  a  nyonph  of  its  host  species 
it  quickly  bores  into  it,  and  begins  its  parasitic  life.  The  most  com- 
plete account  of  the  metamorphosis  of  a  stylopid  yet  published  is 
that  of  Xenos  vespdrum  by  Nassonow  ('92).  An  abstract  of  this 
author's  results  is  given  by  Pierce  ('09,  pp.  47-48) ;  the  more  important 
features  of  them  are  the  following. 

The  campodeiform  triungulinid  grows  rapidly  after  entering  the 
body  of  its  host ;  at  the  first  molt  it  loses  its  legs  and  becomes  scarabsi- 
form ;  later  the  body  becomes  cylindrical.  From  this  point  the  develop- 
ment of  the  two  sexes  is  different.  In  the  case  of  the  females,  there 
are  seven  larval  instars ;  in  the  fifth  instar  the  head  and  thorax  are 
fused,  forming  a  cephalothorax ;  the  seventh  instar  pushes  its  cephalo- 
thorax  out  between  two  of  the  abdominal  segments  of  the  host ;  the 
skin  of  this  instar  becomes  the  "puparium,"  in  which  the  adult  female 
is  inclosed,  and  which  she  never  leaves;  the  adult  female  is  larviform; 
there  is  no  pupal  stage  in  this  sex.  In  the  case  of  males,  the  head  and 
thorax  of  the  fifth  instar  are  fused,  forming  a  cephalothorax;  the 
seventh  instar  is  inclosed  in  the  skin  of  the  sixth,  and  has  strongly  de- 
veloped appendages;  for  this  reason  it  may  be  termed  a  prepupa; 
during  the  seventh  stadium  the  cephalothorax  is  exserted  between 
two  abdominal  segments  of  the  host ;  the  true  pupa  is  formed  within 
the  skin  of  the  seventh  instar;  the  adult  male  thrusts  off  the  cap  of 
the  puparium  and  emerges  as  a  winged  individual. 

The  manner  in  which  the  female  is  fertilized,  inclosed  as  she  is  in 
a  puparium,  has  not  been  determined;  it  has  been  suggested  that  the 
seminal  fluid  is  discharged  into  the  space  between  the  venter  of  the 
female  and  the  puparium,  the  brood  chamber.  If  this  is  true,  the 
mobile  spermatozoa  probably  pass  from  the  brood  chamber  through 
the  genital  apertures  into  the  abdominal  cavity,  where  the  eggs  are 
massed  free.  The  slit  in  the  cephalothorax  of  the  puparium,  through 
which  the  triungulinids  escape,  may  serve  for  the  introduction  of  the 
seminal  fluid  into  the  brood  chamber. 

The  order  Strepsiptera  is  well  represented  in  this  country.  Leng 
('20)  listsninety-seven  American  species,  and  doubtless  there  are  many 
undiscovered  species  here.  The  described  American  species  represent 
five  families  and  eighteen  genera. 

Students  wishing  to  study  the  classification  of  these  insects  should 
consult  the  very  complete  monographs  of  the  order  by  W.  Dwight 
Pierce  ('09,  '11,  and  '18),  and  other  papers  listed  in  these  works. 


CHAPTER  XXV 


ORDER  MECOPTERA* 

The  Scorpion-Flies  and  Their  Allies 

The  winged  members  of  this  order  have  four  wings;  these  are  usually 
long,  narrow,  membranous,  and  furnished  with  a  considerable  number 
of  cross-veins;  the  wings  are  wanting  or  vestigial  in  two  genera.  The 
head  is  prolonged  into  a  deflexed  beak,  at  the  end  of  which  chewing 
month-parts  are  situated.     The  metamorphosis  is  complete. 

This  is  a  small  order  composed  of  very  remarkable  insects.  The 
most  striking  character  common  to  all  is  the  shape  of  the  head,  which 
is  prolonged  into  a  deflexed  beak  (Fig.  674).  The  dorsal  wall  of  this 
beak  is  composed  largely  of  the  greatly  elongated  clypeus  (Fig.  675, 
A,  c);  the  central  portion  of  the  ventral  wall  is  the  greatly  elongated 
submentum  (Fig.  675, 5,  sm) ;  and  on  each  side  of  the  submentimi  there 


Fig.  674. — Head 
and  tail  of 
Panorpa. 


Fig.  675. — Head  of  Panorpa:  A,  dorsal  aspect;  B, 
ventral  aspect;  af,  antennal  foramen;  ca,  cardo; 
e,  eye;  g,  gena;  /,  labrum;  Ip,  labial  palpi;  m, 
mentum;  mp,  maxillary  palpi;  mx,  maxillae;  0, 
ocelli;  sm,  submentum;  st,  stipes.     (After Miyake.) 


is  a  greatly  elongated  stipes  of  the  maxilla,  at  the  distal  end  of  which 
is  borne  the  maxillary  palpus.  The  mentum  and  labium  are  com- 
paratively short;  and  from  each  side  of  the  labitmi  there  extends  a 
labial  palpus.  The  mandibles  are  rather  small  and  slender  and  are 
articulated  to  the  apex  of  the  beak,  and  can  cross  freely. 

The  antennas  are  long,  very  slender,  and  many-jointed.  The 
compound  eyes  are  moderately  large.  There  are  usually  three  promi- 
nent ocelli,  but  these  are  wanting  in  Merope  and  in  Boreus. 

*Mecoptera:  mecos  {fifjKoi),  length;  pteron  (nTepdv),  a  wing. 
(550) 


MECOPTERA 


551 


The  prothorax  is  small ;  the  mesothorax  and  metathorax  are  large. 
The  legs  are  long  and  slender;  the  tarsi  are  five-jointed;  in  some 
genera  there  are  two  tarsal  claws,  in  others  only  one. 

The  wings  are  membranous,  and  are  usually  long  and  narrow,  but 
in  two  genera,  Notiothauma  and  Merope,  the  representatives  of  which 
are  ver\'  rare  insects,  the  wings  are  comparatively  broad.  In  the  genus 
Boreus  the  wings  are  vestigial  or  wanting. 

The  type  of  the  venation  of  the  wings  in  this  order  is  well  shown 
by  the  wings  of  Panorpa  (Fig.  676).     In  the  species  figured  here,  the 


Fig.  676. — Wings  of  Panorpa. 

number  and  arrangement  of  the  wing-veins  in  the  fore  wings  is  that 
of  the  hypothetical  primitive  type,  with  the  addition  of  a  considerable 
number  of  cross- 
veins,  and  an  ac- 
cessory vein  on 
vein  R2.  The  same 
is  true  of  the  hind 
wings  except  that 
each  of  the  branches 
of  cubitus  anasto- 
moses with  the  ad- 
jacent vein;  that  is, 
vein  Cui  anasto- 
moses with  vein  M, 
and  vein  Cu2  with 
the  first  anal  vein 


Fig.  677. — Base  of  hind  wing  of  Panorpa. 


552 


AN  INTRODUCTION  TO  ENTOMOLOGY 


(Fig.  677).  For  further  details  regarding  the  venation  of  the  wings 
in  this  order,  see  "The  "Wings  of  Insects"  (Comstock  '18  a). 

The  metamorphosis  is  complete.  The  larvae  are  caterpillar-like, 
with  three  pairs  of  thoracic  legs  and  with  or  without  abdominal  pro- 
legs.  The  pupae  are  exarate,  that  is,  the  wings  and  legs  are  free,  as 
in  the  Coleoptera  and  Hymenoptera. 

This  order  is  represented  in  our  fauna  bv  six  genera;  these  can  be 
separated  by  the  following  table : 

A.    With  well-developed  wings. 

B.    Wings  long  and  narrow;  ocelli  present. 

C.     Tarsi  with  a  single  claw,  and  fitted  for  grasping Bittacus 

CC.     Tarsi  with  two  claws,  and  not  fitted  for  grasping. 

D.  Tarsal    claws   toothed Panorpa 

DD.      Tarsal    claws   simple Panorpodes 

BB.     Wings  comparatively  wide,  with  many  cross-veins  extending  from  the 

subcosta  to  the  costa;  ocelli  wanting Merope 

AA.     Wings   wanting  or  imperfectly   developed. 

B.     Without  ocelli;  small  insects,  less  than  6  mm.,  in  length BoREUs 

BB.     Ocelli  present;  body  about  20  mm.,  in  length Apterobittacus 

Panorpa  or  the  scorpion -flies. — The  most  common  members  of 
this  order  belong  to  the  genus  Panorpa,  of  which  there  are  nearly 

twenty  described 

North  American 

species.   Figure  678 

represents  a  female 

of  this  genus.      In 

our  more  common 

species    the    wings 

are  yellowish,  spot- 
ted with  black.  The 

males  of  this  genus 

are  remarkable  for 

the  peculiar  form  of 

the  caudal  part  of 

the  abdomen  (Fig. 

679).     This  at  first 

sight  reminds  one  of 

the     corresponding 

part  of  a  scorpion, 

and   suggested   the 

common  name^cor- 

pion-flies  for  these 
insects.     But  in  reality  the  two  are  very  different;  the  last  segment 
of  the  male  Panorpa,  instead  of  ending  in  a  sting,  like  that  of  a  scorpion, 
is  greatly  enlarged  and  bears  a  pair  of  clasping  organs.    The  tarsal 
claws  are  toothed  (Fig.  680,  a) . 

The  adults  are  found  resting  on  the  surface  of  foliage  of  rank 
herbage  growing  on  the  banks  of  shaded  streams  and  in  damp  woods 
where  there  is  a  luxuriant  undergrowth  of  herbaceous  plants.  They 
feed  on  dead  or  injured  insects  and  upon  fruits ;  it  appears  that  they 
rarely  if  ever  capture  living  prey. 


Fig.  678.— Paw - 
orpa,  female. 


Fig.  679. — Abdomen  of 
Panorpa  rufescens. 


Fig.  680. — a,  fore  leg  of  Pan- 
orpa; b,  last  two  segments 
of  tarsus  of  Bittacus,  ap- 
posed; c,  last  three  seg- 
ments of  tarsus  of  Bittacus. 


MECOPTERA 


553 


The  females  lay  their  eggs  in  crevices  in  the  earth.  The  larvae 
are  caterpillar-like  in  form;  they  have  three  pairs  of  true  legs  and 
eight  pairs  of  abdominal  prolegs;  and  the  body  is  armed  with  promi- 
nent spines  (Fig.  68i) ;  the  larvae  are  carnivorous.  The  transformation 
takes  place  in  a  cell  in  the  ground. 

Panorpodes. — The  members  of  this  genus  resemble  Panorpa  in 
general  appearance,  and  as  in  that  genus  the  abdomen  of  the  male  is 
furnished  with  a  pair  of  clasping  organs;  but  in 
Panorpodes  the  tarsal  claws  are  simple.  Only  two 
species  have  been  described  from  North  America. 
These  are  not  common;  and  but  little  is  known 
regarding  their  habits. 

Merope. — This  genus  includes  only  a  single  known 
species,  Merope  tuber.  This  is  an  exceedingly  rare 
insect.  In  this  genus  the  wings  are  comparatively 
wide  (Fig.  682);  and  there  are  many  cross-veins  ex- 
tending from  the  subcosta  to  the  costa.  I  have 
figured  the  venation 
of  the  wings  in  "The 
Wings  of  Insects" 
(Comstock  '18  a). 
The  ocelli  are  wanting. 
The  abdomen  of  the 
male  is  terminated  by 
a  pair  of  long,  stout 
forceps.  This  is  prob- 
ably a  nocturnal  insect 
as  it  is  attracted  to 
lights  at  night.  Its 
life-history  is  un- 
known. 

Boreus. — This    ge- 
nus includes  small  Me- 
coptera,     our    species   Fig.  681. -Larva  of 
Fig.  682.-Merope  tuber,  slightly  measunng    from     2.5 
enlarged.       (Photographed    by   mm.    to     5    mm.    m 
J.  G.  Needham.)  length,  which  are  of- 

ten found  on  snow  in 
winter.  The  wings  of  the  female  are  vestigial  or  wanting;  those  of 
the  male,  imperfectly  developed.  The  ocelli  are  wanting.  The  female 
has  a  long,  protruding  ovipositor,  which  in  some  species  is  nearly  as 
long  as  the  abdomen.  The  larva  differs  from  that  of  Panorpa  in 
lacking  the  abdominal  prolegs.  The  pupa  state  is  passed  in  an  earthen 
cell  in  the  ground.  Four  American  species  have  been  described,  two 
from  the  East  and  two  from  the  West. 

BUtacus.— Insects  belonging  to  this  genus  have  long,  narrow 
wings,  long  legs,  and  a  slender  abdomen.  They  resemble  crane-flies 
very  closely  when  on  the  wing,  but  can  be  distinguished  by  the 
presence  of  two  pairs  of  wings.     They  are  almost  as  common  as 


Panorpa  rufes- 
cens,  first  instar. 
(After  Felt.) 


554 


.47V  INTRODUCTION  TO  ENTOMOLOGY 


Panorpa;  and,  like  the  scorpion -flies,  are  found  among  rank  herbage 
growing  on  the  banks  of  shaded  streams  and  in  damp  woods  where 
there  is  a  luxuriant  undergrowth  of  herbaceous  plants.  When  at 
rest,  they  do  not  sit  on  the  surface  of  foliage  as  does  Panorpa,  but 
hang  suspended,  by  their  front  legs,  from  some  support  (Fig.  683). 
The  members  of  this  genus  capture  and  feed 
upon  living  insects.  They  are  enabled  to  capture 
their  prey  by  means  of  their  curiously  modified 
tarsi,  the  last  two  segments  of  which  are  armed 
with  teeth,  and  the  last  segment  can  be  folded 
back  against  the  next  to  the  last  segment.  In 
this  way  there  is  formed  an  efficient  grasping 
organ  (Fig.  680,  b,  c).  It  is  an  interesting  fact 
that,  while  in  other  predacious  insects  the  fore 
legs  are  the  chief  organs  of  prehension,  in  Bittacus 
the  hind  legs  are  used  for  this  purpose  fully  as 
often  as  the  others,  especially  when  the  Bittacus 
is  hanging  suspended  by  its  fore  legs  and  captures 
an  insect  that  comes  within  reach  of  it. 

Nine  North  American  species  of  Bittacus  have 
been  described. 

ApterobUtacus. — This  genus  includes  a  single 
known  species,  ApterobUtacus  apterus,  found  in  California.  It  re- 
sembles Bittacus  except  that  the  wings  are  completely  wanting. 

A  review  of  the  species  of  the  Mecoptera  of   America  north  of 
Mexico  was  published  by  James  S.  Hine  (Hine  '01). 


Fig.  683.— Natural 
position  of  Bitta 
cus.      (From  Felt.^ 


CHAPTER  XXVI 
ORDER  TRICHOPTERA* 

The  Caddice-Flics 

The  members  of  this  order  have  four  wings;  these  are  membranous 
and  usually  more  or  less  densely  clothed  with  long,  silky  hairs.  In  the 
more  generalized  members  of  the  order,  the  venation  of  the  wings  corre- 
sponds closely  to  that  oj  the  hypothetical  primitive  type  with  but  few  or  no 
accessory  veins;  in  some  of  the  more  specialized  members  of  the  order, 
the  venation  of  the  wings  is  reduced.  The  mouth-parts  of  adults,  except 
the  palpi,  are  vestigial.     The  metamorphosis  is  complete. 

The  caddice-flies  are  moth-like  insects,  which  are  common  in  the 
vicinity  of  streams,  ponds,  and  lakes,  and  are  frequently  attracted 
to  lights  at  night  (Fig.  684).     The  larvae  of 
these  insects  are  the  well-known  caddice- 
worms ;  these  live  in  the  water,  and  most  of 
them  build  cases  about  their  bodies. 

In  the  adult  insect,  the  body-wall  is  soft, 
being  membranous  or  at  the  most  parch- 
ment-like, and  is  thickly  clothed  with  hairs.      Fig-  684.^A  caddice-fly. 
The  two  pairs  of  wings  are  membranous 

and  usually  more  or  less  clothed  with  long,  silky  hair.  The  fore  wings 
are  denser  than  the  hind  wings  and  are  often  slightly  coriaceous;  in 
a  few  forms  the  wings  are  naked.  The  hind  wings  are  shorter  than 
the  fore  wings;  but  they  are  usually  broader;  this  is  due  to  an  ex- 
pansion of  the  anal  area  of  the  hind  wings.  In  a  few  species  the  hind 
wings  are  reduced  so  that  they  are  smaller  than  the  fore  wings;  in  one 
species  the  female  is  apterous,  and  in  another  the  wings  of  the  female 
are  vestigial.  When  not  in  use  the  wings  are  folded  roof-like  over  the 
abdomen. 

The  posterior  lobe  of  the  fore  wings  is  speciahzed  as  a  fibula, 
which  is  well  developed  in  the  more  generalized  forms,  as  Rhyacophila, 
but  more  or  less  reduced  in  the  more  specialized  genera.  The  costal 
border  of  the  hind  wings  is  furnished  with  hamuli  in  some  forms,  as 
in  the  Leptoceridae  and  some  Hy dropsy chidse. 

In  the  more  generalized  forms  the  venation  of  the  wings  cor- 
responds quite  closely  with  the  hypothetical  primitive  type;  this  is 
well  shown  by  the  wings  of  Rhyacophila  fuscula  (Fig.  685).  The 
more  important  modifications  of  this  type  shown  by  the  wings  of 
Rhyacophila  are  the  following :  in  the  fore  wing  the  tips  of  the  second 
anal  vein  and  two  of  the  branches  of  the  third  anal  vein  coalesce; 
the  subcosta  bears  an  accessory  vein;  this,  however,  is  unimportant; 
accessory  veins  borne  by  the  subcosta  exist  in  only  a  few  genera  of 
this  order;  the  coalescence  of  veins  Cu  and  ist  A  at  the  base  of  the 


*Trich6ptera:  trichos  (Opli,  rptx^s),  the  hair;  pteron  {irTepdv),  awing. 
(555) 


556 


AN  INTRODUCTION  TO  ENTOMOLOGY 


wing;  and  the  formation  of  a  serial  vein  consisting  of  the  base  of 
media,  the  posterior  arculus  (pa),  and  the  distal  part  of  vein  Cu.  In 
the  hind  wings,  media  has  been  reduced  to  a  three-branched  condition 
by  the  coalescence  of  veins  M3  and  M4. 

In  the  more  specialized  members  of  this  order  the  specialization 
of  the  preanal  area  of  the  wings  is  always  by  reduction.  In  the  anal 
area  of  the  hind  wings  the  specialization  is  in  some  cases  by  addition, 
resulting  in  a  broadly  expanded  anal  area;  in  others  it  is  by  reduction. 

The  head  is  small ;  the  antennse  are  setaceous,  and  frequently 
several  times  as  long  as  the  bod}';  the  compound  eyes  are  usually 


?d  A    ,st  A   C112       ^"^ 
Fig.  685. — Wings  of  Rhyacophila  fuscula. 

small  and  with  small  facets;  the  ocelli  are  either  present  or  absent; 
when  present  they  are  three  in  nimiber;  the  mandibles  are  mere 
tubercles  at  the  base  of  the  labrum ;  the  maxillae  are  small,  and  ordi- 
narily furnished  with  an  obtuse  maxillary  lobe;  the  maxillary  palpi 
are  well-developed,  and  furnish  characters  which  are  much  used  in 
classification;  the  labium  is  usually  well-developed,  and  bears  three- 
jointed  palpi. 

The  legs  are  long  and  usually  slender;  the  coxse  are  very  large; 
the  femora  are  long  and  slender,  and  generally  without  spines;  the 
tibiae  are  also  long  and  slender;  the  tarsi  are  always  five-jointed. 
The  tibiae  and  tarsi  are  often  furnished  with  black  or  brown,  some- 
times yellow,  spine-like  setae.  In  addition  to  the  spine-like  setae,  the 
tibiae  bear  movable  spurs  either  at  the  apex  only,  or  also  at  some 


TRICHOPTERA 


557 


Fig.  686. — Two  egg-masses 
of  caddice-fliesro,  Phryganea 
interrupta;  h,  Tricenodes  sp. 
(From  Lloyd.) 


distance  before  the  apex ;  these  are  larger  than  the  spine-hke  setae 

and  are  usually  differently  colored.     The  number  of  these  spurs  is 

much  used  in  classification. 

The  eggs  of  caddice-flies  are  round   or  slightly  oval   in  form. 

They  are  laid  either  in  water  or  upon  objects  above  water  from  which 

the  larvae  when  hatched  can  find  their 

way  into  the  water.     Some  species  that 

lay  their  eggs  in  water  descend  below  the 

surface  in  order  to  glue  their  eggs  to  some 

submerged  support.     So  far  as  is  known, 

all  species  of  caddice-flies,  except  some 

of  the  RhyacophilidcC,  lay  their  eggs  in 

a  mass  enveloped  either  in  a  cement,  by 

which  the  mass  is  glued  to  some  support, 

or  in  a  gelatinous  covering.    In  the  latter 

case,  the  covering  absorbs  water  and  thus 

increases  greatly  in  size.    The  form  of  the 

gelatinous  mass  and  the  arrangement  of  the  eggs  within  it  are  often 

characteristic  of  the  species  (Fig.  686). 

The  larv£E  of  most  caddice-flies,  the  caddice-worms,  are  somewhat 
caterpillar-like  (eruciform)  in  shape  (Fig. 
687) ;  but  some  are  more  nearly  campodei- 
form.  Those  that  are  eruciform  build  a 
portable  case  in  which  they  live;  most  of 
the  campodeiform  larva;  do  not  build  port- 
able cases.  In  the  eruciform  larvs  the 
head  is  bent  down,  as  in  a  caterpillar;  in 
the  campodeiform  larvae  the  head  is  hori- 
zontal, the  mouth-parts  projecting  for- 
ward. Both  types  differ  from  the  cater- 
pillars in  having  only  one  pair  of  prolegs, 
the  anal  prolegs.  These  are  each  furnished 
with  a  chitinous  hook.  The  mouth-parts 
are  fitted  for  chewing.  The  thoracic  legs 
are  well  developed.  In  the  case-building 
forms,  the  first  abdominal  segment  often 
bears  three  tubercles,  one  dorsal  and  one 
on  each  side;  these  are  the  "spacing- 
humps,"  and  serve  to  keep  a  space  between 
the  insect  and  its  case  for  the  free  circu- 
lation of  water  for  respiration.  In  several 
families  the  larvae  possess  abdominal  tra- 
cheal gills;  these  are  filamentous  and  are 
sometimes  branched;  they  arise  singly 
or  in  tufts.  With  the  exception  of  a  single 
European  genus,  Enoicyla,  all  caddice- 
worms  are  aquatic. 
Most  caddice-worms  build  portable  cases  in  which  they  live  and 

which  they  drag  about  whenever  they  go,  projecting  only  the  front 


Fig.  687. — A  caddice-worm, 
Anabolia  nervosa:  A,  larva 
extracted  from  its  case; 
B,  one  of  the  dorsal  spaces 
of  the  abdominal  seg- 
ments more  strongly  mag- 
nified.     (From  Sharp.) 


558 


AN  INTRODUCTION  TO  ENTOMOLOGY 


end  of  the  body  and  the  legs  from  the  case  when  they  travel.  The 
cases  of  different  species  differ  greatly  in  form  and  in  materials  used 
in  their  construction;  but  silk  is  used  in  building  all  of  them.  This 
silk,  like  that  of  caterpillars,  is  secreted  by  modified  salivary  glands 
and  is  emitted  through  an  opening  in  the  labium;  but  in  most  cases 
it  is  not  spun  into  a  thread,  but  is  poured  forth  in  a  glue-like  sheet 
upon  the  objects  to  be  cemented  together;  sorae  species,  however, 
build  nets  of  silken  strands. 

Some  caddice-worms  build  their  cases  entirely  of  silk;  but  most 
of  the  case-building  species  use  other  materials  also;  these  may  be 
grains  of  sand,  small  stones,  bits  of  wood,  moss,  or  pieces  of  leaves; 
and  some  species  fasten  shells  of  small  mollusks  to  their  cases.  The 
materials  used  are  glued  together  with  silk;  and  the  case  is  lined  with 
silk,  so  as  to  form  a  suitable  protection  for  the  soft  abdomen.  Ex- 
amples of  different  types  of  cases  are  figured  later. 

When  the  caddice-worms  are  full-grown  they  do  not  leave  the 
water  to  transform,  as  do  nearly  all  other  aquatic  larvee,  the  pupae 
being  as  truly  aquatic  as  the  larvae.  Some  of  the  case-building  species 
change  the  form  and  material  of  their  cases  at  this  time;  and  nearly 
all  of  them  partly  close  their  cases  so  as  to  keep  out  intruders  and  silt ; 
but  usually  provision  is  made  for  the  ingress  of  water  for  respiration. 
Some  species  merelv  cement  a  stone  or  grains  of  sand  over  each  open- 
ing of  the  case;  others  build  a  silken  lid  with  a  slit  in  it;  and  still 
others  build  a  silken  grating  in  each  end  of  the  case.  Frequently 
caddice-worms  leave  the  open  water  in  which  the  larval  life  has  been 
spent  and  seek  some  more  secluded  place  in  which  to  transform,  such 
as  crevices  in  bark  or  among  roots,  or  they  may 
burrow  into  wood  or  into  the  soil. 

The  pupas  are  of  the  exarate  type,  that  is,  the 
wings  and  legs  are  free  (Fig.  688).  Some  pupae 
have  tracheal  gills,  others  do  not;  this,  however, 
is  not  correlated  with  the  presence  or  absence  of 
tracheal  gills  in  the  larva;  tracheal  gills  may  be 
present  in  either  of  these  stages  and  absent  in  the 
other. 

In  the  case  of  those  caddice-flies  that  emerge 
from  rapidly  flowing  water,  as  the  net-building 
species,  the  wings  expand  instantly  when  the  in- 
sect reaches  the  surface  of  the  water  and  are  then 
fitted  for  flight;  it  is  evident  that  if  much  time 
were  required  for  the  wings  to  become  fit  for  use, 
as  is  the  case  with  most  other  insects,  the  wave 
succeeding  that  which  swept  the  insect  from  the 
water  would  sweep  it  back  again  and  destroy  it. 

The  Trichoptera  can  be  regarded  as  beneficial 
insects,  as  the  larva?  form  an  important  element 
in  the  food  of  fishes,  and  especially  of  the  brook  trout.  Sometimes 
in  cities  near  rivers,  the  adults  are  annoying  on  account  of  the  great 
numbers  of  them  that  are  attracted  to  lights. 


Fig.  688.— A,  pupa 
of  Phryganea  pi- 
losa.  (After  Pic- 
tet.)  B,  mandi- 
bles of  pupa  of 
Molanna  angusta- 
ta.     (From  Sharp.) 


TRICHOPTERA  559 

This  order  includes  thirteen  families,  all  of  which  are  represented 
in  North  America.  Nearly  four  hundred  species  have  been  described 
from  this  region.  Among  the  more  important  works  on  the  classification 
of  these  insects  are  McLachlan  ('74-80),  Ulmer  ('07),  andUlmer  ('09). 
This  last -mentioned  work  is  especially  important  for  its  accounts  of 
the  early  stages  of  these  insects. 

The  latest  and  most  extended  work  on  the  life-histories  of  North 
American  caddice-worms  is  that  by  Lloyd  ('21).  In  this  work  there 
is  a  list  of  the  more  important  papers  on  this  subject,  which,  for  this 
reason,  need  not  be  enumerated  here.  This  monograph  by  Mr.  Lloyd 
has  been  of  great  assistance  to  me  in  the  preparation  of  the  following 
account  of  the  habits  of  representatives  of  the  different  families. 

A  monograph  treating  of  all  stages  of  North  American  Trichoptera 
has  been  prepared  by  Dr.  Cornelius  Betten  and  is  to  appear  as  a 
bulletin  of  the  New  York  State  Museum. 

The  following  table  of  families   is  copied  from  Needham  ('18). 

TABLE  OF  FAMILIES  OF  THE  TRICHOPTERA 

For  the  Classification  of  Adults 

A.  Micro-caddice-flies;  very  small,  moth-like,  hairy,  the  fore  wings  bearing 
numerous  erect  clavate  hairs;  the  marginal  fringe  of  the  wings  longer  than 
their  greatest  breadth;  form  of  wings  narrowly  lanceolate;  antenna;  rather 

stout  and  not  longer  than  the  fore  wings,  p.  561 Hydroptilid^ 

AA.    Larger  caddice-flies,  with  broader  wings;  marginal  fringes  never  as  long  as 
the  wings  are  broad;  antennae  usually  longer  than  the  fore  wings. 
B.     Maxillary  palpi  five-jointed. 

C.     Last  joint  of  the  maxillary  palpi  simple,  and  not  longer  than  the  other 
joints. 
D.    Ocelli  present. 

E.     Front  tibiae  with  two  or  three  spurs,  middle  tibiae  with  four  spurs. 

F.     The  first  two  joints  of  the  maxillary  palpi  short  and  thick,  the 

third  joint  much  longer  and  thinner,  p.   560 .  .  .  .Rhyacophilid^ 

FF.     The  second  joint  of  the  maxillary  palpi  much  longer  than  the 

first.      Females,    p.    564 Phryganeid^ 

EE.     Front  tibiffi  with  a  single  spur,  or  with  none;  middle  tibiae  with 

only  two  or  three  spurs.     Females,  p.  568 Limnophilid^ 

DD.    Ocelli  wanting. 

E.     A  closed  cell  in  the  principal  fork  of  the  median  vein  in  the  fore 

wings,     p.  567  Calamoceratid.^ 

EE.    No  closed  cell  in  the  median  fork. 

F.     A  closed  cell  in  the  first  fork  of  the  radial  sector. 
G.    Both  branches  of  the  radial  sector  forked. 
H.     Veins  R,  and  R2  confluent  apicallyor  connected  by  an  apical 
cross-vein  in  the  fore  wing.     Females,  p.  567..0dontocerid^ 

HH.     Veins  Ri   and  R^   not   connected  apically.   p.   569 

Sekicostomatid^ 

GG.     Only  the  anterior  branch  of  the  radial  sector  forked,  p.  566. 

Leptocerid^ 

FF.     No  closed  cell  in  the  first  fork  of  the  radial  sector,  p.  566.  . 

Molannid^ 

CC.     Last  joint  of  the  maxillary  palpi  usually  much  longer  than  the  others, 
twisted,  and  divided  imperfectly  into  subsegments. 

D.     Ocelli  present,   p.    563 Philopotamid/E 

DD.     Ocelli  wanting. 

E.     Front  tibiae  with  three  spurs,  p.   563 PoLYCENTROPiDiE 

EE.    Spurs  of  front  tibiae  fewer  than  three. 


560  AN  INTRODUCTION  TO  ENTOMOLOGY 

F.     Anterior  branch  of   the  radial  sector  in   the  fore  wings  forked. 

p.  562 Hydropsychid^ 

FF.      Anterior  branch   of   the  radial   sector   simple,   p.  564 

PSYCHOMYID^ 

BB.    Maxillary  palpi  with  fewer  than  five  joints. 

C.     Maxillary  palpi   with   four  joints;  ocelh   present.      Males,   p.    564... 

Phryganeid.^ 

CC.    Maxillary  palpi  with  two  or  three  joints. 

D.      Maxillary  palpi   filiform,  with   cylindric   smooth   joints;  fore   tibiae 

with  a  single  spur.     Males,  p.  568 Limnophilid^ 

DD.    Maxillary  palpi  hairy  or  scaly,  appressed  against  and  often  covering 
the  face;  fore  tibias  with  two  spurs.    Males,  p.  569.  .Sericostomatid^ 

TABLE    OF    TRICHOPTEROUS    LARV^ 

The  following  table  will  aid  in  the  classification  of  caddice-worms.  It  is 
based  on  a  more  detailed  table  of  the  family  characters  of  trichopterous  larvae 
given  by  Lloyd  ('21). 

A.    Anal  prolegs  not  fused  in  median  line  to  form  an  apparent  tenth  abdominal 
segment. 

B.      Abdomen   much    wider   than    the   thorax,    p.  561 Hydroptilid^ 

BB.    Abdomen  not  much  wider  than  the  thorax. 

C.     Dorsal  surface  of  the  ninth  abdominal  segment  with  a  chitinous  shield. 

p.  560 Rhyacophilid^ 

CC.     Dorsal  surface  of  the  ninth  abdominal  segment  without  a  chitinous 
shield. 

D.      Tracheal   gills  present,   branched,   p.    562 Hydropsychid^ 

DD.    Tracheal  gills  absent. 

E.     Labrum  entirely  membranous,   white,     p.   563.  .Philopotamid.^ 
EE.     Labrum  entirely  chitinized. 

F.    Frons  long,  extending  back  to  the  caudal  margin  of  the  head.  p.  563 

Polycentropid^ 

FF.     Frons  normal,  p.  564 Psychomyid^e 

AA.    Anal  prolegs  fused  in  median  line  so  as  to  form  an  apparent  tenth  segment. 
B.    Dorsal  surface  of  the  labrum  with  a  row  of  twenty  or  more  heavy  bristles. 

p.  567 CALAMOCERATID.E 

BB.    Dorsal  surface  of  labrum  normal. 

C.      Labrum  much  longer  than  broad,  p.  567 Odontocerid^ 

CC.    Labrum  broader  than  long. 

D.    Metanotum  with  three  pairs  of  plates,    p.  568 Limnophilid^ 

DD.    Metanotum  soft. 

E.     Mesonotum  soft  or  with  one  pair  of  minute  plates,  p.  564 

Phryganeid^ 

EE.     Mesonotum  chitinized. 

F.     Femur  of  hind  legs  divided  into  two  segments  or  apparently  so. 

p.  566 Leptocerid^ 

FF.    Femur  of  hind  legs  not  divided. 
G.    p.  569 Sericostom.\tid  je. 

GG.      p.  566..: MOLANID^ 

Family  RHYACOPHILID^ 

The  larvse  are  campodeiform ;  they  Hve  in  rapidly  flowing  streams 
with  stony  bottoms.  The  American  species  of  this  family  represent 
two  subfamilies.     The  members  of  one  subfamily,  the  Rhyacophilinas, 


TRICHOPTERA 


561 


do  not  build  cases,  but  crawl  about  naked  beneath  stones  seeking  their 
food;  they  feed  on  small  larva.^ 
and    filamentous    alga?.      The 
larva    of    our   most    common 
species,    Rhyacophila  fiiscula, 
when  full-grown  enters  a  crev- 
ice between  two  large  stones 
and  builds  a  wall  of  pebbles 
about  itself;  this  wall  is  ce- 
mented   in    place    with    silk; 
and  the  chamber  thus  inclosed 
is  much  larger  than  the  insect 
(Fig.    689);  it    then    spins    a 
parchment -like  cocoon  about 
its  body,  within  which  it  trans- 
forms.    The  making  of  a  co- 
coon is  a   family  characteris-   „.     ,  ,        ,  ,  ^  „,        .,•,,■,,• 
tic  of  the  RhyacophiHd.;only   ^■^''S.^-'ch'^Se^expS^bfli^t^i'ol 
afewothercaddice-wormsspm        the  stone  beneath  which  is  was.     (From 
cocoons.                                                        Needham  and  Lloyd.) 

The  members  of  the  subfamily  Glossosmatiuce  build  cases  out  of 
sand  or  small  stones.  Our  best- 
known  species  is  Glossosoma  ameri- 
cdna,  the  habits  of  which  are  de- 
scribed by  Lloyd.  Figure  690  repre- 
sents a  dorsal  and  a  ventral  view  of 
the  case.  The  larvse  live  singly  on 
the  stones  of  the  stream's  bottom; 
but  before  pupating  they  congre- 
gate in  dense  colonies  on  the  sides 
and  bottoms  of  stones,  with  their 
cases  placed  edge  to  edge,  sometimes 
one  on  top  of  another.  At  this  time 
the  floor  of  the  case  is  cut  away  and 
the  rim  of  the  cup-like  roof  is  glued  to  the  supporting  rock. 


Fig.  690. — Case  of  Glossosoma  ameri- 
cana:  a,  dorsal  view;  h,  ventral 
view.   (After  Lloyd.) 


Family  HYDROPTILID.^ 


The  Micro-Caddice-Flies 


This  family  is  composed  of  minute  caddice-flies,  which  resemble 
tineid  moths  in  appearance.  The  larvee  are  found  in  both  quiet  water 
and  rapid  streams,  and  often  occur  in  very  great  numbers.  They 
build  cases  which  differ  in  form  in  the  different  species,  but  are  usually 
fiat;  some  are  elliptical,  some  flask -like,  and  others  kidney-shaped; 
all  are  open  at  both  ends;  they  are  much  larger  than  the  larvae. 
They  are  usually  composed  entirely  of  silk ;  but  in  some  species  grains 
of  sand  or  minute  bits  of  vegetable  matter  are  used.     ''Agraylea 


562 


AN  INTRODUCTION  TO  ENTOMOLOGY 


decorates  the 


parchment  with  filaments  of  Spirogyra,  arranged 
concentrically  over  the  sides  in  a  single  ex- 
ternal layer."  (Needham  and  Lloyd.)  When 
moving  about,  the  larva  usually  drags  its  case  on 
one  edge.  There  is  one  species,  Ithytrichia  ccnfusa, 
which  cements  its  case  firmly  to  rocks  in  flowing 
water.  These  cases  are  common ;  they  are  parch- 
ment-like, elliptical,  with  a  small  opening  at  each 
end  (Fig.  691,  2),  and  measure  from  5  mm.  to 
6  mm.  in  length.  They  are  incomplete,  being  ce- 
mented along  the  edges  to  the  rock,  with  no  floor 
below  the  larva.  The  larva  is  very  remarkable  in 
form  (Fig.  691,  i).  When  feeding,  it  protrudes 
the  narrower  part  of  its  body  from  its  case  and 
gathers  food  from  the  surface  of  the  rock;  the 
expanded  abdominal  segments  are  much  wider 
than  the  openings  in  the  case. 


Family  HYDROPSYCHID^ 


The  famil  v  H  vdropsvchidas  of  the  older  authors 

Fig.    egi^-^mytrickmi^^^  ^^gg^  divided  into  four  families  by  Ulmer,— 

2''  case.     ''    (After  Hydropsychidae,  Philopotamidas,  Polycentropidae, 

Lloyd.)  and  Psychomyidae.    It  is  to  this  group  of  families 

that    the    net-spinning    caddice-worms    belong. 

The  best -known  of  these  are  species  of  the  genus  Hydropsyche,  the 

nets  of  which  have  been  described  by  many  writers. 

The  larvae  of  Hydropsyche  live  only  in  rapid  streams  and  on  the 
wave-beaten  shores  of  lakes.  They  are  campodeiform,  and  do  not 
build  portable  cases,  but  live  in  tubes  composed  of  silk  and  debris, 
and  fastened  permanently  in  place;  sometimes  they  establish  them- 
selves in  old  worm-holes  in  submerged 
wood.  The  most  striking  feature  in 
their  habits,  however,  is  the  fact  that 
each  one  builds  a  net  for  the  capture 
of  its  food.  This  net  is  built  adjacent 
to  the  tube  in  which  the  larva  lives;  it 
is  funnel-shaped  and  has  at  its  down- 
stream end  an  opening  in  which  is  built 
a  strainer.  This  is  a  beautiful  object, 
consisting  of  two  sets  of  regularly 
spaced  strands  of  silk  extending  across 
the  opening  at  right  angles  to  each 
other  (Fig.  692).  These  nets  are  often  built  in  crevices  between 
stones;  but  fully  as  often  they  are  built  up  from  a  flat  surface,  as  on 
the  brink  of  a  waterfall.  In  this  case  they  are  in  the  form  of  semi- 
elliptical  cups,  which  are  kept  distended  by  the  current.  Much  of 
the  coating  of  dirt  with  which  rocks  in  such  places  are  clothed  in 
summer  is  due  to  its  being  caught  in  these  nets.     Sometimes  when 


Fig.  692. — Net  of  Hydropsyche. 


TRICHOPTERA  563 

the  net  is  built  up  from  a  horizontal  surface  its  sides  are  supported  by 
bits  of  wood.  Algae,  larvae,  and  other  small  animals  in  the  water  that 
passes  through  the  net  are  held  by  the  strainer  and  thus  made  avail- 
able to  the  caddice-worm  for  food.  When  the  larva  is  full-grown  it 
surrounds  itself  with  a  case  composed  of  fine  sand  or  gravel  in  which 
to  transform;  this  case  is  firmly  cemented  in  place,  and,  in  some 
species  at  least,  is  closed  at  each  end  with  a  silken  grating.  The 
instantaneous  flight  of  the  newly  emerged  adult  when  it  reaches  the 
surface  of  the  water  has  been  referred  to  on  an  earlier  page. 


Family  PHILOPOTAMID^ 

The  larvae  of  members  of  this  family  are  campodeiform  and  live  in 
rapid  streams.  Several  of  them  were  studied  by  Miss  Alice  A.  Noyes, 
but  as  yet  an  account  of  only  one  of 
them,  Chimarrha  aterrima,  has  been 
pubHshed  (Noyes  '14).  This  larva 
spins  a  delicate  silken  net  resem- 
bling in  shape  the  finger  of  a  glove. 
The  average  size  of  the  net  of  a 
growing  larva  is  about  25  mm.  long 
and  3  mm.  wide.  The  nets  are  rarely 
found  singly,  but  are  generally 
placed  five  or  six  in  a  row  (Fig.  693) ; 
sometimes  they  occur  in  great  num- 
bers, completely  covering  the  stones 
with  a  thin,  flocculent  mass  of  dirty 
silk.     There  is  a  large  opening  at 

the  end  of  the  net  facing  the  current,    t^-     ^         m  .     r  /-,  • 

1  11  •  .    .1       1  •    J    i'lg-  DQ.^- — Nets  01  Lhtmarrha  aterrt- 

and  a  smaller  openmg  at  the  hmd       %^a,natma\  size.       (From  Noyes.) 
end.    The  nets  are  fastened  m  place 
at  the  entrance;  the  rest  of  the  sac 

floats  freely,  and  is  kept  distended  by  the  current.  The  net  serves 
both  as  a  hiding-place  for  the  larva  and  as  a  sieve  through  which  the 
flowing  water  is  strained;  the  larva  feeding  on  the  organic  particles 
that  are  entanded  in  it.  The  full-grown  larva  covers  itself  with  an 
irregular  dome  of  pebbles  in  which  to  transform,  and  spins  about  its 
body  a  delicate  cocoon. 


Family  POLYCENTROPID^ 

The  larvae  are  campodeiform;  they  usually  live  in  flowing  water, 
but  some  are  found  in  standing  water.  They  do  not  build  portable 
cases,  but  make  fixed  silken  tubes  or  nets.  The  nets  of  several 
European  genera  have  been  described;  for  an  abstract  of  these 
accounts,  see  Noyes  ('14).  The  nets  of  American  species  have  been 
described  by  Clark  ('91),  Vorhies  (09),  Noyes  ('14),  and  Lloyd  ('21). 


564 


AN  INTRODUCTION  TO  ENTOMOLOGY 


"Several  species  of  the  genus  Polycentropus  live  in  still  or  slowly 
flowing  water  with  sandy  or  muck  bottoms.  These  larvas  spin  sub- 
terranean tubes  of  silk 
which  sometimes  reach 
lo  centimeters  in  length. 
Often  the  tubes  have  one 
or  more  branches,  and  al- 
ways they  contain  a  bulb- 
ous swelling  near  the 
middle  in  which  the  larva 
probably  rests,  and  in 
which  pupation  takes 
place.  In  natural  posi- 
tion the  tubes  are  be- 
neath the  ground,  except 
about  half  an  inch  which 
projects  upward  into  the 
water."  (Lloyd.) 

Two  quite  different  larval  tubes  of  members  of  this  family  are 
described  and  figured  by  Miss  Noyes.  One  of  these  is  represented 
in  Figure  694.  This  tube  is  found  on  the  under  side  of  stones,  and 
is  fastened  along  its  entire  length.  "It  is  21  mm.  long  and  5.5  mm. 
wide,  with  an  expanded  opening  at  either  end.  Connected  with  each 
opening  and  along  either  side  is  a  mass  of  tangled,  silken  threads, 
about  20  mm.  square  and  loosely  attached  to  the  stone.  This  tangled 
mass  may  float  partially  over  the  tube  and  so  obscure  it." 

"I  have  never  observed  the  larvfe  feeding,  but  do  not  doubt  that 
Mayfly  nymphs  and  chironomid  larvae  become  entangled  in  the 
meshes  as  they  crawl  about  over  the  stones,  for  remains  of  these 
forms  are  abundant  in  the  stomach  contents."  (Noyes.) 


Fig.  694. — Dwelling  of  Polycentropus  sp.    (From 
Noyes.) 


Family  PSYCHOMYID.^ 

The  larvffi  are  campodeiform.  There  is  no  account  of  the  life- 
history  of  any  American  species  published.  The  European  species 
do  not  make  portable  cases;  but  the  larvae  live  on  stones  in  long, 
loosely-spun  galleries  of  silk  and  sand  grains.  They  are  found  mostly 
in  swift  water,  but  also  inhabit  ponds  and  lakes. 


Family  PHRYGANEID^ 


The  larvce  are  caterpillar-like,  and  usually  live  in  standing  water 
in  which  plants  are  growing,  or  in  slowly  moving  streams  of  spring 
water.  They  make  portable  cases  which  are  very  regular  in  form. 
As  these  larva?  live  in  quiet  water,  they  can  be  fed  and  reared  in  aquaria 
where  their  habits  can  be  easily  observed.  The  most  extended  account 
of  the  immature  stages  of  these  insects  is  that  of  Lloyd  ('21),  from 


TRICHOPTERA 


565 


Fig, 


which  the  following  brief  notes  are  compiled.  This  author  discusses 
three  species  of  Neuronia-a.nd  three  species  of  Phryganea. 

Neiirdnia.- — The  larvae  are  found 
in  slowly  moving  streams  of  spring 
water;  rarely  the\'  are  found  along 
the  edge  of  the  large,  warm  streams 
where  cool  seepage  enters.  One 
species  was  found  in  a  pond.  The 
cases  are  cylindrical  tubes  of  thin, 
rectangular  bits  of  leaves  arranged 
in  a  series  of  rings  (Fig.  695,  a).  In 
the  cases  of  old  larva:  the  rings  are 
neatly  fitted  without  overlapping; 
young  larvae  sometimes  leave  the 
hind  ends  of  the  leaf-fragments  pro- 
truding in  long  strips.  Unlike  other 
caddice-worms,  these  larvae  often 
abandon  their  cases  and  wander 
naked  through  the  water.  The  form 
of  the  case  indicates  that  they  are 
not  long  retained ;  their  uniform  di- 
ameter proves  that  they  are  con- 
structed more  rapidly  than  the  di- 
ameter of  the  larva  increases.  When 
the  season  for  pupation  draws  near, 
the  larva?  of  Neuronia  burrow  into 
wood,  or  wedge  themselves  beneath 

bark,  or  in  crevices,  or,  if  the  stream  bottom  be  of  clay,  they  may 
burrow  into  the  soil.  When  entering  the  soil  the  larva  stands  on  its 
head,  with  its  case  perpendicular  to  the  bottom,  and  slowly  enters, 
dragging  its  case  with  it. 

Phryganea. — The  larvae  live  in  ponds;  they  dwell,  for  the  most 
part,  among  submerged  plants  above  the  bottom  of  the  pond;  hence 
they  can  be  taken  with  a  water  net.  They  never  abandon  their 
cases  as  do  the  larvas  of  Neuronia.  The  case  is  a  straight  tube  com- 
posed of  narrow  strips  of  leaf  arranged  in  spiral  form  around  the 
circumference  of  the  case  (Fig.  695,  b).  Young  larvas  often  fail  to 
cut  the  leaf-fragments  used  in  the  construction  of  the  case  into  the 
rectangular  form  seen  in  the  cases  of  old  larvse ;  but  the  bases  of  the 
untrimmed  fragments  are  arranged  in  a  spiral  (Fig.  695,  c).  In  pre- 
paring to  pupate,  the  larvas  leave  their  abode  among  living  plants  and 
travel  to  some  submerged  log  or  chunk  of  wood  and  burrow  into  it 
until  the  last  bit  of  the  case  is  concealed.  This  operation  sometimes 
requires  several  days  of  labor.  When  sufficient  depth  is  reached,  the 
larva  spins  a  silken  mesh  across  each  end  of  the  case. 

The  larva  of  a  species  of  Tricenodes  of  the  family  Leptoceridae 
makes  a  case  somewhat  similar  to  that  of  Phryganea;  this  is  described 
in  the  account  of  that  family. 


695. — Cases  of  phryganeids: 
case  of  Neuronia  postica;  b, 
case  of  old  larva  of  Phryganea 
vestita;  c,  case  of  young  larva  of 
Phryganea  vestita.     (After  Lloyd.) 


566 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Family  MOLANNID^ 


Fig.  696. — Case  of  Mo- 
lanna.  (After Lloyd.) 


The  only  members  of  this  family  the  larvae  and  cases  of  which 
have  been  described  in  this  country  belong  to  the  genus  Molanna. 
The  larvce  are  found  on  sandy  bottoms  of 
streams  and  of  lakes.  The  cases  have  been 
figured  by  several  writers,  and  are  very  char- 
acteristic in  form  (Fig.  696).  The  case  is  made 
of  grains  of  sand,  and,  has  .on  each  side  an  ex- 
tension, and  at  the  head  end  a  dorsal  hood, 
which  completely  protects  the  larva  when 
crawling  or  feeding. 

Family  LEPTOCERID^ 

The  larvs  are  caterpillar-like,  and  make 
portable  cases.  Most  species  live  in  standing 
water,  as  in  lakes,  ponds,  and  the  bays  of 
streams;  but  some  are  found  in  flowing  water 
and  on  wave-beaten  shores  of  lakes.  The  cases 
made  by  the  different  species  differ  greatly  in 
form  and  in  the  materials  used  in  their  con- 
struction. Among  the  better-known  species  are  the  following. 
Setodes  grandis. — The 

larva  of  this  species  lives 

among    aquatic    vegeta- 
tion in  ponds  and  lakes. 

Its  case  is  composed  en- 
tirely   of    silk,     and    is 

translucent,  so  that  the 

body  of  the  larva  can  be 

seen   through   it.      It   is 

cylindrical,  tapering,  and 

slightly  curved  (Fig.  697, 

a).     When  ready  to  pu- 
pate, the  larva  fastens  its 

case  to  th  e  stem  of  a  plant 

with  a  band  of  silk,  and 

closes  the  anterior  end  of 

the   case   with    a   silken 

membrane,   in    which 

there  is  a  central  slit  for 

the  ingress  of  water. 
Leptocerus  dncylus. — 

The   larva   is   found   on 

stones   in    the   riffles    of 

streams  and  on  the  stones 

of  wave-beaten   lake 

shores.    Itmakesacaseof  grains  of  sand.    The  larvas  studied  by  Lloyd 


Fig.  697. — Cases  of  leptocerids :  a,  case  of 
Setodes  grandis;  b,  case  of  Leptocerus 
ancylus;  c,  case  of  Mystacides  sepulchralis;  d, 
case   of    Tricenodes.    (After   Lloyd.) 


TRICHOPTERA  567 

at  Ithaca,  N.  Y.,  made  cases  in  the  form  of  curved  cornucopias  (Fig. 
697,  h);  those  found  in  Wisconsin  by  Vorhies,  who  first  described 
the  species,  make  a  case  with  decided  lateral  flanges  and  a  hood  that 
completely  covers  the  head  of  the  larva. 

Mystdcides  sepulchrdlis .■ — The  larva  of  this  species  and  its  case 
were  described  by  Lloyd.  It  was  found  in  ponds  and  in  slow  deep 
pools  of  creeks;  it  lives  among  the  rubbish  on  the  bottom.  The  case 
(Fig.  697,  c)  consists  of  a  slightly  tapering  tube  of  sand  or  of  minute 
fragments  of  bark,  lined  with  silk;  it  measures  about  12  mm.  in 
length.  On  opposite  sides  are  fastened  pine  needles,  or  grass  stems, 
or  slender  sticks,  which  extend  beyond  both  ends  of  the  case.  Before 
pupation  a  sheet  of  silk  with  a  minute  perforation  in  the  center  is 
spun  across  each  end  of  the  case. 

Triccnodes. — The  larvse  of  species  of  this  genus  live  in  ponds  and 
bays  of  creeks  among  branches  of  submerged  plants.  They  are  able 
to  swim  rapidly  from  place  to  place  through  the  open  water.  The  case 
(Fig.  697,  d)  is  made  of  thread-like  fragments  of  leaves  arranged  in  a 
spiral.  It  resembles  in  form  the  case  of  Phryganea  (Fig.  695, 6),  but  is 
much  smaller  and  more  flexible,  and  the  leaf-fragments  are  much 
narrower. 

Family  ODONTOCERID^ 

The  immature  stages  of  only  a  single  species  belonging  to  this  small 
family  have  been  described  in  this  country;  the  following  notes  re- 
garding this  species  are  from  Lloyd  ('21). 

Psilotreta  frontalis. — The  larvse  were  found  in  up- 
land streams  and  were  confined  to  the  riffles  and  the 
portions  of  the  streams  with  stony  bottoms.  The  case 
of  the  mature  larva  (Fig.  698)  is  a  slightly  curved 
cylinder  made  of  sand ;  cases  of  immature  larvas  differ 
only  in  being  tapered  toward  the  caudal  end.  The 
case  of  the  pupa  has  a  fiat  pebble  set  neatly  within 
the  aperture  at  each  end.  All  spaces  around  these 
"stones  are  tightly  closed  with  heavy  silk,  leaving  no 
apertures  for  the  circulation  of  water;  this  is  an  unusual 
feature  in  the  case-building  Trichoptera. 

During  their  early  life  the  larvae  are  free-moving, 
crawling  separately  over  the  bottom  of  the  stream.  But 
in  the  early  spring,  just  before  pupation,  the  larvae 
develop  a  remarkable  gregarious  habit.  Almost  all  of 
the  larvae  within  certain  areas  of  the  stream  congregate 
on  the  sides  of  a  few  selected  stones  in  such  numbers 
that  their  cases  are  sometimes  piled  one  on  top  of  another 
to  the  depth  of  an  inch  or  more,  while  other  stones  in  the  region  are 
entirely  uninhabited.  The  cases  are  always  placed  parallel  to  each 
other,  with  their  cephalic  ends  directed  toward  the  surface  of  the  water. 

Family  CALAMOCERATID^ 

This  is  a  small  family  of  which  only  one  American  larva  is  known. 
The  habits  of  this  species  have  been  described  by  Lloyd,  from  whose 
accounts  I  quote. 


568 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Ganonema  americdna. — The  larvae  were  found  abundant  in  alder- 
bordered  streams.  The  cases  made  by  this  species  differ  greatly 
from  those  of  other  described  American  caddice- 
worms.  The  case  is  made  of  a  single  piece  of  wood 
or  bark  or  a  twig;  this  is  hollowed  from  end  to  end, 
and  lined  with  silk.  Although  common,  they  are 
most  inconspicuous  among  the  debris  on  the  bottom 
of  the  stream.  Figure  699  represents  a  case  with  the 
silk  tube  cut  away,  except  around  the  larva. 

Family  LIAINOPHILID^ 

The  larvae  of  members  of  this  family  are  cater- 
pillar-like, and  are  found  in  a  great  variety  of 
aquatic  situations,  but  especially  in  ponds  and  slow- 
moving  streams,  even  in  those  that  become  dry 
during  the  droughts  of  summer;  a  few,  Neophylax, 
are  found  in  rapids.  Many  of  the  larvae  that  live  in 
quiet  water  can  be  kept  in  aquaria. 

The  cases  made  by  different  members  of  this 
family  differ  greatly  in  form  and  in  the  materials  used 
in  their  construction;  in  some  species  the  case  made 
by  an  old  larva  differs  greatly  from  that  made  by  it 
when  young. 

In  several  genera  of  this  family  the  larvae  make 
cylindrical  cases  of  sticks  and  fragments  of  bark, 
which  are  very  irregular  in  form;  one  of  these  is  represented  by 
Figure  700. 

To  this  family  belong  the  larvae  that  build  cases  of  the  "log-cabin 
type";  these  are  composed  of  sticks  or  of  pieces  of  grass  placed  cross- 
wise of  the  case  (Fig.  701) .  A  case  closely  resembling  this  in  plan  but 
differing  in  appearance  is  made  of  bits  of  moss. 

Among  the  larvae  that  change  the  form  of  their  case  when  full- 
grown  is  Limnophilus  combindtus,  which  is  described  by  Lloyd.    Dur- 


Fig.  699.-Caseof 
Ganonema 
a  me  r  icana. 
(After  Lloyd.) 


Fig.  700. — Case  of  limnophilid  larva. 


Fig.   701.— Log- 
cabin  type  of 


ing  early  life  this  larva  frequents  the  grass  and  sedges  that  fringe  the 
edges  of  streams,  and  makes  a  case  of  the  cross-stick  or  log-cabin  type. 
When  the  time  for  pupation  draws  near,  it  migrates  away  from  the 
grassy  area  and  makes  a  case  differing  entirely  in  appearance  from 


TRICIIOPTERA 


569 


the  lo^f -cabin  type.    Some  individuals  make  a  case  composed  of  small 
chunks  of  bark  (Fig.   702,  a);  others  make  cases  composed  almost 
entirely  of  shells  of  water  snails  (Fig.  702, 
b).  Different  combinations  of  these  types 
are  frequently  found. 

Some  larvffi  of  this  family  make  cases 
of  leaves;  these  are  either  fastened  so 
as  to  form  a  flat  case,  or  arranged  in 
three  planes  so  as  to  form  a  tube,  a  cross- 
section  of  which  is  a  triangle. 

Larvce  of  the  genus  Neophylax  make 
cases  of  sand  with  large  ballast  stones  at 
the  sides;  these  are  similar  in  form  to 
those  made  by  Goera  calcarata  of  the  next 
family,  but  are  more  slender,  smaller,  and 
made  of  lighter  material. 


Family  vSERICOSTOMATID^ 


Fig.  702. — Case  oiLimnophilus 
combinatus.  (After  Lloyd.) 


Fig.  703. — Case  of 
Helicopsyche. 
(From  Lloyd.) 


The  larvae  are  caterpillar-like,  and  are  found  in  streams  and  lakes. 
The  cases  made  by  members  of  the  different  genera 
differ  greatly  in  form;  the  three  following  are  our 
best -known  examples. 

Helicopsyche  horedlis. — The  larvse  of  this  species 
are  found  in  stony  streams  and  along  the  rocky  shores 
of  lakes.  They  make  a  spiral  case  of  grains  of  sand 
(Fig.  703).  This  case  so  closely  resembles  that  of  a 
snail  in  form  that  it  has  been  described  as  the  shell 
of  a  mollusk.  When  about  to  pupate,  the  larvae  fasten 
their  cases  to  a  submerged  rock;  at  this  time  they 
display  a  gregarious  instinct,  large  numbers  of  them  congregating 

within  a  very  small  area. 

They  are  more  easily  found 

at  this  time  than  in  their 

earlier   stages    when    they 

are  living  free   among  the 

sand  and  gravel  of  the  bot- 
tom of  the  stream. 

Goera     calcarata. — The 

larvae   of   this    species    are 

found    in     the     riffles     of 

streams  and    on  stones   in 

wave-beaten  areas  of   lake 

shores,    where   they    crawl 

over  the   surface   of  bare, 

current-swept  rocks.  The 
-Case  of  Goera  larval  case  (Fig.  704)  is  a 
at  a.       (Aft  er  ^y|-,g  made  of  fine  grains  of 

sand  on  each  side  of  which 


Fig.  704.- 
c  alcar 
Lloyd.) 


705. — Case  of 
Brachycentrus 
nigrisoma. 
(From  Lloyd.) 


570 


AN  INTRODUCTION  TO  ENTOMOLOGY 


are  fastened  heavy  ballast  stones,  usually  two  on  each  side. 
Brachycentrus  nigrisoma. — The  larva  of  this  species  builds  a 
case  of  the  remarkable  form  shown  in  Figure  705.  "It  is  constructed 
of  minute  twigs,  root-fibers,  and  fragments  of  wood  cut  to  the 
proper  length  to  give  even  and  straight  edges,  gradually  diverging 
toward  the  anterior  end.  In  cross-section  the  outer  surface  of  the  case 
is  square;  the  interior  is  lined  with  a  cylindrical  tube  of  tough  silk." 
"During  the  first  six  weeks  of  their  lives  the  larvae  are  active,  crawling 
about  in  quiet  eddies  along  the  banks  of  streams  in  search  of  food. 
After  this  period  they  move  to  the  center  of  the  stream  and  live 
sedentary  lives,  with  one  edge  of  the  larger  end  of  their  cases  firmly 
cemented  to  submerged  rocks  or  sticks.  Always  they  inhabit  positions 
on  the  exposed  surface  of  their  support  and  always  they  assume  the 
position  shown  in  Figure  705,  protruding  their  heads  slightly  and 
extending  their  prothoracic  legs  straight  forward.  The  mesothoracic 
legs  are  held  upward  while  the  metathoracic  legs  are  extended  to  the 
sides.  From  this  position  they  eagerly  seize  and  quickly  devour  small 
larvae  or  bits  of  vegetation  that  float  within  their  grasp."    (Lloyd.) 


CHAPTER  XXVII 


ORDER  LEPIDOPTERA^ 


The  Moths,  the  Skippers,  and  the  Butterflies 

The  winged  members  of  this  order  have  four  wings;  these  are  mem- 
branous, and  covered  with  overlapping  scales.  The  mouth-parts  are 
formed  for  sucking.     The  metamorphosis  is  complete. 

The  members  of  this  order,  the  moths,  the  skippers,  and  the 
butterflies,  are  well  known  to  every  ob- 
server of  nature.  Their  most  easily  ob- 
served distinguishing  characteristic  is 
that  which  suggested  the  name  of  the 
order,  the  scaly  covering  of  the  wings 
and  body.  Every  lad  that  lives  in  the 
country  knows  that  the  wings  of  moths 
and  butterflies  are  covered  with  dust, 
which  comes  off  upon  one's  fingers 
when  these  insects  are  handled.  This 
dust  when  examined  with  a  microscope 
is  found  to  be  composed  of  very  minute 
scales  of  regular  form;  and  when  a 
wing  is  looked  at  in  the  same  way,  the 
scales  are  seen  arranged  with  more  or 
less  regularity  upon  it  (Fig.  706). 
The  body,  the  legs,  and  other  appendages  are  also  covered  with  scales. 


Fig.    706.  -Part 
butterfly,   greatly 


L   wing   of 
magnified. 


Fig.  707. — Scales  of  Eiiclea  delphini.      (After 
Kellogg.) 


"Lepidoptera :  lepido  (kfircs,  Xeiridos),  scale;  pteron  {irrepdv),  a  wing. 
(571) 


572  AN  INTRODUCTION  TO  ENTOMOLOGY 

It  is  well  known  that  these  scales  are  merely  modified  setae. 
That  is,  they  are  setas  which,  instead  of  growing  long  and  slender 
as  setae  usually  do,  grow  ver>'  wide  as  compared  with  their 
length.  Even,'  gradation  in  form  can  be  found,  from  that  of 
the  ordinary  seta,  which  occurs  most  abundantly  upon  the  body, 
to  the  short  and  broad  scale,  which  is  best  seen  upon  the  wings 
(Fig.  707).  This  fact  was  pointed  out  by  Reaumur  nearh^  two 
hundred  3'ears  ago;  and  in  recent  times  the  morphological  iden- 
tity of  setas  and  scales  has  been  established  by  studies  of  their 
development.  Mayer  ('96)  gave  a  complete  account  of  the  de- 
velopment of  scales  and  illustrated  his  paper  by  most  excellent 
figures  of  all  stages  of  this  development. 

The  structure  of  scales  is  what  would  be  expected  from  the 
fact  that  they  are  modified  sets,  the  scales,  like  setse,  being 
hollow;  and  the  manner  of  their  attachment  to  the  cuticula  of 
the  body  and  its  appendages  is  the  same  as  that  of  the  setae,  each 
scale  being  provided  with  a  pedicel  which  fits  into  a  cup-like  socket 
in  the  cuticula. 

A  striking  feature  of  the  scales  of  Lepidoptera  is  the  mark- 
ings that  exist  on  their  exposed  surface.  These  may  consist  merely 
c    c     1      °^  many  very  fine  longitudinal  ridges  (Fig.  707);  or  they  may 
Fig.  708 .-Scale    \^Q  series  of  transverse  ridges  between  the  longitudinal  ones  (Fig. 
oi  Seryda    708). 
c  onstans . 

(After    Kel-  A     cross-section      of     certain     scales     indicates     that     the 

logg.)  ridges  are  produced  by  foldings  of  the    outer    wall    (?.  e.,    the 

w^all  of  the   scale  that   is   exposed 

when  the  scale  is  in  place  on  the  ^ 

wing).       Figure       709      represents         <5C3:x:;:«s5^^;^^^Ht;;5jJ^^^^ 
cross-sections  of  a  scale  illustrating  ^j;;?*?^^'^^'^"-^;^ 

this    condition.      In    some    scales, 
however,    the   lumen   of   the   scale 

has   been   filled   to   a   considerable    Fig.   709. — Cross-section  of  scales  of  Par- 
extent  by  chitin,  and  the  origin  of  nassus  sminthens.   (After  Kellogg.) 
the  ridges  is  not  so  obvious. 

The  scales  of  the  Lepidoptera  were  probably  developed  from  that  type  of 
setas  known  as  clothing  hairs,  and  were  primarily  merely  protective  in  function. 
This  is  doubtless  their  chief,  if  not  only,  function  on  most  parts  of  the  body, 
where  they  form  a  very  perfect  armor. 

The  development  of  ridges  on  the  surface  of  scales  adds  greatly  to  their 
stiflfness,  and  thus  increases  their  efficiency  as  a  protective  covering,  as  the 
corrugations  in  the  sheets  of  iron  used  for  covering  the  sides  of  buildings  add  to 
the  stiffness  of  the  metal. 

Upon  the  wings  a  covering  of  rigid  scales  would  serve  not  merely  to  protect 
the  wings  but  would  tend  to  stiffen  them,  and  thus  arose  a  secondary  function  of 
scales  which  has  resulted  in  the  perfecting  of  their  arrangement  upon  the  wings  in 
the  more  specialized  members  of  the  order  as  already  indicated. 

There  are  great  differences  among  the  insects  of  this  order  regarding  the  regu- 
larity of  the  arrangement  of  the  scales  upon  the  wings.  With  some  of  the  more 
generalized  moths  the  scales  are  scattered  irregularly  over  the  surface  of  the 
wings.  But  if  a  wing  of  one  of  the  more  specialized  butterflies  be  examined  with  a 
microscope,  the  scales  will  be  found  arranged  in  regular  overlapping  rows;  the 
arrangement  being  as  regular  as  that  of  the  scales  on  a  fish  or  of  the  shingles  on  a 
roof.  Figure  706  represents  a  small  portion  of  a  wing  of  one  of  the  more  special- 
ized butterflies,  where  the  arrangement  of  the  scales  is  most  perfect.  In  the 
upper  part  of  the  figure  the  membrane  is  represented  with  the  scales  removed. 

Even  in  those  insects  in  which  a  very  perfect  arrangement  of  the  scales  upon 
the  wings  has  been  attained,  great  differences  in  the  degree  of  perfection  of  this 
arrangement  exist  in  the  two  wings  of  the  same  side  and  in  the  different  parts  of 
the  same  wing.     The  arrangement  is  most  perfect  in  those  wings  and  in  those 


LEPIDOPTERA  573 

parts  of  each  wing  that  are  subjected  to  the  greater  strain  during  flight;  and  is 
more  perfect  in  swift-flying  species  than  in  those  of  slow  flight. 

The  taxonomic  vakxe  of  these  differences  in  the  arrangement  of  the  scales  of 
the  wings  of  the  Lepidoptera,  and  also  of  the  different  types  of  scales  found  in 
different  divisions  of  the  order,  was  investigated  by  Professor  Kellogg  ('94),  to 
whose  extended  account  the  reader  is  referred  for  a  discussion  of  this  phase  of  the 
subject. 

A  secondary  use  of  the  scales  of  the  Lepidoptera  is  that  of  ornamentation; 
for  the  beautiful  colors  and  markings  of  these  insects  are  due  entirely  to  the 
scales,  and  are  destroyed  when  the  scales  are  removed. 

The  various  colors  of  insects  and  of  other  animals  are  produced  in  quite 
different  ways ;  and  classifications  of  these  colors  have  been  proposed  based  on  the 
methods  of  their  production.  The  literature  of  this  subject  is  too  extensive  to  be 
referred  to  in  detail  here.  A  most  enjoyable  popular  account  is  given  by  Pro- 
fessor Kellogg  in  his  "/American  Insects"  (Kellogg  '08,  pp.  583-614)  and  a  de- 
tailed analysis  of  the  methods  of  the  production  of  color  is  given  by  Professor 
Tower  in  his  "Colors  and  Color-Patterns  of  Coleoptera"  (Tower  '03). 

Following  the  classification  of  Tower,  the  colors  of  the  scales  of  the  Lepi- 
doptera may  be  either  chemical,  physical,  or  chemico-physical.  The  chemical 
colors  are  produced  by  pigments  in  the  scales;  the  physical  colors  are  produced 
either  by  reflection,  refraction,  or  diffraction  of  light;  and  the  chemico-physical 
colors  are  produced  by  either  a  reflecting,  refracting,  or  diffracting  structure 
overlying  a  layer  of  pigment.  There  are  also  what  Tower  calls  combination 
colors  due  to  a  combination  of  the  causes  just  mentioned. 

As  the  production  of  colors  by  pigments  is  the  most  obvious  method  in  nature, 
it  is  the  one  to  which  the  colors  of  the  Lepidoptera  are  commonly  attributed. 
But  it  is  now  well  known  that  a  large  proportion  of  the  most  beautiful  colors  of 
these  insects  are  either  physical  or  chemico-physical;  this  is  true  of  the  various 
metallic  and  iridescent  colors  so  commonly  found  in  butterflies  and  many  moths. 

Explanations  of  the  methods  of  production  of  physical  colors  are  given  in  text- 
books on  physics;  it  is,  therefore,  only  necessary  here  to  point  out  a  feature  in 
the  structure  of  the  scales  of  Lepidoptera  that  results  in  the  production  of  these 
colors.  This  feature  is  the  presence  of  the  fine  longitudinal  striae  described 
above.  When  the  striae  are  very  fine  and  close  together  they  act  in  the  same  way  as 
does  a  diffraction  grating,  producing  the  beautiful  iridescent  colors.  Kellogg 
('94)  found  that  on  certain  scales  from  a  species  of  Morpho  the  striae  were  from 
,0007  mm.  to  .00072  mm.  apart,  or  at  the  rate  of  about  35,000  to  an  inch. 

The  fact  that  certain  colors  are  due  to  the  way  in  which  light  is  reflected 
from  the  scales  can  be  shown  by  the  following  experiment.  Place  on  the  stage  of 
a  microscope  the  wing  of  a  bright  blue  butterfly,  and  shade  the  specimen  so  that  it 
is  viewed  only  by  transmitted  light  from  the  mirror  of  the  microscope;  when 
examined  in  this  way  the  blue  color  wall  be  absent.  This  is  due  to  the  fact  that  the 
light  passing  directly  through  the  scales  is  not  broken  up,  and  only  the  colors 
produced  by  pigment  are  visible. 

There  is  still  another  function  of  the  scales  of  Lepidoptera;  they  may  serve  as 
the  outlets  of  scent  glands.  As  the  scales  that  serve  this  pvupose  are  found 
chiefly  on  the  wings  of  males,  they  have  received  the  special  name  of  androconia, 
signifying  male  dust.    See  page  100. 

In  the  suborder  Jugatee  and  in  "1^-^ ITca^^i- ^--Zj^Zr^Iir' Zr-^ 
some    of   the   more    generalized        -^  "^C~"~^^^S=     ^ni~5^'~ 

families  of  the  suborder  Frenatas,  ^—z::  ~,^j^^^^^^^^^^f^ 

there  are,  in  addition  to  the  more  — ^~^^jr~  ~-^^~^^^^^^^^^^ 

obvious   setae   and  scales,  many  '^  ~Z^^=    _J^^r~l,-^  ~3z  ~~ 
very  small,  hair-like  structures,         "^j^^^^^^^^^^-'^—  _r^ 

which  differ  from  setse  in  being  di-  — ^^:^^^^^^^^^_^g^^_r~'  ,zr'^_ 

rectly   continuous  with   the   cu-  lif-^C^^^^^^^^E*--'^'  "^  — ~~ 

ticula,  and  not  connected  with  it  j^.               t^    ^    *       •       c            1    .. 
1             ■    ■    .    ,^-              \     j.\.  Fig-  yio- — Part  of  a  wmg  of  an  aculeate 
by  a  jomt  (Fig.  710);  these  are  ^J^h,  with  most  of  the  scales  re- 
termed  the  fixed  hairs  or  aculecB.  moved  so  as  to  expose  the  aculeae. 


574 


AN  INTRODUCTION  TO  ENTOMOLOGY 


They  are  so  small  that  they  can  be  seen  only  by  the  aid  of  a  micro- 
scope, and  being  covered  by  the  scales  they  can  be  seen  only  in 
bleached  and  stained  or  denuded  wings. 

In  the  more  generalized  members  of  this  order,  the  venation  of 
the  wings  corresponds  quite  closely  to  the  hypothetical  primitive 
type.  The  most  striking  divergence  from  this  type  is  the  fact  that 
vein  M  is  only  three-branched.  This  is  probably  due  to  a  coalescence 
of  veins  M4  and  Cuj.  If  this  is  true,  the  vein  that  is  commonly  desig- 
nated as  vein  Cui  is  really  yein  M4  plus  Cui;  but  for  the  sake  of 
simplicity  it  seems  best  to  designate  it  ordinarily  as  vein  Cui.  For  a 
detailed  discussion  of  this  problem,  see  "The  Wing's  of  Insects,"  pp. 

334-337- 

Although  the  wings  of  Lepidoptera,  except  in  certain  specialized 
forms,  are  broadly  expanded,  there  are  but  few  cross-veins,  and  nor- 
mally no  accessory  veins. 

In  the  more  specialized  members  of  this  order  the  number  of  the 
wing- veins  is  reduced.  This  reduction  is  due  in  some  cases  to  the 
atrophy  of  a  vein  or  veins,  as,  for  example,  the  loss  of  the  main  stem 
of  vein  M  in  many  families;  in  other  cases,  it  is  due  to  the  coalescence 
of  adjacent  veins,  as,  for  example,  the  reduction  of  the  number  of 
branches  of  radius  or  of  media  which  has  taken  place  in  many 
members  of  the  order. 

In  many  genera  of  this  order  the  branches  of  radius  of  the  fore  wings 
anastomose  so  as  to  form  one  or  more  closed  cells;  these  have  been 
termed  accessory  cells. 

There  are  several  methods  by  which  the  fore  and  hind  wings  of 
Lepidoptera  are  held  together  in  flight,  in  order  to  insure  their 
synchronous  action.  In  the  suborder  Jugatae  the  posterior  lobe  of 
the  fore  wing  functions  either  as  a  jugum  (see  p.  61)  or  as  a  fibula 
(see  p.  62).     In  most  moths  the  wings  of  each  side  are  imited  by  a 

frenulum  (see  p.  61).  In 
some  moths  and  in  the 
skippers  and  butterflies, 
the  humeral  angle  of  the 
hind  wing  is  greatly  ex- 
panded and  projects  be- 
neath the  fore  wing;  this 
insures  the  synchronous 
action  of  the  two  wings 
and  renders  a  frenulum 
unnecessary ;  in  these 
forms,  which  doubtless 
descended  from  frenate 
Fig.  711.— Wings  of  Obrussa  ochrefasciella,  male,  ancestors,  the  frenulum 
(After  Braun.)  has  been  lost. 

The  frenulum  when 
well  developed  consists  of  a  bunch  of  bristles  situated  at  the  base  of 
the  costa  of  the  hind  wings,  on  the  costal  sclerite.  As  a  rule  these 
bristles  are  separate  in  females,  and  consolidated  into  a  single  strong, 
spine-like  organ  in  males. 


LEPIDOPTERA 


575 


Fig.  7 1 2 . — Diagram  of  a  fore  wing  of  a  noctuid  moth . 
The  lettering  is  explained  in  the  text.  (After 
Crosby  and  Leonard.) 

Six  transverse  lines  or  bands  and  three 


-This  is  a  band  extending  halfway 


In  some  of  the  more  generalized  Lepidoptera  there  is  a  series  of 
shghtly  curved,  spine-hke  setas  on  the  costa  of  the  hind  wing  near  the 
base,  which  aid  in  holding  the  wings  together.  These  setse  lie  beyond 
the  costal  sclerite,  not  on  it  as  does  the  frenulum;  they  are  termed 
by  Braun  ('19)  the  costal  spines.  The  frenulum  and  costal  spines 
are  both  present  in  some  moths  (Fig.  711). 

In   many  moths,   and  ^      tp         st 

especially  in  the  Noc- 
tuidae,  the  fore  wings  are 
marked  by  transverse 
lines  or  bands,  and  by 
spots  that  are  so  uniform 
in  position  in  different 
species  that  they  have 
been  given  names,  which 
are  used  to  designate 
them  in  the  descriptions 
of  those  species  in  which 
they  occur.  Figure  712 
is  a  diagram  of  a  fore 
wing  of  a  noctuid  moth 
indicating  the  positions 
of  the  named  lines  or  bands  and  spots, 
spots  have  been  named,  as  follows: 

The  basal  or  siibbasal  band  (Fig.  712,  b).- 
across  the  wing  near  its  base. 

The  transverse  anterior  band  (Fig.  712  t.  a). — -This  is  often  designated  as  the 
/.  a.  line;  in  some  English  books  it  is  termed  the  first  line. 

The  median  line  (Fig.  712,  m). 

The  transverse  posterior  band  (Fig.  712,  /.  p). — This  is  often  designated  as  the 
/.  p.  line;  it  is  the  secottd  line  of  English  authors. 

The  subterminal  band  (Fig.  712,  5.  /). 

The  terminal  band  (Fig.  712,  /). 

The  orbicular  or  round  spot  (Fig.  712,  0).  —  This  is  a  round  or  oval  spot  situ- 
ated in  the  discal  cell. 

The  reniform  spot  (Fig.  712,  r). — This  is  a  somewhat  kidney-shaped  spot  at  the 
end  of  the  discal  cell. 

The  claviform  spot  (Fig.  712,  c). — An  elongate  spot  extending  from  the  /.  a. 
line  toward  the  /.  p.  line  in  cell  Cu. 

The  typical  mouth-parts  of  adult  Lepidoptera  are  fitted  for  suck- 
ing.   In  some  families,  the  members  of  which  do  not  take  food  during 

the  adult  stadivmi,  the 
mouth-parts  are  vestigi- 
al; and  in  one  family, 
the  A-Iicropterygidae, 
which  is  doubtfully  in- 
cluded in  this  order,  the 
mouth-parts  are  of  the 
mandibular  type. 

^^  ,„„ ^saaaw^  ^^  those  families   in 

^^  ?        "^^^  which  the  typical  form 

of  the  mouth-parts  is 
well  shown,  the  only 
parts  of  these  organs  that 
are  well  developed  are 
the  maxillae  and  the  palpi,  the  other  parts  being  either  absent  or 


Fig.  713. — Maxillae  of  the  cotton-moth, 
and  the  tip  of  the  same  enlarged. 


576  AN  INTRODUCTION  TO  ENTOMOLOGY 

reduced  to  mere  vesti«jes.    When  only  one  pair  of  palpi  are  developed 

the}'  are  the  labial  palpi ; 
when  maxillary  palpi  are 
present  they  can  be  dis- 
tinguished by  their  at- 
tachment to  the  maxillae. 
If  the  head  of  a  but- 
terfly or  of  a  moth  in 
which  the  mouth-parts 
are  not  vestigial  be  ex- 

Tj-     ^^ .     ^  , .        r        -,1  amined,    there    will    be 

t\g.  714. — Cross-section  01  maxillae.  .         ^  .  -  . 

found    a    long    suckmg- 

tube  which  when  not  in  use  is  coiled  on  the  lower  side  of  the  head  be- 
tween two  forward -projecting  appendages.  This  long  sucking-tube  is 
composed  of  the  two  maxillce,  greatly  elongated,  and  fastened  to- 
gether side  by  side.  In  Figure  713  there  is  represented  a  side  view  of 
the  maxillae  of  a  moth;  and  in  Figure  714  a  cross-section  of  these 
organs.  Each  maxilla  is  furnished  with  a  groove,  and  the  two 
maxillae  are  so  fastened  together  that  the  two  grooves  form  a  tube 
through  which  the  liquid  food  is  sucked.  As  a  rule  the  maxillae  of 
insects  of  this  order  are  merely  fitted  for  extracting  the  nectar  from 
flowers,  but  sometimes  the  tips  of  the  maxillae  are  armed  with  spines, 
as  shown  in  Figure  713.  This  enables  the  insect  to  lacerate  the  tissue 
of  ripe  fruits  and  thus  set  the  juice  free,  which  is  then  sucked  up. 
Many  moths  do  not  eat  in  the  adult  state;  with  these  the  maxillae 
are  wanting.  The  two  forward-projecting  organs  between  which  the 
maxillae  are  coiled  when  present  are  the  labial  palpi.  In  some  moths 
the  maxillary  palpi  are  also  developed. 

The  compound  eyes  are  large  and  are  composed  of  many  small 
ommatidia.  The  ocelli,  when  present,  are  two  in  number;  they  are 
situated  one  on  each  side,  above  the  compound  eye  and  near  its  mar- 
gin; the  median  ocellus  is  lacking  throughout  the  order;  and  in  the 
butterflies,  the  skippers,  and  some  families  of  moths,  all  of  the 
ocelli  are  wanting. 

The  antennae  are  alwa^'s  conspicuous ;  they  differ  greatly  in  form 
in  dififerent  divisions  of  the  order,  and,  therefore,  furnish  characters 
that  are  much  used  in  the  classification  of  these  insects.  In  some 
families  the  basal  segment  of  the  antennae  is  greatly  enlarged  and  forms 
what  has  been  termed  the  eye-cap. 

Theprothorax  is  small,  being  reduced  to  a  collar  between  the  head 
and  the  wing-bearing  segments.  In  many  of  the  more  specialized 
Lepidoptera  the  pronotum  is  produced  on  each  side  into  a  flat  lobe 
which  in  some  cases  is  even  constricted  at  the  base  so  as  to  become 
a  stalked  plate;  these  lobes  are  the  patagia. 

The  legs  are  long  and  slender.  In  some  families  the  front  tibiae 
bear  on  their  inner  aspect  a  mobile  pad ;  this  is  termed  the  epiphysis; 
in  some  cases,  at  least,  it  is  a  combing  organ  used  for  cleaning  the 
antennae. 

A  special  feature  of  the  abdomen  is  the  presence  in  the  female 


LEPIDOPTERA 


57^ 


of  a  bursa  copulatrix;  that  of  the  female  of  the  milk-weed  butterfly 
is  figured  on  page  i6o. 

Close  to  the  junction  of  the  thorax  and  abdomen  there  is,  in  the  majority  of 
Lepidoptera,  a  pair  of  organs,  which  are  known  as  the  tympana.  These  are  situ- 
ated on  each  side  near  the  first  abdominal  spiracle.  Several  types  of  these  organs 
have  been  described  by  Forbes  ('i6)  and  by  Eggers  ('19),  which  are  characteristic 
of  certain  families  and  groups  of  families. 

The  first  ty])e  is  that  of  the  Geometridae;  it  appears  superficially  as  a  hollow 
bulla  located  immediately  below  the  spiracle,  oi)ening  forward  against  the  coxa  of 
the  hind  leg.     The  Pyralidas  have  rudimentary  tympana  in  the  same  position. 

The  second  type  is  likewise  wholly  on  the  abdomen,  but  it  is  higher  on  the 
body,  and  its  opening  faces  backward  towards  the  second  abdominal  segment. 
It  characterizes  the  Thatiridae  and  Drepanids. 

The  third  type  presents  a  variety  of  appearances.  Its  essential  part  is  a 
membranous  disk,  the  tympanum  proper,  on  the  metathorax  just  below  the  root  of 
the  wing.  In  the  Dioptidas,  Notodontidae,  Agaristida?,  and  a  few  noctuids  and 
lithosians,  the  disk  lies  exposed  or  is  merely  sunk  in  a  pit  at  the  junction  of  the 
thorax  and  abdomen.  In  other  moths  having  this  type  of  tympana  the  disk  is 
covered  by  a  hood  formed  by  the  side  of  the  first  segment  of  the  abdomen;  in 
the  Arctiida;,  Pericopidae,  Liparidae,  and  the  subfamily  Herminiinae  of  the  Noc- 
tuidas,  this  hood  lies  subdorsally,  wholly  above  the  spiracle;  while  in  the  majority 
of  the  Noctuidae  it  is  lower  and  incloses  the  spiracle,  in  some  cases  (Euteliinae, 
etc.)  being  supplemented  by  a  second  hood  formed  by  the  alula  of  the  hind  wing. 

The  function  of  the  tympana  is  probably  auditory,  as  Eggers  has  described 
chordotonal  organs  in  connection  with  them  in  several  families. 

In  the  Lepidoptera  the  metamorphosis  is  complete.  The  larvae 
are  known  as  caterpillars;  they  van,^  greatly  in  form  and  appearance, 
but  are  usually  cy- 
lindrical, and  pro- 
vided with  from  ten 
to  sixteen  legs, — ■ 
six  thoracic  legs 
and  from  four  to 
ten  abdominal  legs. 
The  thoracic  legs 
have  a  hard  exter- 
nal skeleton ;  and 
are  jointed,  taper- 
ing, and  armed  at 
the  end  with  a  little 
claw.  The  abdom- 
inal legs,  which  are 
shed  with  the  last 
larval  skin;  are 
thick,  fleshy,  with- 
out joints,  elastic  or 
contractile,  and 
armed  at  the  ex- 
tremity with  numer- 
ous minute  hooks 
(Fig.  715); they  are 

termed  prolegs.     When  all  five  pairs  are  present  they  are  borne  by 
the  third,  fourth,  fifth,  sixth,  and  tenth  abdominal  segments. 


Larva  of  a  hawk-moth. 


578 


AN  INTRODUCTION  TO  ENTOMOLOGY 


(a  and  b  from 


The  hooks  or  crochets  with  which  the  prolegs  of  caterpillars  are 
armed  vary  in  their  arrangement  in  different  families  and  thus  afford 
useful  characters  for  the  classification  of  these  larvae.  These  hooks 
are  usually  arranged  in  a  circle  or  in  rows  on  the  tip  of  the  proleg. 
When  they  are  in  a  single  row  or  series,  they  are  said  to  heuniserial; 
when  in  two  concentric  rows,  hiserial;  when  in  several  rows,  multi- 
serial.  When  the  hooks  of  a  row  are  uniform  in  length  throughout 
or  shorter  towards  the  ends  of  the  row,  they  are  said  toheuniordinal; 
when  they  are  of  two  alternating  lengths,  hiordinal;  when  of  several 
lengths,  multiordinal.  The  tip  of  a  proleg  on  which  the  hooks  or 
crochets  are  borne  is  termed  the  planta. 

In  most  lepidopterous  larvce  the  clothing  of  setae  is  comparatively 
inconspicuous;  such  larvae  are  commonly  termed  naked  in  contra- 
distinction to  the 
hairy  caterpil- 
lars. But  in  the 
so-called  naked 
larvae,  each  seg- 
ment of  the  body, 
when  not  too 
highly  special- 
ized, is  armed 
with  a  definite 
number  of  setae 
which  occupy 
definite  posi- 
tions. Each  seta  is  borne  on  a  small  chitinous  tubercle;  the  number 
of  these  setijerous  tubercles  and  the  positions  they  occupy  differ  in  the 
different  families,  and,  therefore,  afford  characters  which  are  much 
used  in  the  classification  of  Lepidoptera. 

The  small  tubercle  bearing  a  single  seta  (Fig.  716,  a)  is  evidently 
the  primitive  form  of  setiferous  tubercle ;  for  it  is  the  only  form  found 
in  the  more  generalized  families.  In  some  of  the  more  specialized 
families  the  tubercles  are  larger  and  many-haired  (Fig.  716,  h)\  this 
type  of  tubercles  is  termed  a  verruca;  it  is  characteristic  of  the  so- 
called  hairy  caterpillars,  as,  for  example,  the  larvae  of  most  of  the 
Arctiidae.  In  the  larvae  of  the  Saturnioidea  and  of  certain  butterflies, 
some  of  the  tubercles  are  spinose  projections  of  the  body-wall  (Fig. 
716,  c);  such  a  projection  is  termed  a  scolus. 

Some  caterpillars  are  clothed  with  more  or  less  nimierous  setae 
which  are  scattered  and  which  have  no  constant  position;  such  setae 
are  termed  secondary  setce,  in  contradistinction  to  those  borne  on 
setiferous  tubercles  which  are  of  a  definite  number  and  occupy  definite 
positions;  these  are  termed  primary  setce.  Among  the  setiferous 
tubercles  that  are  constant  in  position,  there  are  a  few  that  are  not 
present  in  the  first  instar  of  generalized  groups;  although  the  setae 
borne  by  these  tubercles  are  regarded  as  primary  setae  when  con- 
trasted with  secondary  setae,  they  are  distinguished  from  those  found 
in  the  first  instar  as  suhprimary  setce. 


Fig.   716. — Types  of  setiferous  tubercles. 
Dyar.) 


LEPIDOPTERA 


579 


In  order  to  make  use  of  the  primary  and  subprimary  seta  in 
classification,  it  is  necessary  that  each  of  these  setse  should  be  desig- 
nated by  a  distinctive  term.  The  terminology  most  generally  used 
is  that  proposed  by  Dyar  ('94),  who  was  the  first  author  to  base  a 
classification  of  lepidopterous  larvas  on  the  variations  in  the  arrange- 
ment of  the  setiferous  tubercles. 

The  terminology  of  Dyar  was  based  on  a  study  of  the  tubercles 
of  the  abdominal  segments.  He  recognized  on  each  side  of  each  ab- 
dominal segment,  except  the  last  two,  eight  tubercles,  which  he 
numbered  with  Roman  numerals  beginning  with  the  one  nearest  the 
middle  line  of  the  back;  the  ntmiber  VII  was  applied  to  a  group 
of  three  tubercles  on  the  outside  of  the  proleg,  or  in  a  corres- 
ponding position  in  the  legless  abdominal  segments.  Subsequent 
studies,  and  especially  those  by 
Forbes  ('io)and  Fracker  ('15), 
have  revealed  the  presence  of 
setiferous  tubercles  not  num- 
bered by  Dyar.  Figure  717,6, 
represents  the  arrangement  of 
the  tubercles  of  a  middle  ab- 
dominal segment  of  a  noctuid 
larva  as  figured  by  Forbes.  The 
tubercles  are  numbered  ac- 
cording to  the  terminology  of 
D}'ar,  with  the  addition  of 
tubercles  X,  Ilia,  and  IX,  not 
figured  by  Dyar.* 

The  arrangement  of  the 
setiferous  tubercles  on  the 
thoracic  segments  of  any  cater- 
pillar differs  to  a  considerable 
extent  from  that  on  the  ab-  Fig-  7i7-^Arrangement  of  setiferous  tu- 
1        •      1  j_       c  j^i  bercles  m  a  noctuid  larva:  a,  tubercles 

dommal  segments  of  the  same  ^f  ^  metathorax;  6,  tubercles  of  a 
msect.     In  Figure  717,  arepre-  middle    abdominal    segment.       (After 

sents  the  arrangement  of  the         Forbes.) 

tubercles  on  the  metathorax  and  h  that  of  the  tubercles  of  a  middle 
abdominal  segment  of  a  noctuid  larva  as  figured  by  Forbes  ('10). 
This  writer  also  figures  and  numbers  the  setae  on  the  head  of  a 
caterpillar. 

Fracker  ('15)  made  an  extended  study  of  the  classification  of 
lepidopterous  larvas,  which  was  based  quite  largely  on  the  variations 
in  the  number  and  positions  of  the  setiferous  tubercles;  and  his 
paper  is  illustrated  by  a  large  number  of  setal  maps.  This  writer 
proposes  a  new  terminology  for  the  setae,  using  Greek  letters  instead 
of  Roman  numerals. 


*In  diagrams  indicating  the  arrangement  of  setiferous  tubercles,  one  side  of  a 
single  segment  is  represented  as  if  cut  on  the  mid-dorsal  and  mid-ventral  lines, 
and  laid  flat.  The  anterior  edge  is  to  the  left,  and  the  mid-dorsal  line  at  the  up- 
per edge.  In  Figure  717  the  positions  of  the  .spiracle  and  of  the  proleg  are  also 
indicated. 


580  AN  INTRODUCTION  TO  ENTOMOLOGY 

Schierbeek  ('i6  and  '17)  proposes  still  another  terminology  for 
the  setae,  applying  a  Latin  name  to  each. 

A-Iost  caterpillars,  except,  as  a  rule,  the  larvae  of  butterflies, 
spin  a  cocoon.  In  some  instances,  as  in  the  case  of  silk-worms,  a 
great  amount  of  silk  is  used  in  the  construction  of  the  cocoon;  in 
others  the  cocoon  is  composed  principally  of  the  hairs  of  the  larva, 
which  are  fastened  together  with  a  fine  web  of  silk. 

The  pupas  of  the  Lepidoptera  are  typically  of  the  obtected  type; 
that  is,  the  developing  wings,  legs,  mandibles,  maxillae,  and  antennae 
are  glued  to  the  surface  of  the  body  (Fig.  718);  but  in  some  of  the 
more  generalized  forms  these  appendages  are  free.     In  the  Micro- 

jugatae,  which  are  provisionally  in- 
cluded in  this  order,  these  append- 
ages are  free,  the  pupae  resembling 
those  of  the  Trichoptera;  but  in  the 
Hepialidae  the  appendages  are  glued 
to  the  surface  of  the  body  as  in  the 
specialized  Frenatae.  In  some  of  the 
more  generalized  Frenatae,  as  the 
-Pupa  of  a  moth.  Nepticulidae,  and  in  the  Heliozelidae, 

the  appendages  are  all  free ;  between 
this  condition  and  that  of  the  truly  obtected  pupa  of  the  more 
specialized  Frenatae,  various  intergrades  exist. 

The  pupae  of  this  order  vary  also  in  the  number  of  segments  of  the 
body  that  are  movable.  The  eighth,  ninth,  and  tenth  abdominal  seg- 
ments are  always  fixed.  All  of  the.  other  segments  are  movable  in 
the  most  generalized  forms,  and  all  are  fixed  in  the  most  specialized 
forms;  there  are  various  intergrades  between  these  two  extremes. 
Different  pupae  of  this  order  differ  also  in  various  other  ways, 
thus  affording  characters  that  are  of  taxonomic  importance.  It  is 
only  recently  that  these  characters  have  been  used  in  an  extended 
manner.  A  pioneer  paper  in  this  field  is  that  of  Miss  Edna  Mosher 
('16). 

More  than  nine  thousand  species  of  Lepidoptera  are  known  to 
occur  in  America  north  of  Mexico.  These  represent  two  suborders 
and  seventy  families. 

In  popular  language  the  Lepidoptera  includes  two  quite  distinct 
groups  of  insects,  the  moths  and  the  butterflies.  Under  the  term 
moths  are  included  all  of  the  members  of  the  first  suborder,  the 
Jugatae,  and  the  larger  number  of  the  families  of  the  second  suborder, 
the  Frenatcc;  under  the  term  butterflies  are  included  the  remaining 
families  of  the  suborder  Frenatae.  These  two  groups  are  distinguished 
as  follows. 

The  moths. — These  are  the  insects  that  are  commonly  called  millers. 
Most  of  the  species  fly  by  night  and  are  frequently  attracted  to  lights. 
When  at  rest  the  wings  are  either  wrapped  around  the  body,  or 
spread  horizontally,  or  folded  roof -like  on  the  abdomen;  except 
in  a  few  cases  they  are  not  held  in  a  vertical  position  above  the  body. 
The  antennas  of  moths  are  of  various  forms;  they  are  usually  thread- 


LEPIDOPTERA  581 

like  or  feather-like;  only  in  rare  cases  are  they  enlarged  towards  the 
tip.  The  moths  have  been  termed  the  Heterocera*  by  many  ento- 
mological writers,  in  contradistinction  to  Rhopalocera,*  a  term  ap- 
plied to  the  butterflies. 

The  butterflies. — All  of  our  species  of  butterflies  fly  in  the  daytime; 
and,  with  few  exceptions,  they  fold  the  wings  together  above  the 
back  in  a  vertical  position  when  at  rest.  The  antenna;  are  thread-like, 
and  usually  with  a  club  at  the  tip.  It  was  this  feature  that  suggested 
the  term  Rhopalocera,  which  is  applied  to  them. 

The  group  butterflies  as  defined  here  includes  the  representatives 
of  two  quite  distinct  superfamilies,  the  Hesperioidea  or  skippers,  and 
the  Papilionoidea  or  true  butterflies.  The  distinctive  characters  of 
these  two  superfamilies  are  discussed  later. 

The  division  of  the  Lepidoptera  into  moths  and  butterflies  is  an 
artificial  one,  the  group  moths  including  representatives  of  both  of 
the  two  suborders  into  which  the  order  is  divided,  as  indicated  above. 
In  the  natural  classification,  the  primary  division  of  the  order  is 
based  on  differences  in  the  method  of  uniting  the  two  wings  of  each 
side,  and  on  differences  in  the  venation  of  the  hind  wings.  In  one 
suborder,  the  Jugate,  the  posterior  lobe  of  the  fore  wing  is  specialized 
so  as  to  form  an  organ,  a  jugum  or  a  fibula,  which  unites  the  fore  and 
hind  wings ;  and  the  venation  of  the  hind  wings  is  similar  to  that  of 
the  fore  wings.  In  the  other  suborder,  the  Frenatas,  the  two  wings 
of  each  side  are  united  by  a  frenulum  in  the  more  generalized  forms 
and  by  a  substitute  for  a  frenultmi  in  certain  specialized  forms ;  and 
the  venation  of  the  hind  wings  is  quite  different  from  that  of  the  fore 
wings. 

Hilbner's  Tentamen. — At  some  undetermined  date,  but  previous  to  1810  and 
probably  in  1806,  Jacob  Hiibner  distributed  a  two-page  work,  giving  a  classifica- 
tion of  the  Lepidoptera.  This  work  is  commonly  known  as  "Hiibner's  Tenta- 
men," tentamen  being  the  first  word  in  its  long  Latin  title.  Entomologists  differ 
regarding  the  standing  of  this  work;  some  believe  that  it  was  merely  privately 
printed,  while  others  regard  it  as  a  published  work  and  adopt  the  generic  names 
that  were  used  in  it.  This  difference  of  opinion  is  the  cause  of  serious  confusion  in 
the  names  of  certain  genera  and  families.  It  seems  to  the  writer  that  the  evi- 
dence supporting  the  view  that  the  "Tentamen"  was  published  is  conclusive. 
See  "Entomologists  Record  and  Journal  of  Variation,"  Vol.  31  (1919),  vSupple- 
ment. 

SYNOPSIS  OF  THE  LEPIDOPTERA 

The  families  comprising  this  order  are  grouped  in  various  ways  by  different 
writers;  none  of  these  groupings  can  be  regarded  as  final  in  the  present  state  of  our 
knowledge.     The  following  provisional  arrangement  has  been  adopted  for  use  in 
this  book. 
A.    The  Jugate  Lepidoptera. — -Moths  in  which  the  two  wings  of  each  side  are 

united  by  a  jugum  or  by  a  fibula,  p.  592 Suborder  Jugate 

B.    The  Microjugat^. 

C.    The  Mandibulate  Jugates.  p.  592 Family  Micropterygid^ 

CC.    The  Haustellate   Jugates.    p.    593 Family    Eriocraniid^ 

BB.     The  Macrojugat^. 

The    Swifts,    p.    594 Family  Hepialid.-e 

*Heter6cera:  hetero  (eVepos),  other,  different;  ceras  (K^pas),  a  horn. 
*Rhopal6cera :  rhopalon  {pdwaLof),  a  club;  ceras  (Ke'pas),  a  horn. 


582  AN  INTRODUCTION  TO  ENTOMOLOGY 

AA.    The  Frenate  Lepidoptera. — Moths,  skippers,  and  butterflies  in  which  the 
two  wings  of  each  side  are  united  by  a  frenulum  or  by  its  substitute,  a  large 

humeral  area  of  the  hind  wings,  p.  596 Suborder  Frenate 

B.  The  Generalized  Frenate. — Moths  that  are  supposed  to  retain  more 
nearly  than  other  Frenatas  the  form  of  the  primitive  Frenatse,  those  that 
were  the  first  to  appear  on  earth. 

C.  The  Aculeate  Frenat/e. — Moths  in  which  the  aculeas  are  distributed 
over  the  general  surface  of  the  wings. 

The   Incurvariids.   p.   598 Family  Incurvariid^ 

The  Nepticulids.  p.  600 Family  Nepticulid^ 

CC.  The  Non-aculeate  Generalized  Frenatae. — Moths  in  which  the 
aculeae  are  confined  to  small  areas  of  the  wings  or  are  absent. 

The    Carpenter  Moths,    p.  601 Family    Cossid.e 

The    Smoky  Moths,  p.  604 Family  Pyromorphid.e 

The     Dalcerids.     p.  605 Family  Dalcerid^ 

The     Flannel-moths,    p.    606 Family    Megalofygid.-e 

The     Slug-caterpillar-moths,     p.  608 Family  Eucleid.e 

The    Epipyropids.  p.  610 Family  Epipyropid^ 

BB.  The  Specialized  Frenate. — Moths,  skippers,  and  butterflies  that  de- 
part more  widely  than  do  the  Generalized  Frenatae  from  the  primitive  type  of 
Lepidoptera,  being  more  highly  modified  for  special  conditions  of  existence. 
An  indication  of  the  specialized  condition  of  these  insects  is  the  modified 
form  of  the  wings.  In  nearly  all  the  base  of  vein  M  has  been  lost  and  the 
branches  of  this  vein  joined  to  veins  R  and  Cu. 

C.  The  vSpecialized  MiCROFRENATi*;. — Frenulum-bearing  moths  which  are 
usually  of  small,  often  of  minute,  size.  In  many  of  these  moths  the  anal 
area  of  the  hind  wings  is  not  reduced,  having  three  anal  veins;  in  some 
others  the  hind  wings  are  very  narrow  and  a  broad  fringe  acts  as  a  sub- 
stitute for  the  membrane  of  the  anal  area. 

The  Acrolophids.  p.  611 Family  Acrolophid.e 

The    Tineids.    p.    611 Family    Tineid.-e 

The    Bag- worm  Moths,    p.  613 Family    Psychid.e 

The   Tischeriids.    p.    615 Family    Tischeriid.e 

The    Lj'Onetiids.    p.    616 Family    Lyonetiid.^ 

The   Opostegids.      p.     617 Family     Opostegid.^ 

The    Oinophilids.    p.    617 Family    Oinophilid.e 

The   Gracilariids.   p.   617 Family   Gracilariid^ 

The   Coleophorids.   p.   620 Family   Coleophorid.'E 

The   Elachistids.   p.   621 Family   Elachistid-E 

The   Heliozelids.   p.   622 Family   Heliozelid.e; 

The  Douglasiids.  p.  623 Family  Dougl.\siid.« 

The   CEcophorids.      p.     624 Family     O^cophorid.e 

The    Ethmiids.     p.    625 Family    Ethmiid.^ 

The   Stenomids.   p.   625 Family   Stenomid.e 

The  Gelechiids.   p.  625 Family  Gelechiid.e 

The    Blastobasids.    p.    628 Family    Blastobasid.-e  . 

The   Cosmopterygids.    p.    629 Family    Cosmopterygid.e 

The  Scythridids.   p.   631 Family  Scythridid.e 

The   Yponomeutids.  p.  631 Family  Yponomeutid.e 

The   Plutellids.   p.   632 Family   Plutellid.e 

.    The    Glyphipterygids.    p.    633 Family    Glyphipterygid.e 

The  Heliodinids.  p.  634 Family  Heliodinid.'E 

The   Clear-winged  Moths,  p.  634 Family  ^geriid^ 

Superfamily  Tortricoidea 

The  Olethreutids.  p.  639 Family  Olethreutid^ 

The   Typical   Tortricids.   p.   642 Family   Tortricid^ 

The    Phaloniids.    p.    643 Family    Phaloniid.-e 

The    Carposinids.    p.    644 Family    Carposinid.-e 

CC.     The  Pyralids  and  Their  Allies 
Superfamily   Pyr.\lidoidea 

The  Pyralids.    p.    644 Family    Pyralidid.-e 

The  Plume-moths,     p.    652 Family    Pterophorid^ 


LEPIDOPTERA  583 

The  Many-plume    Moths,    p.    653 Family    OrneodidvE 

The  Window- winged    Moths,    p.    653 Family    Thyridid/E 

The  Hyblaeids.    p.    655 Family     Hybl/Eid^ 

CCC.        The     Specialized      Macrofrenat^e.  —  Specialized       Frenats 

which  arc  usually  of  medium  or  large  size.     This  division  includes  certain 

moths  and  all  skippers  and  butterflies.    In  these  insects  the  anal  area  of  the 

hind  wings  is  reduced,  containing  only  one  or  two  anal  veins. 

D.     The  Frenidum-conservers. — Specialized  Macrofrenatae  in  which  the  two 

wings  of  each  side  are  typically  united  by  a  frenulum;  but  in  some  highly 

specialized  genera  of  some  families  (Sphingidae,  Geometrids,  and  Dre- 

panida;)  the  supplanting  of  the  frenulum  by  an  expanded  humeral  angle 

of  the  hind  wing  is  either  far  advanced  or  complete.     This  group  of 

families  includes  only  moths. 

The    hawk-moths    or    sphinxes,    p.    655 Family    Sphingid^ 

Superfamily  Geometroidea 

The    Geometrids.    p.    663 Family    Geometrid^ 

The    Manidiids.     p.     673 Family    Manidiid^ 

The  Noctuids  and  Their  Allies 

The  Dioptids.  p.  673 Family  Dioptid^ 

The  Prominents.  p.  674 Family  Notodontid^ 

The   Tussock-moths,   p.   679 Family   Lymantriid^ 

The   Noctuids.   p.   683 Family   NoCTUiDyE 

The  Foresters,    p.  697 Family  Agaristid^ 

The    Pericopids.    p.    698 Family    Pericopid^ 

The     Arctiids.     p.     699 Family     Arctiid/E 

The  Euchromiids.   p.   706 Family  Euchromiid^ 

The   Eupterotids.    p.    707 Family   Eupterotid^ 

The   Epiplemids.    p.    708 Family   Epiplemid^e 

The    Thyatirids.    p.    709 Family    Thyatirid/E 

The    Drepanids.    p.    710 Family    Drepanid^ 

DD.  The  Frenulum-losers. — SpeciaHzed  Macrofrenatae,  in  which  the 
frenulum  has  been  supplanted  by  a  greatly  extended  humeral  area  of 
the  hind  wings.  In  some  of  the  more  generalized  forms  a  vestigial 
frenulum  persists  (Bombycidae  and  Lacosomidae).  This  division  in- 
cludes three  groups  of  families:  the  Frenulum-] osing  moths,  the  skip- 
pers, and  the  butterflies.  The  grouping  together  of  the  families  in- 
cluded in  this  division  is  merely  provisional,  as  doubtless  the  loss  of  the 
frenulum  has  arisen  independently  several  times. 
E.      The   Frenulum-losing  Moihs. — In    these    moths  the  antennae  are 

usually  pectinate;  they  are  never  enlarged  into  a  club  at  the  tip. 

The  Lacosomids.    p.    712 Family    Lacosomid^ 

Superfamily  Saturnioidea 

The  Royal-moths,  p.  715 Family  Citheroniid^ 

The  Giant  Silk-worms,  p.  719 Family  Saturniid^ 

The    Silk-worms,    p.    727 Family    Bombycid.e 

The   Lasiocampids.   p.    728 Family   Lasiocampid^ 

EE.  The  Skippers. — These  are  day-flying  Lepidoptera  which  resemble 
butterflies  in  usually  holding  their  wings  erect  when  at  rest,  but  are 
distinguished  by  the  peculiar  venation  of  the  fore  wings,  vein  R  being 
five-branched,  and  all  of  the  branches  arising  from  the  discal  cell. 
The  antennee  are  enlarged  into  a  club  towards  the  tip. 
vSuperfamily  Hesperioidea 

The  Giant  Skippers,  p.  733 Family  Megathymid^ 

The  Common   Skippers,   p.   734 Family  Hesperiid^ 

EEE.  The  Butterflies. — Day-flying  Lepidoptera  that  hold  their  wings 
erect  when  at  rest,  that  have  clubbed  antennae,  and  that  diff'er  froin 
the  skippers  in  the  venation  of  the  fore  wings,  some  of  the  branches  of 
vein  R  coalescing  beyond  the  discal  cell. 

Superfamily  Papilionoidea 

The  Swallow-tails  and  the  Parnassians,  p.  740  Family  Papilionid^e 


584  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  Pierids.  p.  744 Family  Pierid^ 

The  Four-footed  Butterflies,  p.  750 Family  Xymphalid^ 

The  Metal-marks,  p.   767 Family  Riodinid^ 

The  Gossamer-winged  Butterflies,  p.  768 Family  LyC'EMD^ 

TABLES    FOR    DETERMINING    THE    FAMILIES    OF    LEPIDOPTERA 

TABLE  A 

A.'^  Wingless  or  with  vestigial  wings.     This  division  includes  only  females.     All 
males  of  Lepidoptera  are  winged. 

B.    The  larvae  case-bearers;  the  adult  female  either  remains  within  the  case  to 
lay  her  eggs,  or  leaves  the  case  and  sits  on  the  outside  of  it.  p.  6i3.Psychid^ 
BB.    The  larvae  not  case-bearers;  the  wingless  adult  not  in  a  case. 

C.     The  adult  female  remains  upon  her  cocoon  to  lay  her  eggs;  the  body  of 

the  adult  is  clothed  with  fine  hairs,  p.  679 Lymantriid/E 

CC.     The  adult  female  is  active  and  lays  her  eggs  remote  from  her  cocoon; 
the  body  of  the  adult  is  closely  scaled,  or  spined,  or  with  bristling  dark  gray 

hair.   p.    663 GeometriD/E 

CCC.     In  addition  to  the  above  there  are  some  arctic  species  of  the  Noc- 
tuidae  and  of  the  Arctiidas  in  which  the  wings  of  the  females  are  vestigial. 
AA.    With  well-developed  wings. 

B.  Fore  and  hind  wings  similar  in  form  and  venation,  the  radius  of  the  hind 
wings  being,  like  that  of  the  fore  wings,  five-branched  (Suborder  Jug.\t^). 
C.    Minute  moths  resembling  tineids  in  appearance. 

D.     Adult  moths  with  well-developed  functional  mandibles;  subcosta  of 

the  fore  wings  forked  near  its  middle,  p.  592 Micropterygid^ 

DD.      Mandibles   of  the   adult    vestigial;  maxillag   formed   for   sucking; 

subcosta  of  fore  wings  forked  near  its  apex.  p.  593 EriocraniidvE 

CC.    Moths  of  medium  or  large  size,  without  functional  mouth-parts,  p.  594 

HEPIALIDyE 

BB.  Fore  and  hind  wings  differing  in  form  and  venation;  the  radial  sector  of 
the  hind  wings  being  unbranched,  and  vein  Ri  of  the  hind  wings  usually 
coalesced  with  vein  Sc  (Suborder  Frenat^). 

C.     Antennae  of  various  forms,  but  rarely  clubbed  as  in  the  skippers  and 

butterflies;  if  the  antennae  are  clubbed  the  hind  wings  bear  a  frenulum. 

D.     The  fringe  on  the  inner  angle  of  the  hind  wings  as  long  as,  or  longer 

than,  the   width  of   the   wing;    the   hind    wings  often   lanceolate,  but 

never  fissured.     (Microfrenatas.)     Pass  to  Table  B. 

DD.     Hind  wings  much  broader  than  their  frijige,  and  not  lanceolate. 

E.    Wings  fissured  deeply. 

F.      Each   wing  divided  into  six  lobes,   p.   653 Orneodid.« 

FF.     Wings  never  more    than  four-lobed;  usually     the   fore   wings. 

bilobed  and  the  hind  wings  trilobed.  p.  652 Pterophorid^ 

EE.    Wings  not  fissured  or  the  front  wings  slightly  fissured. 

F.  Fore  wings  very  narrow,  the  width  at  the  middle  less  than  one- 
fourth  the  length  of  the  wing;  a  considerable  part  of  the  hind 
wings,  and  in  many  cases  of  the  fore  wings  also,  free  from  scales; 
inner  margin  of  fore  wings  and  costal  margin  of  hind  wings  with  a 

series  of  recurved  and  interlocking  spines,  p.    634 ^geriid^ 

FF.  Wings  scaled  throughout,  or  if  clear  with  the  fore  wings  trian- 
gular in  outline;  wings  not  interlocking  at  middle  with  series  of  re- 
curved spines. 

G.     With  a  double  series  of  enlarged  and  divergent  scales  along 
vein  Cu  of  the  hind  wings  below;  wings,  body,  and  legs  very 

long.      {Agdistis.)   p.   652 Pterophorid^. 

GG.    Without  such  scales  on  vein  Cu  of  the  hind  wings. 

H.  Hind  wings  with  three  anal  veins.  Care  must  be  taken  not 
to  mistake  a  mere  fold  in  the  wing  for  a  vein.  When  there  is 
no  thickening  of  the  membrane  of  the  wing  along  a  fold,  it  is 
not  counted  as  a  vein. 


LEPIDOPTERA  585 

I.  \' cins  Sc  -L  Ri  and  Rs  of  the  hind  wings  grown  together  for  a 
greater  or  less  distance  between  the  apex  of  the  discal  cell 
and  the  apex  of  the  wing,  or  in  some  cases  separate  but  very 
closely  parallel,  p.  644 Pyralidid^ 

II.  Veins  Sc  +  Ri  and  R<;  of  the  hind  wings  widely  separate 
beyond  the  apex  of  the  discal  cell. 

J.     The  fringe  on  the  anal  angle  of  the  hind  wings  con- 
siderably longer  than  elsewhere  (sometimes  not  obviously 
so  in  rubbed  specimens) ;  the  spurs  of  the  tibiae  more  than 
twice  as  long  as  the  width  of  the  tibiae.     (Microfrenatae.) 
Pass  to  Table  B.* 
J  J.    The  fringe  on  the  anal  angle  of  the  hind  wings  not  longer 
than  elsewhere  or  but  slightly  so;  the  spurs  of  the  tibiae 
about  as  long  as  the  width  of  the  tibiae. 
K.     Veins  Sc   +   Ri  and  Rs  of  the  hind  wings    grown 
together  to  near  the  end  of  the  discal  cell  (Fig.  734),  or 
anastomosing  beyond  the  middle  of  the  cell  (Fig.  730). 
L.     Small  moths,  chiefly  of  a  smoky  black  color,  with 

thinly   scaled   wings,   p.   604 Pvromorphid^ 

LL.     Moths  of  medium  size,  and  densely  clothed  with 
long,  woolly  hairs,  which  are  light-colored  or  brown. 

p.  606 MEGALOPYGID.E 

KK.    Veins  Sc  +  R,  and  Rs  of  the  hind  wings  separate  or 
grown  together  for  only  a  short  distance. 
L.     1st  and  2d  anal  veins  of  the  fore  wings  united  by  a 
cross-vein. 
M.     Accessory    cell    present  (Hypoptinae).    p.   603. 

CossiD^ 

MM.     Accessory  cell  absent,  p.   613  . ..  .Psychid.^ 

LL.     1st  and  2d  anal  veins  not  united  by  a  cross-vein. 

M.    Vein  M2  of  the  fore  wings  arising  from  the  discal 

cell   nearly   midway   between   veins   Mi   and   M3. 

N.    Vein  M3  of  both  fore  and  hind  wings  coalesced 

with  vein  Cui  for  a  considerable  distance  beyond 

•   the  end  of  the  discal  cell.  p.  673.  .  ..Dioptid.« 

NN.     Veins  M3  and  Cui  not  coalesced  beyond  the 

end  of  the  discal  cell. 

O.      Veins   R2   and   Rj   coalesced   at   base,    but 
separate  from   veins   R^   and   Rj,    which   also 

coalesce    at    base.    p.    712 L.\cosomid^ 

00.    Veins  R,,   Rj,   R4,  and  R5  united  at  base. 

p.    727 BOMBYCID.E 

MM.      Vein  M,  of  the  fore    wings    emerging    from 
the  discal  cell  nearer  to  cubitus  than  to  radius, 
causing  cubitus  to  appear  four-branched. 
N.     Fore  wings  with  an  accessory  cell. 

O.     Moths  with  heavy,   spindle-shaped  bodies, 
and   narrow,    strong   wings,    p.    601.  Cossid/E 
00.    Moths  in  which  the  body  is  slender  and  the 
wings  are  ample. 

P.     Wings  ample  (fore  wings  not  half  longer 
than    wide);  mouth-parts  vestigial,    p.  605. 

D.\LCERID.E 

PP.     Wings    more    or    less    oblong,    usually 
twice  as  long  as  wide;  mouth-parts  usually 
developed    with    scaled    tongue.       (Micro- 
frenatae.)   Pass  to  Table  B. 
NN.      Fore    wings    without    an    accessory    cell. 

*A  few  of  the  Eucleidae  present  these  characters;  but  with  these  moths  the 
wings  are  broad  and  the  base  of  media  extends  through  the  middle  of  the  discal 
cell. 


586  AN  INTRODUCTION  TO  ENTOMOLOGY 

O.  With  some  of  the  branches  of  radius  of  the 
fore  wings  coalesced  beyond  the  apex  of  the 
discal   cell.   p.   608 Eucleid^ 

00.  With  each  of  the  five  branches  of  radius 
of  the  fore  wings  arising  from  the  discal  cell. 

p.  655 Hybl^id^ 

HH.     Hind  wings  with  less  than  three  anal  veins. 

I.  Fore  wings  with  two  distinct  anal  veins  or  with  the  anal 
veins  partly  grown  together  so  as  to  appear  as  a  branched 
vein. 

J.  Anal  veins  of  fore  wings  partly  grown  together  so  as  to 
appear  as  a  branched  vein.  p.  613 Psychid^ 

JJ.  Fore  wings  with  two  distinct  anal  veins  (Harrisina). 
p.  605 Pyromorphid^ 

II.  Fore  wings  with  a  single  fully  preserved  anal  vein,  This 
is  the  second  anal  vein;  the  first  anal  vein  is  absent  or 
represented  merely  by  a  fold;  and  the  third  anal  vein  is 
short,  not  reaching  to  the  margin  of  the  wing,  or  is  wanting; 
usually  when  the  third  anal  vein  is  present  it  is  joined  to 
the  second  anal  vein,  so  that  the  latter  appears  to  be 
forked  towards  the  base. 

J.     Frenulum  present.     In  most  cases,  the  humeral  angle  of 
the  hind  wings  is  not  greatly  expanded. 
K.     The  five  branches  of  radius  and  the  three  branches  of 
media  of  the  fore  wings  all  present,  and  each  one  arising 

separate  from  the  discal  cell.  p.  653 Thyridid^ 

KK.  With  some  of  the  branches  of  radius  of  the  fore 
wings  stalked,  or  else  with  some  branches  coalesced  to 
the  margin  of  the  wing. 

L.    The  fringe  on  the  anal  angle  of  the  hind  wings  con- 
siderably longer  than  elsewhere. 

M.     Veins  Sc  and  R  of  the  hind  wings  seperate,  but 

usually  connected  by  a  more  or  less  distinct  basal 

part  of  vein  Ri.   (Microfrenatae.)  Pass  toTableB. 

MM.     Veins  Sc  and  R'of  the  hind  wings  fused  for  a 

greater  or  less  distance. 

N.      OcelH    present,    p.  683 Noctuid^ 

NN.      Ocelli    absent,    p.    704 Lithosiin.-e 

LL.    The  fringe  on  the  anal  angle  of  the  hind  wings  not 
considerably  longer  than  elsewhere. 
M.     The  basal  part  of  vein  Ri  of  the  hind  wings,  the 
part  extending  from  radius  to  the  subcosta,   ap- 
pearing like  a  cross-vein  which  is  as  stout  as  the 
other  veins;  veins  Sc  -+-  Ri  closely  parallel  to  the 
end  of  the  discal  cell  or  beyond,  p.  655.  Sphingid^ 
MM.     The  basal  part  of  vein  Ri  of  the  hind  wings 
rarely  appearing  like  a  stout  cross-vein;  when  it 
does  appear  like  a  cross-vein,  veins  Sc  +  Ri  and 
Rs  strongly  divergent  from  the  point  of  union  of 
veins  Ri  and  Sc. 

N.  Vein  M2  of  the  fore  wings  not  more  closely 
joined  to  cubitus  than  to  radius,  cubitus  being 
apparently  three-branched. 

O.     The  basal  part  of  the  subcosta  of  the  hind 

wings  extending  from  the  base  towards  the 

apex  of  the  wing  in  a  regular  curve. 

P.    Vein  M2  of  the  hind  wings  arising  nearer  to 

cubitus  than  to  radius;  vein  Mi  of  the  hind 

^  wings  joined  to  radius  before  the  apex  of 

the  discal  cell.  p.  709 Thyatirid^ 

PP.    Vein  Mj  of  the  hind  wings  either  wanting 


LEPIDOPTERA  587 

or  present,  but  when  present  arising  either 
midway    between    radius    and    cubitus,    or 
nearer  to  radius  than  to  cubitus;  vein  Mi  of 
the  hind  wing  joined  to  radius  at  or  beyond 
the  apex  of  the  discal  cell. 
Q.     Veins  Sc  and  R  of  the  hind  wings  sepa- 
rate  at   the   extreme   base,    then   closely 
approximate  or  fused  for  a  greater  or  less 
distance. 

R.  Tongue  (maxillae)  wanting;  fore 
wings  with  veins  R2  +  3  and  R4  +  5 
stalked  together,  northern  species  with 
hyaline    dots   on   fore   wings,    p.    707 . 

EuPTEROTIDyE 

RR.      Tongue  present,   often  weak;  fore 
wings  fully  scaled;  usually  with  acces- 
sory   cell    or    with    veins    R3    and    R4 
stalked  together,  p.  674.   Notodontid^ 
QQ.    Veins  Sc-t-Ri  and  Rs  of  the  hind  wings 
sharply  divergent  from  close  to  base  of 

the  wing.  p.  704 Epiplemid/E 

00.  The  basal  part  of  the  subcosta  of  the  hind 
wings  joined  to  radius  for  a  considerable 
distance  and  then  making  a  prominent  bend 
towards  the  costal  margin  (Fig.  909).  Veins 
Rj  and  R4  of  the  fore  wings  separate  from  each 
other.  (See  also  000.)  p.  712.  Lacosomid^ 
000.  The  basal  part  of  the  subcosta  of  the 
hind  wings  making  a  prominent  bend  into  the 
humeral  area  of  the  wing,  and  usually  con- 
nected to  the  humeral  angle  by  a  strong  cross- 
vein  (Fig.  817). 
P.      Antennae    clubbed,    p.  673.  .Manidiid^ 

PP.      Antennae    not  clubbed,    p.  663 

Geometrid^ 

NN.      Vein   M2   of   the   fore   wings   more  closely 
joined  to  cubitus  than  to  radius ;  cubitus  being  in 
most  cases  apparently  four-branched. 
O.     Small  moths,  with  the  apex  of  the  fore  wings 

sickle-shaped,    p.     710 Drepanid^ 

00.     Apex  of  the  fore  wings  not  sickle-shaped. 
P.     Vein  Sc  of  the  hind  wings  apparently  ab- 
sent, being  fused  except  at  the  extreme  base 
with  radius.     Care  should  be  taken  not  to 
mistake  vein  Mi  for  radius  (see  Fig.  897). 

p.  706 EUCHROMIID^ 

PP.  Veins  Sc  and  R  of  the  hind  wings  dis- 
tinct and  parallel  to  the  point  where  vein  R 
separates  from  the  discal  cell,  and  then 
approaching  very  close  or  fusing  for  a  short 
distance.  (See  also  PPP.) 
Q.      Small   moths    with    snow-white    wings 

(Eudeilinia).    p.    710 Drepanid^ 

QQ.        Moths  that  are  not  white. 

R.  Vein  R5  of  the  fore  wings  stalked  with 
veins  R3  and  R4  (Chrysauginae) .  p.  644. 

Pyralidid^ 

RR.     Vein  Rs    free    {Meskea).     p.    653. 

THYRIDID.E 

PPP.    Veins  Sc  and  R  of  the  hind  wings  not  as 
described  under  PP  above. 
Q.    Antennae  more  or  less  thickened  towards 
the    tip.    p.    697 Agaristid^ 


AN  INTRODUCTION  TO  ENTOMOLOGY 

QQ.    Antenna^  not  clubbed. 

R.  Dorsal  surface  of  the  first  abdominal 
segment  with  two  prominent  rounded 
bosses,  the  hoods  of  the  tympana. 
These  hoods  are  wholly  above  the 
spiracles,  and  separated  by  only  about 
one-third  of  the  width  of  the  abdomen. 
Black  moths  with  white  or  yellow 
bands  or  spots  on  the  wings  and  often 
with  metallic  tints.  Found  only  in  the 
Far  West  or  in  the  Gulf  States,  p.  698. 

Pericopid/e 

RR.  Hoods  of  the  tympana  less  con- 
spicuous dorsally  and  more  widely 
separated. 

S.     Veins  Sc  and  R  of  the  hind   wings 

extending  separate,  or  the  two  joined 

for  a  short  distance  near  the  base  of 

the  wing;  ocelli  present. 

T.      White    or    yellow    species,  with 

palpi  not  reaching  the  middle  of 

the  smooth-scaled  front;  vein  Cu 

apparently  four-branched    in  both 

fore     and    hind    wings    {Haploa). 

p.  700 Arctiid.« 

TT.  Species  with  longer  palpi,  and 
vein  Cu  of  the  hind  wings  ap- 
parently three-branched,  or  species 
of    a    gray    ground  color,  p.    683. 

NoCTUIDiE 

SS.  Veins  Sc  and  R  of  the  hind  wings 
fused  or  closely  parallel  near  the 
middle  of  the  discal  cell,  or  con- 
nected by  a  short  cross-vein  (the 
free  part  of  vein  Ri);  ocelli  absent. 
(See  alsoSSS.)  p.  679.  Lymantriid.'E 
SSS.  Veins  Sc  and  R  of  the  hind 
wings  united  for  one-fifth  or  more  of 
the  length  of  the  discal  cell. 
T.     Ocelli  present  (ArCtiinae).  p.  700. 

Arctiid^ 

TT.     OcelH  absent. 

U.    Fore  wings  with  raised  tufts  of 
scales  (Nolinae).  p.  705.Arctiid^ 
UU.    Fore  wings  smoothly  scaled. 
V.     Vein  M^  of  the  hind  wings 
well  developed    and  aris- 
ing slightly  nearer  to  vein  M^ 
than  to  vein  Mi  {Menopsimus) . 

p.683    NOCTUID^ 

VV.  Vein  M^  of  the  hind 
wings  arising  much  nearer  to 
vein  M3  than  to  vein  Mi,  or 
wanting  (Lithosiinas).  p.    704. 

Arctiid^ 

J  J.    Frenulum  absent. 

K.     Vein    Cu  of    both    fore   and  hind  wings   apparently 
four-branched. 

L.  Small  moths  with  slender  bodies,  and  with  the  apex 
of  the  fore  wings  sickle-shaped ;  humeral  veins  absent, 
p.   710 Drepanid^ 


LEPIDOPTERA  589 

LL.    Moths  of  various  sizes,  but  with  robust  bodies, 

and  with  the  apex  of  the  fore  wings  not  sickle-shaped; 

hind  wings  with  humeral  veins,  p.  728.Lasiocampid^ 

KK.     Vein   Cu  of  both  fore   and  hind  wings  apparently 

three-branched. 

L.    Robust  moths  of  medium  or  large  size,  with  strong 

wings,     p.     714 S.\TURNIOIDE.\ 

LL.     Small  moths  with  slender  bodies  and  weak  wings 

(Dyspteris).   p.   667 Geometrid^ 

CC.    Antennee  thread-like  with  a  knob  at  the  extremity;  hind  wings  without 
a  frenulum;  ocelli  wanting. 

D.  Radius  of  the  fore  wings  five-branched,  and  with  all  the  branches 
arising  from  the  discal  cell;  club  of  antennae  usually  terminated  by  a  re- 
curved hook.     The  skippers,    p.  732 Hesperioide.\ 

DD.  With  some  of  the  branches  of  radius  of  the  fore  wings  coalesced  be- 
yond the  apex  of  the  discal  cell;  club  of  antennte  not  terminated  by  a  re- 
curved hook.     The  Butterflies,     p.  739 Papilionoidea 

TABLE  B 

THE  FAMILIES  OF  THE  MICROFRENAT^ 

Contributed  by  Dr.  William  T.  M.  Forbes 

A.     Basal  segment  of  the  antennae  enlarged  and  concave  beneath,  forming  an 
eye-cap. 

B.    Fore  wings  with  radius,  media,  and  cubitus  unbranched.  p.  6i7.0postegid^ 
BB.    Fore  wings  with  more  complex  venation. 

C.     Discal  cell  of  fore  wings  very  short  and  trapezoidal,  or  absent,  p.  600. 

Nepticulid^. 

CC.    Discal  cell  more  than  half  as  long  as  the  wing. 

D.     Discal  cell  oblique,  its  lower  outer  corner  nearly  touching  the  inner 

margin.     (A  few  species  only.)     p.  628 Blastobasid.e 

DD.    Discal  cell  central  in  the  wing. 

E.     Labial  palpi  minute  and  drooping,  or  absent,  p.  616..  .Lyonetiid^ 
EE.    Labial  palpi  moderate,  upcurved.   {Phyllocnistis  in  part,  and  one  or 

two  Florida  genera.)   p.  617 Gracilariid^ 

AA.    Basal  segment  of  antennas  not  forming  an  eye-cap. 

B.     Palpus  with  the  first  segment  relatively  very  large,  normally  upcurved  to 
the  middle  of  the  front;  when  the  palpus  is  short  the  first  segment  is  longer 

than  the  second,  p.  611 Acrolophid^ 

BB.     First  segment  of  palpus  small. 

C.     Labial  palpi  bristled  on  the  outer  side  of  the  second  segment. 

D.  Aculeae  present  over  the  general  surface  of  the  wings;  female  with 
piercing  ovipositor;  antennae  typically  smooth  and  velvety-looking, 
with  fine  bristles,  or  narrow,  closely  appressed  scales,  sometimes  very 

long.  p.  598 Incurvariid^ 

DD.  Aculeas  absent,  or  present  only  in  a  small  area  at  the  base  of  the 
discal  cell;  ovipositor  membranous,  retractile;  antennae  typically  rough, 
with  an  outer  whorl  of  erect  scales  on  each  segment,  rarely  as  in  D. 

p.  61 1 TlNEID.^ 

CC.    Labial  palpi  scaled  or  loose-hairy  only. 

D.    Maxillary  palpi  well  developed  and  of  the  folded  type. 

E.     Fore  wings  with  all  veins  present  and  with  vein  R;  running  to  the 
outer  margin;  hind  wings  narrow;  vertex  with  a  small,  loose  tuft  only 

(Acrolepia).    p.  632 Plutellid.-e 

EE.    Fore  wings  with  vein  R5  extending  to  the  costa  or  absent. 

F.    Head  smooth;  hind  wings  narrow-lanceolate;  fore  wings  down- 
curved  at  apex.  p.  617 Oinophilid^ 

FF.    Vertex  rough  or  rarely  smooth  in  forms  with  ample  hind  wings; 
fore  wings  flat. 

G.     Aculeas  present,  etc.,  as  in  D  under  C  above,    p.  598 

Incurvariid^ 


590  AN  INTRODUCTION  TO  ENTOMOLOGY 

GG.    Aculese  absent,  etc.,  as  in  DD  under  C  above,  p.  6i  i  ..Tineid^ 
DD.    Maxillary  palpi  porrect  or  vestigial. 

E.     Vertex  and  upper  face  at  least  with  dense  bristly  hairs;  third  seg- 
ment of  labial  palpi  fusiform  and   equal  to  the  second  in  length. 
F.    Aculeae  present,  etc.,  as  in  D  under  C  above,  p.  598  .  Incurvariid^ 
FF.    Aculeae  absent,  etc.,  as  in  DD  under  C  above,  p.  6ii.Tineid/e 
EE.    Face  at  least  smoothly  and  shortly  scaled;  third  segment  of  labial 
palpus  long  and  pointed,  or  very  short  in  forms  with  roughest  vestiture. 
F.    Hind  wings  ample,  with  well-marked  anal  angle,  often  wider  than, 
their  fringe. 
G.     Hind  wings  with  veins  Mi  and  M^  both  lost,  only  one  vein 

being  associated  with  the  R-stem.       p.  644 Carposinid^ 

GG.    Hind  wings  with  vein  Mi  preserved,  associated  with  the  R- 
stem. 

H.  Vein  Cu2  of  the  fore  wings  arising  from  a  point  before  the 
outer  fourth  of  the  discal  cell;  palpus  more  or  less  triangular, 
with  a  short,  blunt,  third  segment,  roughly  scaled  (short  and 
nearly  smooth  in  Laspeyresia,  in  which  there  is  a  strong  fringe 
on  base  of  vein  Cu  of  the  hind   wings,   save   in  L.   lautana). 

p.  639,  642 Olethreutid^  and  Tortricid/e 

HH.  Vein  Cu2  of  the  fore  wings  arising  from  the  outer  fourth  of 
the  discal  cell,  save  in  a  few  Glyphipter\'gidas,  which  have  short, 
smooth-scaled  palpi,  or  second  segment  tufted  and  third  long 
and  slender,  and  no  fringe  on  vein  Cu. 

I.  Vein  1st  A  of  fore  wings  lost  completely;  hind  wings  with 
veins  Rs  and  Mi  connate,  approximate,  or  stalked. 

J.  Palpi  with  third  segment  long,  slender,  and  tapering, 
often  exceeding  vertex,  normally  close-scaled,  save  in 
male  Anarsia  where  veins  R4  and  R;  are  stalked  and  both 
run  to  the  costa.  p.  625 Gelechiid^ 

JJ.  Palpi  with  third  segment  short  and  blunt,  roughly 
scaled;  vein  Rj  normally  running  to  outer  margin,  and 
often  free  from  vein  R4.     p.  643 Phaloniid^ 

II.  Vein  1st  A  preserved,  at  least  at  the  margin  of  the  wing. 
J.     Hind  wings  with  veins  Rs  and  Mi  widely  separate  at 

origin,  more  or  less  parallel. 

K.    Palpi  long,  often  exceeding  vertex;   tongue  distinct. 
L.    Veins  R4  and  R5  stalked  and  both  running  to  costa, 
or  united. 
M.    Vein  M2  of  the  hind  wings  arising- nearer  to  vein 

Mi    than    to    M3.    p.    625 Ethmiid^ 

MM.     Vein  M2  of  the  hind  wings  arising  nearer  to 

vein  Mj  than  to  M,.    p.  624 CEcophorid/E 

LL.       Veins  P.4  and  R5  long  stalked ;  vein  R^  running  to 
outer  margin.     (See  also  LLL.) 
M.    Ocelli  very  large  and  conspicuous  {Allononyma) . 

p.  633 Glyphipterygid^ 

MM.     Ocelli  small  or  absent. 

N.     Vein  M2  of  the  hind  wings  arising  nearer  to 

vein  Mi  than  to  M3.  p.  625 Ethmiid.« 

NN.    Vein  M2  of  the  hind  wings  arising  nearer  to 

vein  M3  than  to  Mi.  p.  624.  .  .CEcophorid^ 

LLL.     Veins  R4  and  R5  separate,  vein  R5  running  to 

outer  margin,  p.  631 Yponomeutid^ 

KK.  Palpi  small,  hardly  exceeding  the  front,  or  obsolete; 
tongue  obsolete;  female  with  a  brush-like  tuft  at  end  of 
abdomen  {Kearfottia,  Solenobia).  p.  614.  .  .  .Psychid/E 
JJ.  Hind  wings  with  veins  Rs  and  Mi  coalesced  or  stalked. 
K.  Wings  narrow;  fore  wings  falcate;  maxillary  palpi 
well  marked  and  porrect  {Cerostoma,  etc.).  p.  631 
Yponomeutid^ 


Hif; 


LEPIDOPTERA  591 

KK.     Wings  broad,  ample,  not  falcate;  maxillary  palpi 
of  folded  type,  inconspicuous,  invisible  in  Setiostoma. 

p.  625 Stenomid^ 

FF.     Hind  wings  with  pointed  apex  and  excavated  below,  rarely 

bifid.      (See    also    FFF.)    p.    625 Gelechiid/e 

FFF.      Hind   wings   narrow-lanceolate   and   ])ointed   or   linear,   and 
much  narrower  than  their  fringe. 

G.  Hind  wings  lanceolate,  though  sometimes  very  small,  and  with 
the  principal  vein  running  nearly  through  its  center,  widely 
separated  from  Sc. 

H.     Hind  wings  with  a  discal  cell.  p.  621 Elachistid^ 

HH.    Hind  wings  without  a  discal  cell. 

I.  Vein  Rs  of  hind  wings  separating  from  media  near  the 
middle  of  the  length  of  the  wing.  p.  623 Douglasiid.<e 

II.  Vein  Rs  of  hind  wings  separating  from  media  near  the 
apex  of  the  wing.  ]).  634 Heliozelid.^ 

GG.  Hind  wings  with  vein  R  closely  parallel  with  or  fused  to  Sc 
near  base.  In  the  broad-winged  Gracilariida;,  veins  Sc  and  R  are 
fused  and  the  base  of  vein  M  is  preserved,  simulating  the  con- 
dition in  G,  but  the  combined  base  of  Sc  and  R  curves  strongly 
into  the  lobed  basal  half  of  costa,  and  then  approaches  or  fuses 
with  AI  at  middle  of  wing,  unlike  the  relation  of  Sc  and  R  in  G. 
H.  Hind  tarsi  with  strong  spinules,  usually  near  apices  of  seg- 
ments, as  well  as  tibise;  posterior  legs  displayed  when  at  rest. 

).  634 HeliodiniDvE 

Tarsi  smooth-scaled,  the  spinules  concealed  in  the  scaHng; 
the  tibiae  often  hairy,  but  rarely  {Acrocercops,  Epermenia) 
bristled. 

I.  Fore  wings  with  only  four  veins  running  from  the  discal 
cell  to  the   costa,  and  five  or  six  to  the    inner    margin. 

p.  631,  632 YpONOMEUTID^  and  PLUXELLIDyE 

II.  Fore  wings  with  five  veins  running  to  costa,  or  only  four  to 
inner  margin. 
J.    Discal  cell  oblique  in  wing;  vein  Cu^  very  short,  running 

directly  across  to  inner  margin. 

K.      Antennas    turned    forward    in    repose;    fore    tibiae 
slender,  with  a  small  epiphysis  at  the  apex  or  none.  p.  620. 

COLEOPHORID^ 

KK.    Antennae  turned  back  in  repose;  fore  tibiae  with  the 

epiphysis   conspicuous,   and   often   more  than   half  as 

long  as  the  tibia;  the  tibiae  rarely  slender. 

L.     Hind  wings  with  veins  Sc  and  R  shortly  fused  near 

base;  fore  wings  with  a  stigma,  and  with  Ri  arising 

near  the  base  of  the  discal  cell  and  R2  near  the  apex  of 

the    cell.    p.    628 Blastobasid^ 

LL.  Hind  wings  with  veins  Sc  and  R  not  fused;  fore 
wings  with  the  space  between  the  origins  of  veins  Ri 
and  R2  only  three  or  four  times  that  between  veins 

R2  and  R3.    p.  629 C0SMOPTERYGID.E 

J  J.         Discal  cell  not  set  obliquely  in  wing;  vein  Cu>  nor- 
mally long  and  parallel  to  the  medial  veins. 
K.     Male  antenna  heavily  ciliate;  accessory  cell  of  fore 
wings  extending  halfway  to  base  of  wing;    head  with  a. 
large,  loose,  but  often  obscure,  semierectile  tuft.  p.  615. 

TlSCHERIID.^ 

KK.    Male  antennae  rarely  ciliate;  accessory  cell  small  or 
absent. 
L.      Palpi  minute  and   drooping;  vertex  tufted;  hind 

wings    hnear    [Bedellia).    p.    616 Lyonetiid^e 

LL.         Palpi  moderate,  with  fusiform  third  segment; 

maxillary   palpi   often    well  developed   and  porrect. 

(See  also   LLL.)      p.    617 Gbacilariid^ 


592  AN  INTRODUCTION  TO  ENTOMOLOGY 

LLL.     Palpi  upturned,  with  acuminate  third  segment, 

often  exceeding  the  vertex;  maxillary  palpi  of  folded 

type  but  ver}^  minute  or  obsolete. 

M.     Vein  Ri  of  the  fore  wings  more  than  twice  as 

long  as  vein  R2  and  arising  before  the  middle  of  the 

discal  cell.    p.  629 Cosmoptervgid.« 

MM.    Vein  Ri  of  the  fore  wings  but  little  longer  than 
vein  R2,  and  arising  beyond  the  middle  of  the  discal 

cell.     p.     631 SCYTHRIDID^ 

Suborder  JUGATE 

This  suborder  includes  those  Lepidoptera  in  which  the  posterior 
lobe  of  the  fore  wing  is  specialized  so  as  to  form  an  organ  which  unites 
the  fore  and  hind  wings;  and  in  which  the  venation  of  the  hind  wings 
is  similar  to  that  of  the  fore  wings. 

The  Jugatae  includes  the  more  generalized  members  of  the  order  Lepidoptera 
now  living,  those  which  are  believed  to  resemble  most  closely  the  primitive  in- 
sects from  which  in  ancient  times  the  Lepidoptera  were  evolved.  In  fact  the  first 
two  families  here  included  in  the  Jugatae  may  be  of  even  more  ancient  origin,  repre- 
senting one  or  two  lines  of  evolution  distinct  from  the  lepidopterous  stem. 

Several  writers  have  called  attention  to  indications  of  trichopterous  affinities 
of  the  two  families  in  question;  and  a  study  of  the  wing- venation  of  these  in- 
sects led  me  to  believe  that  they  are  more  closely  allied  to  the  Trichoptera  than  to 
the  Lepidoptera.  For  this  reason,  in  "The  Wings  of  Insects"  I  classed  them  with 
the  Trichoptera. 

Although  these  indications  of  trichopterous  affinities  are  undoubted,  it  appears 
that  the  view  now  generally  held  is  that,  while  they  show  a  close  community  of 
descent  of  the  Trichoptera  and  the  Lepidoptera,  they  are  not  sufficient  to  warrant 
the  removal  of  the  families  in  question  from  the  Lepidoptera.  I,  therefore,  in- 
clude them,  provisionsally,  in  this  order  in  the  following  account.  For  a  detailed 
discussion  of  this  subject,  see  Braun  ('19)  and  Crampton  ('20  b). 

The  suborder  Jugatae,  as  now  more  commonly  limited,  in- 
cludes several  families,  representatives  of  three  of  which  have  been 
found  in  America;  these  are  the  Micropterygidas,  the  Eriocraniidas, 
and  the  Hepialidae. 

The  members  of  the  first  two  of  these  families  differ  greatly  in 
appearance  from  those  of  the  third  family,  being  very  small  moths 
which  resemble  the  small  tineids  in  size  and  appearance ;  our  largest 
species  has  a  wing  expanse  of  from  12  to  14  mm.  For  this  reason 
they  may  be  known  as  the  Microjugatae.  They  have  also  been  termed 
the  Jugo-frenata,  because,  in  addition  to  having  the  posterior  lobe  of 
the  fore  wing  specialized  so  as  to  form  an  organ  which  serves  in 
uniting  the  fore  and  hind  wings,  there  is  also  a  bunch  of  bristles  borne 
by  the  hind  wing  near  the  humeral  angle,  which  resembles  a  frenulum ; 
these  bristles,  however,  are  not  homologous  with  the  frenulum,  but 
are  the  costal  spines  described  on  page  575.  On  the  other  hand,  the 
members  of  the  third  family  are  mostly  large  moths ;  many  of  them 
are  very  large ;  and  the  smaller  species  have  a  wing-expanse  of  2  5  mm. 
The  members  of  this  family  may  be  known  as  the  Macrojugatae. 

Family  MICROPTERYGID.^ 

The  Mandihidate  Jugates 
The  members  of  this  family  are  small  insects  which  resemble 
tineid  moths  in  general  appearance.     As  with  other  members  of  the 


LEPIDOPTERA 


593 


suborder  Jugatas,  the  venation  of  the  hind  wings  closely  resembles 
that  of  the  fore  wings  (Fig.  719).     But  these  insects  differ  from  all 


Fig.  719.^ — Wings  of  Micropteryx. 
other  Lepidoptera  in  having  in  the  adult  instar  well-developed  func- 
tional mandibles,  and  in  that  the  females  lack  a  bursa  copulatrix. 
Chapman  ('17)  regards  the  presence  of  well-developed  mandibles  and 
the  absence  of  a  bursa  copulatrix  of  sufficient  importance  to  warrant 
the  removal  of  these  insects  from  the  Lepidoptera  and  the  establish- 
ment of  a  distinct  order  for  them ;  for  this  order  he  proposed  the  name 
Zeugloptera. 

Tillyard  ('19)  states  that  the  wing-coupling  apparatus  in  this 
family  functions  differently  from  that  of  the  following  family,  in  that 
in  the  Micropterygidae  the  jugal  lobe  is  bent  under  the  fore  wing  and 
acts  as  a  retinaculum  for  the  bunch  of  costal  spines,  borne  by  the 
hind  wings. 

In  this  family,  the  subcosta  of  the  fore  wings  is  forked  near  its 
middle  (Fig.  719);  the  abdomen  of  the  adult  female  consists  of  ten 
distinct  segments;  and  there  is  no  ovipositor. 

There  is  no  published  account  of  the  transformations  of  our 
American  species.  The  larvae  of  certain  exotic  species  have  been  de- 
scribed; they  are  very  delicate,  have  long  antennae,  and  feed  upon  wet 
moss.  The  pupa  state  is  passed  in  the  ground;  the  pupa  has  large, 
crossed  mandibles.    The  adults  feed  on  pollen. 

Two  American  species  have  been  described;  these  are  Epimar- 
tyria  auricrinella,  which  is  found  in  the  East,  and  Epimartyria  par- 
della,  found  in  Oregon. 

Family  ERIOCRANIID^ 

The  Haustellate  Jugates 

The  members  of  this  family,  like  those  of  the  preceding  one,  are 
small  insects  which  resemble  tineid  moths  in  general  appearance. 


594 


^iV  INTRODUCTION  TO  ENTOMOLOGY 


In  this  family  the  mandibles  of  the  adult  are  vestigial;  the  maxillae 
are  formed  for  sucking,  each  maxilla  forming  half  of  a  long  sucking- 
tube,  as  in  higher  Lepidoptera ;  and  the  females  have  a  bursa  copu- 
latrix  and  a  piercing  ovipositor.  An  easily  observed  recognition 
character  is  the  fact  that  the  subcosta  of  the  fore  wings  is  forked  near 
its  apex  (Fig.  720).  The  jugal  lobe  of  the  fore  wing  extends  back 
above  the  base  of  the  hind  wing  and  is  clasped  over  an  elevated  part 
of  the  hind  wing,  thus  being  of  the  type  described  as  a  fibula  (see 
page  62). 

Our   best-known   representative    of    this    family    is   Mnemonica 
auricydnea.     The  structure  and  transformations  of  this  species  have 


Sc,      Sc2      Ri 


2d  A 


Fig.  720. — Wings  of  Mnemonica. 

been  described  by  Busck  and  Boving  ('14).  The  adult  has  a  wing- 
expanse  of  from  1 2  to  1 4  mm.  The  larva  mines  in  the  leaves  of  chestnut, 
oak,  and  chinquapin  in  early  spring,  making  a  large,  bulgy  blotch 
mine;  it  completes  its  growth  within  a  week  or  ten  days,  and  goes 
into  the  ground  to  transform,  where  it  spins  a  tough  cocoon;  the 
change  to  pupa  takes  place  in  the  following  winter ;  the  adult  emerges 
in  April.  The  pupa  has  long,  arm-like  toothed  mandibles,  with  which 
it  cuts  the  tough  cocoon  and  with  which  it  digs  its  way  up  to  the 
surface  of  the  ground.    This  species  is  found  in  the  East. 


Family  HEPIALID^ 
The  Swifts  or  the  Macrojugatce 
The   members    of   this    family    are    of   medium    or    large    size. 


LEPIDOPTERA  595 

Figure  721  represents  in  natural  size  one  of  the  larger  of  the  American 
species,  but  many  exotic  species  are  larger  than  this  one.  Our 
smaller  species  have  a  wing-expanse  of  at  least  25  mm.  Our  best- 
known  species  are  brown  or  ashy  gray  in  color,  with  the  wings  marked 
with  silvery  white  spots. 

It  is  said  that  these  moths  fly  near  the  earth,  and  only  in  the  eve- 
ning after  sunset,  hiding  under  some  low  plant,  or  clinging  to  the  stalk 
of  an  herb  during  the  dav.  Some  of  them  fly  with  extreme  rapidity, 
with  an  irregular  mazy  flight,  and  have,  therefore,  been  named  swifts 
by  collectors.  So  long  as  either  or  both  of  the  two  preceding  families 
are  retained  in  the  suborder  Jugatas,  the  Hepialidte  may  be  dis- 
tinguished as  the  Macrojugatae. 

In  the  Hepialidffi  the  posterior  lobe  of  the  fore  wing  is  a  slender, 
finger-like  organ,  which  is  stiffened  by  a  branch  of  the  third  anal  vein, 
and  which  projects  beneath  the  costal  margin  of  the  hind  wing.     As 


Fig.  721. — Sthenopis  purpiirascens. 


the  greater  part  of  the  inner  margin  of  the  fore  wing  overlaps  the 
hind  wing,  the  hind  wing  is  held  between  the  two.  This  is  the  type 
of  posterior  lobe  of  the  fore  wing  to  which  the  term  jugum  is  ap- 
phed.    (Figs.  74  and  75.) 

The  larvas  are  cruciform  and  furnished  with  sixteen  legs;  they 
feed  upon  wood  or  bark,  and  are  found  at  the  roots  or  within  the 
stems  of  plants.  They  transform  either  in  their  burrows,  or,  in  the 
case  of  those  that  feed  outside  of  roots,  within  loose  cocoons.  The 
pupae  have  transverse  rows  of  teeth  on  the  abdominal  segments; 
these  aid  them  in  emerging  from  their  burrows. 

This  family  is  represented  in  our  fauna  by  two  genera,  Hepialus 
and  Sthenopis. 

Hepialus. — This  genus  includes  our  smaller  species,  which  range 
in  wing-expanse  from  25  to  55  mm.  In  Hepialus  the  apices  of  the 
fore  wings  are  more  rounded  than  in  Sthenopis.  Ten  North  American 
species  have  been  described. 

Sthenopis. — This  genus  includes  our  larger  species.  In  these  the 
apices  of  the  fore  wings  are  more  pointed  than  in  Hepialus,  and  in 
some  species  are  subfalcate.     Four  species  have  been  found  in  our 


596 


AN  INTRODUCTION  TO  ENTOMOLOGY 


fauna;  one  of  these,  Sthenopis  purpurdscens ,  is  represented  in  Figure 
721. 

The  larva  of  Sthenopis  argenteomaculdtus  bores  in  the  stems  of  the 
speckled  or  hoary  alder  (Alnus  incana) ;  that  of  Sthenopis  thule,  in 
willow. 

Suborder  FRENAT^ 

The  members  of  the  Frenatae  are  most  easily  recognized  by  the 
fact  that  the  venation  of  the  hind  wings  differs  markedly  from  that 
of  the  fore  wings,  being  much  more  reduced.  In  this  suborder, 
vein  Ri  of  the  hind  wings  coalesces  with  subcosta,  the  two  appearing 
as  a  single  vein,  except  that,  in  some  cases,  a  short  section  of  the  base 
of  Ri  is  distinct,  presenting  the  appearance  of  a  cross-vein  between 


ja'yi         2d  A 

Fig.  722.^ — Wings  of  Prionoxystus  rohinia. 

radius  and  subcosta  (Fig.  722,  Ri).  After  the  separation  of  vein  Ri, 
the  radial  sector  continues  unbranched  to  the  margin  of  the  wing 
(Fig.  722,  Rs).  Rarely,  as  in  some  members  of  the  Gracilariidce  and 
of  the  Cosmopterygidae,  vein  Ri  of  the  hind  wings  is  free,  not  co- 
alesced with  vein  Sc. 

The  essential  characteristic  of  the  Frenatse  is  that  they  are 
descendants  of  those  primitive  Lepidoptera  in  which  the  two  wings 
of  each  side  were  united  by  a  frenulimi.  This  fact  should  be  clearly 
understood,  for  in  many  of  the  Frenatae  the  frenulum  has  been  lost. 
The  loss  of  the  frenultim  in  these  cases  is  due  to  its  having  been 
supplanted  by  a  substitute  for  it,  by  an  enlarged  humeral  area  of  the 
hind  wings,  which  causes  the  two  wings  of  each  side  to  overlap  to  a 


LEPIDOPTERA 


597 


great  extent.  This  overlapping  of  the  two  wings  insures  their  syn- 
chronous action;  and  the  frenulum,  being  no  longer  needed  for  this 
purpose,  is  lost.  Illustra- 
tions of  different  stages  in 
the  reduction  and  loss  of 
the  frenulum  are  given  in 
the  discussions  of  family 
characters  given  later. 

As  a  rule  the  frenulum 
of  the  female,  when  present, 
consists  of  several  bristles, 
while  that  of  the  male  con- 
sists of  a  single  strong, 
spine-like  organ.  If  one  of 
the  bristles  of  the  compound 
frenulum  of  a  female  be  ex- 
amined, it  will  be  found  to 
be  a  typical  seta,  containing 
a  single  cavity.  But  if  a 
frenulimi  of  a  male  be  ex- 
amined, it  will  be  found  to 
contain  several  parallel  cav- 
ities. Evidently  the  fren- 
uKmi  of  the  male  is  com- 
posed of  several  setae,  as  is 
that  of  the  female,  but 
these  setae  are  grown  together. 


Fig.  723. 
hook. 


-Wings  of  a  moth :  /  h,  f renulum- 


This  can  be  seen  by  examining  a 
bleached  wing  that  has  been  mounted  in  balsam ;  usually  the  cavities 
in  the  setae  contain  air,  which  renders  them  visible. 

The  frenulum -hook,  which  is  present  in  the  males  of  certain  moths, 
is  a  membranous  fold  on  the  lower  surface  of  the  fore  wing  for  receiv- 
ing the  end  of  the  frenulum,  and  thus  more  securely  fastening  the  two 
wings  together  (Fig.  723,  /  /z).  As  a  rule  the  frenulum-hook  arises 
from  the  membrane  of  the  wing  near  the  base  of  cell  C;  but  in  some 
moths  iCastnia)  it  seems  to  have  been  pulled  back  so  that  it  arises 
from  the  subcostal  vein. 


THE  GENERALIZED  FRENAT^ 


Under  this  heading  are  grouped  those  families  of  moths  that  are 
supposed  to  retain  more  nearly  than  any  other  Frenatffi  the  form  of 
the  primitive  Frenatae,  those  that  were  the  first  to  appear  on  earth. 
In  most  of  the  families  included  here,  the  wings  approach  the  typical 
form,  except  in  the  reduction  of  the  number  of  branches  of  radius  of 
the  hind  wings,  which  is  true  of  all  Frenatse ;  usually  the  base  of  media 
of  one  or  both  pairs  of  wings  is  preserved  throughout  a  considerable 
part,  at  least,  of  the  discal  cell;  and  the  anal  veins  are  well  preserved, 
there  being  two  or  three  in  the  fore  wing  and  three  in  the  hind  wing. 
The  frenulum  is  usually  well  preserved. 


598  .4  7V  INTRODUCTION  TO  ENTOMOLOGY 

There  are  also  included  in  this  group  of  families  those  families 
in  which  the  fixed  hairs  or  aculese  are  retained  over  the  general 
surface  of  the  wings,  even  though  in  some  cases,  as  in  the  Nepticulidas, 
the  venation  of  the  wings  may  be  greatly  reduced.  The  presence  of 
aculeas  distributed  over  the  general  surface  of  the  wings  is  believed 
to  indicate  a  generalized  condition,  as  it  is  found  elsewhere  in  the 
Lepidoptera  only  in  the  Jugatae.  As  this  condition  is  also  found  in 
the  Trichoptera,  it  was  probably  inherited  from  the  stem  form  from 
which  the  Lepidoptera  and  the  Trichoptera  were  evolved.  In  the 
more  specialized  Lepidoptera  the  aculese  are  confined  to  small  areas 
of  the  wing  surface  or  have  been  lost. 

Family  INCURVARIID.E 

This  family  and  the  following  one  differ  from  all  other  Frenatae 
and  agree  with  the  Jugatae  in  having  retained  aculeae  distributed  over 
the  general  surface  of  the  wing  (Fig.  710).  In  this  famity  the  venation 
of  the  wings  is  but  little  reduced;  the  antennae  are  without  an  eye- 
cap;  and  the  females,  so  far  as  is  known,  are  furnished  with  a  piercing 
ovipositor.  The  moths  are  small  or  of  moderate  size.  Many  of  the 
larvae  are  miners  when  young,  and  later  are  case  bearers. 

The  family  Incurvariidae  includes  three  subfamilies,  which  are 
not  very  distinct  but  which,  however,  are  treated  as  families  by  some 
writers. 

Subfamily  Adeline. — These  tiny  moths  are  characterized  by 
the  unusually  long  and  fine  antennae  of  the  males,  which  may  be 
twice  or  more  than  twice  as  long  as  the  wings.  Some  of  the  species 
are  also  conspicuous  on  account  of  their  striking  colors  and  markings. 

The  larv^ae  are  elongate,  cylindrical,  with  thoracic  legs  and  five 
pairs  of  prolegs.  They  are  at  first  miners;  later  they  live  in  portable 
cases.  They  feed  on  the  leaves  of  various  herbs  and  shrubs;  but  none 
of  our  species  is  known  to  be  of  economic  importance.  Nearly  all  of 
our  species  belong  to  the  genus  Adela. 

Subfamily  Incurvariin^..^ — An  interesting  representative  of  this 
division  of  the  family  Incurvariids  is  the  following  well-known  species. 

The  maple-leaf  cutter,  Paraclemaisia  acerifoliella.- — The  larva  in- 
fests the  leaves  of  maple,  and  occasionally  is  so  abundant  that  it  does 
serious  injurv.  The  larva  is  at  first  a  leaf -miner,  like  other  adelids; 
but  later  it  is  a  case-bearer. 

The  leaves  of  an  infested  tree  present  a  strange  appearance  (Fig. 
724).  They  are  perforated  with  numerous  elliptical  holes,  and 
marked  by  many,  more  or  less  perfect,  ring-like  patches  in  which  the 
green  substance  of  the  leaf  has  been  destroyed  but  each  of  which 
incloses  an  uninjured  spot.  These  injuries  are  produced  as  follows: 
The  larva,  after  living  for  a  time  as  a  leaf-miner,  cuts  an  oval  piece 
out  of  a  leaf,  places  it  over  its  back,  and  fastens  it  down  with  silk 
around  the  edges.  This  serves  as  a  house  beneath  which  it  lives. 
As  it  grows,  this  house  becomes  too  small  for  it.  It  then  cuts  out  a 
larger  piece  which  it  fastens  to  the  outer  edges  of  the  smaller  one,  the 


LEPIDOPTERA 


599 


Fig.    724. —  Leaf    infested    by    the 
maple-leaf  cutter. 


larva  being  between  the  two.  Then  it  crawls  halfway  out  upon  the 
leaf,  and  by  a  dexterous  lifting  of  the  rear  end  of  its  body  turns  the 
case  over  so  that  the  larger  piece  is  • 

over  its  back.  When  it  wishes  to 
change  its  location  it  thrusts  out  its 
head  and  fore  legs  from  the  case  and 
walks  off,  looking  like  a  tiny  turtle. 
When  it  wishes  to  eat,  it  fastens  the 
case  to  the  leaf  and,  thrusting  its 
head  out,  eats  the  fleshy  part  of  the 
leaf  as  far  as  it  can  reach.  This 
explains  the  circular  form  of  the 
patches,  the  round  spot  in  the  center 
indicating  the  position  of  the  case. 
The  insect  passes  the  winter  in  the 
pupa  state  within  its  case,  which 
falls  to  the  ground  with  the  infested 
leaf.  The  moth  is  of  a  brilliant  steel- 
blue  or  bluish  green  color,  without 
spots  but  with  an  orange-colored 
head;  it  appears  in  early  summer. 

Subfamily  Prodoxin^..^ — This 
subfamily  includes  the  remarkable 
insects  that  are  known  as  the  yucca- 
moths  and  the  closely  allied  bogus 
yucca-moths. 

The  yucca-moths,  Tegettcula. — Four  species  of  this  genus  are  now 
recognized;  the  best-known  of  these  is  Tegettcula  alba.  The  life- 
history  of  this  species  was  first  described  by  Mr.  C.  V.  Riley  ('73), 
under  the  name  Pronuba  yuccasella;  and  in  most  of  the  accounts  of 
this  insect  this  name  is  used.  The  moth,  however,  was  first  de- 
scribed as  Tegeticula  alba.  The  most  complete  account  of  this  and 
the  allied  species  is  that  of  Riley  ('92). 

This  species  infests  Yticca  filamentosa,  a  plant  not  fitted  for  self- 
pollination  or  for  pollination  by  insects  in  the  ordinary  ways;  in 
fact,  it  is  pollinized  only  by  moths  of  the  genus  Tegeticula,  the 
larvae  of  which  feed  on  its  seeds.  This  is  one  of  the  few  cases  in  which 
a  particular  plant  and  a  particular  insect  are  so  specialized  that  each 
is  dependent  upon  the  other  for  the  perpetuation  of  the  species.  In 
the  female  moth,  the  maxillse  are  each  furnished  with  a  long,  curled, 
and  spinose  appendage,  the  maxillary  tentacle  (Fig.  725,  b),  fitted  for 
the  collection  of  pollen.  After  collecting  a  large  load  of  pollen,  often 
thrice  as  large  as  the  head  (Fig.  725,),  the  female  moth  places  her 
eggs,  by  means  of  her  long,  extensile  ovipositor,  into  an  ovary,  usually 
of  another  flower  than  that  from  which  the  pollen  was  collected. 
After  oviposition,  the  moth  runs  up  to  the  tip  of  the  pistil  and  thrusts 
the  pollen  into  the  stigmatic  opening.  Thus  is  insured  the  develop- 
rhent  of  seeds,  upon  which  the  larvse  hatched  from  the  eggs  placed 
in  the  ovary  are  to  feed.  As  many  more  seeds  are  developed  than  are 
needed  by  the  larvae,   the  perpetuation  of  the  yuccas  is  assured. 


600 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  full-grown  larva  leaves  the  yucca  pod  and  makes  its  way  to 
the  ground,  where  it  spins  a  dense  cocoon  several  inches  belowthe 

surface.  The  adult 
moth  has  a  wing-ex- 
panse of  about  2  5  mm. 
The  front  wings  are 
silvery  white  above ; 
the  hind  wings,  semi- 
transparent. 

The  bogus  \aicca- 
moths,  Prodoxus. — 
The  moths  of  this  ge- 
nus are  closely  allied 
to  the  yucca-moths, 
but  differ  in  the  im- 
portant particular 
that  the  females  lack 
maxillary  tentacles; 
they  are  consequently 
incapable  of  pollinat- 
ing the  yuccas  as  do 
the  true  A^ucca -moths. 
The  larvae  of  Prodoxus 
feed  in  the  flower-stem  or  in  the  flesh  of  the  fruit.  But  as,  in  Yucca 
filamentosa  at  least,  the  flowers  drop  and  the  flower-stem  withers  if 
the  flowers  are  not  pollinated,  the  bogus  yucca-moths  are  dependent 
on  the  true  yucca-moths  for  the  conditions  necessary  for  the  develop- . 
ment  of  their  larvae.  The  pupa  state  is  passed  in  the  burrow  made 
by  the  larva.     Eleven  species  of  Prodoxus   have    been    described. 


Fig.  725. — Tegeticula  alba:  a,  side  view  of  head  and 
neck  of  female  denuded ;  i ,  load  of  pollen ;  2,  maxil- 
lary tentacle;  3,  maxilte;  4,  maxillarj'  palpi;  5, 
antennae;  b,  maxillar\^  tentacle  and  palpus;  c, 
an  enlarged  spine;  d,  maxillary  palpus  of  male;  f, 
scale  from  front  wing;  /,  front  leg;  g,  labial  pal- 
pus; /;•,  i,  venation  of  wings;  j,  last  segment  of 
abdomen  of  female,  with  ovipositor  extruded. 
All    enlarged.    (From    Riley.) 


Family  NEPTICULID^ 


In  this  family,  as  in  the  preceding  one,  fixed  hairs  or  aculeae  are 
distributed  over  the  general  surface  of  the  wings.  In  the  Nepticulidae 
the  venation  of  the  wings  is  much  reduced;  the  basal  segment  of 
the  antennae  is  enlarged  and  concave  beneath,  so  as  to  form  an  eye-cap ; 
the  female  is  without  an  ovipositor;  the  labial  palpi  are  short;  the 
maxillary  palpi  are  long;  and  the  maxillse  are  vestigial. 

This  family  includes  the  smallest  of  the  Lepidoptera,  some  of  the 
-species  having  a  wing-expanse  of  scarcely  3  mm. 

Although  this  family  presents  characteristics  which  indicate  that 
it  should  be  placed  among  the  generalized  Lepidoptera,  the  venation 
of  the  wings  is  greatly  reduced.  This  indicates  that  it  represents  a 
distinct  line  of  development  which  in  some  respects  has  become  more 
highly  specialized  than  are  the  other  families  included  in  this  division 
of  the  Lepidoptera. 

The  f renulimi  of  the  female  consists  merely  of  a  group  of  small , 
functionless  bristles;  but  in  the  male  the  frenulum  is  a  strong,  spine- 


LEPIDOPTERA 


601 


like  organ,  which  hooks  into  a  well-developed  frenulum  hook  (Fig. 
726);  in  most  cases  the  costal  spines  are  well  developed;  this  is 
shown  in  the  accompany- 
ing figure;  and  the  anal 
lobe  of  the  fore  wing  is 
sometimes  quite  distinct. 
With  the  exception  of 
several  gall-making  spe- 
cies of  Ectoedcmia,  the  lar- 
vas  of  all  species  of  which 
the  life-history  is  known 
are  miners  within  the 
tissues  of  leaves  (rarely  in 
fruits)  or  in  bark.  They 
show  a  preference  for  trees 
and  shrubs,  but  some  mine 
in  the  leaves  of  herbaceous 
plants.  The  larva  at  first  makes  a  very  narrow  linear  mine.  This  mine 
may  continue  as  a  linear  mine,  gradually  broadening  throughout  its 
course,  or  it  may  at  some  period  abruptly  enlarge  into  a  blotch.  When 
full-grown,  the  larva,  with  few  exceptions,  leaves  the  mine  and,  drop- 
ping to  the  ground,  spins  a  dense,  flattened  cocoon  amongst  rubbish 
or  in  the  loose  surface  soil.    (Braun  '17.) 

More  than  seventy  species  have  been  described  from  our  fauna, 
and  doubtless  many  more  are  to  be  discovered.  The  Nepticulidas  of 
North  America  was  monographed  by  Braun  ('17). 


Fig.  726. — Wings  of  Obrussa  ochre fasciella,  male. 
(After  Braun.) 


Family  COSSID^ 


The  Carpenter-Moths 


This  family  includes  moths  with  spindle-shaped  bodies,  and  nar- 
row, strong  wings,  some  of  the  species  resembling  hawk -moths  quite 
closely  in  this  respect.  The  larvae  are  borers;  many  of  them  live  in 
the  solid  wood  of  the  trunks  of  trees.  The  wood-boring  habits  of  the 
larvae  suggest  the  popular  name  carpenter-moths  for  the  insects  of 
this  family. 

These  moths  fly  by  night  and  lay  their  eggs  on  the  bark  of  trees, 
or  within  tunnels  in  trees  from  which  adult  carpenter-moths  have 
emerged.  The  caterpillars  are  nearly  naked,  and,  although  furnished 
with  pro-legs  as  well  as  true  legs,  are  grub-like  in  form.  The  pupa 
state  is  passed  within  the  burrow  made  by  the  larva.  When  ready 
to  change  to  an  adult,  the  pupa  works  its  way  partially  out  from  its 
burrow.  This  is  accomplished  by  means  of  backward-projecting  saw- 
like teeth,  there  being  one  or  two  rows  of  these  on  each  abdominal 
segment.  After  the  moths  have  emerged,  the  empty  pupa-skins  can 
be  found  projecting  from  the  deserted  burrows. 


602 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  carpenter-moths  are  of  mediiim  or  large  size.  The  antennce 
of  the  males  are  mostly  bipectinate;  those  of  the  females  are  either 
very  slightly  bipectinate  or  ciliate.  In  a  few  species  the  antennas  are 
lamellate.     The  ocelli  are  wanting,  and  the  maxillae  are   vestigial. 

The  venation  of  the  wings  of  our  most  common  and  most  widely 
distributed  species  is  shown  in  Figure  727.  There  are  two  well-preserved 
anal  veins  in  the  fore  wing,  and  three  in  the  hind  wing.  The  base  of 
media  is  preser^^ed,  and  is  forked  within  the  discal  cell.     In  the  fore 


7^4 — TdA'^^^ 

Fig.  727. — Wings  of  Prionoxystus  robinice. 


wing  the  veins  R3  and  R4+5  anastomose,  forming  an  accessory  cell. 
The  frenulum  is  vestigial  in  this  genus ;  but  in  some  other  genera  it  is 
well  developed. 

Authors  differ  greatly  regarding  the  appropriate  position  of  this 
family  in  the  series  of  families.  Certain  characteristics  of  the  larvae 
indicate  that  it  belongs  somewhere  among  the  specialized  Micro- 
frenatas;  but  I  place  it  here  at  the  beginning  of  the  Non-aculeate 
Generalized  Frenatae  on  account  of  the  generalized  structure  of  the 
wings. 

This  family  is  represented  in  our  fauna  by  thirty-four  described 
species;  it  has  been  monographed  by  Barnes  and  McDunnough 
('11).  The  family  includes  three  subfamilies,  which  are  separated 
as  follows: 


LEPIDOPTERj 


603 


A.     Anal  veins  of  the  fore  wings  united  near  the  margin  of  the  wing  by  a  cross- 
vein HYPOPTIN^ 

AA.    Anal  veins  of  the  fore  wings  not  united  near  the  margin  of  the  wing, by  a 
cross- vein. 
B.    Veins  Rs  and  Mi  of  the  hind  wings  stalked  or  close  together  at  the  end  of  the 

discal  cell;  antennas  of  male  pectinate  throughout Cossin^ 

BB.     Veins  Rs  and  Mi  of  the  hind  wings  widely  separate;  antennas  of  male 
pectinate   on   basal   half    only Zeuzerin^ 

Subfamily  Hypoptin^.- — The  members  of  this  subfamily  are  dis- 
tinguished by  the  presence  of  the  anal  cross-vein  near  the  margin  of 
the  front  v^ings . 
Nearly   one-half    our 
species  belong  to  this, 
subfamily.     They 
have   been   described 
from  Florida,  Texas, 
Colorado,    and   west- 
ward to  California.    I 
have    found    no    ac- 
count   of    the    early 
stages  of  any  of  them. 

Subfamily  Cos- 
sin^,. — This  subfam- 
ily is  represented  in 
our  fauna  by  six  gen- 
era including  fourteen 

species ;  but  most  of  these  are  confined  to  the  Far  West  and  are  known 
only  in  the  adult  state.    Our  best -known  species  are  the  following. 

The  locust-tree  carpenter-moth,  Prionoxystus  rohlnicB.- — Figure  728 
represents  the  female,  natural  size.  The  male  is  but  little  more  than 
half  as  large  as  the  female.  It  is  much  darker  than  the  female,  from 
which  it  differs  also  in  having  a  large  yellow  spot,  which  nearly  covers 
the  outer  half  of  the  hind  wings.  The  moths  fly  in  June  and  July; 
the  larvae  bore  in  the  trunks  of  locust,  oak,  poplar,  willow,  and  other 
trees.  It  is  supposed  that  the  species  requires  three  years  to  complete 
its  transformations.    It  is  found  from  the  Atlantic  Coast  to  California. 

The  lesser  oak  cavpenter-worm,  Prionoxystus  macmurtrei. — This  is 
a  slightly  smaller  species  than  the  preceding.  The  larva  bores  in  the 
trunks  of  oak  in  the  East.  The  moth  has  thin,  slightly  transparent 
wings,  which  are  crossed  by  numerous  black  lines.  The  male  is  much 
smaller  than  that  of  P.  rohinice,  and  lacks  the  yellow  spot  on  the  hind 
wings. 

Subfamily  Zeuzerin^.. — Excepting  three  little-known  species  of 
Hamilcara,  found  in  Texas  and  Arizona,  the  following  species  is  the 
only  representative  of  this  subfamily  in  our  fauna. 

The  leopard -moth,  Zeuzera  pyrina.- — This  species  is  white,  spotted 
with  ntimerous  small,  black  spots,  which  suggested  its  common  name. 
The  adult  has  a  wing-expanse  of  from^o  to  60  mm.    It  is  a  European 


Fig.  728. — Prionoxystus  rohinicE,  female. 


604 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Species,  which  was  first  obsen^ed  in  the  vicinity  of  New  York  Citv  in 
1882;  since  that  time  it  has  spread  to  other  parts  of  the  East.  The 
lar\^a  is  a  very  injurious  borer  in  many  species  of  trees  and  shrubs. 
The  young  larvae  bore  in  the  small  twigs ;  later  they  migrate  to  larger 
limbs  or  to  the  trunk. 


Family  PYROMORPHID^ 


Fig.  729.— .4c- 
oloithus  fal- 
sarius. 


Fig.  730. — Wings  of  Acoloithus  falsarius. 


The  Smoky  Moths 

There  are  but  few  insects  in  our  countr}^  pertaining  to  this  family ; 
only  fifteen  species  are  now  recognized,  but  these  represent  sLx  genera. 

These   are 

small  moths, 
^^^v^^^  which  are 
^^Pft^^  chiefiy  of  a 
"  smoky  black 

color;  some 

are    marked 

with  brighter 

colors;  the 
wings  are  thinly  scaled ; 
and  the  maxillae  are  well 
developed.  The  larvas  are 
clothed  with  tufted  hair; 
they  have  five  pairs  of 
proiegs,  which  are  provided 
with  normal  hooks. 

A  tiny  representative  of 
the  family  which  seems  to  be  not  uncommon  in  the  East  is  Acoloithus 
falsarius.  This  moth  (Fig.  729)  expands  16  mm.  It  is  black,  with 
the  prothorax  of  an  orange  color.  The  venation  of  the  wings  (Fig. 
730)  is  peculiar,  in  that  subcosta  and  radius  of  the  hind  wings  coalesce 
for  onlv  a  short  distance  beyond  the  middle  of  the  discal  cell,  and 
a  stump  of  radius  projects  towards  the  base  of  the  wing,  from  the 
point  of  union  of  the  two  veins.  The  larva  feeds  in  early  siunmer  on 
the  leaves  of  grape  and  of  Virginia  creeper.  It  is  said  that  the  pupa 
state  lasts  fourteen  days  and  is  passed  within  a  parchment-like  cocoon. 
The  adults  frequent  flowers  in  the  daytime. 

Another  well-known  species  is  Pyrcmorpha  dimididta.  This  is 
found  in  the  Atlantic  and  Western  States.  The  entire  insect  is 
smoky  black,  except  the  basal  half  of  the  fore  wings  in  front  of  the 
second  anal  vein,  and  the  basal  half  of  the  costa  of  the  hind  wings, 
which  are  yellow.  The  wings  are  thinly  scaled  and  expand  25  mm. 
or  a  little  more.  The  male  is  larger  than  the  female  and  is  more 
active.  Figure  731  represents  the  venation  of  the  wings.  Some  spe- 
cies of  the  genus  Pyromorpha  are  remarkable  in  that  none  of  the 
branches  of  radius  of  the  fore  wings  coalesce  beyond  the  discal  cell. 


LEPIDOPTERA 


605 


Figure  732  represents  the 
venation  of  the  wings  of 
Pyromorpha  marteni,  a  spe- 
cies found  in  the  Rocky 
Mountains. 

The  species  of  the  genus 
Harrisina  differ  from  the 
typical  form  of  the  family 
in  that  the  anal  area  of  the 
hind  wings  is  greatly  re- 
duced, there  being  only  two 
short,  strongly  curved,  anal 
veins.  As  in  other  mem- 
bers of  the  family,  there  are 
two  well-developed  anal 
veins  preserved  in  the  fore 
wings.  The  following  is 
the  best-known  species  of 
this  genus. 

The  grape-leaf  skeleton- 
izer,  Harnsma  americdna. — 
The  wings  of  this  moth  are 


Fig-   731- — -Wings  of   Pyromorpha  dimidiata 
long  and  narrow  (Fig.  733);  the  abdomen  is  long,  and  widened  towards 


/?.  J^ 


Fig.  732. — Wings  of  Pyromorpha  marteni. 


Fig-   733- — Harrisina 
americana. 

the 'caudal  end.  It  is  green- 
ish black  in  color,  with  the 
prothorax  reddish  orange. 
The  larva  feeds  on  the  leaves 
of  grape  and  of  the  Virginia 
creeper.  An  entire  brood 
of  these  larvae  will  feed  side 
by  side  on  a  single  leaf  while 
young.  This  species  rarely 
becomes  of  economic  im- 
portance. 


Family  DALCERID^ 

In  this  family  the  body  is  small;  the  antennae  are  short;  and 
the  wings  are  broad.  In  the  fore  wings  there  is  a  large  acces- 
sory cell  which  is  ist  R3;  and  in  the  hind  wings  veins  Sc  and  R  are 
connected  at  a  point. 


606 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  best -known  species  in  our  fauna  is  Dalcerides  ingenita,  found 
in  Arizona.  The  expanse  of  the  wings  is  about  25  mm.  The  wings 
are  deep  yellow,  inclining  to  orange,  without  markings.  The  larva 
is  unknown. 

Another  species,  Pinconia  coa,  which  is  not  uncommon  in  Mexico 
has  been  reported  from  Arizona  by  Holland  ('03). 


Family  MEGALOPYGID^ 

The  Flannel-Moths, 

In  this  family  the  wings  are  heavily  and  loosely  scaled,  and  mixed 
with  the  scales  are  long,  curly  hairs ;  these  give  the  wings  the  appear- 
ance of  bits  of  flannel.  It  is 
this  that  suggested  the  com- 
mon name  of  these  moths. 
The  body  is  stout  and  clothed 
with  long  hairs. 

The  venation  of  the  wings 
of  our  most  common  species, 
Lagda  crispdta,  is  represented 
in  Figure  734.  There  are 
three  anal  veins  in  both  fore 
and  hind  wings;  but  in  the 
fore  wings  the  second  and  third 
anal  veins  are  partially  grown 
together.  The  basal  part  of 
media  is  more  or  less  distinctly 
presented  and  divides  the  dis- 
cal  cell  into  two  nearly  equal 
parts.  The  subcosta  and  ra- 
dius of  the  hind  wings  coalesce 
for  nearly  the  entire  length  of 
the  discal  cell.  In  these  moths 
the  maxillae  are  vestigial.  The 
larvse  are  remarkable  for  the 
possession  of  seven  pairs  of 
prolegs ;  these  are  borne  by  ab- 
dominal segments  2  to  7  and  10;  but  those  of  segments  2  and  7  are 
without  hooks.  The  setiferous  tubercles  are  verrucse  bearing  large 
numbers  of  fine  setse ;  so  that  the  body  is  densely  hairy ;  and  inter- 
spersed among  the  fine  setse  are  venomous  setae. 

There  are  only  ten  North  American  species  of  this  family;  these 
represent  four  genera.  Our  most  common  species  are  the  two  follow- 
ing. 

The  crinkled  flannel-moth,  Lagda  crispdta. — This  moth  is  cream- 
colored,  with  the  fore  wings  marked  with  wavy  lines  of  crinkled 
black   and   brownish   hairs.      The   male   is    represented   in    Figure 


LEPIDOPTERA 


607 


Fig-     736. — Old     LOLcjon 
Megalopyge  open  iilai  is. 


735;  the  female  is  larger  expanding,  40  mm.     In  the  female  the  an- 
tennse  are  very  narrowly  pectinate. 

The  lar- 
vae feed  on 

many  trees 

and  shrubs, 

including 

oak,   elm, 

apple,   and 

raspberry. 

They  are 

short,  thick, 
-Lagoa   crispata,    male,     and  fleshy, 

and    are 
covered  with  a  dense  coat  of  long,  silky,  brown  hairs,  which  project 
upward  and  meet  to  fonn  a  ridge  or  crest  along  the  middle  of  the  back ; 
interspersed  among  these  fine  hairs  are  venomous  setce. 

The  cocoons  are  of  a  firm,  parchment-like  texture,  covered  with  a 
thin  w^eb  of  rather  coarse  threads.  Mixed,  with  the  silk  of  the  cocoon 
are  hairs  of  the  lar\'a.     The  cocoon  is  provided  with  a  hinged  lid. 

This  species  is  found  in  the  Atlantic  States. 

Megalopyge  operciddris. — This  species  is  somewhat  smaller  than 
the  preceding  one;  the  male  has  a  wing-expanse  of  about  25  mm., 
and  the  female  of  about  37  mm.  The  fore  wings  are  umber  brown 
at  base,  fading  to  pale  yellow  outwardly;  they  are  marked  with  wavy 
lines  of  white  and  blackish  hairs,  and  the  fore  margins  are  nearly  black. 

The  larvag  are  clothed  with  long,  silky  hairs,  underneath  which  are 
venomous  setae.  The  cocoons  are  firmly  attached  to  a  twig  of  the 
infested  tree,  and  are  each  fur- 
nished with  a  trapdoor.  The  old 
cocoons  that  one  sees  in  collec- 
tions present  the  appearance  rep- 
resented in  Figure  736.  But  I 
found  in  Mississippi  a  cocoon, 
which  I  believe  to  be  of  this 
species,  that  is  of  the  form  shown 
in  Figure  737.  From  this  it  ap- 
pears that  after  the  outer  layer  of  the  cocoon  has  been  made,  the 
larva  constructs  a  hinged  partition  near  one  end  of  it,  and  adds  no 
more  silk  to  that  part  of  the  cocoon  which  is  outside  the  partition. 
This  part  of  the  cocoon  is  quite  delicate,  and  is  destroyed  when  the 
moth  emerges  if  not  before. 


=^^W 


Complete  cocoon  of  Megal- 


This  species  is  found  from  North  Carolina  to  Texas, 
is  a  very  general  feeder;  it  is  often  found  on  oak. 


The  larva 


608 


AN  INTRODUCTION  TO  ENTOMOLOG  Y 


Family  EUCLEID^* 
The  Slug-Caterpillar  Moths 


One  often  finds  on  the  leaves  of  shrubs  or  trees,  elHptical  or  oval 

larvae  that  resemble  slugs  in  the  form  of  the  body  and  in  their  gliding 

motion.    As  these  are  the  larvae  of  moths  they  have  been 

#  termed  slug-caterpillars;  but  they  present  very  little 
similarity  in  form  to  other  caterpillars.  The  resemblance 
to  slugs  is  greatly  increased  by  the  fact  that  the  lower  sur- 
face of  the  body  is  closely  applied  to  the  object  upon  which 
Fig.  738.  the  larva  is  creeping,  the  thoracic  legs  being  small  and  the 
prolegs  wanting.  There  is,  however,  on  the  ventral  side 
of  the  abdomen  a  series  of  sucking-disks,  which  serve  the  purpose  of 
prolegs.  The  head  of  the  larva  is  small  and  retractile.  In  some 
species  the  body  is  naked;  in  others  it  is  clothed  with  tufts  of  hairs; 
and  in  others  there  is  an  armature  of  branching  spines.  Several 
species  bear  venomous  setae. 

The  larvffi  when  full-grown  spin  very  dense  cocoons  of  brown 
silk;  these  are  egg-shaped  or  nearly  spherical,  and  are  furnished  at 
one  end  with  a  cap  which 
can  be  pushed  aside  by  the 
adult  when  it  emerges  (Fig. 
738).  The  cocoons  are  usu- 
ally spun  between  leaves. 
The  moths  are  of  me- 
dium or  small  size ;  the  body 
is  stout,  and  the  wings  are 
heavily  and  loosely  scaled. 
The  maxillae  are  vestigial. 
These  moths  vary  greatly  in 
appearance,  and  many  of 
them  are  very  prettily  col- 
ored. 

Considerable  variation 
exists  in  the  venation  of  the 
wings  in  this  family  (Fig. 
739  and  Fig.  740).  The  base 
of  media  may  be  preserved 
or  wanting;  in  some  species 
it  is  forked  within  the  discal 
cell,  in  others  not.    There  is  , 

also  considerable  variation  '"^ 

in   the   coalescence   of  the         ^^S-  739-— Wings  of  Adonda  spmuloides. 
branches     of    radius,     but 

veins  R3  and  R4  coalesce  to  a  greater  extent  than  any  other  branches 
of  this  vein.    There  is  no  accessory  cell.    In  the  hind  wings  veins  So 

*This  family  is  termed  the  Cochlidiidae  by  some  writers,  and  by  others  the 
Lima  codidae. 


LEPIDOPTERA 


609 


and  R  coalesce  for  a  short  distance  at  the  point  where  vein  Ri  joins 
vein  Sc. 

Only  forty-three 
North  American  spe- 
cies of  eucleids  have 
been  described ;  but 
these  represent  twen- 
ty genera.  The  larva> 
are  rarely  abundant 
enough  to  be  of  eco- 
n  o  m  i  c  importance ; 
they  are  chiefly  inter- 
esting on  account  of 
their  remarkable 
forms.  The  following 
are  some  of  the  bet- 
ter-known species: 

The  saddle-back 
caterpillar,  Sabine 
stimulea.- — This  larva 
can  be  recognized  by 
Figure  741.  Its  most 
characteristic  feature 
is  a  large  green  patch 
on  the  back,  resem- 
bling a  saddle-cloth, 
while  the  saddle  is 
represented  by  an 

oval  purplish  brown  spot.  The  moth  is  dark,  velvety,  reddish  brown, 
with  two  white  dots  near  the  apex  of  the  fore  wings.  The  larva  feeds 
on  oaks  and  oth- 
er forest  trees. 
This  is  one  of  the 
species  that  are 
armed  with  ven- 
omous setas. 

The  spiny 
oak-slug,  Euclea 
delphmii. — This 
larva  (Fig.  742) 
is  one  of  the  most 
common  of  our  slug  caterpil- 
lars and  one  of  those  that  are 
armed  with  venomous  setae. 
It  feeds  on  the  leaves  of  oak,  pear,  willow,  and  other  trees.  The  moth 
(Fig.  743)  is  cinnamon-brown,  with  a  variable  number  of  bright 
green  spots  on  the  fore  wings. 

The  hag-moth,  Phobetron  pithecium. — The  common  name   hag- 
m  oth  is  applied  to  the  larva  of  this  species  on  account  of  its  remarg- 


Fig.  740. 


"/        IS/-  A 
-Wings  of  Packardia  geminata. 


Euclea 


delphinii, 


610 


AN  INTRODUCTION  TO  ENTOMOLOGY 


able  appearance  (Fig.  744).  It  bears  nine  pairs  of  fleshy  appendages 
which  are  covered  with  brown  hairs.  In  the  full-grown  larva  the 
third,  fifth,  and  seventh 
pairs  of  appendages  are 
longest ;  these  are  twist- 
ed up  and  back,  and  sug- 
gest the  disheveled  locks 
of  a  hag.  This  larva 
feeds  on  various  low 
shrubs  and  the  lower 
branches  of  trees.  At 
the  time  of  spinning,  the 
larva  sheds  the  fleshy 
processes,  and  they  re- 
main on  the  outside  of 
the  cocoon. 

The   skiff -caterpillar, 
Prolimacodes  hddia. — This  remarkable  larva   (Fig.    745)  is   not  un- 
common on  oak  and  other  forest  trees.     It  is  pale  apple-green,  with 
a  chestnut-brown  patch  on  its  back.    The  moth 
(Fig.  746)  is  light  cinnamon-brown,  with  a  tan- 
brown  triangular  spot  on  each  fore  wing. 


Fig.  744. — Phobetron  pithe- 
cium,    larva.    (After 
Dyar.) 


Fig-  7 A5-— Prolima- 
codes badia,   larva. 


Family  EPIPYROPID^ 


Fig.  746. — Prolima- 
codes badia. 


This  family  is  represented  in  our  fauna  by  a  single  rare  species 
which  was  found  in  New  Mexico.  Our  species  is  Eptpyrops  barheridna. 
Another  species,  Eptpyrops  ancmala,  has  been  described  from  China; 
and  larvae  that  are  believed  to  belong  to  this  genus  have  been  found 
in  Central  America. 

These  insects  are  remarkable  on  account  of  the  extraordinary 
habits  of  the  larva?,  which  are  found  firmly  attached  to  living  insects 
of  the  family  Fulgorida?.  They  are  usually  attached  to  the  dorsal 
surface  of  the  abdomen  beneath  the  wings  of  their  host.  The  body 
of  the  larva  is  covered  with  a  cottony  coat,  causing  it  to  resemble  a 
Coccus.  It  is  supposed  that  these  larvse  feed  on  waxy  matter  excreted 
by  the  fulgorids. 

For  a  detailed  account  of  our  species,  see  Dyar  ('02). 


THE  SPECIALIZED  MICROFRENAT^ 

In  the  "Synopsis  of  the  Lepidoptera"  given  on  pages  581  to  584 
I  have  grouped  together  under  the  heading  "Specialized  Microfren- 
atas"  twenty-six  families  of  moths,  which  are  more  highly  specialized 
than  are  the  preceding  families,  and  which  as  a  rule  are  composed  of 
small  insects. 

This  group  of  families  includes  most  of  those  families  that  were 
formerly  classed  together  as  the  Microlepidoptera;  but  later  studies 
have  resulted  in  the  removal  from  the  old  group  Microlepidoptera  o 


LEPIDOPTERA  611 

several  families  of  small  moths,  hence  this  name  is  no  longer  distinc- 
tive. Among  the  families  of  small  moths  removed  from  theMicro- 
lepidoptera  are  theMicropterygidas  and  theEriocraniidee.now  placed 
in  the  suborder  Jugate;  the  Incurvariidae  and  the  Nepticulidaj,  placed 
at  the  beginning  of  the  Frenatae;  and  the  group  of  families  now  known 
as  the  Pyralids,  which  are  believed  to  be  genetically  quite  distinct 
from  the  other  families  of  small  moths.  On  the  other  hand,  in  ad- 
dition to  the  families  here  placed  in  this  series  some  authors  include 
the  Cossidse. 

The  families  of  the  Microfrenat£E  are  grouped  into  superfamilies 
in  various  ways  by  different  writers ;  but  none  of  these  groupings  is 
sufficiently  well  established  to  be  adopted  here. 

Family  ACROLOPHID^ 

These  are  large,  stout,  noctuid-like  moths;  some  of  the  species 
have  a  wing-expanse  of  30  mm.  or  more.  The  eyes  are  usually  hairy, 
in  which  respect  they  differ  from  other  "Micros."  The  antennas  are 
without  an  eye-cap.  The  labial  palpi  are  large,  and  usually  upcurved 
to  the  middle  of  the  front;  in  the  males  of  some  species  they  are 
thrown  back  on  the  dorsum  of  the  thorax,  which  they  equal  in  length. 
The  first  segment  is  relatively  very  large;  when  the  palpus  is  short 
it  is  longer  than  the  second  segment ;  the  thorax  is  tufted.  The  vena- 
tion of  the  wings  is  quite  generalized ;  the  base  of  media  is  more  or 
less  preserved,  and  all  the  branches  of  the  branched  veins  are  present ; 
there  are  three  anal  veins  in  both  fore  and  hind  wings;  in  the  fore 
wings  the  tip  of  the  third  anal  vein  coalesces  with  the  second  anal 
vein. 

Forty-two  species  have  been  described  from  our  fauna;  these 
were  formerly  classed  in  several  genera ;  but  recent  writers  refer  them 
all  to  the  genus  Acrolophus. 

The  burrowing  web-worms,  A.  arcanellus,  A.  mortipennellus ,  and 
A.  popeanellus. — The  habits  of  these  three  species  were  described 
by  Professor  Forbes  in  his  Twelfth  Illinois  Report  (1905).  The  larvag 
normally  live  in  the  ground  feeding  on  the  roots  of  grass.  Each  larva 
makes  "a  tubular  web  opening  at  the  surface  and  leading  down  into 
a  vertical  cylindrical  burrow  about  the  diameter  of  a  lead-pencil,  and 
six  inches  to  two  feet,  or  even  more  in  depth."  The  larva  measures 
about  25  mm  in  length.  Sometimes  the  larvae  injure  young  corn 
when  planted  on  sod.  They  surround  the  base  of  each  plant  with  a 
fine  web  mixed  with  earth  and  pellets,  building  this  up  in  the  lower 
blades,  which  they  slowly  eat  away.  As  they  get  larger  they  eat  the 
stripped  plant  to  the  ground.  When  disturbed  they  retreat  into 
their  web-lined  burrows. 

Family  TINEID^ 

The  head  is  usually  clothed  with  erect  hair-like  scales.  The 
antennce  are  shorter  than  the  front  wings.  The  maxillag  are  usually 
small  or  vestigial.    The  maxillary  palpi  are  usually  large  and  folded. 


612 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.   747. — Wings  of   Tinea  parasitella.    (After 

Spuler.) 


The  labial  palpi  are  short  and  clothed  with  bristles  or  with  the  first 
segment  enlarged.  In  the  typical  genera  the  venation  of  the  wings  is 
quite  generalized  (Fig. 
747),  the  base  of  me- 
dia being  preserved  in 
both  fore  and  hind 
wings  and  all  of  the 
veins  characteristic  of 
theFrenatffibeingpres- 
ent ;  but  in  other  gen- 
era the  venation  is 
somewhat  reduced. 

Many  of  the  larvae 
are  case-bearers ;  many 
are  scavengers  or  feed 
on  fungi;  some  feed 
on  fabrics,  especially 
those  that  contain 
much  wool ;  few  if  any 
feed  on  leaves. 

This  is  a  large  family.  More  than  one  hundred  twenty -five  North 
American  species  are  already  known;  fifty  of  these  belong  to  the 
genus  Tinea.    To  this  family  belong  the  well-known  clothes-moths. 

The  naked  clothes-moth,  Tineola  hiselliella. — This  is  our  most 
common  clothes-moth.  Although  the  larva  spins  some  silk  wherever  it 
goes,  it  makes  neither  a  case  nor  a  gallerv^;  it  is,  therefore,  named 
the  naked  clothes-moth.  But  when  the  larva  is  full-grown  it  makes 
a  cocoon,  which  is  composed  of  fragments  of  its  food-material  fas- 
tened together  with  silk.  The  adult  is  a  tiny  moth  with  a  wing- 
expanse  of  from  12  to  16  mm.;  it  is  of  a  delicate  straw-color,  without 
dark  spots  on  its  wings. 

The  case-bearing  clothes-moth,  Tinea  pellionella. — The  larva  of 
this  species  is  a  true  case-bearer,  making  a  case  out  of  bits  of  its 
food-material  fastened  together  with  silk.  The  case  is  a  nearly  cylin- 
drical tube  open  at  both  ends.  The  pupa  state  is  passed  within  the 
case.  The  adult  is  a  small,  silky,  brown  moth,  with  three  dark  spots 
on  each  fore  wing.    It  expands  from  11  to  17  mm. 

The  tube-building  clothes-moth  or  the  tapestry-moth,  Trichoph- 
aga  tapetiella. — The  larva  of  this  species  makes  a  gallery  composed 
of  silk  mixed  with  fragments  of  cloth.  This  gallery  is  long  and  wind- 
ing and  can  be  easily  distinguished  from  the  case  of  the  preceding 
species.  The  pupa  state  is  passed  within  the  gallery.  The  moth 
differs  greatly  in  appearance  from  the  other  two  species,  the  fore 
wings  being  black  from  the  base  to  near  the  middle,  and  white  beyond. 
It  expands  from  12  to  24  mm. 


LEPIDOPTERA 


613 


Family  PSYCHID^ 


The  Bag-Worm  Moths 

The  bag-worm  moths  are  so  called  on  account  of  tiie  silken  sacs 
made  by  the  larv«,  in  which  they  live  and  in  which  they  change  to 
pupse.  In  our  more  conspicuous  and  best-known  species 
the  sac  is  covered  either  with  little  twigs  (Fig.  748)  or, 
in  the  case  of  a  species  that  feeds  on  cedar  or  arbor-vitas, 
with  bits  of  leaves  of  these  plants.  When  the  larva  is 
full-grown  it  fastens  its  sac  to  a  twig  or  other  object 
and  transforms  within  it. 

In  the  adult  state  the  two  sexes  differ  greatly.  The 
female  is  wingless,  and  in  some  genera  the  eyes,  an- 
tennae, mouth-parts,  and  legs  are  vestigial  or  wanting, 
the  body  being  quite  maggot-like.  At  the  caudal  end 
of  the  body  there  is  a  tuft  of  hair-like  scales  which  are 
mixed  with  the  eggs.  In  most  species  the  female  does 
not  leave  the  sac  before  oviposition  but  deposits  her 
eggs  within  it. 

The  male  moths  are  winged;  they  are  small  or  of  Fig.  748. — Bag 
moderate  size.     The  wings  are   thinly   scaled   and   in    °^  Oiketicus 
some  species  nearly  naked;  when  clothed  with  scales    ^^^°^'^- 
they  are  usually  of  a  smoky  color  without  markings.    The  venation 

of    the    wings    varies 
^^Jil  greatly  within  the 

^'^"""^"^  "  family.       Figure     749 

represents  the  vena- 
tion of  our  most  com- 
mon species. 

Only  about  twenty 
species  are  known  from 
our  fauna,  of  which  the 
following  are  most 
likely  to  be  observed. 
Abbot's  bag- worm, 
Oiketicus  abhoti. — This 
species  occurs  in  the 
more  southern  part  of 
our  country.  The  lar- 
va makes  a  bag  with 
sticks  attached  to  it 
crosswise  (Fig.  748). 
The  adult  male  is 
Fig.j^g.—Wingsoi  Thyridopteryx  ephemerce.  sable  brown,  with  a 
formis.  vitreous  bar  at  the  ex- 

tremity of  the  discal 
cell  of  the  fore  wings ;  the  narrow  external  edging  of  the  wings  is  pale ; 
the  expanse  of  the  wings  is  33  mm. 


614  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  evergreen  bag-worm  or  the  bag-worm,  Thyridopteryx  ephe- 
mercBformis.- — This  species  prefers  red  cedar  and  arbor-vitae,  and  for 
this  reason  has  been  named  the  evergreen  bag-worm;  but  it  also 
feeds  on  many  other  kinds  of  trees,  and  as  it  is  the  species  that  is 
mosthkely  to  attract  attention,  and  is  sometimes  a  serious  pest,  it  is 
often  called  the  bag-worm.  It  is  our  best -known  species,  and  its 
life-history  will  serve  as  an  illustration  of  the  habits  of  the  members 
of  the  family  Psychidae. 

The  bag  of  this  species  is  about  the  same  size  as  that  of  Abbot's 
bag -worm  (Fig.  748);  but  it  differs  in  being  covered  with  bits  of 
leaves  when  it  feeds  on  cedar  or  arbor-vits,  or  with  twigs  attached 
lengthwise  when  it  feeds  on  other  trees.  When  full-grown  the  larva 
fastens  the  bag  to  a  twig  with  a  band  of  silk,  and  then  changes  to  a 
pupa.  When  the  male  is  ready  to  emerge,  the  pupa  works  its  way 
to  the  lower  end  of  the  bag  and  halfway  out 
of  the  opening  at  the  extremity.  Then  its  skin 
bursts  and  the  adult  emerges.  The  male  moth 
has  a  black,  hairy  body  and  nearly  naked  wings 
(Fig.  750).  The  adult  female  partly  emerges  from 
the  pupa  skin  and  pushes  her  way  to  the  lower 
end  of  the  bag,  where  she  awaits  the  approach  of 
750. — Thyridop-  the  male.  She  is  entirelv  destitute  of  wings  and 
ephemerce-  ^^gg  ^j^g  genitalia  "of  the  male  can  be 
greatly  extended,  making  possible  the  pairing 
while  the  female  is  still  in  the  bag.  After  pairing,  the  female  works 
her  way  back  into  the  pupa  skin,  where  she  deposits  her  eggs  mixed 
with  the  hair-like  scales  from  the  end  of  her  body.  She  then  works 
her  shrunken  body  out  of  the  bag,  drops  to  the  ground,  and  perishes. 
The  eggs  remain  in  the  pupa  skin  in  the  sac  till  the  following  spring. 

Where  this  insect  is  a  pest,  two  methods  of  control  are  practiced, 
first,  the  bags  are  collected  and  destroyed  in  the  winter,  while  they 
still  contain  the  eggs;  second,  when  impracticable  to  collect  the  bags: 
on  account  of  the  height  of  the  infested  trees,  a  spray  of  arsenate  of 
lead  is  used  in  the  spring  as  soon  as  possible  after  the  larvae  appear. 

Eurycyttarus    confederdta. — This    is  a 

smaller  species  than  the  two  preceding 

ones.     Figure  751  represents  the  sac  of  a 

male  with  the  empty  pupa-skin  projecting 

from  the  lower  end,  and  Figure  752  the 

fully  developed  male.  -^^S-  752. 

Solendbia  walshella. — This  is  a  small 
Fig.  751.  tineid-like  species;  the  male  has  a  wing-expanse  of  about  13 

mm.  and  the  hind  wings  have  a  quite  wide  fringe.  The  fore 
wings  are  light  gray  speckled  with  brown.  The  bag  of  the  larva 
is  about  8  mm.  long,  made  of  silk,  and  covered  with  fine  grains  of 
sand  or  with  particles  of  lichens  and  excrement  of  the  larva.  Cham- 
bers states  that  he  has  sometimes  found  small  molluscan  shells  ad- 
hering to  it.     The  larvae  are  found  on  the  trunks  of  trees  and  feed 


iP|» 


LEPIDOPTERA 


615 


upon  lichens.     Figure  753  represents  the  venation  of  the  wings  of  a 
European  species  of  this  genus. 


Fig.  753- 

ler.) 


-Wings  of  Solenohia.       (After  Spu- 


Family  TISCHERIID^ 

The  vertex  of  the  head 
is  clothed  with  erect,  broad, 
and  short  scales.  The  an- 
tennee  are  long,  with  the 
first  segment  small.  The 
maxillae  are  longer  than  the 
head  and  thorax.  The  max- 
illary palpi  are  small  or  ab- 
sent. The  labial  palpi  are 
short,  porrect,  and  without 
bristles  on  the  outer  side  of 
the  second  segment.  In  the 
front  wings  (Fig.  754),  the 
costal  margin  is  strongly 
arched,  the  apex  is  pro- 
longed into  a  sharp  point, 
the  discal  cell  is  long  and 
narrow,  the  accessory  cell  is 
very  long,  and  the  "base  of 
media  is  preserved.  The  hind  wings  are  long  and  narrow  and  with 
greatly  reduced  venation.    (Fig.  754).    The  hind  tibiae  are  very  hairy. 

Nearly  all  of  our  spe- 
cies belong  to  the  genus 
Tischeria.  The  larvae 
lack  thoracic  legs;  most 
of  them  make  blotch 
mines  in  the  leaves  of 
oak;  but  the  following 
one  infests  apple;  and 
some  other  species  infest 
blackberry  and  rasp- 
berry. 

The  trumpet-leaf 
miner  of  apple,  Tischeria 
malifoliella. — This  spe- 
cies infests  the  leaves  of 
apple  over  the  Eastern 
half  of  the  United  States  and  Canada,  and  sometimes  does  serious 
injury.  The  larva  makes  a  trumpet-shaped  mine  just  beneath  the 
epidermis  on  the  upper  side  of  the  leaf;  the  first  half  of  the  mine  is 
usually  crossed  by  crescent-shaped  stripes  of  white.  There  are  two 
generations  annually  in  the  North,  and  several  in  the  South.  The 
larvae  pupate  in  their  mines.  The  larvae  of  the  last  generation  line 
their  mines  with  silk  and  pass  the  winter  in  them.    They  transform 


Fig-  754- — Wings  of  Tischeria  marginea. 
Spuler.) 


(After 


ei6 


AN  INTRODUCTION  TO  ENTOMOLOGY 


to  pupas  in  the  spring  and  emerge  as  adults  eight  or  ten  days  later. 
The  adult  moth  expands  about  6  mm. ;  it  has  shining  dark  brown  front 
wings,  tinged  with  purplish  and  dusted  with  pale  yellowish  scales. 
To  control  this  pest,  plow  the  orchard  after  the  leaves  have  fallen, 
or  rake  and  bum  the  fallen  leaves. 

Family  LYONETIID^E 


Pig.  755. — Wings  of  Bedellia  somnulentella.    (After 
Clemens.) 


Moths  with  the  head  smooth,  at  least  on  the  front.    The  scape  of 
the  antennae  usually  forms  an  eye-cap.     The  ocelli  and  the  maxillary- 
palpi  are  wanting.  The 
„  5^  labial  palpi  are  usually 

j^j___5^-- ^c:;;;;^  — :::rr::;-^        very  small.  The  wings 

are  ver\'  narrow  (Fig. 
755);  the  hind  wings 
are  often  linear,  with 
the  radial  sector  ex- 
tending through  the 
axis  of  the  wing.  The 
apices  of  the  wings 
are  usually  warped  up 
or  down.  The  larvae 
are  leaf-miners  or  live 
in  webs  between  leaves.  The  following  species  will  serv^e  as  examples 
of  this  family. 

The  morning-glory  leaf-miner,  Bedellia  somnu- 
lentella.-— The  young  larva  makes  a  serpentine 
mine  with  a  central  line  of  frass;  later  it  leaves 
this  mine  and  makes  a  blotch  mine.  The  pupa  is 
naked,  and  fixed  by  the  caudal  end  to  some  cross- 
threads  on  the  under  side  of  the  leaf.  The  adult  is 
yellow  and  expands  about  10  mm. 

The  apple  bucculatrix,  Bucculdtrix  pomifoU- 
ella. — The  larv^a  of  this  species  infests  the  leaves 
of  apple,  and  when  full-grown  it  makes  a  small 
white  cocoon  which  is  attached  to  the  lower  sur- 
face of  a  twig.  These  cocoons  sometimes  occur  in 
great  nimibers,  side  by  side,  on  the  twigs  of  an 
infested  tree  (Fig.  756).  They  are  easily  recog- 
nized by  their  shape,  being  slender  and  ribbed 
lengthwise.  It  is  these  cocoons  that  usually  first 
reveal  the  presence  of  the  pest  in  an  orchard.  They 
are  very  conspicuous  during  the  winter,  when  the 
leaves  are  off  the  trees.  At  this  time  each  cocoon 
contains  a  pupa.  The  adult  moth  emerges  in 
early  spring.  The  eggs  are  laid  on  the  lower  sur- 
face of  the  leaves.  Each  larva  when  it  hatches 
bores  directly  from  the  egg  to  the  upper  surface 
of  the  leaf,  where  it  makes  a  brown  serpentine  mine.     When  these 


Fig.  756. — Cocoons 
of  Bucculatrix 
pomifoliella. 


LEPIDOPTERA  617 

mines  are  abundant  in  a  leaf,  it  turns  yellow  and  dies.  When  the  larva 
has  made  a  mine  from  12  to  18  mm.  in  length,  which  it  does  in  from 
four  to  five  days,  it  eats  its  way  out  through  the  upper  surface.  Then 
somewhere  on  the  upper  surface  of  the  leaf  it  weaves  a  circular  silken 
covering  about  2.5  mm.  in  diameter.  Stretched  out  on  this  network, 
the  larva,  which  is  now  about  2.5  mm.  long,  makes  a  small  hole  in  it 
near  the  edge,  then,  as  one  would  turn  a  somersault,  it  puts  its  head 
into  this  hole  and  disappears  beneath  the  silken  covering,  where  it 
undergoes  a  change  of  skin.  It  remains  in  the  molting  cocoon  usually 
less  than  24  hours.  After  leaving  this  cocoon  it  feeds  upon  the  leaves 
without  making  a  mine;  and  in  a  few  days  makes  a  second  molting 
cocoon  which  differs  from  the  first  only  in  being  about  3  mm.  in 
diameter.  After  leaving  this  it  again  feeds  for  a  few  days,  and  then 
migrates  to  a  twig  where  it  makes  the  long  ribbed  cocoon  within 
which  the  pupa  state  is  passed.  The  adult  is  a  tiny,  light  brown 
moth,  with  the  fore  wings  whitish,  tinged  with  pale  yellowish,  freely 
dusted  with  brown ;  on  the  middle  of  the  inner  margin  there  is  a  dark 
brown  oval  patch. 

The  genus  Bucculatnx,  to  which  the  above  species  belongs,  is 
placed  by  some  writers  in  a  separate  family,  the  BucculatrigidcB. 

The  family  Opostegid^  has  been  established  for  the  genus 
Opostega,  of  which  only  three  species  have  been  found  in  this  country. 
These  are  moths  with  folded  maxillary  palpi,  with  the  scape  of  the 
antennae  forming  a  large  eye-cap,  andwith  radius,  media,  and  cubitus 
of  the  fore  wings  unbranched.  The  hind  wings  are  linear.  The 
combination  of  the  eye-cap  and  the  unbranched  veins  of  the  fore 
wings  is  a  distinctive  feature  of  this  family. 

The  larvae  are  very  slender,  cylindrical,  without  legs,  and  are  bast- 
miners. 

Family  OINOPHILID^ 

This  family  includes  "strongly  flattened  moths,  with  flat  coxae 
closely  appressed  to  the  body,  usually  with  smooth  heads,  rising  to 
a  rounded  ridge  between  the  antennas,  but  often  with  a  loose  tuft 
on  the  vertex,  and  rather  small  maxillary  palpi  of  the  folded  type. 
The  labial  palpi  have  a  well-set-ofi^,  fusiform,  terminal  joint  as  in  the 
Tineidae,  and  are  normally  without  bristles.  The  venation  in  the  known 
genera  is  more  or  less  reduced."  (Forbes.) 

Only  one  species  representing  this  family  has  been  found  in  our 
fauna.  This  is  Phceoses  sabinella,  described  by  Forbes  ('22),  from 
Louisiana  and  Mississippi.  It  is  a  shining  gray-brown  (mouse  gray) 
moth,  with  a  wing-expanse  of  9  mm. 

The  known  larvae  of  this  family  feed  on  decaying  vegetable  matter 
and  fungi. 

Family  GRACILARIID^ 

The  vestiture  of  the  head  varies  greatly;  the  vertex  is  clothed 
with  prominent  scales  in  some  forms,  in  others  it  is  smooth.     The 


618 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig-  757- — Wings  of  Cracilaria.     (After  Spuler.) 


antennae  are  long;  the  scape  forms  an  eye-cap  in  some  species  and 
not  in  others.  The  fore  wings  are  lanceolate,  normal  or  with  some- 
what reduced  vena- 
tion (Fig.  757) ;  usu- 
ally without  an  ac- 
cessory cell,  but 
sometimes  one  is 
present  in  the  genus 
Ornix.  The  hind 
wings  are  lanceolate 
or  linear;  in  many 
members  of  the 
family  they  are  ex- 
panded near  the 
base,  formingamore 
or  less  prominent 
hump  in  the  costal 
margin,  and  in 
some  species  vein  Ri  is  free,  not  coalesced  with  vein  Sc. 

The  adult  moths  when  at  rest  elevate  the  front  part  of  the  body, 
the  fore  legs  being  held  vertically  so  that  the  tips  of  the  wings  touch 
the  surface  on  which  the  insect  rests. 

The  larvae  are  extraordinary;  when  young  they  are  very  much 
flattened  and  have  thin,  blade-like  mandibles  and  vestigial  maxillae 
and  labium;  they  merely  slash  open  the  cells  of  the  leaf  and  suck  up 
the  cell-sap;  later  they  usually  have  normal  mouth-parts  and  eat  the 
parenchyma.  The  young  larvcS  always  make  a  fiat  blotch  mine; 
later  they  make  a  blotch  mine  in  which  the  epidermis  of  one  side  of 
the  leaf  is  thrown  into  a  fold  by  the  growth  of  the  leaf,  i.  e.,  a  tenti- 
form  mine,  or  they  roll  a  leaf.  The  larvae  have  only  fourteen  legs  or 
none,  never  any  on  the  sixth  segment  of  the  abdomen. 

This  is  a  large  famly ;  about  two  hundred  North  American  species 
have  been  described,  and  doubtless  many  more  are  to  be  discovered. 

About  one-half  of  our  described  species  belong  to  the  genus  which 
is  commonly  known  as  Ltthocolletis ,  but  which  is  termed  Phyllonoryc- 
ter  by  those  who  recognize  the  names  in  the  "Tentamen"  of  Hubner. 
The  following  species  will  ser^^e  as  an  example  of  this  genus. 

The  white-blotch  oak-leaf  miner,  Phyllonorycter  hamadryadella. — 
This  little  miner  infests  the  leaves  of  many  different  species  of  oaks, 
and  is  very  common  throughout  the  Atlantic  States.  The  mine  is  a 
whitish  blotch  mine  in  the  upper  side  of  the  leaf,  and  contains  a  single 
larva;  but  often  a  single  leaf  contains  many  of  these  mines  (Fig.  758). 
The  young  larv^a  is  remarkable  in  resembling  more  the  larv^a  of  a  beetle 
than  the  ordinary  type  of  lepidopterous  larv'se  (Fig.  758,  6).  It  is 
nearly  flat ;  the  first  thoracic  segment  is  much  larger  than  any  of  the 
others;  the  body  tapers  towards  the  hind  end;  and  there  are  only  the 
faintest  rudiments  of  legs  discernible.  The  larv^ae  molt  seven  times. 
At  the  seventh  molt  the  form  of  the  body  undergoes  a  striking  change. 


LEPIDOPTERA 


619 


It  now  becomes  cylindrical  in  form,  there  is  a  great  change  in  the 
shape  of  the  mouth-parts,  and  the  fourteen  feet  are  well  developed. 
The  full-grown  cylindrical  larva  measures  about  5  mm.  in  length. 
It  spins  a  cocoon,  which  is  simply  a  delicate,  semi-transparent, 
circular  sheet  of  white  silk,  stretched  over  a  part  of  the  floor  of  the 
mine.  The  pupa  is  dark  brown  in  color,  and  bears  a  toothed  crest 
upon  its  head  (Fig.  758,  n,  0),  which  enables  it  doubtless  to  pierce  or 
saw  its  way  out  from  the  cocoon.  The  moth  is  a  delicate  little  crea- 
ture, whose  wings  expand  a  little  more  than  6  mm.    The  fore  wings 


Fig.  758. — Phyllonorycter  hamadryadella:  a,  mine;  b,  young  larva;  c,  full-grown, 
flat -form  larva;  d,  head  of  same,  enlarged;  e,  antenna  of  same,  enlarged;  /, 
round-form  larva  from  above;  g,  same  from  below;  h,  head  of  same,  enlarged; 
i,  antenna  of  same,  enlarged;  k,  maxilla  and  palpus  of  same,  enlarged;  /, 
labium,  labial  palpi,  and  spinnerets  of  same;  m,  pupa;  n,  side  view  of  pupal 
crest;  0,  front  view  of  same;  g,  cocoon;  Q,  moth.  (From  the  author's  Report 
for  1879.) 


are  white,  with  three,  broad,  irregular,  bronze  bands  across  each,  and 
each  band  is  bordered  with  black  on  the  inner  side.  The  hind  wings 
are  silvery. 

As  this  insect  passes  the  winter  as  a  larva  within  the  dry  leaves, 
the  best  way  to  check  its  ravages  when  it  becomes  a  pest  is  to  rake 
up  and  bum  such  leaves. 

Another  common  oak-leaf  miner  in  the  East  is  Phyllonorycter 
cincinnatiella.  The  larvce  form  large  blotch  mines  on  the  upper 
surface  of  leaves.  In  this  species  the  larv^ae  are  social,  one  mine  often 
containing  from  several  to  a  dozen  larvae.  The  loosened  epidermis  is 
brownish  yellow,  somewhat  puckered,  and  often  covers  nearly   the 


620 


^iV  INTRODUCTION  TO  ENTOMOLOGY 


entire  leaf.  This  species  like  most  other  gracilariids  passes  the  winter 
as  pupffi. 

A  common  miner  in  the  leaves  of  locust  is  Parectopa  rohiniella. 
The  lar\^a  makes  on  the  upper  surface  of  the  leaf  what  has  been 
termed  a  digitate  mine,  that  is  a  blotch  mine  with  a  number  of  lateral 
galleries  running  out  from  it  on  each  side. 

Several  members  of  this  family  make  tentiform  mines  in  the 
leaves  of  apple  and  other  fruit  trees;  but  these  species  are  rareh'  of 
economic  importance. 

Family  COLEOPHORID^* 

Moths  with  a  smooth  head,  without  ocelli,  and  without  maxillarv'- 
palpi.  The  labial  palpi  are  of  moderate  size.  The  antennas  are  held 
extended  forward  in  repose.    The  wings  are  very  narrow.    The  discal 


^^^         Cu,  .J/3       ^J/i+2 

Fig.  759. — Wings  of  Coleophora  laricella.     (After  Forbes). 

cell  of  the  fore  wing  extends  obliquely ;  vein  Cui  and  vein  Cuo  when 
present  are  very  short  (Fig.  759). 

The  larvae  are  usually  leaf-miners  when  young  or  feed  within 
seeds;  later,  with  few  exceptions,  the}"  are  case-bearers. 

Nearly  all  of  our  species  belong  to  the  genus  Coleophora,  of  which 
about  ninety  species  have  been  found  in  this  country.  The  two  follow- 
ing species  are  those  that  have  attracted  most  attention  on  account 
of  their  economic  importance. 

The  pistol  case-bearer,  Coleophora  malivorella. — The  larva  of  this 
species  infests  apple  especially  but  is  also  found  on  quince,  plum,  and 
cherry.  The  larvae  hatch  in  mid-summer  from  eggs  laid  on  the  leaves 
and  eat  little  holes  in  the  leaves.    They  soon  construct  little  pistol- 

*The  typical  genus  of  this  family  is  commonly  known  as  Coleophora,  the  name 
used  for  it  by  Hubner  in  his  "Tentamen."  But  those  writers  who  do  not  recognize 
the  "Tentamen"  as  a  published  work  use  the  later  name  Haploptilia  for  the  genus, 
and  name  the  family  the  Haloptilhd^. 


LEPIDOPTERA 


621 


shaped  cases  composed  of  silk,  the  pubescence  of  leaves,  and  excre- 
ment. The  larva  projects  itself  out  from  the  case  far  enough  to  get 
a  foothold  and 
eats  irregular 
holes  in  the  leaf, 
holding  the  case 
at  a  considerable 
angle  with  the 
leaf.  About  Sep- 
tember first  the 
larvas  migrate  to 
the  twigs  where 
they  fasten  the 
cases  to  the 
bark  (Fig.  760) 
and  hibernate  till 
April,  spending 
about  seven 
months  in  hiber- 
nation. They 
then  pass  to  the 
swelling  buds, 
expanding  leaves 
and     flowers, 

where  they  continue  feeding.    They  become  full-grown  in  the  latter 
part  of  Aiay,  and  then  fasten  their  cases  to  the  smaller  branches. 

After  the  case  is  fastened  to  the 
branch  the  larva  turns  around  in 
it,  and  changes  to  a  pupa;  conse- 
quently the  moth  emerges  from 
the  curved  end  of  the  case. 

The  cigar  case-bearer,  Coleo- 
phora  fletcherclla. — This  species, 
like  the  preceding  one,  is  a  pest 
of  apple  and  other  fruit  trees,  and 
resembles  that  species  to  a  con- 
siderable extent  in  habits.  In 
this  species  the  young  larvee  are 
miners  in  the  leaves  for  two  or 
three  weeks  before  making  their  cases.  The  case  (Fig.  761)  is  com- 
posed of  fragments  of  leaves  fastened  together  b}^  silk. 


Fig.  760. — Coleophora  nialivorella:  a,  apple  twig  showing 
larval  cases  and  work  on  leaves;  b,  larva;  c,  pupa;  d, 
moth;  b,  c,  d,  enlarged.     (After  Riley.) 


Fig.    761. — Cases    of   the    cigar  case 
bearer.     (After  Hammar.) 


Family  ELACHISTID^ 


The  head  is  smooth.  The  scape  of  the  antennse  does  not  form  an 
eye-cap.  The  venation  is  but  slightly  reduced  (Fig.  762).  The  hind 
wings  are  lanceolate,  with  a  well  formed  discal  cell. 

The  larvas  have  sixteen  legs.  Most  of  the  known  species  make 
blotch  mines  in  grasses.     And  some  at  least  when  full-grown  leave 


622 


AN  INTRODUCTION  TO  ENTOMOLOGY 


-V.-/ 


S/  yl      ill  2 


Fig.  762. — Wings  of  Elachista  guadrella.    (After  Spuler.) 


the  mine  and  weave  a  slight  web  from  which  the  pupa  hangs  sus- 
pended, like  the  pupa  of  a  butterfly. 

This  is  a  small 
family;  most  of  our 
Si  ___.-^  '  ^  '   'J^'^—p'^'--^^ ,       species    belong    to 
'^\^ti::^:^^^^^^         the  genus  Elachista. 

Family 
HELIOZELID^ 

The  antennas 
are  from  one-half  to 
two-thirds  as  long 
as  the  front  wings; 
the  scape  is  short 
and  not  enlarged 
so  as  to  form  an 
eye-cap.  The  wings 
(Fig.  763)  are  lan- 
ceolate; in  the  hind  wings  there  is  no  discal  cell,  owing  to  the  coales- 
cence of  the  radial  sector  and  media  for  nearly  the  entire  length  of  the 
wing,  vein  Rg  sep- 
arating near  the 
apex  of  the  wing. 

The  habits  of 
the  larvse  are  well- 
illustrated  by  the 
following  species. 


The  resplendent 
shield -bearer,  Cop- 
todisca  splendorij- 
erella. — This  spe- 
cies infests  the 
leaves  of  apple, 
pear,  quince,  thom- 
apple,  and  wild 
cherry.  The  larva 
is  both  a  miner  and 
a  case-bearer.  It  at 
first  makes  a  linear  Fig-  763-- 
mine;  but  later  this  ^^^-^ 
is  enlarged  into  a 

blotch  mine.  When  full-grown  the  larva  makes  an  oval  case  cut 
from  the  walls  of  its  mine  and  lined  with  silk.  It  then  seeks  a  safe 
place  in  which  to  fasten  this  case.  This  is  usually  on  the  trunk  or 
on  a  branch  of  the  infested  tree  (Fig.  764,  d).  There  are  two  genera- 
tions annually.     The  second  generation  pass  the  winter  as  larvae 


K*+5 


.y^^ 
^e/^ 


-Wings  of  Antispila  pfeifferella.      (After  Spu- 


LEPIDOPTERA  623 

within  their  cases.  The  adult  (Fig.  764.  g),  is  a  brilHantly  colored, 
golden-headed  moth.  The  basal  half  of  the  front  wings  is  leaden- 
gray  with  a  resplendent  luster  and  the  remainder  golden  with  silvery 
and  dark  brown  streaks.    It  expands  about  5  mm. 


Fig.  764. — Coptodisca  splendoriferella:  a,  leaf  of  apple  showing  work;  b,  summer 
larva;  c,  larva  in  case  travelling;  d,  cases  tied  up  for  winter;  e,  hibernating 
larva;  /,  pupa;  g,  moth,  h,  parasite.        (From  the  Author's  report  for  1879.) 

The  sour  gimi  case-cutter,  Antispila  nysscBfoliella. — This  species 
infests  the  leaves  of  Nyssa  sylvdtica.  Its  habits  are  similar  to  those 
of  the  preceding  species. 


Family  DOUGLASIID/E 

The  scape  of  the  antennae  is  small  and  does  not  form  an  eye-cap. 
The  first  segment  of  the  labial  palpi  is  small.  The  ocelli  are  large. 
The  hind  wings  are  lanceolate  and  without  a  discal  cell,  owing 
to  the  coalescence  of  the  radial  sector  and  media.  Vein  Rg  sep- 
arates from  media  near  the  middle  of  the  length  of  the  wing  (Fig.  765) . 


624 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  765. — Wings  of  Tinagma  obscurofasciella. 
Chambers.) 


(After 


This  family  is  represented  in  this  country  by  a  single  species, 

Tinagma  obscuro- 
Sc    c>  fasciella,    the  larva 

of  which  is  a  leaf- 
miner  in  Rosaceas. 


Family 
CECOPHORID^ 

The  head  is  usu- 
ally smooth,  with 
appressed  scales 
sometimes  with 
loose  scales  and 
spreading  side  tufts. 
The  antennffi  usu- 
ally have  a  comb  of  bristles  on  the  scape.  The  labial  palpi  are  well- 
developed,  generaly  curved  upward;  the  terminal  segment  is  acute- 
ly pointed.  The  maxillary  palpi  are  vestigial.  The  wings  are  fairly 
broad,  sometimes  ample 

Sc      y? ^^ 

^^ 


(Fig.  766).  The  venation 
is  but  little  reduced.  In 
the  fore  wings  veins  R4 
and  R5  are  stalked  or  co- 
alesce throughout;  veins 
R2  and  Cu2  arise  well 
back  from  the  end  of  the 
discal  cell;  and  vein  ist 
A  is  preserved.  In  the 
hind  wings  veins  Rs  and 
M:  are  well  separated  and 
extend  parallel.  The 
posterior  tibiag  are  cloth- 
ed with  rough  hairs 
above. 

The  larvae  have  sixteen  legs ;  they  are  often  prettily  marked  with 
dark  tubercles  on  whitish  or  yellowish  ground.  The  different  species 
vary  in  their  habits;  the  majority  of  them  either  live  in  webbed- 
together  leaves  or  blossoms  or  feed  in  decayed  wood;  one  species, 
Endrosis  lacteella,  is  a  stored-food  pest  in  California  and  in  Europe. 

About  one  hundred  species  have  been  described  from  our  fauna; 
many  of  them  are  common.  A  generic  revision  of  the  American 
species  was  published  by  Busck  ('09  a).  The  following  one  is  a  well- 
known  pest. 

The  parsnip  webworm,  Depressdria  heraclidna. — The  larvae  of  this 
species  web  together  and  devour  the  unfolding  blossom-heads  of 
parsnip,  celery,  and  wild  carrot.  After  the  larvae  have  consumed  the 
flowers  and  unripe  seeds  and  become  nearly  full-grown,  they  burrow 


Fig.     766. — Wings    of    Depressaria    heracliana. 


LEPIDOPTERA  625 

into  the  hollow  stems  and  feed  upon  the  soft  lining  of  the  interior. 
Here  inside  the  hollow  stem  they  change  to  pupse.  The  moths  appear 
in  late  July  and  early  August,  and  soon  go  into  hibernation  in 
sheltered  places. 

Family  ETHMIID^ 

This  family  includes  a  small  number  of  moths,  which  were  former- 
ly included  in  the  family  CEcophoridae.  The  family  Ethmiidas  was 
established  by  Busck  Cogb),  who  states  that  the  main  structural 
character  of  the  imago  by  which  this  family  can  be  distinguished 
from  the  CEcophoridae  is  the  proximity  of  vein  M2  in  the  hind  wings  to 
vein  Ml  instead  of  to  vein  M3  as  in  the  CEcophoridae,  it  being  radial 
not  cubital.  Fracker  ('15)  describes  larval  characters  distinctive  of 
the  tvpical  genus  Ethniia. 

The  members  of  this  family  have  broad  wings.  The  fore  wings 
are  usually  bright  colored,  with  striking  patterns,  often  black  and 
white. 

The  larvje,  as  a  rule,  are  social,  living  in  a  light  web.  They  feed 
chiefly  on  plants  of  the  family  Borraginaceae.  ^ 

Most  of  the  species  belong  to  the  genus  Ethmia  of  which  about 
thirt}'  are  now  known. 

Family  STENOMID^ 

This  family  includes  large  moths  as  compared  with  most  "micros." 
The  wings  are  broad,  especially  the  hind  wings.  In  the  fore  wings 
all  of  the  branches  of  the  branched  veins  are  typically  present. 
In  the  hind  wings  vein  Mi  is  joined  at  its  base  to  vein  Rg. 

The  larvae  live  in  webs  on  leaves,  especially  of  oak. 

There  are  about  twenty  North  American  species,  most  of  which 
belong  to  the  genus  Stenoma. 

A  common  species  in  the  Atlantic  States  is  Stenoma  schlcegeri. 
This  is  one  of  our  larger  species,  having  a  wing-expanse  of  30  mm. 
The  moth  is  of  a  dirty  white  color  with  the  fore  wangs  mottled 
with  darker  bands  and  spots,  and  with  a  conspicuous  patch  of 
brown  scales  near  the  base  of  the  inner  margin.  When  at  rest  on  a 
leaf  the  insect  folds  its  wings  closely  about  its  body,  and  resembles 
in  a  striking  manner  the  excrement  of  a  bird. 

Family  GELECHIID^ 

The  head  is  smooth  or  at  most  slightly  ruffled.  The  labial 
palpi  are  long,  curved,  ascending,  and  usually  with  the  terminal  seg- 
ment acutely  pointed.  The  maxillary  palpi  are  vestigial  or  wanting. 
The  venation  of  the  wings  (Fig.  767)  is  more  or  less  reduced;  the 
stem  of  vein  M  is  wanting;  vein  ist  A  is  wanting  in  the  fore  wings; 
and  sometimes  in  the  hind  wings  also.  In  the  fore  wings  the  second 
anal  vein  is  forked  at  the  base,  i.  e.,  the  tip  of  the  third  anal  vein 


626 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  767. 
Busck. 


-Wings  of  Pectinopliora  gossypiella.     (After 


unites  with  it ;  and  in  some  forms,  veins  R4  and  R5  coalesce  through- 
out their  length ,  but 
they  are  usually 
stalked.  The  hind 
wings  are  usually 
more  or  less  trape- 
zoidal;  and  the 
outer  margin  is 
usually  sinuate  or 
emarginate  below 
the  apex. 

The  larvae  vary 
greatly  in  habits ; 
some  are  leaf-min- 
ers; but  more  feed 
in  rolled  or  spun  to- 
gether leaves  or  in 
stems  orseed  heads; 
and  one  is  a  serious 
pest  of  stored  grain. 
This  is  the  larg- 
est family  of  the 
Microf renatae  ; 

more  than  four  hundred  species  have  been  described  from  our  fauna. 

A  revision  of  the 
American  moths 
of  this  family  was 
published  by 
Busck  ('03). 

The  Angou- 
mois  grain-moth, 
Sitoiroga  cerealel- 
la.- — The  larva  of 
this  moth  feeds 
upon  seeds,  and 
especially  upon 
stored  grain.  It 
occurs  through- 
out our  country ; 
but  it  is  especial- 
ly destructive  in 
the  Southern 
States.  In  that 
part  of  the  coun- 
try it  is  extreme- 
ly  difficult  to 
keep  grain  long 
on  account  of 
this  pest  and  cer- 


Fig.  768. — Paralechia  pinifoliella:  larva,  pupa,  adult,  and 
leaves  mined  by  the  larva.  (From  the  Author's  Report 
for  1879.) 


LEPIDOPTERA 


627 


tain  beetles  that  also  feed  on  stored  grain.  The  adult  moth  is  of  a 
very  light  grayish-brown  color,  more  or  less  spotted  with  black;  it 
expands  about  12  mm.  The  common  name  is  derived  from  the  fact 
that  it  has  been  very  destructive  in  the  province  of  Angoumois, 
France.  The  most  effective  method  of  destroying  this  pest  is  by 
the  use  of  carbon  bisulphide  in  the  manner  in  which  it  is  used  against 
the  grain-weevils,  already  described. 

The  pine-leaf  miner,  Paralechia  pinifoliella: — It  often  happens 
that  the  ends  of  the  leaves  of  pine  present  a  dead  and  brown  appear- 
ance that  is  due  to  the  interior  of  the  leaf  having  been  eaten  out. 
This  is  the  work  of  the  pine-leaf  miner  (Fig.  768).  At  the  right 
season  it  is  easy  to  see  the  long,  slender  larva  in  its  snug  retreat  by 
holding  a  leaf  up  to  the  light  and  looking  through  it;  and  later  the 
pupa  can  be  seen  in  the  same  way.  Near  the  lower  end  of  the  tunnel 
in  each  leaf  there  is  a  round  hole  through  which  the  larva  entered 
the  leaf  and  from  which  the  adult  emerges.  We  have  found  this 
insect  in  several  of  the  stouter-leaved  species  of  pine,  but  never  in 
the  slender  leaves  of  the  white  pine.  In  the  North  it  is  most  abundant 
in  the  leaves  of  pitch-pine. 

The  peach  twig-borer,  Andrsia  line- 
atella. — This  pest  is  generally  distribut- 
ed throughout  the  United  States  and 
Canada,  and  sometimes  it  destroys  a 
large  part  of  the  crop  in  some  localities. 
The  young  larvae  hibernate  in  small 
cavities  which  they  excavate  in  the 
bark  of  young  twigs.  In  the  spring  the 
larvae  burrow  into  the  tender  shoots; 
the  leaves  of  the  buds  unfold  and  then 
wither.  There  are  several  generations 
annuallv.  The  summer  generations 
attack  both  twigs  and  fruit. 

The  solidago  gall-moth,  Gnorimo- 
schenia  gallcesoliddginis . — There  are  two 
kinds  of  conspicuous  galls  which  are 
enlargements  of  the  stems  of  golden- 
rod  ;  one  of  these  is  a  ball-like  enlarge- 
ment of  the  stem  and  is  caused  by  the 
larva  of  a  fly,  Eurosta  solidaginis,  de- 
scribed in  the  next  chapter;  the  other 
is  spindle-shaped  (Fig.  769)  and  is 
caused  by  the  moth  named  above.  The 
adult  moth  hibernates.  The  eggs  are 
laid  upon  the  young  goldenrod  plants. 

The  young  larva  eats  its  way  into  the  center  of  the  stalk,  and  causes 
the  growth  of  the  gall.  The  larva  becomes  full-grown  about  the 
middle  of  July ;  then  before  changing  to  a  pupa  it  eats  a  passage-way 
through  the  wall  of  the  gall  at  its  upper  end,  and  closes  the  opening 


Fig.  769. — Gall  of  the  solidago 
gall-moth.    (After  Riley.) 


628  AN  INTRODUCTION  TO  ENTOMOLOGY 

with  a  plug  of  silk,  which  is  so  formed  that  it  can  be 
pushed  out  by  the  adult  moth  when  it  is  ready  to  emerge. 

Some  members  of  the  family  are  leaf-rollers. 
Figure  770  represents  a  leaf  rolled  by  a  gelechiid  larva, 
probably  Anacampsis  innocella.  This  species  infests 
poplar. 

The  pink  bollworm,  Pectinophora  gossypiella. — This 
species  is  regarded  as  one  of  the  most  destructive  cotton 
insects  known  and  ranks  among  the  half-dozen  most 
important  insect  pests  of  the  world.  It  often  reduces 
the  yield  of  lint  fifty  per  cent,  or  more  and  materially 
lessens  the  amount  of  oil  obtained  from  the  seeds. 

The  adult  is  a  small  dark -brown  moth,  with  a  wing- 
expanse  of  from  15  to  20  mm.  Figure  767  represents 
the  shape  and  the  venation  of  the  wings.  The  larva 
eats  the  seeds  and  tunnels  and  soils  the  lint,  causing 
the  arrest  of  growth  and  the  rotting  or  premature  and 
imperfect  opening  of  the  boll  (Busck). 

A  detailed  account  of  this  pest,  illustrated  by  many 
figures  was  published  by  Busck  ('17). 


Family  BLASTOBASID^ 

The  scape  of  the  antenna?  is  armed  with  a  fringe  of 
strong  bristles,  or  pecten.  The  labial  palpi  are  slender 
and  upturned  or  vestigial. 

The  discal  cell  of  the  fore  wings(Fig.  771)  is  long 

compared  with  the  lengths  of  the  apical  veins  (R2  to 

Leaf  rolled  CU2) ;  and  these  veins  arise  from  the  extreme  end  of 

by    a    gele-   the  cell.    As  vein  Ri  arises  near  the  base  of  the  wing  it 

child  larva,   jg  unusually  distant  from  vein  R2;  to  make  up  for  the 

resulting  weakening  of  the  wing,  the  membrane  is  more 

or  less  thickened  along  the  costa;  this  thickening  is  the  so-called 

stigma.    The  hind  wings  are  lanceolate,  and  rather  narrower  than  the 

fore  wings.     Veins  Rs  and  Mi  are  well  separated  at  the  end  of  the 

discal  cell.    Veins  M2,  M3  and  Cui  are  close  together  or  coincident. 

About  one  hundred  species  have  been  described  from  our  fauna; 
among  them  are  the  following. 

The  acorn-moth,  Valenthiia  glmidulella. — The  larva  of  this  species 
lives  as  a  scavenger  in  acorns  that  have  been  destroyed  by  acorn- 
weevils,  Balanius.  The  moth  lays  an  egg  in  the  destroyed  acorn 
after  the  beetle  has  left  it,  and  the  larva  hatching  from  this  egg 
feeds  upon  the  crumbs  left  by  the  former  occupant.  The  larva  passes 
the  winter  within  the  acorn.  The  moths  emerge  at  various  times 
throughout  the  summer. 


70 


LEPIDOPTERA 


629 


The  oak-coccid  blastobasid,  Zenodochium  coccivorella. — The  larva 
is  an  internal  parasite  in  the  gall-like  females  of  the  coccid  genus 
Kermes.    I  found  it  common  at  Cedar  Kevs,  Fla. 


-"^•^  IS/  A    Cm  C,i,  Mi 

Fig.  771. — -Wings  of  Holcocera.     (After  Forbes.) 


Family  COSMOPTERYGID^E 


The  moths  grouped  together  in  this  family  vary  greatly  in 
structure.  The  fore  wings  are  lanceolate,  sometimes  caudate,  i.  e.  with 
the  apex  greatly  prolonged.  Vein  ist  A  arises  out  of  vein  2d  A  or  is 
lost.  The  hind  wings  are  lanceolate  or  linear.  Vein  Ri  is  separate 
from  vein  Sc.     Veins  Rs  and  Mi  are  close  together. 

The  following  species  will  serve  as  examples  of  members  of  this 
family. 

The  palmetto-leaf  miner,  Homaledra  sabalella. — This  species  oc- 
curs only  in  the  South  where  the  saw-palmetto  grows;  but  it  is  of 
general  interest  as  illustrating  a  peculiar  type  of  larval  habit.  The 
larvaj  can  hardly  be  said  to  be  leaf -miners;  for  they  feed  upon  the 
upper  surface  of  the  leaf,  destroying  the  skin  as  well  as  the  fleshy  part 
of  the  leaf.  They  are  social,  working  together  in  small  companies, 
and  make  a  nest  consisting  of  a  delicate  sheet  of  silk  covering  that 
part  of  the  leaf  upon  which  they  are  feeding;  this  sheet  is  covered 
with  what  appears  like  sawdust,  but  which  is  really  a  mass  of  the 
droppings  of  the  larvae  (Fig.  772).  The  full-grown  larva  attains  a 
length  of  12  mm.  The  pupa  state  is  passed  within  the  nest  made  by 
the  larvae.  The  moth  expands  15  mm.  Its  general  color  is  a  delicate 
silvery  gray,  with  a  tinge  of  lavender  in  some  individuals. 

The  cat-tail  moth,  Lymncecia  phragmitella. — The  larva  of  this 
species  feeds  in  the  heads  of  cat-tail,  Typha.  It  winters  in  the  head, 
which  presents  a  tattered  and  frayed  appearance.  The  larvae  spin 
an  abundance  of  silk,  thereby  tying  the  down  or  pappus  together  and 


630 


AN  INTRODUCTION  TO  ENTOMOLOGY 


keeping  it  from  blowing  away.  The  overwintering  larvae  are  half- 
grown.  When  full-grown  some  transform  in  the  heads,  but  many 
go  down  and  bore  in  the  stems  and  transform  there. 

Cosmopteryx. — "The  little  moths  belonging  to  the  genus  Cos- 
mopteryx  are  probably  familiar  to  anyone  who  has  collected  and  ob- 
served insects  in  nature.  Who  has  not  occasionally  on  a  warm  mid- 
sununer  day  met  with  a  slender  little  streak  of  gold  and  silver  sitting 
in  the  sunshine  on  a  leaf  in  a  protected  comer  and  twirling  its  long 
white-tipped  antennae  in  graceful  motions  If,  when  examined  more 
closely,  it  is  found  to  be  a  smooth  shining  little  moth,  brown  with 
silvery  lines  on  palpi  and  antennae,  and  with  a  striking  broad  golden 


Fig.   772. — Homaledra  sabalella:  larva,   pupa, 
(From  the  Author's  Report  for  1879.) 


adult,   and  part  of  injured  leaf. 


or  orange  fascia  across  the  outer  half  of  the  wing,  bordered  on  both 
sides  by  bright  metallic  scales,  then  you  have  a  Cosmopteryx.'' 

"The  larvas  are  leaf -miners,  and  the  mines  are  easily  distinguished 
from  most  others  by  the  scrupulous  cleanliness  with  which  the  larva 
ejects  all  its  frass  through  a  hole,  so  that  the  mine  remains  clear 
and  white.  At  maturity  the  larva  changes  its  color  from  green  to  a 
vivid  purple  or  wine-red,  leaves  the  mine,  and  spins  a  matted  flattened 
cocoon  of  silk."  (Busck  '06). 

Among  the  better-known  members  of  this  family  are  the  following : 
Stagmatophora  gleditschiceella.- — -The  larva  burrows  in  the  thorns  of 
locust. 

Mompha  Eloisella. — There  are  several  species  of  Mompha  that 
infest  the  fruit  and  pith  of  the  evening  primrose.  The  best-known  of 
these  is  this  one. 

Psacaphora  terminella. — The  larva  is  a  miner  in  willow-herb, 
Epilobium. 


LEPIDOPTERA  631 

Family  SCYTHRIDID^ 

This  family  includes  a  group  of  genera  that  are  closely  allied  to 
the  Yponomeutida"  and  are  included  in  that  family  by  some  writers. 
I  do  not  find  that  any  tangible  characters  of  the  adult  insects  separat- 
ing the  two  families  have  been  pointed  out ;  but  there  appear  to  be 
differences  in  the  setal  characters  of  the  larva?  (see  Fracker  '15). 

The  family  is  represented  in  our  fauna  by  only  two  genera,  Scythris- 
and  Epermenia,  including  twenty-two  species.  None  of  these  species 
has  attracted  attention  on  account  of  its  economic  importance. 

The  larvae  of  Scythris  magnatella  feed  on  Epilohium.  They  are 
solitary  when  small,  folding  over  half  of  the  leaf  to  the  midrib  in  the 
central  part  of  its  length,  attached  with  web.  Later  they  form  con- 
siderable web  among  the  leaves.  The  pupa  is  formed  in  a  delicate, 
flossy  web.     (Dyar). 

The  larva  of  Epermenia  pimpinella  feeds  by  forming  a  puffy  mine 
on  Pimpinella  integerrima.  The  pupa  is  inclosed  in  a  frail,  open- 
meshed  cocoon  on  the  under  side  of  a  leaf  or  in  angles  of  leaf -stalks. 
(Murtfeldt.) 

One  of  the  more  common  representatives  of  this  family  is  Scythris- 
eboracensis.  The  adult  is  a  small  black  moth  tinged  with  violet,  with 
a  wing-expanse  of  about  10  mm.    It  is  found  on  flowers. 

Family  YPONOMEUTID^* 

In  this  family  the  ocelli  are  small  or  absent.  In  the  more  typical 
forms  the  wings  are  comparatively  broad,  with  the  venation  but  little- 
reduced.  In  the  fore  wings  all  of  the  branches  of  the  branched  veins 
are  usually  separate,  and  vein  R5  extends  to  the  outer  margin.  In 
the  hind  wings  veins  Rs  and  Mi  are  well-separated.  The  first  anal 
vein  is  distinct  in  both  fore  and  hind  wings. 

Writers  differ  greatly  as  to  the  limits  of  this  family ;  some  include 
in  it  certain  genera  or  groups  of  genera  that  by  others  are  regarded  as 
distinct  families. 

In  its  restricted  sense  the  family  Yponomeutidae  includes  about 
fifty   North    American    species;    among    these   are    the    following. 

The  cedar  tineid,  Argyresthia  thuiella. — This  is  a  small  narrow- 
winged  moth,  which  expands  about  8  mm.  Its  ground  color  is  pearly- 
white,  with  the  fore  wings  dotted  and  marked  with  brown,  especially 
on  the  outer  half  of  the  wing.  The  larva  feeds  on  the  leaves  of  cedar, 
and  when  full-grown  spins  a  small,  conspicuous  white  cocoon  attached 
to  a  leaf. 

The  apple  fruit-miner,  Argyresthia  conjugella.- — The  larva  of  this, 
species  is  a  serious  pest  in  the  apple  orchards  of  western  Canada. 
It  is  pinkish  white  in  color  and  about  9  mm.  in  length.  It  burrows 
in  all  directions  through  the  fruit,  causing  it  to  decay.  The  winter  is 
passed  in  the  pupal  state.  The  cocoons  are  made  under  the  bark  on 
the  trunk  of  the  tree  or  under  leaves  on  the  ground;  they  are  white, 

*An  emended  form  of  this  family  name,  Hyponomeutidas,  is  used  by  some 
writers. 


632 


AN  INTRODUCTION  TO  ENTOMOLOGY 


and  the  outer  layers  have  the  threads  arranged  so  as  to  form  a 
beautiful  openwork  pattern.    The  adult  moth  has  a  wing-expanse  of 
about    12   mm.      It   is  figured  by  Slingerland  and 
Crosby  ('14).  _ 

The  suspended  lace-cocoon,  Urodus  parvula. — 
This  beautiful  cocoon  (Fig.  773)  is  not  uncommon 
in  Florida.  It  is  found  in  various  situations.  I 
found  the  specimen  figured  here  attached  to  an 
orange  leaf.  The  adult  is  a  brownish  moth  without 
markings  and  with  a  wing-expanse  of  28  mm. 

The  ailanthus  webworm,  Atteva  aurea. — The  lar- 
vae live  in  communities  within  a  slight  silken  web 
on  the  Ailanthus;  they  feed  on  the  leaves  and  also 
gnaw  the  leaf-stalks  in  two.    When  the  larva  is  full- 
grown  it  suspends  itself  in  the  middle  of  a  loose  web 
and  transforms  there.     The  adults  appear  in  Sep- 
tember and  October  and  pass  the  winter  in  this  state. 
The  adult  is  very  striking  in  appearance.     The  fore 
wings  are  bright  marigold -yellow  with  four  bands  of 
round   pale  sulphur-yellow   spots  upon  a   brilliant 
steel-blue  ground.    The  hind  wings  are  transparent, 
with  a  dusky  margin  and  blackish  veins.    The  wing- 
expanse  is  about  25  mm. 
The  ermine-moths,    Yponomeuta.- — There  are  several  species  of 
the  typical  genus  of  this  family  that  have  received  the  common  name 
ermine-moths,  because  of  the  color  of  their  fore  wings,  which  are 
snowy  white  dotted  with  black.    One  of  these,  Yponomeuta  padella; 
is  an  introduced  species  which  is  an  apple  and  cherry  pest.     The 
larvae  live  in  a  common  web,  and  in  this  they  spin  their  cocoons. 
The  name  ermine-moths  is  applied  also,  especially  in  England,  to 
some  of  the  Arctiidee  that  are  white  spotted  with  black. 


Fig.  773-— Co- 
coon of  Uro- 
dus  parvula 


Family  PLUTELLID^ 


This  family  is  closely  allied  to  the  Yponomeutidee  and  is  regarded 
by  many  writers  as  a  subfamily  of  that  family.  These  moths  differ 
from  the  Yponomeutidae  in  that  they  hold  the  antennae  extended 
forward  in  repose;  in  this  respect  they  resemble  the  Coleophoridae. 
The  larvcB  differ  from  those  of  the  Yponomeutidae  and  the  Scythrididae 
in  that  their  prolegs  are  longer  than  wide. 

About  fifty  North  American  sepcies  have  been  described;  these 
represent  nine  genera.  The  most  important  species  from  an  economic 
standpoint  is  the  following  one. 

The  diamond-back  moth,  Plutella  maculipennis. — The  larva  of  this 
species  infests  cabbage  and  other  cruciferous  plants,  eating  holes  of 
variable  size  and  irregular  form  in  the  leaves.  It  is  sometimes  also 
a  pest  in  greenhouses,  infesting  stocks,  wall-flowers,  sweet  alyssum, 
and  candytuft.  The  larva  when  full-grown  spins  a  lace-like  cocoon 
attached  to  a  leaf.    The  moth  expands  about  15  mm.    The  fore  wings 


LEPIDOPTERA 


633 


Fig.    774. — Wings    of    Clvphiptervx    thrasonella. 
(After  Spuler.) 


of  the  male  are  ash-colored,  with  a  yellow  stripe  outlined  by  a  wavy 
dark  line  extending  along  the  inner  margin.  When  the  wings  are 
closed,  the  united  yellow 
stripes  form  a  row  of 
three  diamond-shaped 
markings.  These  sug- 
gested the  common  name 
of  the  species.  In  the 
female  the  front  wings 
are  a  nearly  uniform  gray . 
The  hind  wings  in  both 
sexes   are   a    dull    gra>'. 

Family 
GLYPHIPTERYGID.^ 

The  ocelli  are  usually 
large.  The  maxillae  are 
strong  and  clothed  with 
scales.  The  maxillary 
palpi  are  vestigial  or 
wanting.  The  labial  pal- 
pi are  upturned  to  the  middle  of  the  front  or  beyond,  often  beyond 
the  vertex.     In  the  fore  wings  veins  R4  and  Rs  are  usually  separate 

and  vein  Cuo  arises  close  to  the 
angle  of  the  discal  cell.  In  the 
hind  wings  the  second  anal  vein  is 
strongly  forked  at  the  base. 

Nearly  forty  North  American 
species  are  now  known.  These 
represent  two  subfamilies. 

Subfamily  Glyphipterygi- 
N.'E. — This  subfamily  is  composed 
chiefly  of  the  species  of  the  genus 
Glyphlpteryx.  In  this  genus  the 
wings  are  moderately  broad  (Fig. 
774)  and  the  fore  wings  have  a 
lobe-like  prolongation  between 
veins  R4  and  R5.  Ten  species  are 
now  listed  from  our  fauna. 

Subfamily  Choreutin^. — 
In  this  subfamily  the  wings  are 
broad  and  triangular  (Fig.  775), 
and  usually  with  narrow  fringes. 
The  moths  bear  a  striking  re- 
semblance to  tortricids.  The  lar- 
vae live  under  webs  on  leaves  or 


Fig.  775. — Wings  of  Simathis  fabriciana. 
(After  Spuler.) 


between  leaves  that  are  fastened  together. 


634 


AN  INRTODUCTION  TO  ENTOMOLOGY 
Family  HELIODINID^ 


The  hind  wings  are  narrow-lanceolate  and  pointed  or  linear  and 
much  narrower  than  their  fringe.  The  maxillary  palpi  are  minute 
and  porrect.  The  labial  palpi  are  very  short  and  drooping.  The 
maxillae  are  strong.  The  tarsi  are  armed  with  more  or  less  distinct 
whorls  of  bristles;  the  tibiae  are  also  often  armed  with  stiff  bristles. 
Usually  when  at  rest  the  imago  holds  the  posterior  pair  of  legs  ele- 
vated at  the  sides  above  the  wings. 

The  larvae  are  not  well-known ;  those  that  have  been  described  are 
of  various  habits. 

Cycloplasis  panicijoliella.- — The  larva  of  this  species  mines  in  grass, 
Panicum  clandestinum.  Its  mine  is  at  first  a  long  thread-like  line; 
towards  the  latter  part  of  the  life  of  the  larva  it  is  enlarged  into  a 
blotch.  When  the  larva  has  reached  maturity,  it  cuts  a  perfectly 
circular  disk  from  the  upper  cuticle  of  the  leaf,  folds  it  along  its  di- 
ameter and  unites  the  edges  of  the  circumference,  so  as  to  make  a 
semicircle.  When  completed  the  larva,  enclosed  in  its  semicircular 
cocoon,  lets  itself  fall  to  the  ground,  where  it  attaches  the  cocoon  to 
some  adjacent  object.  (Clemens). 

Schreckensteinia  erythriella. — The  larva  feeds  on  sumac  bobs.     It 

is  common;  the  body  is  uniform  dark  green,  but  the  frass  is  scarlet. 

When  full-grown  it  makes  a  lace-like  cocoon  on  the  outside  of  the  bob. 

Schreckensteinia  festaliella. — The  larva  of  this  species  is  an  external 

feeder  on  Ruhus;  it  is 
spiny,  and  when  full- 
grown  makes  a  lace- 
like cocoon. 

Euclemensia  basset- 
tella. — The  larva  is  an 
internal  parasite  in  the 
gall-like  females  of  the 
coccid  genus  Kermes. 
The  adult  is  a  beauti- 
ful greenish-black 
moth,  which  has  its 
fore  wings  marked 
with  reddish  orange  (Fig.  776). 

The  genus  Euclemensia  is  placed  in  this  family  provisionally. 

Family    ^GERIID^ 


Euclemensia  bassettella. 


The  Clear-winged  Moths 

The  clear-winged  moths  constitute  a  very  remark- 
able family,  many  of  them  resembling  bees  or  wasps 
in  appearance  more  than  they  do  ordinary  moths,  a 
resemblance  due  to  their  clear  wings  and  in  some  cases  to  their  bright 
colors  (Fig.  777).    There  are  a  few  moths  in  other  families,  as  the 


Fig.  777. 


LEPIDOPTERA 


635 


clear-winged  sphinxes  and  certain  euchromiids,  that  have  a  greater  or 
less  part  of  the  wings  devoid  of  scales;  but  they  are  exceptions. 
Here  it  is  the  rule  that  the  greater  part  of  one  or  both  pairs  of  wings 
are  free  from  scales;  hence  the  common  name,  clear-winged  moths. 
In  a  small  number  of  members  of  this  family  the  wings  are  scaled 
throughout. 

These  insects  are  of  moderate  size;  as  a  rule  they  have  spindle- 
shaped  antennae,  which  are  terminated  by  a  small  silky  tuft;  some- 
times the  antennae  are  pectinate;  the  margins  of  the  wings  and  the 
veins  of  even  the  clear-winged  species  are  clothed  with  scales;  and 
at  the  end  of  the  abdomen  there  is  a  fan-like  tuft  of  scales. 


Fig.  778. — Wings  of  Synanthedon  exitiosa. 

The  fore  wings  are  remarkable  for  their  extreme  narrowness  and 
the  great  reduction  of  the  anal  area  (Fig.  778) ;  while  the  hind  wings 
have  a  widely  expanded  anal  area.  The  nimiber  of  anal  veins  in  the 
hind  wings  varies  greatly  within  the  family,  the  number  ranging  from 
two  to  four;  where  there  are  four  anal  veins,  it  is  probably  the  third 
anal  vein  that  is  forked. 

Another  remarkable  feature  of  the  wings  of  these  insects  is  that 
in  the  female  the  bristles  composing  the  frenulum  are  consolidated 
as  in  the  male;  this  condition  exists  in  the  females  of  a  few  members 
of  other  families.  The  females  of  the  ^geriidas  possess  a  frenulum 
hook;  but  this  is  not  so  highly  specialized  as  that  of  the  male. 

In  addition  to  the  presence  of  a  highly  specialized  frenulum 
and  a  frenulum -hook,  there  is  a  unique  provision  for  holding  the 
fore  and  hind  wings  together.     The  inner  margin  of  the  fore  wing  is 


636  AN  INTRODUCTION  TO  ENTOMOLOGY 

folded  under;  and  the  radius  of  the  hind  wing  is  armed  with  setae, 
which  hook  into  this  fold. 

The  adults  fly  very  swiftly  and  during  the  hotter  part  of  the  day. 
They  frequent  flowers  thus  increasing  their  resemblance  to  bees  or 
to  wasps.  The  larvee  are  borers,  living  within  the  more  solid  parts 
of  plants.  Some  species  cause  serious  injury  to  cultivated  plants. 
More  than  one  hundred  species  have  been  found  in  America  north  of 
Mexico.    Among  the  better  known  species  are  the  following. 

The  blackberry  crown-borer  or  the  raspberry  root -borer,  Bemhecia 
margindta. — The  larva  of  this  species  burrows  in  the  roots  and  lower 
part  of  the  canes  of  blackberries  and  raspberries,  sometimes  completely 
girdling  the  cane  at  the  crown. 

The  peach-tree  borer,  Synanihedon  exitiosa. — This  is  the  most 

important  enemy  of  the  peach-tree,except  perhaps  the  San  Jose  scale 

in  the  North  and  the  plum  curculio  in  the  South.     In  some  parts  of 

the  country  it  is  difficult  to  find  a  peach-tree  that  is  not  infested  by  it. 

The  eggs  are  laid  on  the  bark  of  the  tree  near  the  ground.    The  larvae 

bore  downward  in  the  bark  of  the  trunk  just  below  the  surface  of  the 

ground.     Their  burrows  become  filled  by  a  gummy  secretion  of  the 

tree.     As  this  oozes  out  in  large  masses  the  presence  of  the  borer  is 

easily  detected  by  it.    The  insect  always  passes  the  winter  in  the  larval 

state.    When  full-grown  the  larva  comes  to  the  surface  of  the  ground 

and  makes  a  cocoon  of  borings  fastened  together  with  silk.     The 

perfect  insects  appear  from  May  till  October; 

-^  y^  the  date  at  which  most  of  them  appear  varies  in 

^--4^    ^— ^     different  sections  of  the  country.     There  is  a 

^B|^HH|^^^^     single  generation  each  year.    The  adults  differ 

^^^^|H^^^^        greatly  in  appearance.     The  general  color  of 

jwl  both  sexes  is  a  glassy  steel-blue.    In  the  female 

) "  1  (Fig.  779)  the  fore  wings  are  covered  with  scales, 

p-g   yyg^^synanthedon   ^^^  there  is  a  bright  orange-colored  band  on  the 

exitiosa,  iemale.      abdomen.    In  the  male  both  pairs  of  wings  are 

nearly  free  from  scales.    The  usual  method  of 

fighting  this  pest  is  to  carefully  watch  the  trees  and  remove  the  larvae 

with  a  knife  as  soon  as  discovered.    Recently  the  use  of  a  toxic  gas, 

paradichlorobenzene,  has  been  found  available  on  trees  six  years  of 

age  and  older;  and  experiments  are  now  being  made  to  determine 

the  practicability  of  its  use  on  younger  trees.     See  U.  S.  Dept.  of 

Agr.  Bull.  1 169,  and  later  bulletins  when  pubhshed. 

The  Pacific  peach-tree  borer,  Synanthedon  opalescens. — On  the 
Pacific  Coast  there  is  a  peach-tree  boier  that  is  distinct  from  the 
above,  and  appears  to  be  an  even  more  serious  pest.  The  larva  is 
more  difficult  to  remove  from  the  tree,  as  it  bores  into  the  solid  wood. 
The  female  of  this  species  lacks  the  orange-colored  band  on  the 
abdomen. 

The  lesser  peach-tree  borer,  Synanthedon  ptctipes. — The  larvae  of 
this  species  infest  peach,  plum,  cherry,  june-berry,  beach-plum,  and 
chestnut.    They  do  not  confine  their  attacks  to  the  crown  but  more 


LEPIDOPTERA 


637 


often  occur  on  the  trunk  and  larger  branches.  This  borer  rarely 
attacks  perfectly  sound,  uninjured  trees  and  is  not  a  serious  pest  in 
orchards  that  receive  good  care.  Both  sexes  of  the  adult  resemble 
the  male  of  the  peach-tree  borer,  having  both  fore  and  hind  wings 
transparent. 

The  imported  currant  borer,  CamcBsphecia  tipuliformis.- — This  is  a 
small  species,  the  adult  having  a  wing-expanse  of  only  about  i8  mm. 
There  are  but  few  scales  on  either  pair  of  wings  except  on  the  tip  and 
discal  vein  of  the  fore  wings  and  the  outer  margin  of  the  hind  wings. 
The  eggs  are  laid  on  the  twigs  of  currant.  The  larvae  penetrate  the 
stem,  and  devour  the  pith ;  in  this  way  they  make  a  burrow  in  which 
they  live  and  undergo  their  transformations.  The  perfect  insects 
appear  in  June.  Before  this  time  the  leaves  of  the  infested  plant  turn 
yellow.  If  such  plants  be  cut  and  burned  in  A4ay  the  pest  will  be 
destro3^ed. 

The  squash-vine  borer,  Melittia  satyriniformis- — The  larva  of  this 
species  (Fig.  780)  does  great  damage  by  eating  the  interior  of  squash- 
vines;  it  also 
sometimes  in- 
fests pump- 
kin-vines and 
those  of  cu- 
cumber and 
melon.  It  is 
most  destruc- 
tive to  late 
squashes . 
When  full- 
grown  the  lar- 
vae leave    the 

vines  and  enter  the  ground,  where  they  make  tough  silken  cocoons,  a 
short  distance  below  the  surface,  in  which  the  winter  is  passed.-  The 
adults  appear  soon  after  their  food-plants  start  growth.  The  fore 
wings  of  the  adult  are  covered  with  scales  and  the  hind  legs  are 
fringed  with  long,  orange-colored  scales.  To  check  the  ravages  of 
this  pest,  the  vines  should  be  collected  and  destroyed  as  soon  as 
the  crop  is  harvested  in  order  to  destroy  the  larvae  that  are  still  in 
them;  the  land  should  be  harrowed  in  the  fall  to  expose  the  cocoons 
and  then  plowed  deeply  the  following  spring  in  order  to  bury  them  so 
deeply  that  the  moths  can  not  emerge.  If  the  vine  is  covered  with  earth 
two  or  three  feet  from  its  base  it  will  produce  a  new  root  system  which 
will  sustain  the  plant  in  case  the  main  stem  is  injured  at  the  base. 
Where  late  squashes  are  grown  early  squashes  can  be  used  as  trap 
plants.  Borers  can  be  removed  from  the  vines  with  a  knife;  when 
this  is  done  the  vine  should  be  cut  lengthwise,  and,  after  the  larva  is 
removed,  the  vine  covered  with  earth;  if  this  is  done  carefully  the 
wound  will  soon  heal. 

The  pine  clear-wing  moth,  Parharmonia  pmi. — Frequently  there 
may  be  seen  on  the  trunks  of  pine-trees  large  masses  of  resinous  gum 


satyriniformis, 


squash-vine 


638 


AN  INTRODUCTION  TO  ENTOMOLOGY 


mingled  with  sawdust-like  matter.  These  are  the  results  of  the  work 
of  the  larvae  of  this  insect,  which  bore  under  the  bark  and  into  the 
superficial  layers  of  the  wood.  The  adult  resembles  the  female  of 
the  peach-tree  borer,  but  the  abdomen  is  more  extensively  marked 

with  orange  beneath. 


i'^^  2d  A     ^stA 
Fig.   781. — Wings  of  Archips  cerasivorana. 


K,      Rj^  R,  /?^  SUPERFAMILY 

TORTRICOIDEA 

The  Tortricids 

The  tortricids  are 
generally  small  moths ; 
but  as  a  rule  they  are 
larger  than  the  mem- 
bers of  most  of  the 
families  of  the  Micro- 
frenatas.  They  have 
broad  front  wings, 
which  usually  end 
squarely.  The  costa 
of  the  front  wings 
curves  forward  strong- 
ly near  the  base  of  the 
wing.  When  at  rest 
the  broad  front  wings 
fold  above  the  body 
like  a  roof.  The  moths 
are  variegated  in  color,  but  are  usually  brown,  gray,  or  golden  rather 
than  of  brighter  hues.  As  a  rule  the  hind  wings  are  of  the  color  of 
the  body  and  without  markings.  The  venation  of  the  wings  of  a 
common  species  is  represented  by  Figure  781. 

The  larvae  vary  greatly  in  habits.  Many  of  them  are  leaf -rollers. 
It  was  this  habit  that  suggested  the  name  Tortrix  for  the  typical  genus, 
from  which  the  names  of  one  family  and  of  the  superfamily  are 
derived.  A  large  portion  of  the  rolled  leaves  found  upon  shrubs  and 
trees  are  homes  of  tortricid  larvcC ;  but  it  should  be  remembered  that 
the  leaf-rolling  habit  is  not  confined  to  this  family.  While  many  are 
leaf-rollers  probably  a  larger  niimber  are  borers  in  stems,  buds,  or 
fruits. 

About  eight  hundred  North  American  species  of  the  Tortricoidea 
have  been  decribed.  This  superfamily  includes  four  families,  which, 
can  be  separated  by  the  following  table. 

A.  Both  veins  Mi  and  M2  of  the  hind  wings  lost.  p.  644 Carposinid^ 

AA.    Vein  M,  of  the  hind  wings  present,  vein  M2  either  present  or  lost. 

B.    With  a  fringe  of  long  hairs  on  the  basal  part  of  vein  Cu  of  the  hind  wings,  on 

the  upper  side  of  the  wing.     Do  not  mistake  a  bunch  of  long  hairs  arising 

from  the  wing  back  of  vein  Cu  for  this  fringe. 


LEPIDOPTERA  639 

C.     Fore  wings  with  veins  R4  and  R5  stalked  or  united,  veins  M^,  M3,  and 

Cui  diverging  or  parallel.     (A  few  species  only),  p.  642  ....  .  Tortricid^ 

CC.     Fore  wings  with  veins  R4  and  Rs  separate,  or  with  veins  M2,  M.,,  and 

Cur  converging  strongly  toward  the  margin  of  the  wing.  p.  639 

OLETHREUTID.E 

BB.    Without  a  fringe  of  long  hairs  on  the  basal  part  of  vein  Cu  of  the  hind 
wings. 

C.    Fore  wings  with  the  distal  part  at  least  of  vein  1st  A  preserved.     Vein 
CUi  of  the  fore  wings  arising  from  a  point  before  the  outer  fourth  of  the 
discal  cell. 
D.     Veins  Mi  and  M2  of  the  fore  wings  somewhat  approximate  at  the 

margin  of  the  wing   {Laspeyresia  lautana)  p.  639 Olethreutid^ 

DD.     Veins  Mi  and  M2  of  the  fore  wings  divergent  or  parallel,  p.  642 

TORTRIGID^ 

CC.     Both  fore  and  hind  wings  with  vein  istA  lost,  vein  Cuj  of  the  fore 
wings  arising  from  the  outer  fourth  of  the  discal  cell.  p.  643  Phaloniid^ 

Family  OLETHREUTID^* 

As  a  rule  the  members  of  this  family  are  easily  distinguished  from 
all  other  tortricids  by  the  presence  of  a  fringe  of  long  hairs  on  the 
basal  part  of  cubitus  of  the  hind  wings,  on  the  upper  side  of  the 
wing.  This  fringe  is  lacking  in  a  few  members  of  this  family  and  is 
present  in  a  few  members  of  the  next  family. 

This  is  the  largest  of  the  families  of  tortricids;  more  than  four 
hundred  North  American  species  have  been  described.  The  following 
species  are  among  those  most  likely  to  be  observed,  and  will  serve 
to  illustrate  the  differences  in  habits  of  the  different  species. 

The  codlin-moth,  Carpocdpsa  pomonella.- — This  is  the  best  known 
and  probably  the  most  important  insect  enemy  of  the  apple.  The 
larva  is  the  worm  found  feeding  near  the  core  of 
wormy  apples.  The  adult  (Fig.  782)  is  a  beautiful 
little  creature  with  finely  mottled  pale  gray  or  rosy 
fore  wings.  There  is  a  large  brownish  spot  near  the 
end  of  the  fore  wing,  and  upon  this  spot  irregular, 
golden  bands.  The  moth  issues  from  the  pupa  state  Fig-  782.— tar- 
in  late  spring  and  lays  its  eggs  singly  on  the  surface  onlua 
of  the  fruit  or  on  adjacent  leaves.  As  soon  as  the 
larva  hatches  it  burrows  into  the  apple  and  eats  its  way  to  the  core, 
usually  causing  the  fruit  to  fall  prematurely.  When  full  grown  the 
larva  burrows  out  through  the  side  of  the  fruit,  and  undergoes  its 
transformations  within  a  cocoon,  under  the  rough  bark  of  the  tree, 
or  in  some  other  protected  place.  The  number  of  generations  annually 
varies  in  different  parts  of  the  country.  As  a  rule  there  is  in  the  North 
one  full  generation  and  usually  a  partial  second ;  where  the  season  is 
longer  there  are  two  or  three  generations.  The  larvae  winter  in  their 
cocoons  transforming  to  pupae  during  early  spring. 

The  method  of  combating  this  pest  that  is  most  commonly  em- 
ployed now  is  to  spray  the  trees  with  a  solution  of  arsenate  of  lead, 
four  to  six  pounds  of  arsenate  of  lead  in  one  hundred  gallons  of  water, 
just  after  the  petals  fall  and  before  the   young   apples   are   heavy 

*This  family  is  the  Eucosmidae  of  some  writers,  and  the  Epiblemidce  of  others. 


640 


AN  INTRODUCTION  TO  ENTOMOLOGY 


enough  to  droop.  The  falling  spray  lodges  in  the  blossom  end  of  the 
young  apple,  and  many  of  the  larvae  which  attempt  to  enter  at  this 
point,  the  usual  place  of  entrance,  get  a  dose  of  poison  with  their 

first  meal. 

The  pine-twig  moths, 
Evetria. — The  genus  Eve- 
rtia  includes  many  spe- 
cies that  infest  the  twigs 
and  smaller  branches  of 
various  species  of  pine. 
Some  of  our  best  known 
species  were  described 
under  the  generic  name 
Retinia  but  now  the  old- 
er name  Evetria  is  applied 
to  them.  The  following 
species  are  well-known. 
Evetria  ccmstockidna. 
■ — This  species  (Fig.  783) 
illustrates  well  the  hab- 
its of  the  boring  species. 
The  larva  infeststhe  small 
branches  of  pitch-pine. 
It  is  a  yellowish-brown 
caterpillar,  which  makes 
a  burrow  along  the  cen- 
tre of  the  branch.  Its 
presence  may  be  detect- 
ed by  the  resin  that  flows 
out  of  the  wound  in  the 
twig  and  hardens  into  a 
lump.  Two  of  these 
lumps  are  shown  in  the 
figure,  one  of  them  split 
lengthwise,  and  the  oth- 
er with  a  pupa-skin  pro- 
jecting from  it.  The  lar- 
va, pupa,  and  adult  are 
also  figured.  The  moth 
is  represented  natural  size;  the  darker  shades  are  dark  rust-color, 
and  the  lighter,  light-gray.  The  insect  winters  as  a  larva;  the  adult 
emerges  in  May  and  June. 

Evetria  frustr ana. — This  species  infests  the  new  growth  of  several 
species  of  pine,  spinning  a  delicate  web  around  the  terminal  bud,  and 
mining  both  the  twig  and  the  bases  of  the  leaves.  The  larva,  pupa, 
and  adult  are  represented  somewhat  enlarged  in  the  figure.  An  in- 
fested twig  is  also  shown  (Fig.  784). 

The  grape-berry  moth,  Polychrosis  vitedna.- — The  most  common 
cause  of  wormy  grapes  is  the  larva  of  this  moth.    The  moth  emerges 


Fig.  -j^T,.— Evetria 
adult,  and  work. 
for  1879.) 


'oiiislockiaiia:    larva,    pupa, 
(From  the  Author's  Report 


LEPIDOPTERA 


641 


in  the  spring  from  its  cocoon  on  a  fallen  leaf  where  it  has  passed  the 
winter  in  the  pupa  state.  The  first  generation  of  larvae  make  a  slight 
web  among  the  blossom  buds  into  which  they  eat  destroying  many 
embryo  grapes.  When  full-grown  the  larva  passes  to  a  leaf  and  makes 
a  very  peculiar  cocoon.  It  cuts  a  semicircular  incision  in  the  leaf, 
bends  over  the  flap  thus  made,  fastens  its 
free  edge  to  the  leaf,  and  lines  the  cavity 
thus  enclosed  with  silk;  here  it  trans- 
forms to  a  pupa.  The  moths  of  the  second 
and  later  generations  lay  their  eggs  on  the 
berries,  and  the  larvae  bore  into  them 
and  feed  on  the  pulp  and  seeds.  The  most 
efficient  method  of  control  of  this  pest  is 
by  spraying  with  a  solution  of  arsenate  of 
lead,  six  pounds  of  the  poison  in  one  hun- 
dred gallons  of  water.  The  first  applica- 
tion should  be  made  shortly  after  the 
fruit  sets,  and  one  or  two  more  at  intervals 
of  ten  da  vs. 


Fig.  784. — Evetria  frustrana: 
larva,  pupa,  adult,  and 
work.  (From  the  Au- 
thor's   Report    for    1879.) 


The  bud-moth,  Tmetocera  ocelldna. — 
The  larva  of  this  insect  is  a  pest  infesting 
apple-trees.  It  works  in  opening  fruit-buds 
and  leaf-buds,  often  eating  into  them, 
especially  the  terminal  ones,  so  that  all 
new  growth  is  stopped.  It  also  ties  the 
young  leaves  at  the  end  of  a  shoot  to- 
gether and  lives  within  the  cluster  thus  formed,  adding  other  leaves 
when  more  food  is  needed.  Sometimes  so  large  a  proportion  of  the 
fruit-buds  are  destroyed  as  to  seriously  reduce  the  amount  of  the 
crop.  The  pupa  state  is  passed  within  the  cluster  of  tied  leaves  or 
within  a  tube  formed  by  rolling  up  one  side  of  a  leaf,  and  lasts  about 
ten  days.  The  moth  expands  about  1 5  mm. ;  it  is  of  a  dark  ashen  gray, 
with  a  large,  irregular,  whitish  band  on  the  fore  wing. 

The  clover-seed  caterpillar,  Laspeyresia  inter stinctdna. — This  is  a 
common  pest  which  feeds  in  the  heads  of  clover,  especially  red  clover, 
destroying  many  of  the  unopened  buds  and  some  of  the  tender  green 
seeds,  and  spoiling  the  head  as  a  whole.  It  sometimes  greatly  dimin- 
ishes the  crop  of  seed.  There  are  three  generations  annually.  The 
last  generation  passes  the  winter  in  the  pupa  state  as  a  rule;  but 
some  larvae  hibernate  under  rubbish.  The  adult  is  a  pretty  brown 
moth,  with  a  series  of  silvery  marks  along  the  costal  margin  of  the 
fore  wings,  and  two  on  the  inner  margin,  which  form  a  double  crescent 
when  the  wings  are  closed  on  the  back.  This  moth  expands  10  mm. 
If  the  hay  is  cut  early  and  stored  the  larvee  will  be  destroyed  while 
still  in  the  heads. 


Nest  of  Archips  rosana. 


w/m 


Fig.    7^.— Arch- 
ips rosana. 


Q42  AN  INTRODUCTION  TO  ENTOMOLOGY 

Family  TORTRICID^ 

The  Typical  Tortricids 

The  tortricidae  differ,  as  a  rule, 
from  the  preceding  family  in  lacking 
a  fringe  of  long 
hairs  on  the  basal 
part  of  the  cubitus 
of  th^  hind  wings. 
In  the  fore  wings 
the  distal  part  of 
the  first  anal  vein 
is    preserved,    and 

vein  Cu2  arises  from  a  point  before  the  outer  fourth  of  the  discal  cell 
In  a  recent  list  165  North  American  species 

are    enumerated;  these   represent    15    genera. 
Several  of  our  better-known^  members  of 

this  family  belong  to  the  genus  Archips.    This 

is  the  genus  Caccecia  of  those  writers  who  do 

not  recognize  the  names  proposed  by  Hubner 

in  his  "Tentamen."     These  insects  have  been 

named  the  ugly-nest  tortricids;  ugly  dwelling 

being  the  meaning  of  Caccecia,  and  also  descrip- 
tive of  the  nests  of  the  larvae  of  these  insects. 

The  four  following  species  are  common. 

The  rose  ugly-nest  tortricid,  Archips  rosana. 

■ — The  larva  of  this  species  feeds  within  the 

webbed-together  leaves  of  rose  and  a  number 

of  other  plants.    Figure  785  represents  the  nest 

of  a  larva  in  a  currant  leaf;  and  Figure  786  the 

adult  of  this  species.    This  moth  expands  about 

20    mm.      The    fore    wings    are    olive-brown, 

crossed  by  bands   of  darker  color;  the  hind 

wings  are  dusky.    This  species  differs  from  the 

two  following  in  that  each  larva  makes  a  nest  for 

itself. 

The  cherry-tree  ugly-nest  tortricid,  Archips 

cerasivordna. — This    species    lives    upon    the 

choke-cherry  and  sometimes  upon  the  culti- 
vated cherry.     The  larvae,  which  are  yellow, 

active  creatures,  fasten  together  all  the  leaves 

and  twigs  of  a  branch  and  feed  upon  them 

(Fig.  787),  an  entire  brood  occupying  a  single 

nest.     The  larvee  change  to  pups  within  the 

nest;  and  the  pupa,  when  about  to  transform, 

work  their  wa\^  out  and  hang  suspended  from 

the  outer  portion  of  the  nest,  clinging  to  it 

only  by  hooks  at  the  tail  end  of  the  bodv. 


Fig.  787.  — Nest  of 
Archips  cerasivor- 
ana. 

Here  thev  transform, 


LEPIDOPTERA  643 


im 


leaving  the  empty  pupa  skins  projecting  from  the  nest,  as  shown  in 

the  figure.    The  moths  vary  in  size,  the  wing  ex- 
panse of  those  we  have  bred  ranging  from  20  mm. 

to  nearly  30  mm.     The  wings  are  bright  ochre- 

\-ellow;  the    front    pair    marked    with    irregular 

brownish  spots  and  numerous  transverse  bands 

of  leaden  blue  (Fig.  788,  male;  Fig.  789,  female),   p.  —Archips 

The  oak  ugly-nest  tortricid,  Archips  fervidana.       f^  /^  ^  j-  ^  or  ana 

— The  nests  of  this  species  are  common  on  our       male. 

oak-trees  in  late  summer.    They  are  merely  a  wad 

of  leaves  fastened  together.    Each  nest  contains  several  larvce;  later 

the  empty  pupa-skins  may  be  found  clinging  to  the  outside  of  the 
nest  as  in  the  preceding  species. 

The  fruit-tree  ugly-nest  tortricid,  Archips 
argyrosptla. — This  is  one  of  the  most  destructive 
of  the  leaf -rollers  infesting  fruit  trees.  It  is  a  very 
general  feeder  attacking  both  fruit  and  forest  trees. 
The  eggs  are  laid  on  the  bark  of  the  twigs  in  June. 

Fig.  789— Archips  The  larvaj  hatch  about  May  ist  of  the  following 

female "' "'^ '^  ""'  ^'^^^  ^^^  ^^^^^  ^^^  Opening  buds,  w^here  they  roll 
and  fasten  the  leaves  loosely  together  with  silken 
threads.  After  the  fruits  set,  they  are  often  included  in  the  nests 
and  ruined  by  the  caterpillars  eating  large  irregular  holes  in  them. 
The  pine-leaf  tube-builder,  Eulia  pinatubdna. — One  of  the  most 
interesting  of  tortricid  nests  occurs  commonly  on  white  pine.  Each 
nest  consists  of  from  six  to  fifteen  leaves  drawn  together  so  as  to  form 
a  tube,  and  is  lined  with  silk.  This  tube  serves  as  a  protection  to  the 
larva,  which  comes  out  from  it  to  feed  upon  the  ends  of  the  leaves 
of  which  the  tube  is  composed;  in  this  way  the  tube  is  shortened. 
I  bred  the  moth  from  nests  collected  at  Ithaca,  N.  Y.;  and  have 
found  similar  nests  as  far  south  as  Florida.  The  moth  expands  12 
mm.  Its  head,  thorax,  and  fore  wings  are  of  a  dull  rust-red  color, 
with  two  oblique  paler  bands  crossing  the  fore  wings,  one  a  little 
before  the  middle,  the  other  a  little  beyond  and  parallel  with  it. 


Family  PHALONIIDtE 

In  this  family  and  in  the  following  one  the  first  anal  vein  is  lost 
in  both  fore  and  hind  wings  and  vein  Cuo  arises  from  the  outer  fourth 
of  the  discal  cell.  In  this  family  vein  Mi  of  the  hind  wings  is  pre- 
served, usuallv  stalked  with  vein  Rg.  The  palpi  of  the  two  sexes  are 
alike. 

More  than  one  hundred  North  American  species  have  been  de- 
scribed, and  constantly  others  are  being  found.  Comparatively  little 
is  known  about  the  habits  of  our  species ;  but  most  of  the  European 
species  whose  habits  are  known  are  borers,  chiefly  in  herbaceous  plants. 

The  juniper  web-worm,  Phalonia  rutildna. — This  is  an  imported 
species  which  has  attracted  attention  by  its  injuries  to  junipers,  the 


644  AN  INTRODUCTION  TO  ENTOMOLOGY 

leaves  of  which  it  fastens  together  with  silk.  In  this  way  it  makes  a 
more  or  less  perfect  tube  within  which  it  lives,  but  from  which  it 
issues  to  feed.  Themoth  expands  about  1 2  mm.  andhas  bright,  glossy, 
orange  fore  wings,  crossed  by  four  reddish  brown  bands. 

Family  CARPOSINID^ 

This  family  is  distinguished  from  the  preceding  one  by  the  fact 
that  in  the  hind  wings  both  vein  Mi  and  vein  M2  are  completely  lost, 
and  the  palpi  of  the  male  are  short  while  those  of  the  female  are  long. 
This  is  a  small  family,  only  five  North  American  species  are  now 
listed,  and  very  little  is  known  regarding  the  habits  of  these. 

The  currant-fruit-worm,  Carposina  Jernalddna. — In  the  unpub- 
lished notes  of  the  late  Professor  M.  V.  vSlingerland,  I  find  an  account 
of  this  insect.  The  larva  feeds  within  the  fruit  of  the  currant,  eating 
both  the  pulp  and  the  seeds.  The  infested  fruit  soon  drops.  When 
full-grown  the  larva  leaves  the  berry  and  goes  into  the  ground  to 
transform.  The  adult  emerges  in  the  following  spring  about  the  time 
the  currants  are  turning  red. 

SuPERFAMiLY  PYRALIDOIDEA 

The  Pyralids  and  their  Allies 

This  group  of  families  includes  a  very  large  number  of  small  or 
moderate-sized  moths,  of  fragile  structure,  normally  with  firmly  and 
finely  scaled  wings,  and  with  the  anal  area  of  the  hind  wings  broad. 
The  first  anal  vein  of  the  fore  wings  is  almost  always  lost,  and  there 
is  no  accessory  cell.  In  the  hind  wings  there  are  usually  three  anal 
veins;  and  veins  Sc  and  R  are  separate  along  the  discal  cell,  but 
grown  together  or  closely  parallel  for  a  short  distance  beyond  the  cell. 
The  maxillee  are  scaled  at  their  base;  and  the  maxillary  palpi  when 
present  are  of  the  porrect  type.  The  labial  palpi  often  project 
beak-like. 

The  larvae  are  characterized  by  the  presence  of  only  two  setae  on 
the  prespiracular  wart  of  the  prothorax,  and  by  setae  IV  and  V  of  the 
abdomen  being  close  together. 

This  superfamily  includes  the  five  following  families,  which  can 
be  separated  by  the  characters  given  in  Table  A,  page  584. 

Family  PYRALIDID^ 

The  Pyralids 

The  members  of  this  family  found  in  our  fauna  are  mostly  small 
moths,  but  a  few  are  of  moderate  size ;  some  tropical  species,  however, 
are  quite  large.  So  large  a  portion  of  the  species  are  small  that  the 
family  has  been  commonly  classed  with  the  preceding  families  as 
Microlepidoptera. 


LEPIDOPTERA 


645 


The  members  of  the  different  subfamilies  of  this  family  differ  so 
greatly  in  appearance  that  it  is  not  possible  to  give  a  general  descrip- 
tion that  will  serve  to  distinguish  it ;  a  very  large  portion  of  the  species 
have  a  special  look,  due  to  their  thin  and  ample  hind  wings  with  large 
anal  areas;  it  is  necessary,  however,  to  study  structural  characters  to 
find  evidences  of  a  common  bond. 

The  body  is  slender ;  the  head  is  prominent ;  the  ocelli  are  usually 
present;  the  antennge  are  almost  always  simjjle,  but  frequently  the 
antennae  of  the  male  have  a  process  on  the  scape  or  a  notch  and  tuft 
on  the  clavola;  and  the  palpi  are  usually  moderate  in  size  or  long; 
but  very  often  they  project  beak-like;  for  this  reason  the  name 
snout-moths  is  often  applied  to  this  family. 


Id  A 
Fig.  790. — Wings  of  Nomophila  noctuella.     Fig.  791. — Wings   of  Tlascala  redtictella. 


As  a  rule  there  are  three  anal  veins  in  the  hind  wings  and  one  in 
the  fore  wings.  The  discal  cell  is  always  well-formed,  but  there  is  no 
accessory  cell.  In  most  cases  the  pyralids  can  be  recognized  by  the 
fact  that  the  subcosta  and  radius  of  the  hind  wings  are  separate  along 
the  discal  cell,  but  grown  together  for  a  short  distance  beyond  the 
cell,  after  which  they  are  again  separate  (Fig.  790).  In  some  genera 
these  two  veins  do  not  actually  coalesce,  but  extend  very  near  to- 
gether for  a  short  distance  (Fig.  791).  The  two  types,  however,  are 
essentially  the  same. 

This  is  one  of  the  larger  families  of  the  Lepidoptera ;  nearly  one 
thousand  species  have  been  described  from  America  north  of  Mexico 
alone.  The  family  is  divided  into  many  subfamilies, representatives 
of  fifteen  of  which  are  found  in  our  fauna.  The  best  known  species, 
those  that  have  attracted  attention  on  account  of  their  economic 
importance,  belong  to  the  subfamilies  discussed  below. 


646 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  792. — Des- 
mia  funeralis. 


Subfamily  PYRAUSTIN^ 

The  Pyraustids 

This  is  one  of  the  larger  of  the  subfamiHes  of  the  Pyrahdidae; 

about  three  hundred  species  have  been  described 

^^-s,^,>^^^    from  America  north  of  Mexico.    This  subfamily  in- 

^HmUSr     eludes  many  small  moths;  but  it  contains  also  the 

^^Bxf^^r        majority  of  the  larger  species  of  pyralids;  some  of 

I  the  species  are  very  striking  in  appearance. 

The  members  of  this  subfamily  differ  from  other 
pyralids  by  the  following  combination  of  characters. 
There  is  no  fringe  of  long  hairs  on  the  basal  part  of 
vein  Cu  of  the  hind  wings;  veins  R2  and  R5  of  the  fore  wings  arise 

from  the  discal  cell 
distinct  from  vein 
R4  (Fig.  790);  and 
the  maxillary  palpi 
are  never  very  large 
and  triangular. 
Among  our  better 
known  species  are 
the  following. 

The  grape  leaf- 
folder,  Desmia  fun- 
eralis.— This    is    a 
common   species 
throughout    the 
United  States,  the  larva  of  which  feeds 
on  the  leaves  of  grape.    The  larva  folds 
the  leaf  by  fastening  two  portions  to- 
gether by  silken  threads.     When  full 
grown  it  changes  to  a  pupa  within  the 
folded  leaf.     The  moth  is  black  with 
shining  white  spots.     The  male   (Fig. 
792)  differs  from  the  female  in  having  a 
knot-like  enlargement  near  the  middle 
of  each  antenna.    There  is  some  vari- 
ation in  the  size  and  shape  of  the  white 
spots  on  the  wings.    In  some  specimens 
the  white  spot  of  the  hind  wings  is  sep- 
arated into  two  or  three  spots.    There 
are  two  generations  of  this  species  in  the 
North  and  three  or  more  in  the  South. 
The  basswood  leaf-roller,  Pantogrd- 
pha  limdta.- — -Our  basswood  trees  often 
present  a  strange  appearance  in  late 
summer  from  the  fact  that  nearly  every 
leaf  is  cut  more  than  half  way  across  the 
middle,  and  the  end  rolled  into  a  tube  (Fig.  793) .    Within  this  tube  there 


Fig-  793- — Nest  of  larva  of  Pa7i- 
tographa  limata. 


LEPIDOPTERA 


647 


Fig.  794. —  Pantographa 
limata. 


lives  a  bright  green  larva,  with  the  head  and  thoracic  shield  black.  When 

full  grown  the  larv^a  leaves  this  nest  and  makes  a  smaller  and  more 

simple  nest,  which  is  merely  a  fold  of  one 

edge  of  the  leaf,  or  sometimes  an  incision  is 

made  in  the  leaf  extending  around  about 

two-thirds  of  a  circle  and  the  free  part  bent 

over  and  fastened;  in  each  case  the  nest  is 

lined  with  silk,  thus  forming  a  delicate  co- 
coon.    Here  the  larva?  pass  the  winter  in 

fallen  leaves.     At  Ithaca,  N.  Y.,  Professor 

Slingerland  found  that  the  larvas  did  not 

pupate   till   the   following   July,    and   that 

adults  emerged  in  August.    The  adult  moth  expands  about  33  mm.; 

it  is  straw-colored  with  many  elaborate  markings  of  olive  with  a 

purplish  iridescence  (Fig.  794). 

The  melon-worm,  Diaphaniahyalindta. — This  beautiful  moth  (Fig. 

795)  is  often  a  serious  pest  in  our  Southern  States,  where  the  larva  is 

very  destnictive  to  melons  and  other  allied  plants.    The  young  larvae 

feed  on  the  foliage;  the  older  ones  mine  into  the  stems  and  fruit. 

The  insect  passes  the 
winter  as  a  pupa  in  loose 
silken  cocoons  in  dead 
leaves  or  under  rubbish. 
The  moth  is  a  superb 
creature,  with  glistening 
white  wings  bordered 
with  black,  and  with  a 
spreading  brush  of  long 
scales  at  the  end  of  the 
abdomen.  This  species 
appears  to  be  injurious 
only  in  the  Gulf  States, 
but  the  moths  have  been 
taken  as  far  north  as 
Canada. 

The  most  practicable 
method  of  protecting 
cantaloupes  and  cucimi- 
bers  from  this  pest  is  by 
planting  stmimer  squash- 
es among  them  as  a  trap 
crop  at  intervals  of  about 
two  weeks  so  as  to  fur- 
nish an  abundance  of 
buds  and  blossoms  dur- 
ing July  and  August. 
The  earlier  squash  vines 

should  be  removed  and  destroyed  before  many  worms  have  reached 

maturity  on  them;  and  after  the  crop  is  harvested  the  vines  and 

waste  fruits  should  be  gathered  and  destroyed. 


Fig-  795- — Diaphania  hyalinala:  larvae,  cocoon', 
and  adults.  (From  the  Author's  Report  for 
1879.) 


648  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  pickle-worm,  Diaphdnia  nitiddlis. — This  species  is  closely 
allied  to  the  preceding  one.  The  wings  of  the  moth  are  yellowish 
brown  with  a  purplish  metallic  reflection;  a  large  irregular  spot  on 
the  front  wings  and  the  basal  two-thirds  of  the  hind  wings  are  semi- 
transparent  yellow.  The  tip  of  the  abdomen  is  ornamented  with  a 
brush  of  long  scales,  as  in  the  preceding  species.  The  range  and 
habits  of  this  species  are  quite  similar  to  those  of  the  melon-worm; 
and  it  should  be  fought  in  the  same  way. 

The  Wehworms.- — The  larvae  of  many  pyralids  have  the  habit  of 
spinning  a  silken  web  beneath  which  they  retreat  when  not  feeding, 
and  on  this  account  have  been  termed  webworms.  Several  species 
of  these  webworms  belong  to  this  family;  among  them  are  the  follow- 

The  cabbage  webworm,  Hellula  midalts.- — This  species  infests 
various  cruciferas  in  the  Gulf  and  South  Atlantic  States.  The  larva 
is  about  12  mm.  in  length,  of  a  grayish  yellow  color,  striped  with  five 
brownish-pur[3le  bands. 

The  garden  webworm,  Loxostege  siniildlis.- — This  species  is  most 
injurious  in  the  Southern  States  and  in  the  Mississippi  Valley.  It 
infests  various  garden  crops  and  corn  and  cotton.  The  larva  varies 
in  color  from  pale  and  greenish  yellow  to  dark  yellow  and  is  marked 
with  numerous  black  tubercles. 

The  European  corn-borer,  Pyraiista  nubildlis. — This  is  a  greatly 
feared  pest  which  has  recentlv  appeared  in  this  country.  It  is  a 
borer  in  the  stems  of  plants,  in  which  it  winters  as  a  partly  grown  larva. 
Its  favorite  food  appears  to  be  corn  and  especially  sweet  corn ;  but  it 
infests  other  cultivated  plants,  as  dahlias  and  gladiolus,  and  many 
large-stemmed  weeds.  The  full-grown  larva  measures  about  20  mm. 
in  length;  the  adult  moth  has  a  wing-expanse  of  from  25  to  30  rmn. 
As  this  is  written,  efforts  are  being  made  by  the  National  Government 
and  by  several  State  Governments  to  prevent  the  spread  of  this  pest ; 
and  many  circulars  and  bulletins  are  being  published  regarding  it. 

Subfamily  NYMPHULIN^ 
The  Aquatic  Pyralids 

This  subfamily  is  of  especial  interest  as  the  larvse  are  nearly  all 
aquatic,  differing  in  this  respect  from  nearly  all  other  Lepidoptera. 
The  larvae  of  most  of  the  species  live  upon  plants,  like  water  lilies 
and  pond  weeds,  that  are  not  wholly  submerged;  but  in  some  species 
the  larva  has  a  true  aquatic  respiration,  being  furnished  with  tracheal 
gills.  In  our  best  known  species,  these  trachael  gills  are  numerous 
and  form  a  fringe  on  each  side  of  the  body  of  long  slender  filaments, 
which  are  simple  in  some  species  and  branched  in  others. 

The  larvae  vary  greatly  in  habits ;  some  species  live  free  upon  the 
plants  they  infest;  in  some  species,  each  larva  makes  a  case  of  two 
leaf  fragments  fastened  together  at  the  edges;  most  of  the  described 
larvae  live  in  quiet  waters,  lakes,  ponds,  or  pools,  but  the  larva  of 


LEPIDOPTERA  649 

Elophila  fidicdlis  was  found  by  Lloyd  ('14)  to  live  beneath  sheets  of 
silk  spun  over  exposed  surfaces  of  current-swept  rocks,  in  a  rapid 
stream. 

In  the  case  of  several  species  whose  life-history  has  been  deter- 
mined the  pupal  stadium  is  passed  in  a  cocoon  beneath  the  surface 
of  the  water. 

An  exception  to  the  usual  habits  of  larva  of  this  subfamily  is 
presented  by  Eurrhypara  urttcdta,  introduced  from  Europe  to  Nova 
Scotia;  this  species  is  not  aquatic,  but  feeds  on  nettle. 

Subfamily  PYRALIDIN^ 
The  Typical  Pyralids 

This  is  a  small  subfamily;  only  twenty-four  species  are  now  enu- 
merated in  our  lists,  and  these  are  mainly  from  the  far  Southwest. 
The  best-known  species  are  the  two  following: 

The  meal  snout-moth,  Pyralis  farindlis. — The  larva  of  this  species 
feeds  on  meal,  flour,  stored  grain,  and  old  clover  hay.  It  makes  little 
tubes  composed  partly  of  silk  and  partly  of  the  fragments  of  its  food. 
It  rarely  occurs  in  sufficient  numbers  to  do  serious  injury;  and  its 
ravages  can  be  checked  by  a  thorough  cleaning  of  the  infested  places, 
or  when  practicable  by  the  use  of  carbon  bisulphide.  The  moth  is 
commonlv  found  near  the  food  of  the  larva,  but  is  often  seen  on 
ceilings  of  rooms  sitting  with  its  tail  curved  over  its  back.  It  expands 
about  25  mm. ;  the  fore  wings  are  light-brown,  crossed  by  two  curved 
white  lines,  and  with  a  dark  chocolate-brown  spot  on  the  base  and 
tip  of  each. 

The  clover-hay  worm,  Hypsopygia  costdlis. — The  larva  of  this 
species  sometimes  abounds  in  old  stacks  of  clover-hay,  and  especially 
near  the  bottom  of  such  stacks.  As  the  infested 
hay  becomes  covered  with  a  silken  web  spun  by  the 
larva,  and  by  its  gunpowder-like  excrement,  much 
more  is  spoiled  than  is  eaten  by  the  insect.  Such  hay 
is  useless  and  should  be  burned,  in  order  to  destroy 

the  insects.    The  moth  expands  about  20  mm.    It  is      pig.    7^5. Hy- 

a  beautiful  lilac  color,  with  golden  bands  and  fringes  p  s  0  p  y  gi  a 
(Fig.  796).  c  0  s  t  all  s  . 

Subfamily  CRAMBIN^ 

The  Close-wings 

Although  this  is  not  a  large  subfamily,  there  being  only  about  one 
hundred  and  thirty  species  known  in  our  fauna,  the  members  of  it 
are  more  often  seen  than  any  other  pyralids.  The  larvse  of  most  of 
the  species  feed  on  grass;  and  the  adults  fly  up  before  us  whenever  we 
walk  through  meadows  or  pastures.  When  at  rest,  the  moths  wrap 
their  wings  closely  about  the  body;  this  has  suggested  the  name  close- 


650 


AN  INTRODUCTION  TO  ENTOMOLOGY 


wings  for  the  insects  of  this  family.  When  one  of  these  moths  aHghts 
on  a  stalk  of  grass  it  quickly  places  its  body  parallel  with  the  stalk, 
which  renders  it  less  conspicuous  (Fig.  797).  Many  of 
the  species  are  silver}^  white  or  are  marked  with  stripes 
of  that  color. 

About  seventy  of  our  species  belong  to  the  genus 
Crambus.  The  moths  of  this  genus  are  often  seen;  but 
the  larvae  usually  escape  observation.  They  occur 
chiefly  at  or  a  little  below  the  surface  of  the  ground, 
where  they  live  in  tubular  nests,  constructed  of  bits  of 
earth  or  vegetable  matter  fastened  together  with  silk. 
They  feed  upon  the  lower  parts  of  grass  plants;  and 
sometimes  on  other  crops  planted  on  sod  land  infested 
by  these  insects.  Thus  Crambus  caliginosellus  is  known 
as  the  corn-root  webworm  on  account  of  its  injury  to 
young  com  plants  which  it  bores  into  and  destroys ;  it 
is  also  known  as  the  tobacco  stalk -worm,  on  account  of 
similar  injury  to  young  tobacco  plants. 

Another  species  of  this  genus,  Crambus  hortuellus ,  is 

known  as  the  cranberry  girdler.     This  sometimes  does 

Crambus.        considerable  injurv^  in  cranberry  bogs  by  destroying 

the  bark  of  the  prostrate  stems  of  the  vines. 

To  this  subfamily  belong  the  larger  com  stalk-borer,   Diatrcea 

zeacolella,  which  sometimes  bores  into  the  stalks  of  young  corn  in  the 

Southern  States,  and  the  sugar-cane  borer,  Diatr<sa  sacchardlis,  which 

bores  into  the  stalks  of  sugar-cane. 


Subfamily  GALLERIIN^ 
The  Bee-moth  Subfamily 


This  is  a  small  subfamih',  of  which  only  seven  species  have  been 
found  in  our  fauna.  The  best  known  of  these  is  the  bee-moth,  Galleria 
mellonclla.  The  larva  of  this  species  is  a  well-known  pest  in  apiaries. 
It  feeds  upon  wax ;  and  makes  silk-lined  galleries  in  the  honey-comb, 
thus  destroying  it.  When  full  grown  the  larva  is  about  25  mm.  in 
length.  It  lies  hidden  in  its  gallerv^  during  the  day,  and  feeds  only 
at  night,  when  the  tired-out  bees  are  sleeping  the  sleep  of  the  just. 
When  ready  to  pupate  the  caterpillar  spins 
a  tough  cocoon  against  the  side  of  the  hive. 

The  moth  has  purplish-brown  front 
wings,  and  brown  or  faded  yellow  hind 
wings.  The  fore  wings  of  the  male  are 
deeply  notched  at  the  end,  while  those  of 
the  female  (Fig.  798)  are  but  slightly  so. 
The  female  moth  creeps  into  the  hive  at 
night  to  lay  her  eggs. 

This  pest  is  found  most  often  in  weak  colonies  of  bees,  which  it 
frequently  destroys.     The  best  preventive  of  its  injuries  is  to  keep 


Fig.    798. — Galleria 
lonella. 


met- 


LEPIDOPTERA  651 

the  colonies  of  bees  strong.    Of  course  the  moths  and  larvae  should 
be  destroyed  whenever  found. 

Subfamily  PHYCITIN^ 
The  Phycitids 

Our  most  common  members  of  this  subfamily  are  small  moths 
with  rather  narrow  but  long  fore  wings,  which  are  banded  or  mottled 
with  shades  of  gray  or  brown.  The  subfamily  is,  however,  a  large 
one  and  other  types  of  coloration  occur.  In  this  subfamily  there  is  a 
fringe  of  long  hairs  on  the  basal  part  of  vein  Cu  of  the  hind  wings; 
the  radius  of  the  fore  wings  is  only  four-branched  (Fig.  791) ;  and  the 
frenulum  of  the  female  is  simple.  This  is  a  very  large  subfamily; 
more  than  three  hundred  species  have  been  described  from  our  fauna, 
and  there  are  doubtless  many  undescribed  species  in  this  country. 

The  larvce  of  the  different  species  vary  greatly  in  habits.  Some 
live  in  flowers,  some  fold  or  roll  leaves  within  which  they  live  and 
feed;  some  are  borers;  others  feed  upon  dried  fruits,  or  flour  and 
meal;  and  one,  at  least,  is  predacious,  feeding  on 
coccids.  Usually  the  larva  lives  in  a  silken  tube  or 
case,  lying  concealed  by  day  and  feeding  by  night. 
The  case  made  by  certain  of  the  leaf-eating  species  is 
very  characteristic  in  form  (Fig.  799),  being  strongly 
tapering  and  much  curved ;  in  this  instance  the  case 
is  composed  largely  of  the  excrement  of  the  larva. 

The  following  species  are  those  that  have  at- 
tracted most  attention  on  account  of  their  economic 
importance.  Fig.   799- 

The  Indian-meal  moth,  Plodia  interptmctella. — This  is  the  best- 
known  of  the  species  that  infest  stored  provisions.  The  larva  is  the 
small  whitish  worm,  with  a  brownish-yellow  head,  that  spins  thin 
silken  tubes  through  meal  or  among  3'east-cakes,  or  in  bags  or  boxes 
of  dried  fruits.  The  moth  expands  about  15  mm.  The  basal  two- 
fifths  of  the  fore  wing  is  dull  white  or  cream  colored;  the  outer  part 
reddish  brown,  with  irregular  bands  of  blackish  scales. 

The  Mediterranean  flour-moth,  Ephestia  kuhniella,  is  an  even 
more  serious  pest  than  the  preceding  species,  which  it  resembles  in 
habits.  It  has  become  ver}^  troublesome  in  recent  years  in  flouring- 
mills.     The  moth  expands  about  25  mm.  and  is  grayish  in  color. 

When  this  pest  or  the  Indian-meal  moth  infests  a  limited  stock  of 
flour,  meal,  or  other  cereal,  the  most  economical  way  to  combat  it  is 
to  feed  the  infested  product  to  stock,  and  then  thoroughly  clean  the 
storage  bin  or  pantry.  In  mills,  where  an  entire  building  must  be 
treated,  fumigation  with  hydrocyanic  acid  gas  is  probably  the  best 
method  of  destroying  the  pest.  This  should  be  done  under  the 
direction  of  an  expert. 


652 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Zimmennann's  pine-pest,  Pinipestis  zimmermanni ,  is  a  common 
species,  the  larva  of  which  is  a  borer.     It  infests  the  tnmks  of  pine, 

causing  large  masses 
of  gum  to  exude.  The 
moths  appear  in  mid- 
summer. 

The  coccid-eating 
pyralid,  LcetUia-  cocci- 
divora,  differs  from  the 
other  members  of  this 
family  in  being  preda- 
cious. It  feeds  on  the 
eggs  and  young  of  va- 
rious  scale-insects 
{Pulvinaria,  Dactylop- 
ius,  and  Lecanmm). 
Figure  800  represents 
the  different  stages  of 
this  insect  enlarged, 
and  the  moths  natural 
size  resting  on  egg- 
sacs  of  Pulvinaria. 
Like  other  members  of 
this  family  the  larva 
spins  a  silken  tube, 
within  which  it  lives. 
On  a  thickly-infested 
branch  these  tubes 
may  be  found  extend- 
ing from  the  remains 
of  one  coccid  to  an- 
other. 

To  this  subfamily 
belong  also  the  goose- 
berry fruit  worm,  Zo- 
phodia  grossuldricB, 
which  feeds  within  the 
fruit  of  the  gooseberry  and  currant,  and  the  cranberry  fruit -worm, 
Mineola  vacclnii,  which  bores  into  cranberry  fruit. 


Fig.  800. — LcetUia  coccidivora:  a,  egg;  b,  larva;  c, 
pupa;  d,  adult;  e,  e,  moths  natural  size,  resting  on 
egg  sacs  of  Pulvinaria. 


Family  PTEROPHORID^ 
The  Plume-moths 


The  plume-moths  are  so  called  on  account  of  the  remarkable  form 
of  the  wings  in  most  species;  the  wings  being  split  by  longitudinal 
fissures  into  more  or  less  plume-like  divisions.  In  most  species  each 
fore  wing  is  separated  into  two  parts,  by  a  fissure  extending  about  one- 
half  the  length  of  the  wing;  while  each  hind  wing  is  divided  into 


LEPIDOPTERA  653 

three  parts  by  fissures  extending  farther  towards  the  base  of  the 
wing.  In  a  species  found  in  Cahfornia,  Agdistis  adaciyla,  the  wings 
are  not  divided. 

One  hundred  species  belonging  to  this  family  have  been  found  in 
America  north  of  Mexico. 

One  of  our  most  common  species  is  the  gartered  plirme,  Oxyptilus 
periscelidactylus .  This  is  a  small  moth,  expanding  about  15  mm. 
It  is  of  a  yellowish  brown  color  marked  with  dull 
whitish  streaks  and  spots  (Fig.  801).  The  larvae 
hatch  early  in  the  spring  and  feed  upon  the  newly- 
expanded  leaves  of  the  grape.  They  fasten  together 
several  of  them,  usually  those  at  the  end  of  a  shoot, 
with  fine  white  silk ;  between  the  leaves  thus  folded 
the  caterpillars  live  either  singly  or  two  or  three  ^^f;  w"^'T^''^-^" 
together.  They  become  full-grown  and  change  to  ceiidactyitis.^^' 
pupae  early  in  June.  The  pupa  is  not  enclosed  in  a 
cocoon,  but  is  fastened  to  the  lower  side  of  a  leaf  by  its  tail  by  means 
of  a  few  silken  threads,  in  nearly  the  same  way  the  as  chrysalids  of 
certain  butterflies  are  suspended.  The  pupa  state  lasts  about  eight 
days. 

Family  ORNEODID^ 

The  Many-plume  Moths 

These  insects  resemble  the  plume-moths  in  having  the  wings 

fissured;  but  here  the  fissuring  is  carried  to  a  much  greater  extent 

.  than  in  that  famil\%  each  wing  being  divided 

I >  into  six  plumes  (Fig.  802). 

'      ,  As  yet  only  a  single  species  of  this  family 

SB^>i^>i^^^^^^      has  been  found  in  North  America.     This  is 

^^^^al^^BBT       Orneodes  huhneri.     It  is  an  introduced  species. 

'^8HM|S|^?^  European  authors  state  that  the  larva  feeds 

***^^^  on   the   flowers   of   Lonicera,    Centaur ea,    and 

fT  Scabiosa    arvensis.      It    transforms    either    in 

'    ^  the  flower-head  or  in  the  ground.    This  species 

Pig   802. Orneodes      ^^^    been    mistaken    for    another    European 

hiibneri.  species,  Orneodes  hexadactyla,  and  is  commonly 

known  under  this  name. 

Family  THYRIDID^ 

The  Window-winged  Moths 

Excepting  some  subtropical  species  found  in  the  Gulf  States  and 
California  our  members  of  this  family  can  be  easily  recognized  by 
the  presence  of  curious  white  or  yellowish  translucent  spots  upon  the 
wings ;  it  is  these  spots  that  suggest  the  name  window -winged  moths 
for  the  family. 


654 


AN  INTRODUCTION  TO  ENTOMOLOGY 


In  this  family  the  antennas  are  either  strictly  filiform  or  slightly 
thickened  in  the  middle;  the  ocelli  are  wanting;  the  palpi  project 

horizontally,  and  are 
somewhat  longer  than 
the  head;  and  the  max- 
illas  are  strongly  de- 
veloped. The  venation 
of  the  wings  of  Thyris  is 
represented  by  Figure 
803.  Here  all  of  the 
branches  of  radius  of  the 
fore  wings  are  present 
and  each  arises  from  the 
discal  cell.  This  is  a 
rather  unusual  condition, 
but  it  occurs  in  the  next 
family,  in  certain  genera 
of  other  families  of  moths, 
and  in  the  skippers.  In 
one  of  our  thyridids, 
Meskea,  which  is  found 
in  the  Gulf  States,  veins 
R3  and  R4  are  stalked. 

This  family  is  poorly 
represented  in  our  fauna, 
only  eleven  species,  rep- 
from  the  United  States. 

This  is  the  most  common 


Fig.  803. — Wings  of  Thyris  maculata. 
resenting  six  genera  have  been  described 


Fig.  804.— 
Thyris  mac 
ulata. 


Fig.     805.- 
lugtibris. 


-Thyris 


The  spotted  thyris,  Thyris  maculata 

representative  of  this  family  in  the 

i^---^ — ^     Eastern  and  Middle  States  and  it 

^f^tt09  occurs  also  in  the  West.  This 
•^l^'*^  species  (Fig.  804)  is  brownish  black, 
sprinkled  with  rust-yellow  dots; 
the  outer  margin  of  the  wings,  es- 
pecially of  the  hind  wings,  is  deeply 
scalloped,    with   the    edges   of  the 

indentations  white.    There  is  on  each  wing  a  translucent  white  spot, 

that  of  the  hind  wing  is  larger,  kidney-shaped,  and  almost  divided 

in  two. 

The  mournful  thyris,  Thyris  lugUhris. — This  is  a  larger  species 
found  in  the  Southern  States  and  as  far  north  as  New  York.  It  can 
be  recognized  by  Figure  805.  It  is  brownish  black,  marked  with 
yellow,  and  with  the  translucent  spots  yellowish.  The  larva  is  said 
to  infest  grape. 

Dysodia  oculatdna.  —This  is  a  yellow  and  brown  species,  with  a 
single  translucent  spot  in  each  wing;  those  of  the  hind  wings  are 
crescentic.    The  larvae  infest  various  flowers  and  seeds,  and  beans. 


LEPIDOPTERA  655 

Family  HYBL^ID^ 

This  family  is  represented  in  our  fauna  by  a  single  species, 
HyblcEa  piiera,  which  is  found  in  Florida.  This  moth  has  a  wing- 
expanse  of  about  35  mm.  The  fore  wings  are  brown  mottled  with 
indistinct  spots  of  a  darker  shade;  the  hind  wings  are  brown,  with  a 
median  band  of  three  bright  yellow  spots  margined  with  orange,  and 
a  similar  terminal  spot.  This  is  probably  an  introduced  species. 
In  India  the  larva  is  a  leaf -roller  on  teak. 

This  species  has  been  placed  in  the  family  Noctuidse  in  our  lists 
of  Lepidoptera;  but  it  is  much  more  closely  related  to  the  Thyrididas. 
The  venation  of  the  wings  is  quite  similar  to  that  of  Thyris;  but  the 
maxillary  palpi  are  large  and  triangular  and  the  first  anal  vein  of 
the  hind  wings  is  present  although  weak;  while  in  theThyrididae  the 
maxillary  palpi  are  minute  and  the  first  anal  vein  is  lost. 

THE   SPECIALIZED   MACROFRENAT^ 

In  the  families  included  under  this  heading  the  insects  are  usually 
of  medium  or  large  size.  This  division  includes  certain  moths  and 
all  skippers  and  butterflies.  In  these  insects  the  anal  area  of  the  hind 
wings  is  reduced,  containing  only  one  or  two  anal  veins.  In  some  the 
frenulum  is  well-preserved,  in  others  it  is  replaced  by  a  broadly  ex- 
panded anal  area  of  the  hind  wing. 

Family  SPHINGID^ 

The  Hawk-moths  or  Sphinxes 

Hawk-moths  are  easily  recognized  by  the  form  of  the  body,  wings 
and  antenna?.  The  body  is  very  stout  and  spindle-shaped ;  the  wings 
are  long,  narrow  and  very  strong;  the  antennas  are  more  or  less 
thickened  in  the  middle  or  towards  the  tip,  which  is  frequently  curved 
back  in  the  form  of  a  hook;  rarely  the  antennae  are  pectinated.  The 
sucking-tube  (maxilla?)  is  usually  very  long,  being  in  some  instances 
twice  as  long  as  the  body;  but  in  one  subfamily  it  is  short  and  mem- 
branous. When  not  in  use  it  is  closely  coiled  like  a  watch-spring  be- 
neath the  head.    None  of  the  species  has  ocelli. 

The  venation  of  the  wings  (Fig.  806)  is  quite  characteristic;  the 
most  distinctive  feature  is  the  prominence  of  the  basal  part  of  vein 
Ri  of  the  hind  wing,  the  part  that  extends  from  the  stem  of  radius 
to  the  subcosta.  This  free  part  of  vein  Ri  has  the  appearance  of  a 
cross-vein  and  is  as  stout  as  the  other  veins.  In  the  comparatively 
few  cases  in  other  families  where  the  free  part  of  the  vein  Ri  has  the 
appearance  of  a  cross- vein  it  is  rarely  as  strong  as  the  other  veins.  In 
the  hawk-moths  the  frenulum  is  usually  well-preserved,  but  in  a  few  it 
is  wanting  or  vestigial.  In  many  genera  veins  Ro  and^^Rs  of  the  fore 
wings  coalesce  throughout  their  length,  which  results  in  the  radius 
being  only  four-branched. 


656 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Some  of  the  hawk-moths  are  small  or  of  mediiim  size;  but  most 
of  them  are  large.     They  have  the  most  powerful  wings  of  all  Lepi- 

doptera  in  our  fauna. 
As  a  rule  they  fly  in 
the  twilight,  and  have 
the  habit  of  remaining 
poised  over  a  flower 
while  extracting  the 
nectar,  holding  them- 
selves in  this  position 
by  a  rapid  motion  of 
the  wings.  This  atti- 
tude and  the  whir  of 
the  vibrating  wings 
give  them  a  strong 
resemblance  to  hum- 
ming-birds, hence they 
are  sometimes  called 
humming-bird  moths; 
but  they  are  more 
often  called  hawk- 
moths,  on  account 
of  their  long,  narrow 
wings  and  strong 
flight. 

Of  all  the  beauti- 
fully arrayed  Lepidop- 
tera  some  of  the  hawk- 
moths  are  the  most 
truly  elegant.  There 
is  a  high-bred  tailor- 
made  air  about 
their  clear-cut  wings,  their  closely  fitted  scales  and  their  quiet  but 
exquisite  colors.  The  harmony  of  the  combined  hues  of  olive  and 
tan,  ochre  and  brown,  black  and  yellow,  and  greys  of  every  con- 
ceivable shade,  with  touches  here  and  there  of  rose  color,  is  a 
perpetual  joy  to  the  artistic  eye.  They  seldom  have  vivid  colors 
except  touches  of  yellow  or  pink  on  the  abdomen  or  hind  wings, 
as  if  their  fastidious  tastes  allowed  petticoats  only  of  brilliant  colors 
always  to  be  worn  beneath  quiet-colored  overdresses. 

The  larvce  of  the  Sphingidee  feed  upon  leaves  of  various  plants 
and  trees  and  are  often  large  and  quite  remarkable  in  appearance 
(Fig.  807).  The  body  is  cylindrical  and  naked  and  usually  has  a 
horn  on  the  eighth  abdominal  segment.  Sometimes  instead  of  the 
horn  there  is  a  shiny  tubercle  or  knob.  We  cannot  even  guess  the 
use  of  this  horn,  unless  it  is  ornamental,  for  it  is  never  provided  with 
a  sting.  These  caterpillars  when  resting  rear  the  front  end  of  the  body 
up  in  the  air,  curl  the  head  down  in  the  most  majestic  manner,  and 
remain  thus  rigid  and  motionless  for  hours.    When  in  this  attitude 


Fig.    806. — Wings   of   Protoparce   quinquemaculata. 


LEPIDOPTERA 


657 


they  are  supposed  to  resemble  the  Egyptian  Sphinx,  and   so   the 
typical  genus  was  named  Sphinx  and  the  family  the  Sphingidee. 

Aiost  species  pass  the  pupa  state  in  the  ground  in  simple  cells 
made  in  the  eatth;  some,  however,  transform  on  the  surface  of  the 
ground  in  imperfect  cocoons 
composed  of  leaves  fastened 
together  with  silk. 

One  hundred  species  of 
hawk-moths  occur  in  this 
country.  The  following  are 
some  of  the  more  common 
ones. 

The  modest  sphinx,  Pa~ 
chy sphinx  modesta. — It  was 
probably    the    quiet    olive 
tints  in  which  the  moth  is 
chiefly  clothed  that  suggest- 
ed the  name  modesta  for  it, 
but  it  is  one  of  the  most 
beautiful  of  our 
hawk -moths.     The 
body  and   basal 
third    of    the    fore 
third    of    the    fore 
color;   while  the 


Fig.    807. 
larva. 


-Sphinx     chersis, 


wings  are  pale  olive;  the  outer 
wings  is  a  darker  shade  of  the  same 
middle  third  is  still  darker  (Fig.  808). 
The  hind  wings  are  dull  carmine  red  in  the  middle  or,  in  the  eastern 
race,  a  deeper  crimson;  there  is  a  bluish-gray  patch  with  a  curved 
black  streak  over  it  near  the  anal  angle.  The  larva  feeds  on  poplar 
and  cotton-wood.     When  full-grown  it  is  75  mm.  long,  of  a  pale-grcon 


Fig.  808. — Pachysphinx  modesta. 

color,  and  coarsely  granulated,  the  granules  studded  with  fine  white 
points,  giving  the  skin  a  frosted  appearance;  these  are  wanting  in 
the  eastern  race. 

The  twin-spotted  sphinx,  Snierinthus  gemindtus . — This  exquisite- 
ly-colored moth  expands  about  60  mm.     The  thorax  is  gray  with  a 


658 


AN  INTRODUCTION  TO  ENTOMOLOGY 


velvety  dark  brown  spot  in  the  middle.     The  fore  wmgs  are  gray, 
with  a  faint  rosy  tint  in  some  specimens,  and  tipped  and  banded  with 

brown  as  shown  in  Fig- 
ure 809.  The  hind  wings 
are  deep  carmine  at  the 
middle,  and  are  bordered 
with  pale  tan  or  gray. 
Near  the  anal  angle  there 
is  a  large  black  spot  in 
which  there  is  a  pair  of 
blue  spots,  which  sug- 
gested the  name  gemin- 
Y.g.S09.^Smerinthusgemmatus.  ^^^^        r^^^    ^^^,^    ^^^^^ 

Upon  the  leaves  of  apple,  plum,  elm,  ash,  and  willow. 

Harris's  sphinx,  Lapara  bombycoides .—This  sphinx  has  interested 
us  chiefly  on  account  of  the  habits  and  mark- 
ings of  its  larva  (Fig.  810).  It  feeds  upon  the 
foliage  of  pine,  and  is  colored  with  alternating 
green  and  white  longitudinal  stripes ;  the  dorsal 
stripe  is  green  spotted  with  red.  It  has  a  way 
of  hanging  head  downward  in  a  pine  tassel 
that  conceals  it  entirely  from  the  sight  of  all 
but  ver>^  sharp  eyes,  its  stripes  giving  it  a  close 
resemblance  to  a  bunch  of  pine  leaves.  The 
moth  expands  about  50  mm.;  it  is  gray  with 
the  fore  wings  marked  by  several  series  of  small 
brown  spots. 

The  pen-marked  sphinx.  Sphinx  chersis.— 
This  moth  is  of  an  almost  evenly  distributed 
ashy-gray  color.  This  sombre  color  is  relieved 
somewhat  by  a  black  band  on  each  side  of  the 
abdomen,  marked  with  four  or  five  white  trans- 
verse bars;  by  two  dark  brown,  smoky  bands 
which  cross  the  hind  wings;  and  by  a  series 
of  black  dashes  on  the  fore  wings,  one  in  each 
cell  between  the  apex  of  the  wing  and  the  anal 
vein .  These  dashes  appear  as  if  drawn  casually 
with  a  pen.  The  larva  (Fig.  807)  is  not  un- 
common upon  ash  and  lilac;  it  is  greenish  or 
bluish  white  above,  and  darker  below;  there 
are  seven  oblique  yellow  bands  on  the  sides  of 
the  body,  each  edged  above  with  dark  green. 
When  disturbed  it  assumes  the  threatening  at- 
titude shown  in  the  figure. 

The  tomato-worm,  Protoparce  quinquemaculdta. — This  larva  is  the 
best  known  of  all  our  sphinxes,  as  it  may  be  found  feeding  on  the 
leaves  of  tomato,  tobacco,  or  potato  wherever  these  plants  are  grown 
in  our  country.  It  resembles  in  its  general  appearance  the  larva  of 
Sphinx  chersis  (Fig.  807);  but  is  stouter  and  has  a  series  of  pale 


8  I  o. — La  par  t 
ombycoides 
larva. 


LEPIDOPTERA  659 

longitudinal  stripes  low  down  on  each  side,  in  addition  to  the  oblique 
stripes ;  and  its  favorite  attitude  is  with  the  fore  end  of  the  body 
slightly  raised.  It  is  usually  green,  but  individuals  are  often  found 
that  are  brown,  or  even  black.  There  appear  at  frequent  intervals 
in  the  newspapers  accounts  of  people  being  injured  by  a  poison  ex- 
creted by  the  caudal  horn  of 
this  larva;  but  there  is  abso- 
lutely no  foundation  whatever 
for  such  stories.  The  pupa 
(Fig.  8i  i)  is  often  ploughed  up 
in  gardens,  and  attracts  at- 
tention on  account  of  its  cur- 
rious  tongue-case  a  part  of  Fig.  8ii. — Protoparce  guinquemacidata, 
which  is  free  resembling  the  pupa. 
handle  of  a  pitcher.    The  moth 

is  a  superb  creature,  expanding  four  or  five  inches.  It  is  of  many 
delicate  shades  of  ash-gray,  marked  with  black  or  very  dark  gray; 
there  are  a  few  short  black  dashes  on  the  fore  part  ofthe  thorax,  and 
some  irregular  black  spots  edged  with  white  on  the  posterior  part; 
the  abdomen  is  gray  with  a  black  middle  line,  and  five  yellow,  almost 
square  spots  along  each  side.  Each  of  these  spots  is  bordered  with 
black,  and  has  a  white  spot  above  and  below,  on  the  edge  of  the 
segment.  The  hind  wings  are  crossed  by  four  blackish  lines,  of 
which  the  two  intermediate  are  zigzag. 

The  most  practicable  method  of  control  of  this  pest  in  a  small 
garden  or  in  a  larger  field  where  the  larv«  are  not  nimierous  is  by 
hand-picking;  when  they  are  numerous  they  can  be  destroyed  by 
spraying  with  arsenate  of  lead;  use  two  or  three  pounds  of  the  paste 
dissolved  in  fifty  gallons  of  water.  Paris  green  is  liable  to  burn  the 
foliage  of  tomato. 

The  tobacco-worm,  Protoparce  sexta. — This  species  closely  re- 
sembles the  preceding  and  the  two  are  often  mistaken  the  one  for 
the  other.  The  larvee  have  similar  habits,  feeding  on  the  same  plants ; 
but  in  this  species  the  larva  lacks  the  series  of  longitudinal  stripes 
characteristic  of  the  tomato  worm.  The  moths  are  easily  distin- 
guished; this  species  is  brownish  gray  instead  of  ashy  gray;  at  the 
end  of  the  discal  cell  of  the  fore  wings  there  is  a  distinct  white  spot; 
and  the  two  dark  bands  crossing  the  middle  of  the  hind  wings  are  not 
zigzag,  and  are  less  distinctly  separate;  often  they  are  united  into  a 
single  broad  band. 

The  hog-caterpillar  of  the  vine,  Ampeloeca  myron. — ^There  is  a 
group  of  hawk -moths  the  larvee  of  which  have  the  head  and  first  two 
thoracic  segments  small,  while  the  two  following  segments  are  greatly 
swollen.  These  larvae  from  a  fancied  resemblance  to  fat  swine  have 
been  termed  hog-caterpillars;  and  the  present  species,  which  is  com- 
mon on  grape,  has  been  named  the  hog-caterpillar  of  the  vine.  It  is 
a  comparatively  small  species,  the  full-grown  larva  being  but  little 
more  than  50  mm.  long.  There  is  a  row  of  seven  spots  varying  in 
color  from  red  to  pale  hlac,  each  set  in  a  patch  of  pale  yellow,  along 


660 


AN  INTRODUCTION  TO  ENTOMOLOGY 


%.   ic^WS&^MM/^ 


Fig.    812. —  Ampelceca   myron, 
with  cocoons  of  parasites. 


the  middle  of  the  back.     A  white  stripe  with  dark  green  margins 
extends  along  the  side  from  the  head  to  the  caudal  horn,  and  below 

this  are  seven  oblique  stripes.  This 
larva  is  often  infested  by  braconid 
parasites;  and  it  is  a  common  oc- 
currence to  find  one  of  them  with 
the  cocoons  of  the  parasites  attached 
to  it  (Fig.  812).  The  pupa  state  is 
passed  on  the  surface  of  the  ground 
larva  within  a  rude  cocoon  made  by- 
fastening  leaves  together  with  loose 
silken  threads.  The  adult 
expands  about  55  mm.  The  fore 
wings  are  olive  gray,  with  a  curved,  olive-green,  oblique  band  crossing 
the  basal  third,  a  discal  point  of  the  same  color,  and  beyond  this  a 
large  triangular  spot  with  its  apex  on  the  costa  and  its  base  on  the 
inner  margin. 

The  pandorus  Sphinx,  Pholus  panddrus. — This  magnificent  moth 
expands  from  100  to  112  mm.  The  ground  color  of  its  wings  is  pale 
olive,  verging  in  some  places  into  gray ;  the  markings  consist  of  patches 
and  stripes  of  dark,  rich  velvety  olive,  sometimes  almost  black  (Fig. 
813).  Near  the  inner  margins  of  both  pairs  of  wings  the  lighter  color 
shades  out  into  pale  yellow,  which  is  tinged  in  places  v/ith  delicate 
rose-color.     These  markings  show  a  harmony  of  contrasting  shades 


Pholus  pandorus. 


rarely  equalled  elsewhere  by  nature  or  art.  The  larva  is  one  of  the 
hog-caterpillars.  It  feeds  upon  the  leaves  of  Virginia-creeper.  When 
young  it  is  pinkish  in  color,  and  has  a  long  caudal  horn ;  as  it  matures 
it  changes  to  a  reddish  brown,  and  the  horn  shortens  and  curls  up 
like  a  dog's  tail  and  finally  disappears,  leaving  an  eye-like  tubercle. 
The  caterpillar  has  on  each  side  five  or  six  cream-colored  oval  spots, 
enveloping  the  spiracles. 

The  white-lined  sphinx,  Celerio  linedta. — This  moth  can  be  easily 
recognized  by  Figure  814.  Its  body  and  fore  wings  are  olive-brown; 
there  are  three  parallel  white  stripes  along  each  side  of  the  thorax; 


LEPIDOPTERA 


661 


the  outer  one  of  these  extends  forward  over  the  eyes  to  the  base  of  the 
palpi;  on  the  fore  wings  there  is  a  buff  stripe  extending  from  near 
the  base  of  the  inner  margin  to  the  apex,  and  veins  R5  and  2d  A  are 
Hned  with  white;  the  hind  wings  are  black  vrith  a  central  reddish 


Celerio  lineata. 


band.  The  larva  is  extremely  variable  in  color  and  markings.  It 
feeds  on  many  plants,  among  which  are  apple,  grape,  plum,  and 
currant. 

The  thysbe  clear-wing,  Hmnorrhdgia  thysbe. — There  is  a  group  of 
hawk-moths  that  have  the  middle  portion  of  the  wings  transparent, 
resembling  in  this  respect  the  ^geri- 
idse  and  certain  of  the  Euchromiidas ; 
but  they  are  easily  recognized  as 
hawk-moths  by  the  form  of  the 
body,  wings,  and  antennas.  One  of 
the  more  common  of  these  is  the 
thysbe  clear-wing  (Fig.  815).  The 
scaled  portions  of  the  wings  are  of  a 
dark  reddish  brown ;  but  this  species 
is  most  easily  distinguished  from  all 
our  other  species  by  a  line  of  scales 
dividing  the  discal  cell  lengthwise 
and  representing  the  position  of  the  base  of  vein  M.  The  larva  of 
this  species  feeds  on  the  different  species  of  Viburnum,  the  snow -hewy, 
and  hawthorn. 

The  bimiblebee  hawk-moth,  Hcemorrhdgia  diffinis. — This  clear- 
wing  appears  to  be  about  as  common  as  the  preceding,  and  resembles 
it  somewhat.  It  lacks,  however,  the  line  of  scales  in  the  discal  cell, 
and  the  body  is  more  nearly  yellow  in  southern  specimens.  This 
color  probably  suggested  the  name  bumblebee  hawk-moth,  given  to 
this  insect  nearly  one  hundred  years  ago  by  Smith  and  Abbott. 
The  larva  feeds  on  the  bush  honeysuckle  (Diervilla)  and  the  snow- 
berry  (Symphoricarpus)^ 


Fig.   815. — HcEinorrhagia  thysbe. 


662 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fi?.  8 1 6. — A  measuring-worm. 


SuPERFAMiLY  GEOMETROIDEA 

The  Geometrids  or  the  Measuring-worms 

The  superfamily  Geometroidea  is  composed  of  those  moths  the 
larvae  of  which  are  known  as  measuring-worms,  span-worms,  or  loopers. 
These  larvae  are  very  famiHar  objects, 
attracting  attention  by  their  pecuhar 
manner  of  locomotion.    They  progress 
by   a    series   of   looping    movements. 
They  first  cling  to  the  supporting  twig 
or  leaf  by  their  thoracic  legs ;  then  arch 
up  the  back  while  they  bring  forward 
the  hinder  part  of  the  body  and  seize 
the  support,  at  a  point  near  the  thoracic 
legs,  by  the  prolegs  at  the  caudal  end  of 
the  body;  then,  letting  loose  the  thor- 
acic legs  (Fig.  8 1 6),  they  stretch  the  body  forward,  thus  making  a 
step;  this  process  is  then  repeated. 

It  was  this  peculiar  man- 
ner of  locomotion  that  sug-  /^^ 
gested  the  name  of  the  typic- 
al    genus,    Geometra,    from            ' 
the  Greek  word  meaning  a 
land-measurer. 

Correlated  with  this 
mode  of  walking  there  has 
been  a  loss  in  nearly  all 
members  of  the  family  of 
the  first  three  pairs  of  pro- 
legs. 

Frequently  measuring- 
worms  when  resting  cling  by 
their  caudal  prolegs  and 
hold  the  body  out  straight, 
stiff,  and  motionless,  appear- 
ing like  a  twig ;  this  is  doubt- 
less a  protective  resem- 
blance. 

The  geometrid  larvae  are 
leaf-feeders,  and  some  spe- 
cies occur  in  such  large  num- 
bers as  to  be  serious  pests. 
The  pupae  are  slender, 
and  some  species  are  green 
or  mottled   in   this    state. 


Fig.    817. — Wings   of    Caripeta   angustiorata. 


The  pupa  state  is  passed  in  a  very  flimsy  cocoon  or  in  a  cell  in  the 
ground. 

The  moths  are  of  medium  size,  sometimes  small,  but  only  rarely 
very  large.     Usually  the  body  is  slender,  and  the  wings  broadband 


LEPIDOPTERA  663 

delicate  in  appearance.  This  appearance  is  due  both  to  the  thinness 
of  the  membrane  and  to  the  fineness  of  the  scales  with  which  the 
wings  are  clothed.  These  moths  occur  on  the  borders  of  woods  and 
in  forests,  rarely  in  meadows  and  pastures.  Their  flight  is  neither 
strong  nor  long  sustained.  Many  species  when  at  rest  hold  the  wings 
horizontally  and  scarcely  overlajiping;  but  other  species  assume  other 
positions. 

In  the  geomctrids  the  frenulmn  is  usually  well-preserved,  but  in 
a  few  it  is  wanting  or  vestigial.  A  striking  feature  of  the  wing-venation 
is  the  fact  that  the  basal  part  of  the  subcosta  of  the  hind  wings  makes. 
a  prominent  bend  into  the  humeral  area  of  the  wing  and  is  usually 
connected  to  the  humeral  angle  by  a  strong  cross-vein  (Fig.  817), 

A  monograph  of  the  geometrid  moths  found  in  the  United  States 
was  published  by  Packard  ('76). 

The  superfamily  Geometroidea  includes  two  families;  but  one  of 
these,  the  Manidiidas-is  represented  in  our  fauna  by  a  single  rare  species. 

Family  GEOMETRIDvE 

In  this  family  the  antennas  are  not  clubbed,  as  in  the  next  family. 
The  other  distinctive  features  of  the  Geometridae  are  those  given, 
above  in  the  characterization  of  the  superfamily  Geometroidea. 

There  occur  in  our  fauna  representatives  of  six  subfamilies  of  the 
Geometridae ;  these  can  be  separated  by  the  following  table : — ■ 

A.    Eyes  small  and  oval.  p.  664 Brephin^' 

AA.    Eyes  round  and  usually  large. 

B.    Vein  M2  of  the  hind  wings  vestigial,  being  represented  merely  by  a  fold  in 
the  wing  or  by  a  non-tubular  thickening  (Fig.  817).  p.   670.  .Geometrin^ 
BB.    Vein  M2  of  the  hind  wings  well-preserved. 

C.    Vein  M2  of  the  hind  wings  arising  much  nearer  to  vein  M,  than  to  vein 

M3  (Fig.  820).    Wings  usually  green,  p.  665 Hemithein^e; 

CC.     Vein  M2  of  the  hind  wings  arising  nearly  midway  between  veins  Me 

and  M3  or  nearer  to  vein  M3  than  to  vein  Mj.    Wings  rarely  green. 

D.    Veins  Sc  +  Ri  and  Rs  of  the  hind  wings  extending  distinctly  separate 

from  each  other,  except  that  they  are  connected  by  the  free  part  of  vein 

R,  near  the  middle  of  the  discal  cell  (Fig.  821).  p.  666.  . . .  Larentiin^e 

DD.    Veins  Sc  -|-  R,  and  Rs  of  the  hind  wings  approximated  or  coalesced 

for  a  greater  or  less  distance. 

E.  Veins  Sc  -|-  Ri  and  Rs  of  the  hind  wings  closely  approximated  but 
not  coalesced  along  the  second  fourth  (more  or  less)  of  the  discal 
cell.    With  transverse  rows  of  spines  on  abdominal  segments.     {Pal- 

aacrita).     p.  670 Geometrin^ 

EE.    Veins  Sc  -f-  Ri  and  Rs  of  the  hind  wings  coalesced  for  a  greater  or 
less  distance.    Abdomen  without  transverse  rows  of  spines. 
F.     Veins  Sc  -(-  Ri  and  Rs  of  the  hind  wings  coalesced  for  a  short 
distance  near  the  beginning  of  the  second  fourth  of  the  discal  cell^ 

thence  rapidly  diverging  (Fig.  821).  p.    666 Acidaliin^ 

FF.  Veins  Sc  -j-  Ri  and  Rs  of  the  hind  wings  coalesced  to  or  beyond 
the  middle  of  the  discal  cell  (Fig.  823),  or  with  a  short  fusion  near 
the  end  of  the  discal  cell. 

G.    Fore  wings  with  one  or  two  accessory  cells,  p.  666. .  Larentiin^ 
GG.    Fore  wings  without  an  accessory  cell.  p.  664.  .CENOCHROMiNiE 


664  AN  INTRODUCTION  TO  ENTOMOLOGY 

Subfamily  BREPHIN^ 

The  members  of  this  subfamily  are  most  easily  distinguished 
from  other  geometrids  by  the  fact  that  their  eyes  are  small  and  oval. 
It  is  represented  in  our  fauna  by  only  five  species,  of  which  the  follow- 
ing one  is  the  best -known. 

Brephos  mfans. — This  interesting  species  has  been  found  only  in 
the  northeastern  part  of  our  country;  its  range  is  from  Labrador  to 
New  York.  It  is  a  blackish -brown  moth  with 
the  fore  wings  marked  with  pinkish  white 
and  the  hind  wings  with  reddish  orange  (Fig. 
8 1 8).  The  specimen  figured  is  a  male.  In 
the  female  the  black  border  on  the  outer 
margin  of  the  hind  wings  is  narrower,  and 
the  subterminal,  light  band  on  the  fore  wings 
is  more  distinctly  marked.  In  the  larva  the 
Fig.  8i8.—Bi'ephos  infans.  prolegs  are  all  present;  but  the  first  three 
pairs  are  stunted.  The  full-grown  larva 
measures  30  mm.  in  length.  The  color  of  the  larva  on  the  dorsiun 
varies  from  apple-green  to  blue-green  according  to  age.  The  food- 
plant  is  white  birch. 

Subfamily  CENOCHROMIN.^ 

This  subfamily  is  represented  in  our  fauna  by  only  three  species 
of  which  only  the  following  one  is  well  known. 

The  fall  canker-worm,  Alsophila  pometdria.- — The  canker-worms 
are  well-known  pests,  which  are  often  very  destructive  to  the  foliage 
of  fruit-trees  and  shade-trees.  Although  they  attack  many  kinds  of 
trees,  the  apple  and  the  elm  are  their  favorite  food-plants. 

There  are  two  species  of  canker-worms  which  resemble  each  other 
to  such  an  extent  that  they  were  long  confounded;  but  they  differ 
structurally,  being  members  of  different  subfamilies;  and  they  dift'er 
also  in  habits.  The  two  species  agree  in  being  loopers  or  measuring- 
worms  in  the  larval  state,  in  the  possession  of  ample  wings  by  the 
adult  male,  and  in  the  adult  female  being  wingless.  They  are  easily 
distinguished  however,  in  all  stages,  the  eggs,  larvee,  and  adults 
differing  markedly. 

The  fall  canker-worm  is  so  called  because  the  greater  number  of 
the  moths  mature  in  the  autumn  and  emerge  from  the  ground  at  this 
season;  but  a  considerable  number  come  out  of  the  ground  in  the 
winter  during  warm  weather,  and  in  the  spring.  As  the  females  are 
wingless  they  are  forced  to  climb  up  the  trunks  of  trees  in  order  to 
lay  their  eggs  in  a  place  from  which  the  larvae  can  easily  find  their 
food.  The  eggs  appear  as  if  cut  off  at  the  top,  and  have  a  central 
puncture  and  a  brown  circle  near  the  border  of  the  disk.  They  are 
laid  side  by  side  in  regular  rows  and  compact  batches,  and  are 
generally  exposed.  They  hatch  in  the  spring  at  the  time  the  leaves 
appear;  and  the  larvee  mature  in  about  three  weeks.    In  this  species 


LEPIDOPTERA  665 

there  is  a  pair  of  vestigial  prolegs  on  the  fifth  abdominal  segment. 
The  pupa  state  is  passed  beneath  the  ground  in  a  perfect  cocoon  of 
fine  densely  spun  silk.     The  adult  male  is 
represented  by  Figure  819.     There  is  a  dis- 
tinct whitish  spot  near  the  apex  of  the  fore 
wings.     The  moths  of  both  sexes  lack  the 
abdominal  spines  characteristic  of  the  spring 
canker-worm.    In  the  fall  canker-worm  veins 
Sc  -f-  Ri  and  Rs  of  the  hind  wings  coalesce 
for  a  considerable  distance  along  the  second 
fourth  of  the  discal  cell ;  and  veins  Rs  and  Mi 
of  the  hind  wings  separate  af  the  apex  of  the  Fig.   819. — Alsophila  pom 
discal  cell.  ^'^''^'a- 

Control  of  canker-worms. — The  two  spe- 
cies of  canker-worms  are  sufficiently  alike  in  habits  to  warrant  our 
combating  them  by  similar  methods.  The  fact  that  in  each  the 
female  is  wingless  and  is  thus  forced  to  climb  up  the  trunks  of  trees 
in  order  to  place  her  eggs  in  a  suitable  place  has  suggested  the  method 
of  defence  that  has  been  most  generally  used  in  the  past.  This  is 
to  place  something  about  the  trunks  of  the  trees  which  will  make  it 
impossible  for  the  wingless  female  to  ascend  them.  Some  viscid  sub- 
stance, as  tar,  printers'  ink,  or  melted  rubber,  either  painted  on  the 
trunk  of  the  tree  or  upon  a  paper  band  which  is  tacked  closely  about  the 
tree,  is  the  means  usually  adopted.  Many  other  devices  have  been 
recommended.  In  the  use  of  this  method  of  prevention,  operations 
should  be  begun  in  the  autumn,  even  when  it  is  the  spring  canker- 
worm  that  is  to  be  combated ;  for  in  this  species  some  of  the  moths 
emerge  in  the  fall  or  during  the  winter. 

Although  the  method  just  described  is  still  the  most  available  one 
when  tall  shade-trees  are  to  be  protected,  it  is  now  rarely  used  in 
orchards.  Here  the  spraying  of  the  trees  with  Paris-green  or  arsenate 
of  lead  soon  after  the  leaves  appear  is  found  more  practicable.  This 
method  has  also  the  advantage  of  enabling  the  fruit-grower  to  reach 
other  important  pests,  as  the  codlin-moth,  at  the  same  time. 

Subfamily  HEMITHEIN^ 
The  Green  Geometrids 

As  a  rule  the  members  of  this  subfamily  are  bright  green  in  color; 
and  as  we  have  but  few  other  geometrids  of  this  color,  the  subfamily 
may  be  well  termed  the  green  geometrids.  The  distinctive  structure 
that  characterizes  this  subfamly  is  the  fact  that  vein  M2  of  the  hind 
wings  arises  much  nearer  to  vein  Mi  than  to  vein  M3    (Fig.  820). 

This  is  a  comparatively  small  subfamily,  including  1 7  genera  and 
64  species.    The  following  species  will  serve  as  an  example. 

The  raspberry  geometer,  Synchldra  cerdta.- — -The  larva  of  this  spe- 
cies feeds  on  the  fruit  and  foliage  of  raspberry,  but  chiefly  on  the  fruit. 
It,  like  some  other  members  of  this  subfamilv,  has  the  curious  habit 


666 


AN  INTRODUCTION  TO  ENTOMOLOGY 


of  covering  its  body  by  attaching  to  it  bits  of  vegetable  matter,  so 
that  it  is  masked  beneath  a  tiny  heap  of  rubbish.    The  wings  of  the 

adult  are  of  a  delicate  pale 
green  color  crossed  by  two 
lines  of  a  lighter  shade ;  the 
face  is  green;  and  the  ab- 
domen is  not  marked  with 
pink  and  white  ocellate 
spots,  as  is  the  case  in  cer- 
tain allied  species. 


Subfamily 
ACIDALIIN^ 

The  members  of  this  sub- 
family are  most  easily  rec- 
ognized by  the  venation  of 
the  hind  wings  (Fig.  821). 
In  these  veins  Sc+Ri  and 
Rs  coalesce  for  a  short  dis- 
tance near  the  beginning  of 
the  second  fourth  of  the 
discal  cell  and  then  diverge 
rapidly.  The  greater  num- 
ber of  our  common  species 
are  of  medium  size,  with 
whitish  wings  crossed  by 
from  two  to  four  indistinct 
lines,  and  with  the  head 
black  in  front ;  some  are  pure 
white,  and  others  are  brown  marked  with  reddish  lines.  Eighty-six 
species  are  now  listed  from  this  country. 

The  chickweed  geometer,  Hcematopis  gratdria. — This  little  moth 
(Fig.  822)  is  very  common  in  our  meadows  and  gardens  during  the 
summer  and  autumn  months.  Its  wings  are  reddish  yellow,  with  the 
fringes  and  two  transverse  bands  pink.  It  is  found  from  Maine  to 
Texas.  The  larva  feeds  on  the  common  chickweed,  Alsine  media. 
The  sweet-fern  geometer,  Cosymbia  lumendria. — This  moth  is 
grayish  white,  with  three  rows  of  black  dots  extending  across  the 
wings,  one  marginal,  one  submarginal,  and  one  near  the  base  of  the 
wings;  near  the  center  of  each  wing  there  is  a  small  reddish  ring. 
The  moth  has  a  wing  expanse  of  from  20  to  25  mm.  The  larva  is 
common  on  sweet-fern,  Comptoma;  it  also  feeds  on  birch. 


Fi?.  820. — Wings  of  Dichorda  iridaria. 


Subfamily  LARENTIIN^ 

In  this  subfamily  the  branches  of  radius  of  the  fore-wings  anasto- 
mose so  as  to  form  one  or  two  accessory  cells,  this  anastomosis  involv- 


LEPIDOPTERA 


667 


ing  veinRi  (Figs.  823  and  824). 
In  the  hind  wings  in  most  of 
the  genera  veins  Sc+Ri  and 
Rg  coalesce  to  or  beyond  the 
middle  of  the  discal  cell  or  with 
a  short  fusion  near  the  end  of 
the  discal  cell  (Fig.  823);  but 
in  certain  genera,  where  the 
costal  area  of  the  hind  wings  is 
greatly  expanded,  these  veins 
extend  distinctly  separate  from 
each  other,  except  that  they 
are  connected  by  the  free  part 
of  vein  Ri  near  the  middle  of 
the  discal  cell  (Fig.  824).  In 
a  few  genera  belonging  to  other 
subfamilies  veins  Sc+Ri  and 
Rs  of  the  hind  wings  coalesce 
to  the  middle  of  the  discal  cell, 
but  these  genera  lack  the  ac- 
cessory cell  in  the  fore  wings 
characteristic  of  this  subfamily. 
This  subfamily  ranks  sec- 
ond in  size  among  the  geom- 
etrid  subfamilies,  including 
365  North  American  species; 
these  represent  58  genera. 
Many  of  the  species  are  very  common ;  among  them  are  the  following. 

The  white-striped 

^^^  <^  J*  ^^^M     black,  Trichodezia  al- 

^■Byfi^^^     b  ov  itt  dta.—This 

^^^^mB^Z      beautiful  little  moth, 

^^yi^^y        which  occurs  from 

the  Atlantic  to  the 

Pacific,  is  the  most 

easily  recognized 
member  of  the  family.  It  expands 
about  22  mm.  and  is  of  a  uniform  black 
color,  with  a  single,  very  broad  white 
band  extending  across  the  fore  wing  from 
the  middle  of  the  costa  to  the  inner  angle, 
where  it  is  usually  forked.  The  fringe  of 
the  wings  is  white  at  the  apical  and  inner 
angles  of  both  pairs;  sometimes  the 
white  is  lacking  on  the  inner  angle  of  the 
hind  wings.  The  early  stages  are  un- 
known. 

The  bad-wing,  Dyspteris  abortivdria. 
— It  is  easy  to  recognize  this  moth  (Fig.   pig_    823.- 
825)  by  the  peculiar  shape  of  its  wings,       mendica. 


Fig.    821 


id  A 

-Wings    of  Acidalia  enudeata. 


Fig.  82  2.—HcEma- 
topis  grataria. 


-Wings     of     Eudule 


668 


AN  INTRODUCTION  TO  ENTOMOLOGY 


the  hind  wings  being  greatly  reduced  in  size.    It  is  of  a  beautiful  pea- 
green  color,  with  two  white  bands  on  the  fore  wings  and  one  on  the 

hind  wings.     In  color  it  re- 


R,^.. 


sembles  members  of  the  He- 
mitheinse;  but  the  structure 
of  its  wings  (Fig.  824)  shows 
that  it  belongs  in  the  Laren- 
tiinae.  The  larva  feeds  on  the 
leaves  of  grape,  which  it  rolls. 
The  scallop-shell  moth, 
Calocalpe  undtddta. — This  is 
a  pretty  moth,  with  its  yel- 
low wings  crossed  by  so  many 
fine,  zigzag,  dark  brown  lines 
that  it  is  hard  to  tell  which  of 
the  two  is  the  ground-color 
(Fig.  826).  It  lays  its  eggs  in 
a  cluster  on  a  leaf  near  the  tip 
of  a  twig  of  cherry,  usually 
wild  cherry.  The  larvae  make 
a  snug  nest  by  fastening  to- 
gether the  leaves  at  the  end 
of  the  twig;  and  within  this 
nest  (Fig.  827)  they  live,  add- 
ing new  leaves  to  the  outside 
as  more  food  is  needed.  The 
leaves  die  and  become  brown, 
and  thus  render  the  nest  con- 
spicuous. There  are  two  gen- 
erations in  the  year.  The  lar- 
vse  of  the  fall  brood  are  black 
above,  with  four  white  or 
green  stripes,  and  flesh-colored  below;  the  larvae  of  the  summer  brood 
are  black  only  on  the  sides.  When  full-grown  they  descend  to  the 
ground  to  transform,  and  pass  the  winter  in  the  pupa  state. 

The  diverse-line  moth,  Lygris  diver silinedta. — This  moth  has  pale 

ochre-yellow  wings, 

with  a  brownish  shade 

near  the  outer  margin, 

and  crossed  by  many 

diverging  brown  lines 

(Fig.  828).     It  varies 

from  37  to  50  mm.  in 

expanse.  We  have  oft- 
en found  this  moth  on 

the  side  of  our  room, 

resting    on    the    wall, 
head  downward,  and  with  its  abdomen  hanging  down  over  its  head 
in  a  curious  manner.    The  larva  feeds  on  the  leaves  of  grape.    There 


Wings   of    Dyspleris    ahortivaria. 


Fig.  825. — Dyspleris  aborti 
varia. 


Calocalpe  un- 


LEPIDOPTERA 


669 


are  two  broods;  the  first  brood  infests  the  vines  during  June;  the 
second,  in  the  autumn  and  early  spring,  wintering  as  larvae. 

The  spear-marked  black,  Rheum- 
dptera  hastdta.- — This  is  a  black-and- 
white  species,  which  is  found  from  the 
Atlantic  to  the  Pacific.  It  is  much 
larger  than  the  white-striped  black 
described  above,  expanding  35  mm. 
It  is  black,  striped  and  spotted  with 
white ;  It  varies  greatly  as  to  the  nvmn- 
ber  and  extent  of  the  white  markings. 
The  most  constant  mark  is  a  broad 
white  band  crossing  the  middle  of  the 
fore  wings,  and  often  continued  across 
the  hind  wings.  Near  the  middle  of  its 
course  on  the  fore  wing  this  band  makes 
a  sharp  angle  pointing  outward;  and 
just  beyond  the  apex  of  this  angle  there 
is  usually  a  white  spot.  This  spot  and 
angular  band  together  form  a  mark 
shaped  something  like  the  head  of  a 
spear.  In  some  individuals  the  white 
predominates,  other  individuals  are  al- 
most entirely  black,  excepting  the  spear 
mark.  In  the  East,  there  is  more  white 
on  the  fore  wings  than  on  the  hind 
wings;  this  form  is  the  variety  gothi- 
cdta;  in  some  parts  of  the  West  and  in 
Europe  there  is  more  white  on  the  hind 
wings  than  on  the  fore  wings.  Accord- 
ing to  European  authorities  the  larva 
is  brown  or  blackish  brown,  with  a 
darker  fine  along  the  middle  of  the 
back,  and  a  row  of  horse-shoe-shaped 
spots  on  the  sides.  It  feeds  on  birch 
and  sweet  gale.  It  is  gregarious,  a 
colony  of  larva;  spinning  together  the 
leaves  of  the  food-plant,  and  thus  forming  a  nest  within  which  they 

live  and  feed. 

The  larva  has 

not  yet  been 

observed  in 

this    country. 
The  beg- 
gar,  Eudule 

mendlca.  ■ — 
Fig.  82H.—Lygi'isdivcrsilineata.    One    of     the 

most  delicate- 
winged  moths  that  we  have  in  the  northern  Atlantic  States  is  this 


Fig.  827. — Eggs  and  nest  of  Calo- 
calpe  undulata. 


Fig.  829. — Eudule  mendica. 


670 


AN  INTRODUCTION  TO  ENTOMOLOGY 


species  (Fig.  829).  Although  the  wings  are  yellowish  white  in  color 
they  are  almost  transparent.  On  the  fore  wings  there  are  two  trans- 
verse rows  of  pale  gray  spots,  and  a  single  spot  near  the  outer  margin 
between  veins  M,3  and  Cui.  (This  spot  was  indistinct  in  the  specimen 
figured.)  The  moth  is  common  in  midsiimmer.  The  larva  feeds  on 
violet. 

Subfamily  GEOMETRIN^ 

Nearly  all  of  the  members  of  this  subfamly  can  be  easily  recognized 
as  such  by  the  fact  that  vein  M2  of  the  hind  wings  is  wanting,  being 
represented  merely  by  a  fold. 

This  is  by  far  the  largest  of  the  subfamilies  of  the  Geometridae; 
it  includes  more  than  500  North  American  species;  these  represent 
124  genera.    The  following  are  some  of  the  more  common  species. 

The  currant  span-worm,  Cymatophora  rihedria. — There  are  several 
species  of  insects  that  are  popularly  known  as  currant-worms.  The 
most  common  of  these  are  larv^ae  of  saw-flies,  which  can  be  easily 
recognized  by  the  large  number  of  prolegs  with  which  the  abdomen 


Fig.  830. — Cymatophora  ribearia. 


Fig.   831. — Cingilia  catenaria. 


is  furnished.  In  addition  to  the  saw-flies  there  is  a  yellow  looper 
spotted  with  black,  which  often  appears  in  such  great  nimibers  on 
currant  and  gooseberry  bushes  as  to  suddenly  strip  them  of  their 
foliage. 

This  larva  has  been  named  the  currant  or  gooseberry  span-worm. 
When  full-grown  it  measures  about  2  5  mm.  in  length,  and  is  of  a  bright 
yellow  color,  with  white  lines  on  the  sides  and  with  numerous  black 
spots  and  round  dots.  It  has  only  four  prolegs.  There  is  only  one 
generation  a  year;  the  larva  matures  in  May  or  June;  the  pupa  state 
lasts  about  a  "fortnight;  the  moth  flies  during  the  svimmer  month  sand 
oviposits  on  the  twigs  of  the  plants ;  and  the  eggs  remain  unhatched 
till  the  following  spring.  The  moth  (Fig.  830)  is  pale  yellow,  with  the 
wings  marked  by  irregular  dusky  spots,  which  sometimes  form  one 
or  two  indefinite  bands  across  them. 

The  chain-dotted  geometer,  Cingilia  catenaria.— This  moth  has 
snow-white  wings  marked  with  zigzag  lines  and  with  dots  of  black  as 
shown  in  Figure  83 1 .  The  head  is  ochreous-yellow  in  front ;  and  the 
thorax  is  yellowish  at  the  base  of  the  patagia.    The  moth  flies  during 


LEPIDOPTERA  671 

September  and  October.  The  larva  feeds  on  various  shrubs  and  trees. 
The  pupa  state  is  passed  in  a  slight  but  well-formed  web  of  yellow 
threads,  which  is  formed  between  twigs  or  leaves,  and  through  which 
the  pupa  can  be  seen. 

The  evergreen  nepytia,  Nepytia  semiclusdria. — This  beautiful  moth 
(Fig.  832)  is  common  in  the  vicinity  of  pines,  spruce,  fir,  and  hemlock 
during  August  and  September.  It  varies 
from  a  smoky-ash  color  to  almost  snow- 
white;  the  wings  are  marked  with  black. 
The  larv^a  feeds  on  the  leaves  of  Conifers. 
It  is  reddish  yellow  above,  with  lateral 
yellow  bands  below,  while  on  each  side  are 
two  pairs  of  black  hair-lines.  There  are 
black  spots  above  on  the  segments.    When 

full-grown  it  is  a  litle  more  than  25  mm.   

long  and  spins  a  loose  cocoon  among  the  —  8^,2.— Nepytia  semidusa- 
leaves.    The  chrysalid  is  green  with  white       ria. " 
stripes  and  is  very  pretty. 

The  spring  canker-worm,  Paleacrita  verndta.—The  eggs  are  ovoid 
in  shape,  and  are  secreted  in  irregular  masses,  usually  under  loose 
scales  of  bark  or  between  the  leaflets  of  the  expanding  buds.  The 
larvae  hatch  about  the  time  the  leaves  expand,  and  become  full-grown 
in  from  three  to  four  weeks.  They  vary  greatly  in  color,  and  are 
marked  on  the  back  with  eight  narrow,  pale,  longitudinal  lines  which 
are  barely  discernible;  the  two  lateral  lines  of  each  side  are  much 
farther  apart  than  the  others;  and  there  are  no  prolegs  on  the  fifth 
abdominal  segment  as  in  the  fall  canker-worm.  The  pupa  state  is 
passed  below  the  surface  of  the  ground  in  a  simple  earthen  cell,  which 
is  lined  with  very  few  silken  threads.  The  adult  moths  usually  emerge 
early  in  the  spring  before  the  leaves  expand;  but  they  sometimes 
appear  late  in  the  fall,  or  on  warm  days  during  the  winter  when  the 
ground  is  thawed.  In  both  sexes  the  adult  of  this  species  is  dis- 
tinguished by  the  presence"  of  two  transverse  rows  of  stiff  reddish 
spines,  pointing  backwards,  on  each  of  the  first  seven  abdominal  seg- 
ments. 

Regarding  the  control  of  canker-worms  see  page  665. 

The  lime-tree  winter-moth,  Erannis  tilidria. — This  species  (Fig. 
833)  resembles  the  canker-worms  in  many  particulars.  The  larva  is 
a  looper  which  infests  both  fruit  and  forest  trees;  and  in  the  adult 
state  the  male  has  well-developed  wings,  while  the  female  is  wingless. 

The  eggs  are  oval,  of  a  pale  yellow  color,  and  covered  with  a  net- 
work of  raised  lines.  They  are  thrust  by  the  female  under  loose  bark 
and  in  crevices  on  the  trunk  and  large  limbs.  They  hatch  in  May, 
and  the  larvae  attain  their  full  growth  in  the  latter  part  of  June.  The 
larva  is  yellow,  marked  with  ten  crinkled  black  lines  along  the  top  of 
the  back;  the  head  is  rust-colored,  and  the  venter  yellowish  white. 
There  is  a  second  form  of  the  larva  which  is  brown  above  with  slate 
color  towards  the  sides.  When  full-grown  the  larva  measures  about 
30  mm.  in  length.     The  pupa  state  is  passed  in  the  ground.     The 


672 


AN  INTRODUCTION  TO  ENTOMOLOGY 


moths  issue  in  October  or  November;  and  then  the  wing;less  females 
ascend  the  trees  to  oviposit  as  do  the  females  of  the  canker-worms. 
The  female  is  represented  in  the  lower  left-hand  part  of  the  figure. 


Fig.  833. — Erannis  tiliaria.     (From  The  Author's  Report  for  1879.) 

She  is  grayish  in  color,  with  two  black  spots  on  the  back  of  each 
segment  except  the  last,  which  has  only  one.  The  male  has  pale 
yellow  and  brown  or  buff  fore  wings,  with  a  central  spot  and  a  band 

beyond  the  middle,  while  the  hind 
wings  are  much  lighter.  This  insect 
'  can  be  combated  by  the  same  meth- 
tods  as  are  used  against  canker 
worms. 

The  notched-wing  geometer,  En- 
nomos  magndrius.- — -This  is  one  of  the 
larger  of  our  geometrids.    The  larva 
is  a   common   looper  upon  maple, 
chestnut,  and  birch  trees,  and  meas- 
ures about  58  mm.  in  length  when 
full-grown.    It  spins  a  rather  dense, 
spindle-shaped  cocoon  within  a  clus- 
ter of  leaves.     The  moth   (Fig.  834)  is  ochre-yellow   with   reddish 
tinge.    The  wings  are  shaded  towards  the  outer  margin  with  brown, 
and  are  thickly  spotted  with  small  brown  dots. 


Fig.  834. — Ennomos  magnarius. 


LEPIDOPTERA 


673 


The  pepper-and-salt  currant-moth,  Amphldasis  cognatdria. — 
This  moth  (Fig.  835)  differs  remarkably  in  appearance  from  most 
geometrids,  the  body  being  stouter,  and  the  wings  appearing  heavier. 


Amphidasis  cogna- 


Fig.  836. — Phryganidia  calif ornicu. 


It  can  be  easily  recognized  by  its  evenly  distributed  pepper-and-salt 
markings.  The  larva  feeds  on  various  plants,  but  is  found  most  often 
on  currant. 

Family  MANIDIID^ 

This  family  is  repre- 
sented in  our  fauna  by  „    /^.^ 
a  single,  recently  discov-                                                     ^^^r^ZP^^f^* 

ered  species,  .4 nurapteryx  ^>Xy^ i /? 

crenuldta,  found  in  Ari-  ^<:^^^  5 

zona.  In  the  genus  i4wM- 
rapteryx  the  antennae 
are  gradually  enlarged 
toward  the  tip  forming  a 
long  slender  club;  the 
maxillae  ■  are  well-devel- 
oped ;  the  eyes  are  hairy 
and  overhung  by  long 
cilia;  and  the  frenulum 
is  well-developed. 

Our  species  was  de- 
scribed by  Barnes  and 
Lindsey  in  "Entomo- 
logical News,"  vol.  30, 
p.  245. 

Family  DIOPTID^ 
The  Dioptids 
The  only  member  of 


Fig. 


2d  A 
837. — ^Wings  of  Phryganidia. 


this  family  that  is  well 
known  in  this  country  is 
Phryganidia  californica,  which  occurs  in  California.  This  is  a  pale- 
brown  insect,  with  nearly  transparent  wings  (Fig.  836).  The  veins 
of  the  wings  are  dark,  which  renders  them  prominent.  In  the  males 
there  is  a  yellowish  spot  just  beyond  the  discal  cell.    The  venation 


674 


AN  INTRODUCTION  TO  ENTOMOLOGY 


of  the  wings  (Fig.  837)  is  very  different  from  that  of  any  other  insect 

that  occurs  in  this  countr\^ 

The  XoxYse.  feed  upon  the  leaves  of  live-oaks,  and  sometimes  occur 

so  abundantly  as  to  almost  strip  the  trees  of  their  foliage.    They  are 

said  to  feed  singly,  and  appear  to  make  little  if  any  use  of  the  anal 

feet  as  a  means  of  loco- 
motion, generally  carry- 
ing the  last  segment  of  the 
body  elevated  in  the  air. 

Family 
NOTODONTID^ 

The  Prominents 

This  family  includes 
moths  of  moderate  size, 
only  a  few  of  the  larger 
ones  expanding  more 
than  50  mm.  The  body 
is  rather  stout  and  dense- 
ly clothed  with  hair,  and 
the  legs,  especially  the 
femora,  are  clothed  with 
long  hairs.  The  wings 
are  strong,  and  not  very 
broad,  the  anal  angle  of 
the  hind  wings  rarely 
reaching  the  end  of  the 
abdomen.  In  their  gen- 
eral appearance  many  of 
these  moths  bear  a  strong  resemblance  to  noctuids;  but  they  can  be 
easily  distinguished  from  the  Noctuidae  by  the  position  of  vein  M2 
of  the  fore  wings,  which 
does  not  arise  nearer  to 
vein  Cu  than  to  vein  R, 
as  it  does  in  that  family; 
and  the  fact  that  in  this 
family  veins  Sc-fRi  and 
Rs  of  the  hind  wings  do 
not  coalesce  (Fig.  838). 
The  first  anal  vein  is 
wanting  in  both  fore  and 
hind  wings ;  and  in  some 
species  an  accessory  cell  is  present  in  the  fore  wings. 

In  some  species  the  front  wings  have  a  prominence  or  backward 
projecting  lobe  on  the  inner  margin,  which  suggested  the  common 
name  of  prominents  for  these  insects  (Fig.  839).  The  name  is  more 
generally  appropriate,  however,  for  the  larvas,  as  a  much  larger  pro- 
portion of  them  than  of  the  adults  bear  striking  prominences. 


Fig.  838. — Wings  of  Hyperceschra  stragula. 


Fig.  839. — Pheosia  rimosa. 


LEPIDOPTERA 


675 


The  larv£c  feed  upon  the  leaves  of  shrubs  and  trees.  Our  most 
common  species  live  exposed ;  but  some  species  live  in  folded  leaves. 
They  are  either  naked  or  clothed  with  hairs.  A^any  species  have  only 
four  well-developed  prolegs,  the  anal  pair  being  rudimentary,  or  trans- 
formed into  elongated  spikes.  Some  species  are  hump-backed;  and 
spines  or  fleshy  tubercles  are  often  present.  The  transformations  occur 
in  slight  cocoons  or  in  the  ground. 

The  family  Notodontid^e  is  represented  in  this  countrv'-  by  about 
one  hundred  species.  A  monograph  of  the  family  was  published  by 
Packard  ('95)  in  which  there  are  many  colored  figures  of  larv«.  The 
following  are  some  of  the  more  common  species. 

The  handmaid  moths,  Datana.- — Among  the  more  common  repre- 
sentatives of  the  Notodontida^  are  certain  brown  moths  that  have  the 
fore  wings  crossed  with  bars  of  a  different  shade  (Fig.  840)  and  that 
bear  on  the  fore  part  of  the  thorax  a  conspicuous  patch  of  darker 
color.  In  most  of  our  species  the  fore 
wings  are  also  marked  with  a  dot  near 
the  center  of  the  discal  cell  and  a  bar 
on  the  discal  vein.  These  moths  be- 
long to  the  genus  Datd^a.  The  com- 
mon name,  handmaid,  is  a  translation 
of  the  specific  name  of  our  most  com- 
mon species,  D.  mimstra.  But  as  this 
species  is  now  generally  known  as  the 
yellow-necked  apple-tree  worm,  and  as 
all  of  our  species  are  dressed  in  sober 
attire  as  becomes  modest  servants,  we  have  applied  the  term  hand- 
maid moths  to  the  entire  genus. 

The  larvae  of  the  handmaid  moths  are  easily  recognized  by  their 
peculiar  habits.  They  are  common  on  various  fruit  and  forest  trees, 
but  especially  on  apple,  oak,  and  hickory. 


Fig.  840. — Datana. 


Fig.  841. — Datana,  larva. 

They  feed  in  colonies ;  and  have  the  habit  of  assimiing  the  curious 
attitude  shown  in  Figure  841.    The  body  is  black  or  reddish,  marked 


676 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.    842a. — Syiiiiiierista    albifrons. 


with  lines  or  stripes  of  yellow  or  white.  Owing  to  the  gregarious 
habits  of  these  larvae  they  can  be  easily  collected  from  the  trees  they 
infest. 

All  the  species  that  we  have  studied  agree  in  being  single-brooded, 
the  moths  appearing  in  midsummer;  the  eggs  are  laid  in  a  cluster 
on  a  leaf;  the  larvae  are  conspicuous  in  August  and  September.  In 
some  of  the  species  the  larvae  have  the  curious  habit  of  leaving  the 
branch  upon  which  they  are  feeding  when  the  time  to  molt  arrives, 
the  whole  colony  gathering  in  a  large  mass  on  the  trunk  of  the  tree, 
where  the  molt  takes  place.  The  pupa  state  is  passed  in  the  ground, 
in  a  very  light  cocoon  or  in  none  at  all,  and  lasts  about  nine  months 
in  the  species  that  we  have  bred. 

The   white-tipped  moth,    Symnierlsta  albifrons.- — This  beautiful 
moth,  which  is  quite  common,  can  be  easily  recognized  by  the  ac- 
companying figure  (Fig.  842,  a) ;  the 
white  patch ,  which  extends  along  the 
costa  of  the  fore  wing  for  half  the 
length  from  the  tip,  being  very  char- 
acteristic.   The  larva  (Fig.  842, b)  is 
quite   common   in   the  autumn   on 
leaves  of  oak.  It  is  known  as  the  red- 
humped  oak-caterpillar;  it  is  smooth 
and  shining,  with  no    hairs;   along 
each   side   of  the  back   there  is  a 
yellow  stripe,  and  between  these,  on 
the  back,  fine  black  lines  on  a  pale  lilac  ground;  on  each  side  below 
the  yellow  stripes  there  are  three  black  lines,  the  lowest  one  just 
above  the  spiracles.    The  head  is  orange-red ;  and  there 
is  an  orange-red  hump  on  the  eighth  abdominal  seg- 
ment. 

The  two-lined  prominent,  Heterocdmpa  bilinedta. — 

The  larva  of  this 
species(Fig.843) 
is  much  more  apt 
to  be  observed 
-Symmerista  albifrons,  larva.  than    the    adult. 

It  IS  common  m 
the  latter  part  of 
the  summer  and  in  early  autumn,  feeding  on  the  leaves  of  elm,  beech, 
and  basswood.  It  measures  when  full-grown  about  37  mm.  in  length. 
Its  ground-color  is  usually  green,  but 
sometimes  claret-red.  There  is  a  pale 
yellow  stripe  along  the  middle  of  the  back, 
and  on  each  side  a  stripe  of  the  same  color. 
The  course  of  these  side  stripes  is  very 
characteristic;  passing  back  from  the 
head,  they  converge  on  the  prothorax;  on 
the  mesothorax  and  metathorax  they  are 

separated  from  the  dorsal  line  only  by  a  narrowband  of  red  or  purple; 
on  the  first  abdominal  segment  thev  diverge  to  the  lateral  margin  of 


,S426, 


Fig.    843. — Heterocampa 
lineata,  larva. 


hi- 


LEPIDOPTERA 


677 


the  back,  but  converge  again  on  the  seventh  and  eighth  abdominal 
segments.  This  >'ello\v  subdorsal  line  is  bordered  without  by  a  milk- 
white  stripe;  and  extending  from  this  stripe  over  the  side  of  the  body 
there  is  a  whitish  shade  which  fades  out  below.  The  moth  is  ash 
colored,  with  the  fore  wings  crossed  by  two  wavy  lines  between  which 
the  wing  is  darker;  between  the  outer  wavy  line  and  the  outer  margin 
of  the  wing  there  is  a  faint  band. 

Antlered  larvce. — Among  the  remarkable  forms  exhibited  by  no- 
todontian  larvae  are  those  of  the  freshly-hatched  larvee  of  two  species 
of  Heterocampa.  Figure  844  repre- 
sents the  first  instar  of  Heterocampa 
varia,  which  has  on  the  first  thoracic 
segment  a  pair  of  large  antler-like 
horns,  and  other  horns  on  several  of 
the  abdominal  segments.  In  the 
second  instar  all  of  these  horns  are 
wanting  except  small  vestiges  of  the 
first  pair.    This  species  feeds  on  oak. 

The  freshly  hatched  larva  of 
Heterocampa  guttivitta  is  also  ant- 
lered. The  horns  borne  by  the  pro- 
thorax  are  four-branched  and  there 

are  eight-pairs  of  horns  on  the  abdomen.  As  in  the  preceding  species 
all  of  these  horns  are  wanting  in  the  second  instar  except  vestiges  of 
the  first  pair.  This  species  feeds  especially  on  maple,  but  has  been 
found  on  other  trees. 


Fig.  844. —  Heterocampa  varia,  larva. 
(After  Packard.) 


Fig.  845. — Schiziira  concinna,  larva. 


The  red-humped  apple-worm,  Schiziira  concinna.- — The  larva  of  this 
species  (Fig.  845)  is  common  on  apple  and  allied  plants.  The  head 
is  coral-red ,  and  there  is  a  hump  of  the  same  color  on  the  back  of  the 
first  abdominal  segment;  the  body  is  striped  with  slender  black, 
yellow,  and  white  lines,  and  has  two  rows  of  black  spines  along  the 
back,  and  other  shorter  ones  upon  the  sides.  When  not  eating,  the 
larvae  remain  close  together,  sometimes  completely  covering  the 
branch  upon  which  they  rest.  This  species  passes  the  winter  in  the 
pupa  state.    The  adults  appear  in  June  and  July. 


678  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  Mocha-stone  moths,  Meldlopha. — To  the  germs, Melalophahe- 
long  several  species  of  brownish-gray  moths,  whose  fore  wings  are 
crossed  by  irregular  whitish  lines.  It  was  these  peculiar  markings, 
resembling  somewhat  those  of  a  moss-agate,  that  suggested  the 
popular  name  given  above.  The  larvae  feed  on  poplar  and  willow, 
and  conceal  themselves  within  nests  made  by  fastening  leaves  to- 
gether.   Our  most  common  species  is  the  following. 

Melalopha  indiisa.- — ^The  adult  (Fig.  846)  is  a  brownish-gray  moth 

with  the  fore  wings  crossed  by  three  irregular  whitish  lines.    The  basal 

line  is  broken  near  the  middle  of  the  wing;  and  the  intermediate  one 

forms  an  inverted  Y,  the  main  stem  of  which  joins  the  third  line  near 

the  inner  margin  of  the  wing,  making  with  it  a  prominent  V.     These 

lines  are  bordered  without  by  rust-red;  there  is  a  chocolate-colored 

spot  near  the  apex  of  the  fore  wings,  and  an  irregular  row  of  blackish 

^^^  ^g^      dots  near  the  outer  margin.     The  hairs  of 

^^^^^^^^H      the  thorax  form  a  prominent  crest,  the  fore 

^H^Hjj^H^^^Pr       side  of  which  is  a  rich  dark  brown.     The 

^^HHHBH^p         hind  wings  are  crossed  by  a  wavy  band, 

^H^^l^^j^         which    is   light   without   and   dark   within. 

W  The  eggs  are  nearly  spherical  and  smooth ; 

They  are  deposited  in  a  cluster  a  single  layer 

?i«.f  ''''^'^'"''""  deep  on  a  leaf  (Fig.  847).  When  the  larvs 
hatch  they  make  a  nest  either  by  fastening 
several  leaves  together  or,  as  is  the  case  when  they  infest  poplar,  by 
folding  the  two  halves  of  a  single  leaf  together;  frequently  in  the  latter 
case  the  tip  of  the  leaf  is  folded  in  as  shown  in  the  figure.  Within 
this  nest  the  entire  colony  lives,  feeding  on  the  parench>Tiia,  and 
causing  the  leaf  to  turn  brown.  Later  other  leaves  are  added  to  this 
nest  or  additional  nests  are  made  among  adjoining  leaves.  All  of 
these  infested  leaves  are  securely  fastened  to  the  twig  by  bands  of 
silk.  When  the  larvse  become  large  they  leave  their  nests  at  night 
to  feed  upon  other  leaves.  These  they  entirely  consume  excepting 
the  petioles,  midribs,  and  larger  veins.  We  have  seen  on  poplar 
a  nest  composed  of  only  three  leaves  which  contained  one  hundred 
and  twenty-five 
half -grown  larvae ; 
all  of  the  leaves, 
about  thirty  in 
number,  arisinj 
from  the  end  of  the 
branch  bearing  this 
nest  had  been  con- 
sumed. 

The    full-grown  

larva   measures    35    p-      847.— Eggs,  larva,  and  nest  of  Melalopha  inclusa. 
mm.  m  length,     jt       *=     ^'        ^^-^  '  ' 

is  striped  with  pale  yellow  and  brownish  black,  and  bears  a  pair  of 

black  tubercles  close  together  on  the  first  abdominal  segment,  and  a 

similar  pair  on  the  eighth  abdominal  segment.     The  cocoon  is  an 


X 


LEPIDOPTERA  679 

irregular  thin  web;  it  is  made  under  leaves  or  other  rubbish  on  the 
ground.  The  insect 
remains  in  the  pupa 
state  during  the  win- 
ter, and  emerges  as  a 
moth  in  the  latter  part 
of  June  or  later.  In 
the  South  this  species 
infests  willow  as  well  ^. 

as     poplar,    and     is  ^'^-  H^-Schtzura  ipomecB,  larva. 

double-brooded . 

Among  the  more  grotesque  larvae  belonging  to  this  family  are 
those  of  the  genus  Schizura,  of  which  we  have  several  species.  Figure 
848  represents  the  larva  of  Schizura  ipomeoe.  At  the  left  in  the  figure 
is  shown  a  front  view  of  the  longest  tubercle.  This  species  feeds  on 
oak,  maple,  and  many  other  plants.  In  the  Gulf  States  it  feeds  on 
Ipomea  coccinea,  which  fact  suggested  its  specific  name. 


Family  LYMANTRIID^ 

The  family  Liparidce  of  some  writers 

The  Tussock-moths 

The  larvas  of  these  moths  are  among  the  most  beautiful  of  our 
caterpillars,  being  clothed  with  brightly-colored  tufts  of  hairs;  and 
it  is  to  this  characteristic  clothing  of  the  larvae  that  the  popular 
name  tussock-moths  refers. 

The  adult  moths  are  much  plainer  in  appearance  than  the  larvas ;. 
and  in  the  genera  Hemerocampa  and  Notolophus,  to  which  our  most 
common  species  belong,  the  females  are  practically  wingless,  the  wings 
being  at  most  short  pads,  of  no  use  as  organs  of  flight. 

The  tussock-moths  are  of  medium  size,  with  the  antennae  of  both 
sexes  when  winged  pectinated,  those  of  the  males  very  broadly  so;. 
the  wingless  females  have  serrate  or  narrowly  pectinate  antennae. 
The  ocelli  are  wanting.  The  legs  are  clothed  with  woolly  hairs; 
when  the  insect  is  at  rest  the  fore  legs  are  usually  stretched  forward, 
and  are  very  conspicuous  on  account  of  these  long  hairs.  The  venation 
of  the  wings  is  quite  similar  to  that  of  the  Noctuidse,  but  in  the 
L3Tnantriid£e  the  point  at  which  veins  Sc  -|-  Ri  and  Rs  of  the  hind 
wings  anastomose  is  farther  from  the  base  of  the  wing  (Fig.  849). 
In  some  genera  these  two  veins  are  separate  being  connected  only  by 
the  free  part  of  vein  Ri.  The  tussock-moths  are  chiefly  nocturnal; 
but  the  males  of  some  of  them  fly  in  the  daytime. 

The  larvae  of  our  native  species  are  very  characteristic  in  appear- 
ance.   The  body  is  hairy;  there  are  several  conspicuous  ttifts  of  hairs 
on  the  dorsal  aspect  of  the  abdomen,  and  at  each  end  of  the  body  there 
re  long  pencils  of  hairs;  on  the  sixth  and  seventh  abdominal  seg- 


680 


^A^  INTRODUCTION  TO  ENTOMOLOGY 


ments  there  is  on  the  middle  of  the  back  of  each  an  eversible  gland 
supposed  to  be  a  scent-organ  similar  to  the  osmateria  in  the  larvae 
of  Papilio,  and  it  is  stated  that  a  fine  spray  of  liquid  is  sometimes 
thrown  from  them. 


R^RJi, 


Fig.    850. — Hemerocam- 
pa  leiicostigma. 


Fig.   849. — Wings  of  Hemerocampa  leiicos- 
tigma. 


Excepting  a  few  rare  forms 
our  native  species  pertain  to 
the  genera  Hemerocampa,  Noto- 
lophus,  and  Olene.  In  the  first 
two  of  these  genera  the  males 
are  winged  and  the  females  are 
nearly  wingless.  In  Olene  both 
sexes  are  winged.  Our  best 
known  of  the  native  members 
of  this  family  are  the  follow- 
ing. 

The  white-marked  tussock- 
moth,  Hemerocampa  leucosttg- 
ma. — This  is  our  most   com- 


mion  representative  of  the  family.  It  frequently  occurs  in  such  great 
numbers  that  it  seriously  injures  the  foliage  of  shade-trees  and  or- 
chards. The  male  (Fig.  850)  is  of  an  ashy  gray  color;  the  fore  wings 
are  crossed  by  undulated  bands  of  darker  shade  and  bear  a  conspicu- 


^'^£> 


Fig.  851. — IleDierocanipaleucostigma,  larva. 

ous  white  spot  near  the  anal  angle.  The  female  is  white  and  resembles 
a  hairy  grub  more  than  a  moth.  She  emerges  from  her  cocoon  and 
after  pairing  lays  her  eggs  upon  it,  covering  them  with  a  frothy  mass. 
The  larva  (Fig.  851)  is  one  of  the  most  beautiful  of  our  caterpillars. 


LEPIDOPTERA  G81 

The  head  and  the  glands  on  the  sixth  and  seventh  abdominal  seg- 
ments are  bright  vermilion  red.  There  is  a  velvety  black  dorsal  band, 
bordered  with  yellow  subdorsal  stripes;  and  there  is  another  yellow 
band  on  each  side  just  below  the  spiracles.  The  prothorax  bears  on 
each  side  a  pencil  of  long  black  hairs  with  plume-like  tips;  a  similar 
brush  is  borne  on  the  back  of  the  eighth  abdominal  segment,  and  the 
first  four  abdominal  segments  bear  dense  brush-like  tufts  of  cream- 
colored  or  white  hairs. 

When  this  insect  becomes  a  pest  the  larvae  can  be  destroyed  by 
spraying  the  infested  trees  with  Paris-green  water;  or  the  egg-bear- 
ing cocoons  can  be  collected  during  the  winter  and  destroyed.  These 
cocoons  are  attached  to  the  trunks  of  the  trees  and  to  neighboring 
objects,  or  to  twigs.  In  the  latter  case  they  are  usually  partially 
enclosed  in  a  leaf.  Cocoons  not  bearing  eggs  should  not  be  destroyed, 
as  many  of  them  contain  parasites.  Owing  to  the  wingless  condition 
of  the  female  this  pest  spreads  slowly. 

The  well-marked  tussock-moth,  H enter ocampa  plagiata. — The 
male,  like  that  of  the  preceding  species,  is  of  an  ashy  gray  color;  but 
the  markings  of  the  fore  wings  are  much  more  distinct.  The  female  is 
light  brown.  She  lays  her  eggs  in  a  mass  on  her  cocoon,  covering 
them  with  hair  from  her  body.  The  larva  closely  resembles  the  pre- 
ceding species  in  the  form  and  arrangement  of  its  tufts  of  hair,  but 
differs  markedly  in  color,  being  almost  entirely  light  yellow.  There 
is  a  dusky  dorsal  stripe  and  a  velvety  black  spot  behind  each  of  the 
tufts  of  the  first  four  abdominal  segments.  The  head  and  the  glands 
on  the  sixth  and  seventh  abdominal  segments  are,  like  the  body,  light 
yellow. 

The  California  tussock-moth,  Hemerocampa  vetusta.- — The  two 
species  of  Hemerocampa  described  above  are  found  only  in  the  East ; 
this  species  is  found  in  California,  where  it  is  common  on  live  oak  and 
yellow  lupin  trees,  and  has  injuriously  infested  apple  and  cherry 
orchards.  The  larvae  have  black  heads,  crimson  hair-bearing  warts 
and  prolegs,  and  the  four  tussocks  or  brush-like  tufts  of  hairs  on  the 
back  are  often  dark  gray  with  brownish  crests.  In  general  the  life- 
history  of  this  species  is  similar  to  that  of  the  two  eastern  species. 

The  old  tussock-moth,  Notolophus  antlqua: — The  male  is  of  a  rust- 
brown  color;  the  fore  wings  are  crossed  by  two  deeper  brown  bands 
and  have  a  conspicuous  white  spot  near  the  anal  angle.  The  body  of 
the  grub-like  female  is  black,  clothed  with  yellowish  white  hairs;  she 
lays  her  eggs  on  her  cocoon,  but,  unlike  the  three  preceding  species, 
does  not  cover  them  with  anything.  The  larva  differs  from  either  of 
the  preceding  in  having  an  extra  pair  of  pencils  of  plume-like  hairs 
arising  from  the  sides  of  the  second  abdominal  segment ;  the  head  is 
jet-black;  the  glands  on  the  sixth  and  seventh  abdominal  segments 
are  vermilion-red  or  sometimes  bright  orange;  and  the  tubercles  on 
the  sides  of  the  back  of  the  second  and  third  thoracic  and  the  sixth 
and  seventh  abdominal  segments  are  orange-red  or  yellow  margined 
with  pale  yellow. 


682 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  852. — Porthetria  dispar. 


The  gypsy  moth,  Porthetria,  dispar. — This  is  a  European  species 
which  was  introduced  into  Massachusetts  in  1866  by  a  French 
naturaHst  who  was  conducting  experiments  with  silk-worms.  Some 
of  the  insects  escaped  from  him  into  a  neighboring  woodland  and  be- 
came established  there;  but  they  did  not  attract  particular  attention 
till  about  twenty  years  later.  It  was  then  realized  that  this  species 
is  a  serious  pest.  Since  then  millions  of  dollars  have  been  expended  by 
the  State  of  Massachusetts  and  the  Federal  Government  in  an  un- 
successful effort  to  exterminate  it.  It  has  spread  over  a  large  part 
of  New  England,  and  isolated  colonies  have  been  found  in  New  York. 

The  larv^a  has  a  wide  range  of  food- 
plants,  feeding  on  the  foliage  of 
most  forest  and  fruit  trees.  The 
male  moth  is  yellowish  brown;  the 
female  white  (Fig.  852).  In  each 
the  fore  wings  are  crossed  by  many 
dark  lines  and  bear  a  black  lunule 
on  the  discal  vein.  The  specimen 
figured  is  unusually  small.  The  eggs 
are  laid  in  a  mass  on  any  convenient 
object  and  are  covered  with  hair 
from  the  abdomen  of  the  female.  The  larva  differs  greatly  in  appear- 
ance from  those  of  the  preceding  genera,  lacking  the  peculiar  pencils 
and  tufts  of  hair;  but  the  characteristic  glands  of  the  sixth  and 
seventh  abdominal  segments  are  present  and  are  red.  The  body  is 
dark  brown  or  black,  finely  reticulated  with  pale  yellow,  and  with 
narrow  yellow  dorsal  and  subdorsal  lines.  On  the  dorsal  aspect  of 
each  segment  there  is  a  pair  of  prominent,  rounded  tubercles  bearing 
spiny  black  hairs.  The  first  five  pairs  of  these  tubercles  are  bluish, 
the  others  dark  crimson-red.  There  are  also  two  rows  of  tubercles 
on  each  side  of  the  body  which  bear  longer  hairs. 

The  brown-tail  moth,  Euproctis  chrysorrhcea. — The  brown-tail 
moth  is  another  European  pest,  which  was  introduced  into  Massa- 
chusetts at  some  unknown  date.  It  first  attracted  attention  by  its 
ravages  in  1897,  and  since  then  has  spread  over  a  considerable  part  of 
New  England  and  has  extended  into  New  Brunswick  and  Nova  Scotia. 
The  wings  of  the  female  moth  are  white;  and  the  tip  of  the  abdomen 
bears  a  tuft  of  yellowish  brown  hairs,  hence  the  popular  name  of  the 
insect.  The  female  expands  about  37  mm.  The  male  is  a  little 
smaller  than  the  female;  and  the  brownish  tuft  at  the  end  of  the 
abdomen  is  not  so  conspicuous  as  in  the  female.  The  larva  feeds  on 
the  foliage  of  fruit-trees  and  of  almost  all  kinds  of  shade-trees  except 
conifers.  The  eggs  are  laid  in  an  elongate  mass  on  the  underside  of 
a  leaf,  during  July.  The  egg-mass  is  covered  with  brownish  hairs 
from  the  tip  of  the  abdomen  of  the  female.  The  eggs  hatch  in  two  or 
three  weeks.  The  larvae  hatching  from  an  egg-mass  feed  together  on 
adjoining  leaves  at  the  tip  of  a  branch.  These  they  web  together  with 
siUc,  making  a  nest  within  which  they  pass  the  winter  in  a  partially 
grown  condition.     In  early  spring  the  larvae  leave  their  winter  quar- 


LEPIDOPTERA  683 

ters  and  feed  on  the  expandinj^  foliage.  They  become  full  grown  in 
five  or  six  weeks;  and  then  spin  thin  cocoons  of  white  silk  in  curled 
leaves,  crevices  in  bark  of  trees,  or  under  any  convenient  shelter. 
About  three  weeks  later  the  moths  emerge. 

The  full-grown  larva  of  the  brown-tail  moth  measures  about  37 
mm.  in  length.  It  is  nearly  black  in  ground  color,  clothed  with  tufts 
of  brownish  barbed  hairs,  and  has  a  row  of  nearly  white  tufts  on  each 
side  of  the  body.  In  the  center  of  the  sixth  and  seventh  abdominal 
segments  are  small,  red,  retractile  tubercles.  The  barbed  hairs  borne 
by  the  subdorsal  and  lateral  tubercles  are  venomous  and  produce  an 
inflamation  of  the  skin  of  man  much  like  that  caused  by  poison  ivy. 
As  the  cast  skins  of  the  larva?  are  blown  about  by  the  wind,  people 
are  frequently  badly  poisoned  where  this  pest  is  common. 

To  control  this  pest  the  nests  in  which  the  larvae  hibernate  should 
be  collected  dunng  the  winter  and  burned. 


Family  NOCTUID^ 
The  Noctuids  or  the  Owlet-Moths 

If  only  our  fauna  be  considered,  this  is  the  largest  of  all  of  the 
families  of  the  Lepidoptera;  more  than  2500  species  of  noctuids  are 
now  know  to  exist  in  America  north  of  Mexico.  The  great  majority 
of  the  moths  that  fly  into  our  houses  at  night,  attracted  by  lights, 
are  members  of  this  family.  The  nocturnal  habits  of  these  insects, 
and  the  fact  that  often  when  they  are  in  obscurity  their  eyes  shine 
brightly  suggested  the  name  of  the  typical  genus,  Nociua,  from  the 
Latin  for  owl,  as  well  as  the  popular  name  owlet -moths,  by  which 
they  are  known.  Similar  popular  names  have  been  given  them  in 
several  other  languages. 

Although  there  exist  within  the  limits  of  the  family  great  differences 
in  size,  form,  and  coloring,  most  of  the  species  are  dull-colored  moths 
of  medium  size. 

In  the  typical  noctuids,  the  body  is  large  in  proportion  to  the  size 
of  the  wings;  the  front  wings  are  strong,  somewhat  narrow,  and 
elongated,  the  outer  margin  being  shorter  than  the  inner  margin; 
and  when  at  rest,  the  wings  are  folded  upon  the  abdomen,  giving  the 
insect  a  triangular  outline.  The  antennas  are  thread-like,  fringed 
with  hairs,  or  brush-like,  usually  pectinate  in  the  males.  Two  ocelli 
are  almost  always  present.  The  labial  palpi  are  well  developed,  and 
in  some  species  quite  prominent.  The  maxillae  are  quite  long  and 
stout  in  most  species.  The  thorax  is  heavy  and  stout.  In  the 
majority  of  the  species  the  scales  or  the  dorsal  surface  of  the  thorax 
are  turned  up  more  or  less,  forming  tufts.  The  abdomen  is  conical 
and  extends  beyond  the  anal  angle  of  the  hind  wings  when  these 
are  spread.  The  venation  of  the  wings  of  a  member  of  this  family  is 
represented  by  Figure  853.  Vein  M2  of  the  fore  wings  arises  much 
nearer  to  vein  M3  than  to  vein  Mi;  there  is  usually  an  accessory  cell; 
the  first  anal  vein  is  wanting,  and  the  third  anal  vein  may  be  present 


684 


AN  INTRODUCTION  TO  ENTOMOLOGY 


with  its  tip  joined  to  the  second  anal  vein  near  its  base.  On  the  hind 
wings  veins  So  +  Ri  and  vein  Rs  coalesce  for  a  short  distance  near  the 
base  of  the  wing ;  vein  M2  may  be  either  well  preserved  or  much  weak- 
er than  the  other  veins,  or  in  a  few  cases  lost;  and  there  is  considerable 
variation  in  the  point  of  origin  of  this  vein. 


id  A  ^^\d  A 
Fig.  853.^ — Wings  of  Catocala  fraxini. 


The  majority  of  the  larvs  are  naked,  of  dvdl  colors,  and  provided 
with  five  pairs  of  prolegs.  As  a  rule  they  feed  on  the  leaves  of  plants, 
but  some  are  borers  and  some  gnaw  into  fruits.  Among  them  are 
some  of  the  more  important  insects  injurious  to  agriculture. 

The  family  Noctuidee  has  been  divided  into  many  subfamilies. 
In  the  following  pages  the  more  important  of  those  represented  in 
our  fauna  are  briefly  discussed,  in  order  to  show,  as  well  as  possible 
in  a  limited  space,  the  variations  in  form  included  in  this  family,  and 
to  indicate  the  position  of  our  more  important  species. 


«ir 


LEPIDOPTERA  685 

There  is  a  group  of  moths,  the  deltoids,  which  are  placed  at  the 
foot  of  this  family  on  account  of  their  apparent  relationship  to  the 
geometric! s  and  to  the  pyralids.  These  moths  are  usually  of  dull 
colors  and  of  meditmi  size.  The  name  deltoids  was  suggested  by  the 
triangular  outline  of  the  wings  when  at  rest,  which  is  well  represented 
by  the  Greek  letter  delta.  When  in  this  position  the  wings  slope 
much  less  than  with  other  noctuids,  the  attitude  being  more  like  that 
assumed  by  the  geometrids;  but  the  hind  wings  are  more  nearly 
covered  than  with  the  geometrids.  Many  of  the  deltoids  have  very 
long  palpi,  resembling  in  their  size  those  of  the  pyralids.  The  del- 
toids include  the  two  following  subfamilies. 

The  subfamily  Hypenin^.. — A  representative  of  this  subfamily  is 
the  following  species. 

The  green  clover-worm,  Plathypena  scdbra. — This  is  a  common 
deltoid.    The  usual  food-plant  of  the  larva  is  clover,  but  it  occasion- 
ally defoliates  peas,  beans,  and  lima  beans. 
It  is  a  slender  green  worm  measuring  when 
full-grown  1 6  mm.  in  length  and  only  about 
2.5  mm.  in  width  in  its  widest  part;  it  has 
a  narrow  subdorsal  whitish  line  and  a  lateral 
one  of  the  same  color.    When  ready  to  trans- 
form it  webs  together  several  leaves  and      Fig.  854.— Plathypena 
passes  the  pupa  state  in  the  nest  thus  made.         scabra. 
The  adult  (Fig.  854)  is  a  blackish  brown  moth, 

with  an  irregular  grayish  shade  on  the  outer  half  of  the  fore  wings, 
and  with  very  broad  hind  wings.  The  palpi,  which  are  not  well 
shown  in  the  figure,  are  long,  wide,  and  flattened;  they  project 
horizontally  like  a  snout. 

The  hop-vine  deltoid,  Hypena  hilmuli.  —  This  species  is  closely 

allied  to  the  preceding  and  has  often  been  confounded  with  it.    The 

larva  feeds  on  the  leaves  of  hop,  and  is  sometimes  a  serious  pest. 

The   subfamily   Herminin^.. — The  following  species  will   serve 

as  an  example  of  this  subfamily. 

Epizeuxis  lubricdlis .—This  is  one  of  the  most  abundant  of  our 
deltoids.  In  this  species  (Fig.  855)  the  fore 
wings  are  chocolate-brown,  crossed  with 
yellowish  lines;  the  hind  wings  are  much 
lighter.  The  palpi  are  long;  but  they  are 
curved  over  the  head,  so  that  they| appear 
short  when  seen  from  above,  as  represented 
„  .  •  ,  ,  •  in  the  figure.  The  larva  feed  son  dead  leaves. 
-EpTzeuxts  lubn-  ^^^  subfamily  EREBiN^..-More  than  1 20 
species  belonging  to  this  subfamily  are  now 
listed  from  our  fauna.  The  three  following  will  serve  as  examples. 
The  black  witch,  Erebus  odora.— -This  is  the  most  magnificent  in 
size  of  all  of  the  noctuids  found  in  this  country  (Fig.  856).  There  is 
much  variation  in  the  depth  of  coloring.  The  individual  figured  is  a 
female;  in  the  male  the  fore  wings  are  more  pointed  at  the  apex  and 
the  medium  band  is  indistinct.  It  is  a  native  of  the  West  Indies; 
but  it  is  believed  that  it  breeds  in  the  extreme  southern  portion  of 


686  AN  INTRODUCTION  TO  ENTOMOLOGY 

the  United  States.     Isolated  individuals  are  found  in  the  North  in 


Fig.  856. — Erebus  odora. 

late  summer  or  autumn.    These  are  found  as  far  north  as  Canada 

and  west  to  Colorado,  and  even  in 
California.  These  have  doubtless 
flown  north  from  their  southern 
breeding  places,  possibly  from  Cuba 
or  Mexico. 

The  larva  feeds  on  certain  tropic- 
al leguminous  trees.  Cassia  fistula, 

r.-     o.^      c    7-  >.<         j-u  .  ■  PithecolobiMm,  and Saman. 

Frg.  857.-Scohopteryx  hbatnx.  ^^^     scalloped     owlet,     Scolldp- 

teryx  libatrix. — This  moth  is  easily 
recognized  by  the  shape  of  its  wings,  the  outer  margins  of  which  are 
deeply  cut  and  scalloped  (Fig.  857).  The  color  of  the  fore  wings  is 
soft  brownish  gray,  slightly  powdered  with  rust-red,  and  frosted  with 
white  along  the  costa.  There  is  an  irregular  patch  of  rust-red  reach- 
ing from  the  base  to  the  middle  of  the  wing,  a  single,  white,  transverse 
line  before  the  middle,  and  a  double  one  beyond  the  middle.  The  larva 
feeds  on  willow.  This  species  is  found  in  all  parts  of  the  United  States 
and  in  Europe. 

The  cotton-worm,  Alabama  argilldcea. — Excepting  perhaps  the 
cotton-boll  weevil,  this  is  the  most  important  insect  pest  in  the 
cotton-growing  states.  The  adult  insect  (Fig.  858)  is  a  brownish 
moth  with  its  fore  wings  crossed  with  wavy  lines  of  darker  color  and 
marked  with  a  bluish  discal  spot  and  two  white  dots  as  shown  in  the 
figure.     This  moth  is  found  in  the  Northern  States  and  even  in 


LEPIDOPTERA 


687 


Canada  in  the  latter  part  of  the  summer  and  in  the  autumn.     But 
this  occurrence  in  the  North  is  due  to  migrations  from  the  South, 
as  the  insect  can 


^ 


not  survive  the 
winter  north  of 
the  Gulf  States. 
The  larva  feeds 
on  the  foliage  of 
cotton ;  and  as 
there  are  five  or 


^^^^^^ 


Fig.   858. 
cea. 


-Alabama   argilla- 


Fig.   859. — Autographa  fal- 
cifera. 


SIX  generations  m 
a  year,  the  mul- 
tiplication of  in- 
dividuals is  very  rapid,  and  the  injury  to  the  cotton  great. 

The  best-known  way  of  combating  this  pest  is  by  the  use  of  Paris 
green.    Dusting  machines  drawn  by  horses  are  in  common  use. 

The  subfamily  PlusiiN/E  includes  nearly  seventy  North  American 
species.  In  a  large  number  of  these  the  fore  wings  are  marked  with 
metallic-colored  scales.  The  most  common  form  of  this  marking  is  a 
silvery  spot,  shaped  something  like  a  comma,  near  the  center  of  the 
wing  (Fig.  859).  Insome 
of  the  species  the  metallic 
markings  cover  a  large 
portion  of  the  fore  wings, 
in  others  they  are  want- 
ing. 

The  larvae  have  only 
three  pairs  of  prolegs,  the 
first  two  pairs  being 
wanting ;  due  to  this  fact 
they  walk  with  a  looping 
motion  (Fig.  860)  resem- 
bling somewhat  that  of 
the  geometrids. 

The  two  following 
species  have  attracted  at- 
tention by  their  injuries 
to  cultivated  plants ;  the 
celery  looper,  Autographa 
falctfera,  and  the  cabbage 
looper,  Autographa  bras- 
sic(2. 

The  subfamily  Cato- 
CALiN^..^ — To  this  sub- 
family belong  the  "mider- 
wings"  and  their  allies. 
Here  belong  nearly  two 
hundred  North  American  species 
most  likely  to  attract  attention. 


Fig.  860. — The  cabbage-looper,  A  utographa  brassi- 
cce:  a,  male  moth;  b,  egg;  c,  full-grown  larva; 
d,  pupa  in  cocoon.  (After  Howard  and  Chitten- 
den.) 


The  following  are  some  of  those 


688 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fie;.  86i. — Catocala  ilia. 


The  undenvings  or  catocalas,   Catocala. — The  most  striking  in 
appearance  of  the  noctuids,  if  we  except  the  black  witch  andoneortwo 

aUied  species,  are 
the  moths  belong- 
ing to  the  genus 
Catocala.  These 
moths  are  of  large 
size,  often  expand- 
ing 75  mm.  or  more. 
The  fore  wings  are 
usually  brown  or 
gray,  marked  with 
wavy  or  zigzag 
lines.  The  ground- 
color of  the  hind 
wings  is  black ;  but 
in  many  species 
these  wings  are  conspicuously  banded  with  red,  yellow,  or  white. 
This  peculiarity  has  suggested  the  name  underwings  by  which  these 
insects  are  commonly  known  in  England.  The  genus  is  a  very  large 
one;  more  than  loo  species  are  now  known  from  this  country;  and 
many  of  these  are  extremely  variable,  so  that  nearly  twice  that 
number  of  named  forms  are  now  recognized.  The  ilia  underwing, 
Catocala  Uia,  will  serve  as  an  example  (Fig.  86i).  The  larv^se  of  the 
underwings  feed  on  the  leaves  of  various  forest-trees.  Many  species 
infest  oak  and  hickory.  By  careful  search  both  the  adults  and  larvse 
can  be  found  resting  on  the  trunks  of  these  trees ;  but  it  needs  sharp 
eyes  to  do  it,  as  the  colors  of  these  insects  are  usually  protective, 
the  bright-colored  hind  wings  of  the  moths  being  covered  by  the  fore 
wings  wh.en  the  insect  is  at  rest. 

The  clover-looping-owlets,  Cmiurgia.- — Among  the  more  common 
noctuids  that  occur  in  our  meadows  and  pastures,  and  that  fly  up 
before  us  as  we  walk  through  them,  are  two  species  belonging  to  the 
genus  CcBnurgia.  These  may  be  called  the  clover-looping  owlets;  for 
the  larvae  feed  on  clover,  and,  as  they  have  only  three  pairs  of  prolegs 
they  walk  in  a  looping  manner.  One 
of  these  species  is  CcBtiiirgia  erechtea. 
This  moth  (Fig.  862)  has  dark  or  light 
drab-gray  fore  wings,  which  are  marked 
by  two  large  dark  bands,  as  shown  in 
the  figure.  These  bands  are  always 
separate,  distinct,  and  well  defined 
towards  the  inner  margin  in  the  male; 
in  the  female  the  markings  are  much 
less  distinct,  the  bands  usually  in- 
visible. ^^S-  "^62. — CcEHurgia  erechtea. 

The  other  common  species  of  this 
genus  is  Ccsnurgia  crassiiiscida.     In  this  species  the  fore  wings  have 
either  a  distinct  violaceous  brown  or  a  red  or  buffv  shade,  with  the 


LEPIDOPTERA  689 

two  large  dark  bands  very  variable,  often  shading  into  the  ground- 
color on  the  outer  edge  or  coalescing  near  the  inner  margiri ;  all  the 
markings  are  equally  distinct  in  both  sexes. 

Parallelia  histriaris. — This  moth  (Fig.  863)  is  brownish  in  color, 
and  has  the  fore  wings  crossed  by  two  parallel  lines.  The  larva  feeds 
on  the  leaves  of  maple. 

Zale  lundta.- — This  is  a  brownish  moth  with  marbled  wings.  It 
varies  greatlv  in  its  markings.     Figure   864  represents  a  variety 

Fig.  863. — Parallelia  bistriaris-  ^^^^     ^H     ^^B^^ 

Fig.  864. — Zale  limata. 

which  has  been  named  edusa,  and  which  does  not  show  well  the  lunate 
mark  on  the  hind  wings  that  probably  suggested  the  name  of  the 
species.  The  larva  feeds  on  the  leaves  of  rose,  willow,  maple,  plum, 
and  other  plants. 

The  subfamily  Erastriin^.. — In  this  subfamily  the  moths  are  of 
small  or  moderate  size ;  and  some  of  them  bear  a  strong  resemblance 
to  tortricids.    Many  of  the  species  are  marked  with  bright  colors,  and 
especially  with  white.    The  two  following  spe- 
cies will  serve  to  illustrate  this  group. 

Chamyris  cermtha. — This  moth  (Fig.  865) 
is  white,  with  the  fore  wings  marked  with  shades 
of  olive,  brown,  and  blue.  The  hind  wings  have 
a  narrow  border  of  dark  scales,  within  which 
there  may  be  a  cloudy  shade  as  shown  in  the 
figure,  or  this  shade  may  be  wanting.  The  Fig-  865. — Chamyris  cer- 
larva  feeds  on  the  leaves  of  apple.  imha. 

Tarachidia  candefdcta.- — This  species  (Fig. 
866)  is  also  largely  white,  with  the  fore  wings  marked  with  shades  of 
olive,  brown,  and  yellow.     The  amount  of  yellow  varies  greatly  in 
different   individuals.      The   larva   feeds   on   the 

^^_^_^  ^  leaves  of  Ambrosia  artemisicBfolia. 

^H^^^^^jy  The  subfamily  Apatelin.'E. — This  is  a  large 

^iBSSfSBm         subfamily,  including  more  than  600  North  Amer- 
^^^^W^  ican  species.     The  various  species  grouped  to- 

Fig.  866. Tara-      gether  here  exhibit  great  differences  in  appear- 

chidia  cande-      ance.    Among  those  that  are  most  likely  to  attract 
facta.  attention  are  the  following. 

The  typical  genus,  Apatela,  includes  nearly 
100  North  American  species.  This  genus  is  named  Acronycta  by 
those  authors  who  do  not  recognize  the  names  proposed  by  Hiibner 


690 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.    867. — Apatela    morula. 


in  his  "Tentamen,"  of  which  Apatela  is  one.    The  fore  wings  of  these 
moths  are  generally  light  gray  with  dark  spots,  and  in  many  species 

have  a  dagger-like  mark  near  the 
anal  angle.  On  this  account  they 
have  received  the  name  of  daggers. 
The  larvae  exhibit  much  diversity  in 
appearance;  those  of  some  species 
are  hairy  like  the  larvae  of  arctiids, 
while  others  are  nearly  naked. 

The  ochre  dagger,  Apatela  moru- 
la.—This  moth  (Fig.  867)  is  pale 
gray  with  a  yellowish  tinge.  Besides 
the  black  line  forming  part  of  the 
dagger  near  the  anal  angle  of  the 
fore  wing,  there  is  a  similar  black  line  near  the  base  of  the  wing, 
and  a  third  near  the  outer  margin  between  veins  Mi  and  Mo.  The 
larva  feeds  on  elm  and  basswood.  When  full-grown  it  is  mottled 
brown  and  greenish  like  bark;  it  is  clothed  with  but  few  scattered 
hairs,  and  has  a  hump  on  the  first,  fourth,  and  eighth  abdominal  seg- 
ments. 

The  American  dagger,  Apatela  americdna. — This  is  a  gray  moth 
resembling  in  its  general  appearance  the  preceding,  but  with  the  black 
lines  on  the  fore  wings  much  less  distinct.  Its  larva,  however,  is  very 
different  (Fig.  868).  This  larva  looks  like  an  arctiid,  being  densely 
clothed  with  yellow  hairs.  But  these  hairs  are  scattered  over  the 
surface  of  the  body  instead  of  growing 
from  tubercles  as  with  the  larvae  of 
arctiids.  Along  the  sides  of  the  body 
and  at  each  end  are  a  few  scattered 
hairs  that  are  longer  than  the  gen- 
eral clothing,  and  there  are  two 
pairs  of  long  black  pencils  borne  by 
first  and  third  abdominal  segments, 
and  a  single  pencil  on  the  eighth  ab- 
dominal segment.  When  at  rest  the 
larva  remains  curled  sidewise  on  a 
leaf,  as  shown  in  the  figure.  It  feeds 
on  maple,  elm,  and  other  forest  trees. 

The  witch-hazel  dagger,  Apatela 
hamamelis. — In  the  latter  part  of 
sumaner  and  in  autumn  what  is  be- 
lieved to  be  the  larva  of  this  species  is 
common  on  the  leaves  of  witch-hazel, 
oak,  and  other  forest  trees.  It  differs 
greatly  in  appearance  from  the  pre- 
ceding species,  being  nearly  naked 
(Fig.  869).  When  at  rest  it  usually 
lies  curled  as  shown  in  the  figure. 
It  varies  in  color  from  light  yellow  to  reddish  brown.    Its  most  char- 


Fig.  868. — -Apatela  americana,  larva. 


LEPIDOPTERA 


691 


Fig.  869. — Apatela  hama- 
melis,  larva. 


acteristic  feature  is  a  double  row  of  milk-white  spots  along  the  middle 
of  the  back. 

The  copper  hindwing,  Amphipyra  pyramidoides . — The  fore  wings 
of  this  moth  (Fig.  870)  are  dark  brown,  shaded  with  paler  brown,  and 
with  dots  and  wavy  lines  of  a  glassy  gray  or  dull  whitish  hue.  The 
hind  wings,  except  the  costal  third,  are  reddish  with  more  or  less  of  a 
coppery  luster.  This  suggests  the  popular 
name.  The  larva  feeds  on  the  leaves  of 
grape  and  of  Virginia-creeper. 

The  many-dotted  apple-worm,  Balsa 
maldna.  In  June,  and  again  in  August  or 
September,  there  is  sometimes  found  on 
apple-trees,  in  considerable  numbers,  a 
rather  thick,  cylindrical,  light-green  worm, 
an  inch  or  more  in  length,  with  fine,  white, 
longitudinal  lines  and  numerous  whitish 
dots.  These  are  the  larvae  of  the  little  moth 
represented  by  Figure  871.  The  fore  wings 
of  this  moth  are  ash-gray,  marked  by  ir- 
regular, blackish  lines.  The  larvae  feed  on 
the  leaves  of  many  other  trees  beside  apple. 
The  moth  has  been  found  throughout  the 
eastern  half  of  our  country. 

The  hop-plant  borer,  Gortyna  immdnis. — This  is  a  well-known  pest 

in  the  hop-growing  regions.  The  moths  deposit  their  eggs  on  the  tips 

of  the  hop-vines  just  as  they  begin  to 

y        climb.    The  young  larva  burrows  into 

^^^^jx^^^         y\^^^^^    the  vine  just  below  the  tip  and  spends 

^^m^^^^j^^^S^Ktm    the  early  part  of  its  life  in  the  vine  at 

^|^^^^HMnB9^H|^     this  point,  causing  the   injury  called 

^^^^^gl^Bp^^SK         by  growers  "mufflehead."    Later   the 

^^HB^H^^^^r  larva  burrows  to  the  base  of  the  vine, 

^^gp'  |H    "*^  where  it  feeds  upon  the  stems.    In  this 

▼  stage   it    is   known   as  the  hop-grub. 

The  pupa  stage  is  passed  in  the  ground 
near  the  infested  roots.     The   moths 
emerge  in  the  autumn  or  in  the  follow- 
ing spring.    To  check  the  ravages  of  this  pest  the  muffleheads  should 
be  picked  off  and  destroyed  while  the  larvae  are  still  in  them. 

The  divers,  Bellura. — The  genus  Beliura  contains  three  North 
American  species,  i?.  melanopyga,B.  diffusa,  and  B.  gortynoides.  The 
first  two  of  these  species  were  bred  by  the  writer 
from  the  leaf-stalks  of  the  yellow  pond-lily,  the 
habits  of  the  third  species  are  as  yet  undescribed. 
The  larvae  of  the  first  two  species  are  able  to  de- 
scend into  water  and  remain  there  for  a  long  time ; 
for  this  reason  the  common  name  the  divers  is 
proposed  for  them. 

The  black-tailed  diver,  Bellura  melanopyga. — 
Only  the  female  of  this  species  has  been  described. 


Fig.  870 
des. 


-Amphipyra  pyramidoi- 


^^P 


Fig.  87. 

atia. 


-Balsa  mat- 


in this  sex  the 


692  ^A^  INTRODUCTION  TO  ENTOMOLOGY 

thick  tuft  of  hair  at  the  caudal  end  of  the  body  is  black  or  blackish. 
The  larva  of  this  species  was  first  observed  in  Florida  (Comstock  '8i). 
A  detailed  account  of  its  habits  was  later  published  by  Welch  ('14), 
who  studied  it  at  Douglas  Lake,  Michigan.  It  is  at  first  a  leaf-miner 
in  the  leaves  of  the  yellow  pond-lily,  later  it  is  a  borer  in  the  leaf- 
stalks.    Its  habits  are  similar  to  those  of  the  following  species. 

The  brown-tailed  diver,  Bellura  diffusa. — Shortly  after  the  dis- 
covery of  the  preceding  species  in  Florida,  the  writer  studied  larvae 
with  similar  habits  at  Ithaca,  N.  Y.  From  these  larvae  were  bred 
moths  which  proved  to  be  Bellura  diffusa.  In  this  species  the  anal 
tuft  of  the  female  is  dark  brown.  In  the  male  there  is  a  series  of  dark 
tufts  on  the  basal  abdominal  segments. 

The  young  larvae  of  this  species  were  not  observed ;  doubtless  they 
are  leaf -miners  like  those  of  the  preceding  species.  The  older  larvas 
live  in  the  leaf-stalks  of  the  pond-lily,  a  single  larva  in  a  leaf-stalk. 
The  larva  bores  a  hole  from  the  upper  side  of  the  leaf  into  the  petiole, 
which  it  tunnels  in  some  instances  to  the  depth  of  two  feet  or  more 
below  the  surface  of  the  water.  This  necessitates  its  remaining  below 
the  surface  of  the  water  while  feeding.  The  writer  has  seen  one  of 
these  larvaj  remain  under  water  voluntarily  for  the  space  of  a  half- 
hour.  The  tracheae  of  these  larvae  are  unusually  large,  and  we 
believe  that  they  serve  as  reservoirs  of  air  for  the  use  of  the  insect 
while  under  water.  The  form  of  the  hind  end  of  the  larva  has  also 
been  modified,  so  as  to  fit  it  for  the  peculiar  life  of  the  insect.  The 
last  segment  appears  as  if  the  dorsal  half  had  been  cut  away ;  and  in 
the  dorsal  part  of  the  hind  end  of  the  next  to  the  last  segment,  which, 
on  account  of  the  peculiar  shape  of  the  last  segment,  is  free,  there  open 
a  pair  of  spiracles  much  larger  than  those  on  the  other  segments. 
When  not  feeding  the  larva  rests  at  the  upper  end  of  its  burrow,  with 
the  segment  bearing  these  large  spiracles  projecting  from  the  water. 

The  white-tailed  Bellura,  Bellilra  goriynoides. — In  this  species  the 
anal  tuft  of  the  adult  female  is  white.  The  habits  of  the  larva  have 
not  been  described. 

The  cat-tail  noctuids,  Arzama  and  Archanara. — Two  or  more 
species  of  noctuids  infest  the  cat-tail  plant,  Typha,  in  this  country. 
The  larvae  of  both  are  at  first  leaf-miners,  later  they  bore  in  the  stalks. 
Our  most  common  species  is  Arzama  ohllqua.  According  to  the 
observations  of  Claassen  ('21)  the  full-grown  larva  overwinters  in  its 
burrow  in  the  cat-tail  plant  and  transforms  in  the  spring.  But  the 
late  Professor  D.  S.  Kellicott,  who  made  a  special  study  of  this 
species,  informed  me  in  a  letter  written  in  1882,  that  the  larva  leaves 
the  cat -tail  plant  in  the  fall  and  conceals  itself  under  bark,  in  old 
wood  and  even  in  the  ground  until  spring  when  it  pupates,  and 
emerges  as  a  moth  in  May.  It  is  evident,  therefore,  that  individuals 
of  this  species  difl'er  as  to  the  location  in  which  they  pass  the  winter. 

Figure  872  represents  either  a  variety  of  this  species  or  a  closely 
allied  species.  It  was  determined  for  me  byGrote  in  1882  SiS  Arzama 
ohliqua.  I  collected  larvas  of  this  form  in  winter  from  under  bark  of 
fence-posts  near  water. 


LEPIDOPTERA 


693 


Irazama    obliqua. 
Within 


Fig. 


Sy^.—Psychom- 
t>ha    epimenis. 


The  grape-vine  epimenis,  Psychomorpha  epimenis. — This  is  a  vel- 
vety-black species  with  a  large  white  patch  on  the  outer  third  of  the 
front  wings  and  a  brick-red  patch  on  the 
hind   wings    (Fig.    873).      The   larva   re- 
sembles somewhat  that  of  Alypia  figured 
on  a  later  page,  but  it  is  bluish  and  has 
only    four   light   and    four   dark  stripes 
on  each  segment.     It  feeds  upon  the  ter- 
minal shoots  of  grape  and  Virginia-creeper 
in  spring^  drawing  the  leaves  together  by 
a  weak  silken  thread  and  destroyiug  them. 
When  ready  to  transform,  which  is  us- 
ually towards  the  end  of  May,  it  either 
enters  the  ground  or  bores  into  soft  wood  to  form  a  cell, 
this  it  remains  until  the  following  spring. 
^^  The  beautiful  wood-nymph,  Euthisandtia  grd- 

^^^^^X^^^%   ^^- — ^^^^  moth  (Fig.  874)  well  deserves  the  popu- 
^^^^■^■^    lar  name  that  has  been  applied  to  it.  Its  front 
^^mm^^m      wings  are  creamy  white,  with  a  glassy  surface;  a 
^^^^^^       wide  brownish  purple  stripe  extends  along  the 
costal  margin,  reaching  from  the  base  to  a  little 
beyond  the  middle  of  the  wing,  and  on  the  outer 
margin  is  a  band  of  the  same  hue,  which  has  a 
wavy  white  line  running  through  it,  and  is  margined 
internally  with  a  narrow  olive-green  band.    On  the  inner  margin  is  a 
yellowish    olive-green    cloud.      The   hind   wings    are    pale    ochre- 
yellow,  with  a  brown  band  on  the  outer  margin.    The  wing  expanse 
is  about  40  mm.     The  moth  appears 
during  the  latter  part  of  June  or  early 
in  July.     The  larva  of  this  species  is 
pale  bluish,  crossed  by  bands  of  orange 
and  many  fine  black   lines.      It  also 
bears  a  resemblance  to  that  of  Alypia, 
but  may  be  distinguished  by  having  on- 
ly six  transverse  black  lines  on  each  seg- 
ment.   It  has  the  same  food-plants  as 
the  species  described  above.    It  trans- 
forms in  a  cell  in  the  ground  or  in  soft 
wood. 

The  pearl  wood-nymph,  Euthisanotia  unio. — This  moth  closely 
reembles  the  species  just  described,  but  is  smaller,  expanding  a  little 
less  than  37  mm.  The  outer  border  of  the  front  wings  is  paler  and 
mottled;  and  the  band  on  the  hind  wings  extends  from  the  anal 
angle  to  the  apex.  The  larva  resembles  that  of  E.  grata;  it  feeds  upon 
the  leaves  of  Euphorbia  color atum,  and  perhaps  on  grape  also. 

The  subfamily  Cuculliin^. — This  subfamily  is  of  considerable 
size,  264  North  American  species  are  now  listed.  Among  them  are 
the  following. 


874. — Euthisanotia    grata. 


694 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig-  875. — Cucullia  speyeri. 


The  hooded  owlets,' CwcwZ/^'a. — We  have  several  common  grayish 
moths,  in  which  the  fore  wings  are  marked  with  nimierous  irregular 
dashes  of  dark  color,  and  in  which  the 
thorax  is  furnished  with  a  prominent 
tuft  of  scales.  These  moths  belong  to 
the  genus  Cucullia.  Figure  875  repre- 
sents Cucullia  speyeri.- — ^These  insects 
evidently  have  the  power  of  moving 
this  tuft  of  scales;  for  sometimes  it 
projects  forward  over  the  head  as 
shown  in  the  figure,  while  in  other  speci- 
mens of  the  same  species  it  may  be  di- 
rected backward;  in  this  case  it  is 
much  less  conspicuous.  The  larvee  of 
the  hooded  owlets  feed  upon  the  leaves 
of  goldenrod  and  other  Compositas. 
The  subfamily  Hadenin^.- — About  370  North  American  species 
are  included  in  this  subfamily;  among  them  are  the  following. 

The  army -worm,  Ctrphis  imipiincta. — The  army-worm  is  so  called 
because  it  frequently  appears  in  great  numbers,  and,  after  destroying 
the  vegetation  in  the  field  where  the 
eggs  are  laid,  marches  like  an  army 
to  other  fields.  This  insect  occurs 
throughout  the  United  States  east  of 
the  Rocky  Mountains  and  is  present 
every  year;  but  it  attracts  attention 
only  when  it  appears  in  great  num- 
bers. The  larva  is  from  40  to  50mm. 
long  when  full-grown,  and  is  striped 
with  black,  yellow,  and  green.  The 
adult  is  of  a  dull  brown  color,  marked 
in  the  center  of  each  fore  wing  with 
a  distinct  white  spot  (Fig.  876).  In 
seasons  of  serious  outbreak  of  this 
pest  it  usually  appears  first  in  limit- 
ed areas,  in  meadows  or  pastures. 
If  it  is  discovered  before  it  has  spread 

from  these  places  it  can  be  confined  by  surrounding  the  field  with  a 
ditch,  or  it  may  be  destroyed  by  spraying  the  grass  with  Paris  green 
water.  Ordinarily,  however,  the  worms  are  not  observed  until  after 
they  have  begun  to  march  and  are  wide  spread.  In  such  cases  it  is 
customary  to  protect  fields  of  grain  in  their  path  by  surrounding 
them  with  ditches  with  vertical  sides ;  it  is  well  to  dig  holes  like  post- 
holes  at  intervals  of  a  few  rods  in  the  bottom  of  such  ditches.  The 
worms  falling  into  the  ditch  are  unable  to  get  out,  and  crawl  along 
on  the  bottom  and  fall  into  these  deeper  holes.  We  have  seen  these 
insects  collected  by  the  bushel  in  this  way. 

The  zebra-caterpillar,  Ceramica  picta. — Cabbage  and  other,  garden 
vegetables  are  often  subject  to  the  attacks  of  a  naked  caterpillar. 


Fig.  876. — Cirphis  iinipuncla. 


LEPIDOPTERA 


695 


Fig.  S77. — Ceramica  picki,  larva. 


which  is  of  a  light  yellow  color,  with  three  broad,  longitudinal  black 
stripes,  one  on  each  side  and  the  top  of  the  back.  The  stripes  on  the  sides 
are  broken  by  numerous  pure 
white  lines  (Fig.  877).  When 
full-grown  the  larva  enters  the 
ground  where  it  makes  a  slight 
silken  cocoon  in  which  to  trans- 
form. There  are  two  generations 
a  year.  The  adult  (Fig.  878)  has 
dark  chestnut-brown  fore  wings 
and  pale  yellowish  hind  wings. 

Certain  members  of  this  sub- 
family have  attracted  attention  on  account  of  their  ravages  as  cut- 
worms.    Several  of  these  belong  to  the  genus  Polia,  the  Mamestra 
of  some  authors,  which  includes  more  than  100  North  American  spe- 
cies.    The  majority  of  our  described 
cutworms   pertain   to   the   next    sub- 
family. 

The  subfamily  Agrgtin.^.. — This 
is  one  of  the  larger  of  the  subfamilies 
of  noctuids,  including  more  than  550 
described  North  American  species. 
Here  belong  the  larger  number  of  those 
noctuids  that  are  known  as  cutworms ; 
but  other  members  of  this  subfamily 
exhibit  quite  different  habits. 

The  com  ear-worm  or  the  cotton  boll-worm,  Heliothis  obsoleta. — 
This  is  a  widely  distributed  pest,  the  larva  of  which  infests  many 
different  plants.  It  is  often  found  feeding  on  the  tips  of  ears  of 
growing  corn,  especially  of  sugar-corn;  in  fact  it  is  the  worst  insect 
pest  of  sugar-corn.  And  it  is  also  one  of  the  more  important  of  the 
pests  of  cotton,  ranking  next  to  the  boll-weevil  and  the  cotton-worm; 
the  larva  bores  into  the  pods  or  bolls  of  the  cotton,  destroying  them. 
It  frequently  infests  tomatoes,  eating  both  the  ripe  and  the  green 
fruit.  Occasionally  it  is  found  within  the  pods  of  peas  and  of  beans, 
eating  the  immature  seeds.  It  also  bores  into  the  buds,  seed-pods, 
and  flower-stalks  of  tobacco.  The  full-grown  larva  measures  from 
30  to  40  mm.  in  length.  It  varies  greatly  in  color  and  markings.  The 
pupa  state  is  passed  in  the  ground.  The  nimiber  of  generations 
annually  varies  according  to  latitude;  there  is  probably  only  one  in 
Canada,  but  in  the  Gulf  States  there  are  from  four  to  six.  Like  the 
larva,  the  moth  is  extremely  variable  in  color  and  markings. 

The  evening  primrose  moth,  Rhodophora  florida. — This  is  a  very 
beautiful  moth  with  most  interesting  habits.  It  is  quite  common, 
flying  at  night  about  evening  primroses,  both  wild  and  cultivated, 
and  hiding  during  the  day  in  the  partially  closed  flowers.  It  expands 
about  30  mm.  The  fore  wings  are  bright  pink  or  rosy  red  from  the 
base  to  the  subterminal  line,  beyond  which  they  are  pale  yellow,  like 


Ceramica   picta. 


696  AN  INTRODUCTION  TO  ENTOMOLOGY 

the  flowers  of  the  evening  primrose.  The  hind  wings  are  white. 
The  fading  petals  of  the  primrose  turn  pinkish,  and  the  pink  color  of 
the  closed  fore  wings  renders  the  moth  invisible  when  in  old  flowers, 
while  the  yellow  tips  of  the  fore  wings  protruding  from  a  flower  still 
fresh  and  yellow,  forms  an  equally  perfect  protection  from  observa- 
tion. This  moth  in  its  passage  from  flower  to  flower  transports  pollen 
and  is  the  special  means  of  insuring  the  cross-fertilization  of  the  even- 
ing primrose.  It  attaches  its  eggs  to  the  stalks  of  the  flower  buds  or 
near  them.  The  larvag  feed  on  the  petals  of  the  flowers  and  bore 
into  the  buds  and  seed-vessels.  They  are  bright  green,  covered  with 
numerous,  elevated,  white  granules;  when  full-grown  they  measure 
30  mm.  in  length.  Their  color  is  protective.  There  is  a  single  genera- 
tion each  year. 

Cut  worms.- — Few  pests  are  more  annoying  than  the  rascally  little 
harvesters  that  nightly,  in  the  spring,  cut  off  our  com  and  other 
plants  before  they  are  fairly  started.  There  are  many  species  of  these 
cut-worms,  but  they  are  all  the  larvas  of  owlet-moths.  In  general 
their  habits  are  as  follows:  The  moths  lay  their  eggs  during  mid- 
summer. The  larvae  soon  hatch,  and  feed  upon  the  roots  and  tender 
shoots  of  herbaceous  plants.  At  this  time,  as  the  larvffi  are  small  and 
their  food  is  abundant,  they  are  rarely  observed.  On  the  approach 
of  cold  weather  they  bury  themselves  in  the  ground  and  here  pass 
the  winter.  In  the  spring  they  renew  their  attacks  on  vegetation; 
but  now,  as  they  are  larger  and  in  cultivated  fields  the  plants  are 
smaller,  their  ravages  quickly  attract  attention.  It  would  not  be  so 
bad  if  they  merely  destroyed  what  they  eat;  but  they  have  the  un- 
fortunate habit  of  cutting  off  the  young  plants  at  the  surface  of  the 
ground,  and  thus  destroy  much  more  than  they  consume.  They  do 
their  work  at  night,  remaining  concealed  in  the  ground  during  the 
daytime.  When  full-grown  they  form  oval  chambers  in  the  ground 
in  which  they  pass  the  pupa  state.  The  moths  appear  during  the 
months  of  June,  July,  and  August. 

There  are  some  exceptions  to  these  generalizations:  some  species 
of  cut-worms  ascend  trees  during  the  night  and  destroy  the  young 
buds ;  many  pass  through  two  generations  in  the  course  of  a  year ; 
and  a  few  pass  the  winter  in  the  pupa  state. 

Cut -worms  can  be  destroyed  by  poisoned  baits  of  fresh  clover  or 
other  green  vegetation,  or  with  poisoned  dough  made  of  bran. 
Much  can  be  done  by  making  holes  in 
the  ground  with  a  sharpened  stick,  as 
a  broom -handle.  The  holes  should  be 
vertical,  a  foot  deep,  and  with  smooth 
sides.  On  the  approach  of  day  the  cut- 
worms will  crawl  into  such  holes  to  hide 
and  will  be  unable  to  crawl  out  again. 
Fig.  879.— ^gro/M  c-nigrum.  One   of   our   cut-worms,    which    is 

known  as  the  spotted  cut-worm,  is  the 
larva  of  the  black-c  owlet,  A  gratis  c-nigrum.  This  moth  (Fig.  879) 
is  one  of  the  most  common  species  attracted  to  lights.  It  occurs 
throughout  our  country  and  in  Europe. 


LEPIDOPTERA 

Family  AGARLSTID^ 

The  Foresters 


697 


The  validity  of  this  family  is  in  doubt.    Some  of  the  best-known 
genera  that  were  formerly  included  in  it  have  been  transferred  to  the 
NoctuidcE ;  and  it  is  an  open 
question  whether  or  not  the 
remaining  genera  should  be 
similarly  transferred. 

The  character  that  is 
used  to  distinguish  these 
moths  from  the  Noctuidge 
is  that  the  antennas  are  more 
or  less  thickened  towards 
the  tip,  while  in  the  Noctu- 
idse  the  shaft  of  the  antennee 
tapers  regularly.  The  ve- 
nation of  the  wings  (Fig. 
880)  is  very  similar  to  that 
of  some  noctuids. 

The  larvffi  are  but  slight- 
ly clothed  and  live  exposed 
on  the  leaves  of  plants. 
They  are  distinguished  from 
those  of  the  Noctuida;  only 
in  color,  nearly  all  of  the 
species  being  transversely 
striped.  Our  more  common 
species  feed  chiefly  on  grape 
and  Virginia-creeper,  which 
they  sometimes  injure  to  a  serious  extent.  In  such  cases  they  can  be 
destroyed  by  the  use  of  arsenical  poisons,  even  in  vineyards  in  the  East, 
as  the  application  would  have  to  be  made  early  in  the  season  and  the 
summer  rains  would  wash  the  poison  from  the  vines.  The  pupa  state 
is  passed  either  in  an  earthen  cell  or  in  a  very  slight  cocoon. 

The  family  as  now  restricted  is  one  of  limited  extent,  only  sixteen 
North- American  species  are  known.  The  larger  number  of  these  occur 
in  the  Far  West  or  in  the  Gulf  States.  The  following  are  the  best- 
known  species. 

The  eight-spotted  forester,  Alypia  octomaculdta. — This  species  is 
of  a  deep  velvety-black  color.  The  front  wings  have  two  large  sulphur- 
yellow  spots;  and  the  hind  wings,  two  white  spots.  The  tegulas  are 
sulphur-yellow.  In  markings  both  sexes  of  this  species  closely  re- 
semble the  male  of  the  following  species  represented  in  Figure  882. 

The  larva  (Fig.  881)  feeds  upon  the  leaves  of  grape  and  Virginia- 
creeper,  and  sometimes  occurs  in  such  large  numbers  as  to  do  serious 
injury.  The  ground-color  of  the  larva  is  white,  with  eight  black  stripes 
on  each  segment,  and  a  broader  orange  band,  bounded  by  the  two 


Fig.      880. — Wings     of      Copidryas     gloveri. 


698 


AN  INTRODUCTION  TO  ENTOMOLOGY 


middle  stripes; 
elevated  spots. 


Fig.  88 1. — Alypia  octomaculata,  larva. 


the  orange  bands  are  marked  by  black,  conical, 
There  are  usually  two  broods  each  year,  the  moths 
appearing  on  the  wing  in 
May  and  August,  the 
caterpillars  in  June  and 
July,  and  in  September. 
The  pupa  state  is  passed 
in  an  earthen  cell  in  the 
ground. 

This  species  is  found 
in    the    Atlantic    States 
from  Massachusetts  to  Texas. 

Langton's  forester,  Alypia  langtdnii. — This  species  resembles  the 
preceding  in  general  appearance,  but  the  females 
can  be  readily  distinguished  by  the  hind  wings 
bearing  only  a  single  spot,  which  is  yellow.  The 
males  are  dimorphic;  in  one  form  the  males  re- 
semble the  females  in  having  a  single  spot  on  the 
hind  wings,  in  the  other  form  there  are  two  spots 
(Fig.  882).  This  species  is  found  in  northern  New 
York,  the  mountains  of  New  Hampshire,  Canada 
to  the  Pacific  Coast,  and  the  mountains  of  Cali- 
fornia.   The  larva  feeds  on  fireweed,  Epilobium  angustifolium 


Fig.  882. — Alypia 
langtonii. 


Family  PERICOPID^ 
The  Pericopids 

These  beautiful  in- 
sects occur  within  the 
limits  of  our  country 
only  in  the  far  West  and 
in  the  Gulf  States.  They 
resemble  the  wood- 
nymph  moths  in  their 
strongly  contrasting 
colors;  but  can  be  dis- 
tinguished from  them  by 
the  position  of  the  origin 
of  vein  M2  of  the  hind 
wings,  which  appears  to 
be  a  branch  of  cubitus 
(Fig.  883). 

This  family  is  repre- 
sented in  our  fauna  by 
only  four  species;  but 
these  represent  three  gen- 
era. Our  most  common 
species  is  GnophcBla 


LEPIDOPTERA 


699 


latipennis,  ysfhich.  is  found  in  the  Rocky  Mountains  and  in  the  Pacific 
States,  in  the  foot-hills  of  the  Sierra  Nevadas.  The  wings  of  this 
species  are  black  spotted  with 
yellow.  There  is  some  varia- 
tion in  the  number  and  size  of 
the  spots  on  the  wings.  Figure 
884  represents  a  specimen  tak- 
en in  Colorado.  This  is  the 
variety  known  as  vermiculdta. 
The  larva  feeds  on  Merten- 
sia;  when  full-grown  it  meas- 
ures about  30  mm.  in  length. 
The  body  is  blackwith  sulphur- 
yellow  interrupted  bands  and 
steel-blue  tubercles.    There  are 

three  pairs  of  the  blue  tubercles  on  each  side  of  each  segment;  each 
tubercle  bears  some  short  whitish  hairs. 


Gnophala  latipennis. 


Family  ARCTIID^ 
The  Tiger-Moths  and  Footman-Moths  or  Arctiids 
The  Arctiida^  includes  stout-bodied  moths,  with  moderately  broad 
wings,  which  in  the  majority  of  cases  are  conspicuously  striped  or 

spotted,  suggest- 
ing the  popular 
name  tiger- 
moths;  some  of 
the  species,  how- 
ever, are  unspot- 
ted. A  large  pro- 
portion of  the 
species  are  ex- 
ceedingly beauti- 
ful; this  renders 
the  famly  a  fa- 
vorite one  with 
collectors.  As  a 
rule,  when  at 
rest,  the  wings 
are  folded,  roof- 
like  upon  the 
body.  Most  of 
the  moths  fly  at 
night,  and  are  at- 
tracted to  lights. 
The  ocelli  are 
present  in  the 
first  subfamily, 
absent  in  the 
Pig    885__wings  of  Halisidota  sp.  other  two.     The 


700  AN  INTRODUCTION  TO  ENTOMOLOGY 

palpi  are  short  .usually  but  little  d  eveloped .  The  maxillas  are  present , but 
they  are  often  weak.  The  most  important  features  in  the  venation 
of  the  wings  are  the  following;  first,  the  union  of  veins  M2  and  M3 
of  the  fore  wings  with  cubitus,  making  it  apparently  four-branched, 
in  a  few  lithosiids  these  branches  of  media  are  wanting;  and  second, 
the  coalescence  of  the  subcosta  and  radius  of  the  hind  wings  for  a 
considerable  distance  (Fig.  885).  The  extent  of  the  union  of  these  two 
veins  varies  greatly  in  the  different  genera;  it  is  for  at  least  a  fifth, 
usually  a  half  of  the  length  of  the  discal  cell,  but  not  beyond  the  end 
of  the  cell. 

The  larvae  of  the  tiger-moths,  except  that  of  Utetheisa,  are  clothed 
with  dense  clusters  of  hairs.  In  fact  a  large  proportion  of  our  common 
hairy  caterpillars  are  members  of  this  family.  In  some  species, 
certain  of  the  clusters  of  hairs  are  much  larger  than  the  others,  re- 
sembling in  this  respect  the  clothing  of  the  tussock-moths.  A'lost 
larvas  of  the  arctiids  feed  upon  herbaceous  plants,  and  many  species 
seem  to  have  but  little  choice  of  food -plant;  but  certain  common 
species  feed  upon  leaves  of  forest-trees. 

The  family  Arctiidas  is  divided  into  three  subfamilies,  each  of 
which  is  regarded  as  a  distinct  family  by  some  writers.  These  sub- 
families can  be  separated  as  follows : 

A.       Ocelli    present,    p.  700 Arcthn^ 

AA.    Ocelli  absent. 

B.     Fore  wings  with  raised  scale-tufts,  p.  705 Nolin^ 

BB.      Fore-wings   smoothly   scaled,   p.    704 Lithosiin^ 

Subfamily  ARCTIIN^ 
The    Tiger-Moths 
The  presence  of  ocelli  distinguishes  the  members  of  this  subfamily 
from  those  of  the  other  two.    It  is  the  largest  of  the  three  subfamilies, 

including  about  125  North 
American  species.  The  follow- 
ing are  some  of  the  more  com- 
mon representatives. 

The  genus  Haploa.- — Among 
the  more  beautiful  of  the  tiger- 
moths  is  a  genus  the  species  of 
which  are  snow-white  or  light 
yellow  with  the  fore  wings 
Fig.  8H6.~Haploa  contigua.  hi^nd^d  with  brown.     In  most 

species  the  hmd  wmgs  are  un- 
spotted and  are  snow-white,  but  in  some  the  hind  wings  are  yellow. 
These  moths  constitute  the  genus  Hap- 
loa. A  species  common  in  the  Atlantic 
States  and  represented  by  Figure  886  is 
Haploa  conttgua.  The  insects  of  this 
genus  vary  greatly  in  their  markings. 
The  Bella-moth,  Utetheisa  bella. — 
This  is  a  whitish  moth  with  lemon-yel- 
low or  orange-colored  fore  wings,  cross- 
ed by  six  transverse  white  bands,  each  Fig.  887.— Utetheisa  bella 


^-' 


LEPIDOPTERA 


701 


Fig.    888. — Euchcetias    egle,    larva. 


containing  a  series  of  black  dots  (Fig.  887) ;  the  hind  wings  are  pink, 
with  a  black  outer  margin,  which  is  bordered  within  by  a  narrow  white 
line.    The  species  occurs  throughout  the  Atlantic  States. 

The  harlequin  milk- 
weed caterpillar,  Euchce- 
tias  egle. — This  larva  is 
the  most  common  cater- 
pillar found  on  milkweed. 
It  is  clothed  with  tufts  of 
orange,  black,  and  white; 
those  at  each  end  of  the 
body  are  longer  than  the 
others  and  are  arranged 
radiately  (Fig.  888). 
When  full  grown  the  lar- 
va makes  a  felt-like  co- 
coon composed  largely  of 
its  hairs.  The  adult  has 
mouse-gray  wings ;  the 
abdomen  is  yellow,  with 
a  row  of  black  spots 
along  1:he  middle  of  the 
back. 

The  genus  Apantesis. — A  very  large  number  of  species  of  tiger- 
moths  belong  to  the  genus  Apantesis.    These  are  perhaps  the  most 

striking  in  appearance  of  all 
members  of  the  family.  The 
fore  wings  are  velvety  black 
marked  with  yellowish  or 
pink  bands;  in  some  species 
the  lighter  color  predomin- 
ates, so  that  the  fore  wings 
appear  to  be  yellow  or  pink, 
spotted  with  black.  The 
hind  wings  are  red,  pink,  or 
yellow,  and  are  margined 
or  spotted  with  black.  The 
thorax  is  usually  marked 
with  three  black  stripes,  of  which  the  lateral  ones  are  borne  by  the 
patagia  and  tegulae.  There  is  also  a  black  line  or  a  row  of  black  spots 
along  the  middle  of  the  back  of  the  abdomen,  and  a  similar  row  of 
spots  on  each  side.  Our  most  common  species  of  this  genus  is  virgo 
(Fig.  889).  The  larva  of  this  species  feeds  on  pigweed  and  other  un- 
cultivated plants,  and  winters  in  the  larval  state. 

The  salt-marsh  caterpillar,  Estigmene  acrcBa. — The  popular  name 
of  this  insect  was  given  to  it  by  Harris,  nearly  a  century  ago,  and 
was  suggested  by  the  fact  that  the  salt-marsh  meadows  near  Boston, 
where  is  now  the  Back  Bay  quarter  of  the  city,  were  overrun  and 
laid  waste  in  his  time  by  swarms  of  the  larvcc.  But  the  name  is 
misleading,    as   the   species   is   widely   distributed   throughout    the 


Fig.  889. — Apantesis  virgo. 


702  AN  INTRODUCTION  TO  ENTOMOLOGY 

United  States,  and  infests  a  great  variety  of  grasses  and  garden 
crops.    The  moth  (Fig.  890)  is  white,  marked  with  yellow  and  black. 

There  are  many  black  dots  on 
the  wings,  a  row  of  black  spots 
on  the  back  of  the  abdomen,  an- 
other row  on  the  venter,  and  two 
rows  on  each  side.  The  sexes 
differ  greatly  in  the  ground-color 
of  the  wings ;  in  the  female,  this 
is  white  throughout ;  in  the  male. 
Fig.  8go.—Estigmene  acrcea.  only  the  upper  surface  of  the  fore 

wings  is  white,  the  lower  surface 
of  the  fore  wings  and  the  hind  wings  above  and  below  being  yellow. 
The  number  and  size  of  the  black  spots  on  the  wings  vary  greatly. 
There  are  usually  more  submarginal  spots  on  the  hind  wings  than 
represented  in  our  figure. 

The  fall  webworms,  Hyphdntria  cunea  and  Hyphantria  textor. — 
A  very  common  sight  in  autumn  in  the  North  and  in  midstimmer  in 
the  South  is  large  ugly  webs  enclosing  branches  of  fruit  or  forest  trees. 
These  webs  are  especially  common  on  apple  and  on  ash;  but  the 
insects  that  make  them  infest  more  than  one  hundred  kinds  of  trees. 
These  webs  differ  from  those  made  by  the  apple-tree  tent-caterpillar 
in  being  much  lighter  in  texture  and  in  being  extended  over  all  of 
the  leaves  fed  upon  by  the  colony;  and  they  are  also  made  later  in 
the  year.  Each  web  is  the  residence  of  a  colony  of  larvae  which  have 
hatched  from  a  cluster  of  eggs  laid  on  a  leaf  by  the  parent  moth. 
It  is  a  disputed  point  whether  there  are  one  or  two  species  of  fall 
webworms.  In  the  North  the  adults  are  all  snow-white  in  color  and 
there  is  only  a  single  generation  annually.  This  form  is  the  Hyphan- 
tria textor  of  those  who  believe  that  there  are  two  species. 

In  the  South,  some  of  the  moths  have  the  fore  wings  thickly 
studded  with  dark  brown  points,  some  are  pure  white,  and  every 
gradation  exists  between  these  two  types.  Of  this  southern  form 
there  are  two  generations  annually.  This  form  is  known  as  Hyphantria 
cunea;  which  name  should  be  applied  to  both  the  northern  and 
southern  forms  if  they  prove  to  be  specifically  identical,  cuneahemg 
the  older  specific  name. 

Both  forms  winter  in  the  _  pupa  state. 

The  Isabella  tiger-moth,  Isia  isahella. — "Hurrying  along  like  a 
caterpillar  in  the  fall"  is  a  common  saying  among  country  people  in 
New  England,  and  probably  had  its 
origin  in  observations  made  upon 
the  larva  of  the  Isabella  tiger-moth. 
This   is   the   evenly   clipped,   furry 
caterpillar  reddish  brown  in  the  mid- 
dle and  black  at  either  end,  which  is 
seen  so  commonly  in  the  autumn       ^'''''-  "-''i-^-^-^'"  i^<-iMla,  larva. 
and  early  spring  (Fig.  891).     The 

extent  of  the  black  color  varies  in  different  individuals;  rarely,  es- 
pecially on  the  West  Coast  the  body  is  all  brown.    In  the  spring  after 


LEPIDOPTERA 


703 


feeding  for  a  time  the  larva  makes  a  blackish -brown  cocoon  composed 
largely  of  its  hair.  The  adult  is  of  a  dull  grayish  tawny-yellow,  with 
a  few  black  dots  on  the  wings,  and  frequently  with  the  hinder  pair 
tinged  with  orange-red.  On  the  middle  of  the  back  of  the  abdomen 
there  is  a  row  of  about  six  black  dots,  and  on  each  side  of  the  body  a 
similar  row  of  dots. 

The  yellow-bear,  Diacrisia  virginica. — The  larva  of  this  species  is 
one  of  the  most  common  hairy  caterpillars  found  feeding  on  herba- 
ceous plants.  It  was  named  by  Harris  the  yellow-bear  on  account  of 
the  long  yellow  hairs  with  which  the  body  is  clothed.  These  hairs 
are  uneven  in  length,  some  scattered  ones  being  twice  as  long  as  the 
greater  number  of  hairs.  The  long  hairs  are  more  nimierous  near  the 
caudal  end  than  elsewhere,  but  are  nowhere  gathered  into  pencils  as 
with  the  tussock-caterpillars.  This  larva  varies  greatly  in  color. 
The  body  is  most  often  of  a  pale  yellow  or  straw  color,  with  a  black, 
more  or  less  interrupted,  longitudinal  line  along  each  side,  and  a 
more  or  less  distinct  transverse  line  of  the  same  color  between  each 
of  the  segments.  Sometimes  the  hairs  are  foxy  red  or  light  brown, 
and  the  body  brownish  or  even  dark  brown.  The  head  and  the  ends 
of  the  feet  and  forelegs  are  yellowish,  and  the  venter  is  dusky.  The 
larva  feeds  on  almost  any  plant.  The 
cocoon  is  light,  and  is  composed  almost 
entirely  of  the  hairs  of  the  caterjiillar. 
This  insect  passes  the  winter  in  the 
pupa  state;  and  it  is  probable  that 
there  are  usually  two  or  more  broods 
each  year;  but  these  are  not  well 
marked.  The  moth  (Fig.  892)  is  snowy 
white,  with  the  wings  marked  by  a  few 
black  dots;  these  vary  in  number,  but 
there  are  rarely  more  than  three  on  either  wing.    There  is  a  row  of 


Fig.  892. — Diacnsia  virginica. 


Fig.  893. — Halysidota  carycz,  larva. 

black  spots  on  the  back  of  the  abdomen,  and  another  on  each  side, 
and  between  these  a  longitudinal  deep  yellow  stripe. 


704 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  hickory  tiger-moth,  Halysidota  cdryce. — One  of  the  most  abun- 
dant of  caterpillars  in  the  Atlantic  States  and  westward  during  the 
months  of  August  and  September  is  one  clothed  with  dense  tufts  of 
finely  barbed  white  hairs.  (Fig.  893) ;  there  is  a  ridge  or  crest  of  black 
hairs  on  the  middle  of  the  back  of  the  abdominal  segments,  a  few 
long  white  hairs  projecting  over  the 
head  from  the  thorax,  and  others  pro- 
jecting back  from  the  last  segment; 
there  are  also  two  pairs  of  pencils  of 
black  hairs,  one  on  the  first  and  one  on 
the  seventh  abdominal  segment,  and  a 
similar  pair  of  pencils  of  white  hairs  on 
the  eighth  abdominal  segment.  This 
larva  feeds  on  hickory,  butternut,  and 
other  forest-trees.  Its  grayish  cocoons, 
composed  almost  entirely  of  the  hair  of  the  larva,  are  often  found 
under  stones,  fences,  and  other  similar  places.  The  fore  wings  of  the 
adult  (Fig.  894)  are  dark  brown  spotted  with  white. 


Fig.  894. — Halysidota  carycE. 


Subfamily  LITHOSIIN^ 
The  Footman-Moths 


The  Lithosiinffi  include  small  moths  with  rather  slender  bodies, 
filiform  antennee,  and  usually  narrow  front  wings  and  broad  hind 
wings.  As  a  rule  they  are  closely  scaled  insects  of  sombre  colors, 
a  fact  that  has  won  for  them  the  title  of  footman-moths;  but  in  case 
of  some  of  the  species  their  livery  is  very  gay.  Some  species  fiy  by 
day,  while  others  are  attracted  to  lights  at  night. 

The  Lithosiinaj  differ  from  the  preceding  subfamily  and  agree 
with  the  following  one  in  lacking  ocelli.  They  differ  from  the  following 
subfamily  in  having  the  fore  wings  smoothly  scaled.  The  venation 
of  the  wings  differs  greatly  in  the  different  genera.  In  some  genera 
veins  M2  and  M3  o-*^  the  fore  wings  are  wanting. 

The  larvae  are  cylindrical  and  covered  with  short,  stiff  hairs.  The 
majority  of  the  species  whose  transformations  are  known  feed  upon 
lichens.    They  transform  in  very  delicate  cocoons  or  have  naked  pupae. 

This  subfamily  includes  about  fifty  North  American  species,  of 
which  the  following  are  some  of  the 
more  common  ones. 

The  striped  footman,  Hypoprepia 
minidta.- — This  beautiful  moth  is  of  a 
deep  scarlet  color,  with  three  broad 
lead  colored  stripes  on  the  front  wings. 
Two  of  the  stripes  extend  the  entire 
length  of  the  wings;  while  the  third  is 
between  these  and  extends  from  the 
end  of  the  discal  cell  to  the  outer  margin  (Fig.  895).  The  outer  half 
of  the  hind  wings  is  also  slate-colored.    Vein  M2  of  the  fore  wings  is 


Fig.  895. — Hypoprepia  miniata. 


LEPIDOPTERA  705 

present;  but  Vein  M2  of  the  hind  wings  is  wanting.  The  larva  feeds 
upon  hchens,  and  may  be  found  under  loose  stones  or  on  the  trunks  of 
trees.  It  is  dusky,  and  thinly  covered  with  stiff,  sharp,  and  barbed 
black  bristles,  which  grow  singly  from  small  warts.  The  cocoon  is 
thin  and  silky. 

The  painted  footman,  Hypoprepia  fucosa.- — This  species  is  very 
similar  to  the  preceding  one  and  has  been  confounded  with  it.  With 
the  painted  footman  the  ground-colors  of  the  fore  wings  is  partly 
yellow  and  partly  pink. 

The  clothed-in-white  footman,  Clemensia  albdta.- — The  specific 
name  of  this  insect  is  somewhat  misleading;  for  although  the  general 
color  of  the  moth  is  white,  there  are  so  many  ashen  and  gray  scales, 
and  dark  spots,  that  the  general  effect  is  gray.  On  the  front  wings 
the  more  prominent  black  syjots  are  six  or  seven  on  the  costa,  one  on 
the  discal  vein,  and  a  row  of  small  ones  on  the  outer  margin.  The 
hind  wings  are  white,  but  finely  dusted  with  gray  scales.  With  this 
species  Vein  M2  is  present   in  both  fore  and  hind  wings. 

The  banded  footman.  Hike  unifasciata.- — This  little  beauty  (Fig. 
896)  occurs  in  the  Atlantic  States  from  New  York  to  Texas.  The  fore 
wings  are  lead-colored,  and  crossed  by  a  yellow  band, 
which  extends  also  along  the  inner  margin  to  the 
base  of  the  wings.  The  hind  wings  are  pink  except 
the  apex,  which  is  lead-colored.  There  is  much  varia- 
tion in  the  width  of  the  yellow  band.  Fig-  8g6.—Illice 

There  are  several  closely  allied  species  which  are  "  nifasctata. 
difficult  to  distinguish  from  this  one. 

The  pale  footman,  Crambidia  pallida.- — This  moth  is  of  a  uniform 
drab  color,  with  the  abdomen  and  the  inner  part  of  the  hind  wings 
paler;  it  expands  22  mm.  The  moths  of  the  genus  Crambidia  can  be 
recognized  by  the  fact  that  veins  M2  and  M3  of  the  fore  wings  are 
both  wanting,  leaving  cubitus  only  two-branched. 

The  two-colored  footman,  Tigrioides  bicolor. — This  is  larger  than 
the  preceding  species,  expanding  from  2  5  to  3  7  mm.  It  is  slate-colored, 
with  the  palpi,  the  prothorax,  the  costa  of  the  fore  wings  and  the  tip 
of  the  abdomen  yellow.  Vein  M2  of  the  fore  wings  is  wanting,  leaving 
cubitus  apparently  three-branched. 

Subfamily  NOLINtE 

The  Nolinse  are  small  arctiids  in  which  the  ocelli  are  wanting  and 
in  which  there  are  tufts  of  raised  scales  on  the  fore  wings.  It  is  a  small 
subfamih'  including  only  fifteen  North  American  species.  Our  most 
common  species  is  the  following. 

Celama  triquetrdna. — This  is  a  gray  moth  with  a  wing-expanse  of 
17  to  20  mm.  On  the  fore  wings  there  is  a  short  black  or  dark  brown 
stripe  at  the  base  of  the  costa,  and  beyond  this  two  spots  of  the 
same  color,  the  outer  one  is  near  the  middle  of  the  length  of  the  costa. 
The  larva  infests  the  fohage  of  apple,  but  not  in  sufficient  numbers 
to  be  a  pest. 


706  AN  INTRODUCTION  TO  ENTOMOLGOY 

Family  EUCHROMIID^ 

The  family  SyntomidcB  oj  various  lists. 

These  moths  are  most  easily  distinguished  from  the  allied  families 
that  are  represented  in  this  country^  by  the  structure  of  the  hind 

wings  (Fig.  897);  in  these 
the  subcosta  is  apparently 
absent  except  at  the  base  of 
the  wing,  where  it  is  sepa- 
rate from  radius  for  a  short 
distance.  Occasionally 
forms  are  found  in  which 
the  tip  of  subcosta  is  sepa- 
rated from  radius.  In  some 
of  the  more  specialized 
forms,  the  hind  wings  are 
greatly  reduced  in  size  and 
the  venation  is  reduced. 

Among  the  better- 
known  representatives  of 
this  family  are  a  small  nvmi- 
ber  of  bluish-black  or  brown 
moths  which  have  more  or 
less  vermilion  or  yellow  on 
the  head,  prothorax,  and 
patagia.  These  moths  are 
of  medium  size,  expanding 
from  30  to  50  mm.  The  dull 
color  of  the  wings  is  usually 


Fig.  897. — Wings  of  Ctenucha  virginica. 


relieved  by  the  bright  color  of  the  head  and  patagia ;  and  by  a  layer 
of  blue  scales  covering  the  thorax  and  abdomen ;  but  in  some  species 
these  are  wanting.    The  larvas  feed  on  grasses.    Some  of  them  strongly 


Fig.  898. — Ctenucha  virginica. 


Fig.  899. — Scepsis  fulvicollis. 


resemble'those  of  the  Arctiidae  in  appearance  as  well  as  in  habits,  being 
thickly  clothed  with  hair;  they  also  spin  cocoons  similar  to  those  of 
arctiids.  Our  common  forms  of  this  group  represent  two  genera, 
Ctenucha  and  Scepsis.    In  the  East  we  have  only  a  single  species  of 


LEPIDOPTERA  707 

each  of  these  genera,  Ctenucha  virgtnica,  which  is  represented  by 

Figure  898,  and  Scepsis  fulvicolHs,  represented  by  Figure  899.    The 

larvae  of  both  of  these  species  feed  on  grasses. 
Closely  allied  to  these  is  another  species, 

which   is   common   in   the   East,   Lyconiorpha 

pholus.     This  is  black  with  the  basal  half  of 

the  fore  wings  and  the  basal  third  of  the  hind 

wings  yellow   (Fig^goo).     A  variety  of  this     Yig.^oo.-Lvcomorpha 

species  occurs  m  Caliiornia  and  other  parts         pholus. 

of  the  West  in  which  the  lighter  parts  of  the 

wings  are  pinkish  instead  of  yellow.     These  moths  occur  in  stony 

places,  where  the  larvae  feed  on  lichens  growing  on  rocks. 

In  the  extreme  southern  part  of  this 
country  and  in  the  regions  south  of  that, 
there  occur  highly  specialized  members 
of  this  family,  in  which  the  hind  wings  are 
greatly  reduced  in  size,  and  the  veins  of 
the  hind  wings  coalesce  to  a  remarkable 
degree.    In  some  of  these  forms  the  discal 

.^.  ^"  portion  of  the  wings  bears  but  few  if  any 

fcra.''''^  '"^'"   scales.    Cosmosoma  myrodora  from  Flori- 

da (Fig.  901)  will  serve  as  an  example  of 

these.    In  this  species  the  body  and  legs  are  bright  red ,  with  the  head 

end  of  abdomen,  and  a  dorsal  band  blue-black;  the  veins  and  borders, 

of  the  wings  are  also  black. 

Family  EUPTEROTID^E 

This  family  is  represented  in  North  America  by  a  single  genus, 
■Apatelodes ,  of  which  only  three  species  occur  in  our  fauna.  These 
moths  bear  a  striking  resemblance  to  the  Notodontidae,  but  differ  in 
lacking  maxillae.  The  moths  usually  have  hyaline  dots  on  the  fore 
wings  near  the  apex.  The  venation  of  the  wings  is  very  similar 
to  that  of  the  Notodontidae.  Vein  Cu  of  the  hind  wings  is  apparently 
three-branched,  and  in  our  species  the  frenulum  is  normal.  The  egg 
is  flat,  wafer-like,  unlike  that  of  the  Notodontidae  which  is  spherical 
with  the  micropyle  at  the  top.  The  larvae  are  cylindrical  and  are 
covered  with  numerous  secondary  setae,  some  short,  others  much 
longer;  there  are  no  fleshy  protuberances  or  verrucae  present.  The 
mediodorsal  setae  are  usually  grouped  into  a  distinct  tuft  on  each 
segment,  sometimes  forming  long  pencils.  The  pupa  state  is  passed 
in  the  ground.     Our  two  best-known  species  are  the  following. 

Apatelodes  torrefacta. — The  moth  is  soft  velvety  ashen.  The  fore 
wings  are  falcate  and  are  crossed  by  four  wavy,  brown  lines;  there  is 
a  hyaline  dot  near  the  apex,  margined  externally  with  reddish  brown; 
there  is  a  double  reddish  brown  spot  near  the  base  of  the  inner  margin. 
The  wings  expand  from  45  to  50  mm. 

The  larva  is  a  yellowish  or  whitish,  long-haired  caterpillar,  about 
50  mm.  long.     There  are  conspicuous  pencils  of  dark  hairs  on  the 


708 


AN  INTRODUCTION  TO  ENTOMOLOGY 


dorsimeson  of  the  last  two  thoracic  segments  and  the  eighth  abdominal 
segment.    It  occurs  in  midsummer  on  various  shrubs  and  trees. 

Apatelodes  angelica. — The  moth  (Fig.  902)  is  of  a  pale  soft  steel- 
gray,  with  the  outer  margins  of  the  wings  toothed.  The  fore  wings 
are  crossed  by  two  bands  of  a  darker  shade.  The  hyaline  spot  near 
the  apex  of  the  wings  is  usually  doubled ;  and  there  is  no  brown  spot 
near  the  base  of  the  inner  margin  as  in  A.  torrefacta.  The  wings  ex- 
pand from  47  to  50  mm. 


Fig.  902. — Apatelodes  angelica.     (From  Packard.) 


The  larva  (Fig.  902)  feeds  on  ash  and  on  lilac.  It  is  grayish  brown : 
the  setae  of  the  dorsimeson  are  comparatively  short,  but  are  grouped 
in  a  small  tuft  on  each  body  segment;  no  pencils  are  present. 


Family  EPIPLEMID^ 


This  family  includes  moths  in  which  the  body  is  slender  and  the 
wings  ample.  In  their  general  appearance,  these  moths  resemble 
geometrids;  but  can  be  distinguished  from  them  by  the  venation  of 


LEPIDOPTERA  70  9 

the  hind  wings  in  which  veins  Sc+Ri  and  Rg  separate  near  the  base 
of  the  wing  and  are  strongly  divergent,  resembhng  in  this  respect  the 
Lacosomidae.  In  the  fore  wings,  vein  Cu  is  apparently  three-branched 
and  veins  R5  and  Mi  are  stalked  and  are  well  separated  from  vein  R4. 
The  frenulum  is  present  in  our  species.  The  moths  rest  with  the  fore 
wings  spread  and  the  hind  wings  separated  from  them  and  partly 
rolled  about  the  body. 

Only  five  North  American  species  of  this  family  have  been  de- 
scribed, but  these  represent  four  genera.  Two  of  these  genera, 
Philagraula  and  Schindax,  are  each  represented  by  a  single  species 
found  in  Florida. 

Calltzzia  amordta. — This  is  the  best-known  of  our  species;  it  is 
found  both  in  Canada  and  the  United  States.  The  moth  expands 
about  20  mm.  It  is  pearly-ash  colored.  Both  pairs  of  wings  are 
crossed  near  the  middle  of  their  length  by  two  wavy  dark  lines,  which 
are  connected  by  a  bar  of  the  same  color  near  the  inner  margin  of  the 
fore  wings.  On  the  fore  wings  there  is  a  third  similar  line  near  the 
outer  margin.  The  larva  feeds  on  the  leaves  of  Lonicera  dioica.  The 
pupa  state  is  passed  at  the  surface  of  the  ground. 

Calleddpteryx  dryopterata. — This  species  is  found  in  the  Atlantic 
States.  The  moth  is  pale  ochreous  in  color,  sometimes  of  a  pale 
wood-brown.  Both  pairs  of  wings  are  crossed  by  two  transverse 
dark  lines.  The  wing  expanse  is  20  mm.  The  larva  feeds  on  Vi- 
burnum nudum.    The  pupa  state  is  passed  between  the  leaves. 

Family  THYATIRIDyE 

The  Thyatirids 

The  family  Thyatiridae  includes  moths  of  medium  size  with  elon- 
gated wings.  The  front  wings  are  usually  slightly  widened  at  the 
anal  angle  (Fig.  903),  and  in  our  more  common  species  are  conspicu- 
ously marked  with  wavy  or  zigzag  lines.  The  antenuce  are  filiform 
and  more  or  less  velvety  or  pubescent  in  the  male,  and  the  maxillse 
are  well  developed.  The  moths  fly  by  day, 
and  when  at  rest  fold  their  wings  roof-like 
upon  the  abdomen. 

The  venation  of  the  wings  is  illustrated 
by  Figure  894.  The  important  features  to 
be  noted  are  the  following:  In  the  front 
wing  vein  M2  arises  midway  between  veins 

Ml  and  M3.  In  the  hind  wing  vein  Sc-fRi  Yig.<)02,.-Hahrosyne scripta. 
and  vein  Rg  are  closely  parallel  for  a  space 

beyond  the  end  of  the  discal  cell  and  vein  Mi  is  jointed  to  vein  Rs 
by  a  comparatively  long  cross-vein  (Fig.  904,  c.v.),  so  that  the  two 
appear  to  separate  before  the  end  of  the  discal  cell.  In  the  males  the 
tip  of  the  frenulum  is  knobbed. 

The  larvae  are  naked,  and  live  upon  the  leaves  of  shrubs  and  trees. 
They  often  conceal  themselves  in  a  case,  made  by  loosely  fastening 
together  leaves,  or  by  folding  a  single  leaf. 


710 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Only  twelve  species  are  known  in  our  fauna;    these   represent 
five  genera. 

One  of  the  more  common  species  is  Habrosyne  scnpta.    This  has 
fawn-colored  front  wings,  conspicuously  marked  with  light  bands 

and  zigzag  lines  (Fig. 
903).  According  to 
Thaxter,  it  lays  its 
eggs  late  in  July,  in 
chains  of  five  or  six, 
on  the  leaves  of  rasp- 
berry, upon  which  the 
larvae  feed.  The  ma- 
ture larva  is  rich  yel- 
low-brown, often  al- 
most black,  with  a 
distinct  dorsal  black 
line.  The  lateral  por- 
tions are  more  yellow 
with  blackish  mott- 
lings.  When  at  rest  the 
larva  either  elevates 
the  cephalic  and  cau- 
dal ends  of  the  body, 
like  the  notodontids, 
so  that  the  head  rests 
upon  the  caudal  seg- 
ments, or  conceals  it- 
self in  a  case  formed 
by  curling  down  the 
edge  of  a  leaf.  It 
makes  a  •  very  slight 
cocoon  late  in  August. 
Another  common 
species  is  Pseudothya- 
ttra  cymatophoroides .  This  species  is  slightly  larger  than  the  preceding 
one,  expanding  nearly  50  mm.  The  front  wings  are  silky  gray  tinted 
with  rose.  They  are  marked  with  a  black  spot  at  the  base,  a  double 
or  triple  line,  forming  a  black  band  at  the  end  of  the  basal  third  of  the 
wing,  two  black  spots  on  the  outer  half  of  the  costa,  a  black  spot  at 
the  anal  angle,  and  a  row  of  black  points  on  the  outer  margin.  There 
is  a  variety,  expultrix,  which  lacks  the  black  band  and  the  four  black 
spots.  The  larva  of  this  species  has  been  found  on  red  oak;  it  is  of 
a  rich  yellow-brown,  mottled  with  fine  dark  lines,  and  lives  in  a  case 
made  by  fastening  leaves  together;  some  specimens  have  several 
cream-white  spots.  It  makes  a  slight  cocoon  late  in  September;  the 
adult  emerges  in  June. 

Family  DREPANID^ 
The  Drepanids 
The  typical  members  of  this  family  are  small,  slender-bodied 
moths,  which  can  be  easily  recognized  by  the  sickle-shaped  apex  of 


Fig.  904. — Wings  of  Habrosyne  scripta. 


LEPIDOPTERA 


711 


the  front  wmgs  (Fig.  905).     An  approach  to  this  form  of  wing  is 

represented  by  some  saturnians  and  by  certain  geometrids;  but  the 

former  are  larger,  stout -bodied  moths,  and  both 

differ  in   wing-venation,    cubitus   of  the   fore 

wings    appearing    only    three-branched    with 

them,  whereas  it  appears  to  be  four-branched 

with  the  drepanids. 

In  addition  to  the  more  typical  members 
of  this  family,  which  are  known  as  the  hook-tip 
moths,  there  occurs  in  our  fauna  a  single  species, 
EudeiUnia  hermimdta,  in  which  the  fore  wings 
are  not  falcate  (Fig.  go6). 

In  this  family  veins  Sc+Ri  and  vein  Rs  of  the  hind  wings  are 
closely  parallel  or  coalesced  for  a  space  beyond  the  end  of  the  discal 
cell,  resembling  in  this  respect  the  Thyatiridce.    But  the  Thyatiridee 


Fig-   905-~Drepana  ar- 
ctiata. 


/?,  R^j^. 


Fig.  906. — Wings  of  EudeiUnia  herminiata. 


2dA 

Fig.  907. — Wings  of  Drepana  arcuata. 


are  true  frenulum-conservers,  while  the  Drepanidas  exhibit  a  very 
anomalous  condition  as  regards  the  preservation  or  loss  of  the 
frenulum. 

While  the  form  of  the  hiimeral  angle  of  the  hind  wings  in  the 
Drepanidas  is  that  characteristic  of  the  frenulimi-losers,  some  of  these 
moths  retain  the  frenulum  and  in  others  it  is  lost  (Fig.  907  and  908). 
When  the  frenulum  is  present  it  is  borne  at  the  end  of  a  long  costal 
sclerite. 


712 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  larvae  are  remarkable  in  having  the  anal  prolegs  vestigial, 
and  the  caudal  segment  prolonged  into  a  more  or  less  lizard-like  tail. 

They  live  upon  the  foliage 
of  shrubs  and  trees,  and 
transform  in  a  web  between 
leaves,  or  in  a  case  in  a 
rolled  leaf. 

Only  six  species  belong- 
ing to  "this  family  occur  in 
our  fauna.  These  represent 
three  genera;  the  venation 
of  the  wings  of  a  species  of 
each  of  these  genera  is 
figured  here. 

Our  most  common 
hook -tip  moth  is  Drepana 
arcudta.  The  typical  form 
of  this  species  is  of  a  dirty 
white  color  marked  with 
dark  brownish  lines  and 
bands  as  shown  in  Figure 
905.  A  summer  form  of 
this  species  differs  in  being 
of  a  light  ochre-yellow  color 
and  in  the  course  of  the 
wavy  lines  on  the  front 
wings;  this  was  described 
as  a  distinct  species  under 
the  specific  name  gemcula. 
These  two  forms  are  found  in  the  Atlantic  States.  A  third  form  of 
this  species  occurs  in  California ;  this  was  described  under  the  specific 
name  siculifer. 

Our  single  representative  of  this  family  that  is  not  a  hook-tip  moth 
is  Eudeiltnia  herminidta.  This  is  a  small  moth  with  delicate  snow- 
white  wings,  which  expands  from  18  to  25  mm.  .  The  venation  of  the 
wings  is  shown  in  Figure  906.  The  larva  lives  on  cornel;  the  caudal 
prolongation  of  the  body  is  very  short.  This  species  is  found  in  the 
Atlantic  States. 


Fig. 


2d  A 

-Wings  of  Or  eta  rosea. 


Family  LACOSOMID^ 


This  family  is  of  special  interest  on  account  of  the  structure  of 
the  wings  of  its  members.  While  these  moths  clearly  belong  to  the 
series  of  frenulimi-losing  moths,  having  the  himieral  angle  of  the 
hind  wings  greatly  expanded  so  that  a  frenulimi  is  not  needed  to 
insure  the  synchronous  action  of  the  fore  and  hind  wings,  they  retain 
a  vestige  of  a  frenulum  (Fig.  909).  This  vestige,  however,  is  very 
small  and  is  probably  no  longer  of  any  use.  It  was  the  presence  of 
this  vestige  that  first  suggested  to  the  writer  that  those  families  of  the 


LEPIDOPTERA 


713 


Lepidoptera  which  he  termed  Frenulum-losers  were  descended  from 
frenulum-bearing  ancestors  (Comstock  '93). 

The  Lacosomidas 
seem  to  be  the  sole  sur- 
vivors of  a  very  distinct 
hne  of  descent.  In  many 
respects  they  appear  to 
be  closely  allied  to  the 
BombycidcB  and  to  the 
Saturnioidea ;  but  they 
differ  markedly  both  in 
the  structure  and  in  the 
habits  of  the  larvae ;  and, 
too,  the  wings  of  the 
adult,  although  at  first 
sight  resembling  those  of 
the  silk -worm,  are  really 
quite  different.  In  the 
coalescence  of  the 
branches  of  radius  of  the 
fore  wings  veins  R3  and 
R4  remain  widely  sepa- 
rate, while  in  the  Bomby- 
cidae  and  in  the  Saturni- 
oidea these  are  the  first 
branches  to  coalesce. 

This  is  a  small  New 
World  family .  Members 
of  it  are  distributed  over 
a  large  part  of  the  West- 
em  Hemisphere ;  but  so  far  as  is  now  known  only  three  species  occur 
in  the  United  States.  Two  of  our  species  are  found  in  the  East ;  the 
third  one,  Lacosoma  arizonicum,  was  described  from  Arizona. 

Melsheimer's  sac-bearer,  Cicmnus  melsheimeri. — The  larva  feeds 
on  the  leaves  of  various  species  of  oak.  The  habits  of  the  young 
larvae  have  not  been  described.  The  older  larvae  make  cases  of  leaves 
in  which  they  live  and  which  they  carry  about  (Fig.  910).    The  adult 

moth  (Fig.  911) 

is   of   a   reddish 

gray  color,  finely 

sprinkled  all 

over  with  minute 

black  dots ;  there 

is  a  small  black 

spot  at  the  end 

of  the  discal  cell 

of  the  fore  wings ; 
and  both  pairs  of  wings  are  crossed  by  a  narrow  blackish  band. 


Fig.  909. — Wings  of  Cicinnus  melsheimeri. 


Fig.  910. — Case  of  larva  of 
Cicinnus. 


^i» 


Fig.    911- 
meri. 


-Cicinnus    melshei- 


714 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Lacosoma  chiridota. — Although  this  is  the  rarer  of  our  two  eastern 
species  its  complete  life-history  has  been  pubHshed  by  Dyar  ('oo). 
He  found  the  larvae  common  on  scrub  oaks  on  Long  Island.  The  eggs 
are  laid  on  the  edge  of  the  leaf  or  on  one  of  its  points.  The  first  three 
instars  live  under  a  net  of  silken  threads  on  the  upper  surface  of  a  leaf. 
At  the  end  of  the  third  stadium  the  larva  begins  to  make  a  case; 
but  the  larva  does  not  leave  its  net  and  construct  a  complete  case 
until  during  the  fifth  stadium.  At  the  end  of  the  sixth  stadium  "the 
larva  spins  up  one  end  of  the  case  and  hibernates.  Pupation  in  the 
spring.  A  single  brood  in  the  year."  The  moth  is  somewhat  smaller 
than  the  preceding  species,  and  darker  yellowish  brown  in  color;  the 
outer  margins  of  the  fore  wings  are  more  scalloped. 

SuPERFAMiLY  SATURNIOIDEA 
The  Saturnians 


The  superfamily  Satumioidea  includes  the  largest  of  our  native 
moths;  in  fact  nearly  all  of  our  very  large  moths  belong  to  it,  but  it 
also  includes  a  considerable  nimiber  of  species  of  moderate  size. 

These  moths  are  most  easily  distinguished  from  other  moths  by 
the  structure  of  their  wings.  Here,  as  with  the  skippers  and  the  butter- 
flies, the  frenulum  is  lost 
and  its  place  is  taken  by  a 
greatly  expanded  humeral 
angle  of  the  hind  wing  (Fig. 
912),  which,  projecting  un- 
der the  fore  wing,  insures 
the  acting  together  of  the 
two  in  flight  without  the  aid 
of  a  frenulum.  This  losing 
of  the  frenulimi  is  also  char- 
acteristic of  the  Lasiocam- 
pidas  and  of  some  members 
of  the  Drepanidae;  but  the 
saturnians  differ  from  these 
moths  in  that  vein  M2  arises 
midway  between  radius  and 
cubitus  or  is  more  closely 
united  to  radius  than  to  cu- 
bitus, leaving  the  latter  ap- 
parently three-branched 
while  in  the  Lasiocampidffi 
and  in  the  Drepanidae  cubi- 
tus   appears    to    be    four-  '"^ 

branched.     In  the  Lacoso-      Fig-     912.— Wings     of     atheroma     regalis. 
midas  and  in  the  Bombyci- 

dae  the  humeral  angle  of  the  hing  wings  is  greatly  expanded,  but  in 
each  of  these  families  a  vestige  of  a  frenulum  is  retained. 


LEPIDOPTERA 


715 


In  the  Satumioidea  the  branches  of  radius  of  the  fore  wings  are 
crowded  closely  together  and  at  least  one  of  them  is  lost.  In  all  of 
our  species  the  antennae  are  naked  or  bear  vefy  few  scattered  scales. 

This  superfamily  includes  two  families,  the  North  American  forms 
of  which  can  be  separated  as  follows. 

A.  Vein  Mi  of  the  fore  wings  coalesced  with  radius  to  a  point  beyond  the  apex  of 
the  discal  cell;  vein  Mt  of  the  hind  wings  joined  to  radius  by  the  cross-vein 
r-m  (Fig.  912),  Antennas  of  males  pectinated  but  little  more  than  half  way  to 
the  apex.     p.    715 Citheronud^ 

AA.  Vein  Mi  of  both  fore  and  hind  wings  joined  to  radius  by  the  cross-vein 
r-m  (Fig.  919),  or  rarely  {Coloradia)  coalesced  at  its  base  with  radius  in  both 
fore  and  hind  wings.  Antennas  of  males  pectinated  to  the  apex.  p.  719.  .  . 
Saturniid^ 


Family  CITHERONIID^ 

The  Royal-Moths 


The  royal-moths  are  stout-bodied  and  hairy,  with  sunken  heads 
and  strong  wings.  The  species  are  of  medium  or  large  size,  some  of 
them  being  nearly  as  large  as  the 
largest  of  our  moths.  There  are  two 
anal  veins  in  the  hind  wings;  vein 
Ml  of  the  fore  wings  separates  from 
radius  beyond  the  apex  of  the  discal 
cell  (Fig.  912  and  913);  veins  Mi 
and  M2  of  the  hind  wings  are  joined 
to  radius  by  vein  r-m.  The  anten- 
nse  of  the  males  are  broadly  pecti- 
nated, but  for  only  little  more  than 
half  their  length.  The  palpi  and 
the  maxillae  are  very  small. 

The  larvas  are  armed  with  horns 
or  spines,  of  which  those  on  the 
second  thoracic  segment,  and  some- 
times also  those  on  the  third,  are 
long  and  curved.  These  caterpillars 
eat  the  leaves  of  forest-trees,  and  go 
into  the  ground  to  transform,  which 
they  do  without  making  cocoons. 
The  rings  of  the  pupa  bear  little 
notched  ridges,  the  teeth  of  which, 
together  with  some  strong  prickles 
at  the  hinder  end  of  the  body,  assist 

it  in  forcing  its  way  upwards  out  of  the  earth.  A  monograph  of  this 
family  including  many  colored  figures  of  moths  and  larv«  was 
published  by  Packard  ('05). 

This  is  a  small  family;  it  is  not  represented  in  Europe,  and  less 
than  twenty  species  are  known  to  occur  in  this  country.  The  more 
common  ones  are  the  following. 


Fig.  913.- 
iensis. 


id  A 

Wings  of  Anisota  virgin- 


716 


AN  INTRODUCTION  TO  ENTOMOLOGY 


LEPIDOPTERA  717 

The  regal-moth,  Cither onia  regalis. — This  is  the  largest  and  most 
magnificent  of  the  royal-moths  (Fig.  914).  The  fore  wings  are  olive- 
colored,  spotted  with  yellow,  and  with  the  veins  heavily  bordered 
with  red  scales.  The  hind  wings  are  orange-red,  spotted  with  yellow, 
and  with  a  more  or  less  distinctly  marked  olive  band  outside  the 
middle.    The  wings  expand  from  100  to  150  mm. 

When  fully  grown  the  larva  measures  from  100  to  125  mm.  in 
length.  It  is  our  largest  caterpillar,  and  can  be  readily  recognized 
by  the  very  long  spiny  horns  with  which  it  is  armed.  Those  of  the 
mesothorax  and  metathorax  are  much  longer  than  the  others.  Of 
these  there  are  four  on  each  segment ;  the  intermediate  ones  measure 
about  1 5  mm.  in  length.  This  larva  feeds  on  various  trees  and  shrubs. 
It  is  known  in  some  regions  as  the  hickory  horned  devil. 

The  imperial-moth,  Basilona  imperidlis. — This  moth  rivals  the 
preceding  species  in  size,  expanding  from  100  to  137  mm.  It  is  sul- 
phur-yellow, banded  and  speckled  with  purplish  brown.  The  full 
grown  larva  (Fig.  915)  measures  from  75  to  100  mm.  in  length.  It  is 
thinly  clothed  wth  long  hairs,  and  bears  prorriinent  spiny  horns  on 
the  second  and  third  thoracic  segments.     In  the  early  larval  stages 


Fig.  915. — Basilona  imperial  is,  larva. 

these  thoracic  horns  are  very  long  and  spiny,  resembling  those  of  the 
larva  of  the  regal-moth.  The  larva  feeds  on  hickory ,  pine,  oak,  butter- 
nut, and  other  forest-trees. 

The  two-colored  royal-moth,  Adelocephala  h'lcolor. — In  this  species 
the  upper  side  of  the  fore  wings  and  the  under  side  of  the  hind  wings 
are  yellowish  brown,  speckled  with  black.  The  under  side  of  the 
fore  wings  and  the  upper  side  of  the  hind  wings  are  to  a  considerable 
extent  pink.  There  is  usually  a  dark  discal  spot  on  the  fore  wings, 
upon  which,  especially  in  the  males,  there  may  be  two  white  dots. 
This  species  is  more  common  in  the  Southern  States  than  in  the 
North.  The  expanse  of  wings  in  the  male  is  50  mm. ;  in  the  female, 
60  mm.  The  larva  feeds  on  the  leaves  of  the  honey-locust  and  of  the 
Kentuckv  coffee-tree. 

Anisota.—To  the  genus  Anisdta  belong  four  species  of  moths  that 
occur  in  the  Eastern  United  States.     These  moths  are  dark  yellow 


718  AN  I  NT  ROD  UCTION  TO  ENTOMOLOG  Y 

purplish  red,  or  brownish  in  color,  and  agree  in  having  the  fore  wings 
marked  with  a  white  discal  dot.  The  larvae  feed  on  the  leaves  of  oak; 
they  are  more  or  less  striped  and  are  armed  with  spines.  These  in- 
sects hibernate  as  pupae. 

In  determining  these  moths,  the  student  should  remember  that 
the  two  sexes  of  the  same  species  may  differ  more  in  appearance 
than  do  individuals  of  different  species  but  of  the  same  sex.  The 
sexes  can  be  distinguished,  as  already  indicated,  by  the  antennae. 
The  three  species  can  be  separated  as  follows. 

The  rosy-striped  oak-worm,  Anisota  virginiensis. — The  wings  of 
the  female  are  purplish  red,  blended  with  ochre-yellow;  they  are 

very  thinly  scaled,  and  consequent- 
ly almost  transparent;  and  are  not 
speckled  with  small  dark  spots 
(Fig.  916).  The  wings  of  the  male 
are  purplish  brown,  with  a  large 
transparent  space  on  the  middle 
(Fig.  917).  The  larva  is  of  an  ob- 
scure gray  or  greenish  color,  with 
dull  brownish  yellow  or  rosy  stripes, 
and  with  its  skin  rough  with  small 
^.  white  warts.    There  is  a  row  of  short 

male' ^'         "''"   ■"''^''''''''''   ^^-   spines  on  each   segment,   and  two 

long  spines  on  the  mesothorax. 
The  orange-striped  oak-worm,  Anisota  senatoria. — The  wings  of 
the  female  are  more  thickly  scaled  than  in  the  preceding  species  and 
are  sprinkled  with  numerous  blackish  dots; 
in  other  respects  the  two  are  quite  similar  in 
coloring.     The  male  differs  from  that  of  A. 
virginiensis  in  lacking  the  large  transparent 
space  on  the  middle  of  the  wings.    The  larva 
is  black,  with  four  orange-yellow  stripes  on 
the  back  and  two  along  each  side ;  its  spines 
are  similar  to  those  of  the  preceding  species. 
The  spiny  oak-worm,  Anisota  stigma.- — 
The   female   closely  resembles   that   of  ^.   „. 
senatona;  ^nd  as  both  species  are  variable  ^\nl\^^\r"'''  '"'^'"' 
it  is  sometimes  difficult  to  determine  to  which 
a  given  specimen  belongs.    In  A.  stigma  the 

wings  are  rather  darker  and  have  a  greater  number  of  blackish  spots, 
and  the  hind  wings  are  furnished  with  a  middle  band  which  is  heavier 
and  more  distinct  than  in  A.  senatoria.  The  male  differs  from  that  of 
the  other  two  species  in  quite  closely  resembling  the  female  in  color- 
ing, and  in  having  the  wings  speckled.  The  larva  differs  from  the 
other  species  of  Anisota  in  having  long  spines  on  the  dorsal  aspect 
of  the  third  thoracic  and  each  abdominal  segment  in  addition  to  the 
much  longer  spines  on  the  mesothorax.  It  is  of  a  bright  tawny  or 
orange  color,  with  a  dusky  stripe  along  its  back  and  dusky  bands 
along  its  sides. 


V 


LEPIDOPTERA  719 

The  rosy  Anisota,  Anisota  ruhicunda. — The  wings  of  this  moth 
(Fig.  918)  are  pale  yellow,  banded  with  rose-color.  The  distribution 
of  the  color  varies  greatly  in 
difTerent  specimens.  In  some 
the  pink  of  the  fore  wings  pre- 
dominates, the  yellow  being  re- 
duced to  a  broad  discal  band, 
while  in  one  variety  the  ground- 
color is  yellowish  white  and  the 
pink  is  reduced  to  a  shade  at  the 
the  base  and  a  narrow  stripe  out- 
side the  middle.  The  hind  wings 
may  be  entirely  vellow,  or  may  t^-         ^      <    •    . 

have    a   pink  band   outside  the  ^'^-  9i«---l«"«''^  mk^cunda. 

middle.     The  expanse  of  wings 
in  the  male  is  35  to  43  mm.  in  the  female  50  mm.  or  more. 

The  larva  of  this  species  is  known  as  the  green-striped  maple- 
worm,  and  is  sometimes  a  serious  pest  on  soft-maple  shade-trees. 
It  measures  when  full  grown  about  37  mm.  It  is  pale  yellowish 
green,  striped  above  with  eight  very  light,  yellowish  green  lines, 
alternating  with  seven  of  a  darker  green,  inclining  to  black.  There 
are  two  prominent  horns  on  the  second  thoracic  segment,  and  two 
rows  of  spines  on  each  side  of  the  body,  one  above  and  one  below  the 
spiracles.  And  on  the  eighth  and  ninth  abominal  segments  there  are 
four  prominent  dorsal  spines.  The  species  is  one-  or  two-brooded, 
and  winters  in  the  pupa  state. 

Family  SATURNIID^ 
The  Giant  Silk-Worms 

The  large  size  of  members  of  this  family  and  the  ease  with  which 
cocoons  of  some  of  the  species  can  be  collected  render  them  well 
known  to  every  beginner  in  the  study  of  entomology.  They  are 
stout-bodied,  hairy  moths  with  more  or  less  sunken  heads  and  strong 
wide  wings.  The  palpi  are  small,  and  the  maxillae  but  little  developed, 
often  vestigial.  The  sexes  of  these  moths  can  be  ditinguished  by  the 
fact  that  the  antenna  of  the  males  are  more  broadly  pectinated  than 
are  those  of  the  females. 

The  family  includes  our  largest  lepidopterous  insects  and  all  of 
our  species  are  above  medium  size.  They  can  be  distinguished  from 
the  Citheroniidse,  some  of  which  rival  them  in  size,  by  the  form  of  the 
antennse  of  the  males,  which  are  pectinated  to  the  apex;  and  in  all  of 
our  genera,  except  Colorddia,  which  is  found  in  the  Rocky  Mountains, 
vein  Ml  of  both  fore  and  hind  wings  is  joined  to  radius  by  the  cross- 
vein  r-m  (Fig.  919). 

The  wings  are  often  fumishedwith  transparent,  window-like  spots. 
The  frenulum  is  completely  lost.  The  humeral  angle  of  the  hind 
wings  is  largely  developed,  and  is  usually  strengthened  by  a  deep 


720 


AN  INTRODUCTION  TO  ENTOMOLOGY 


furrow,  the  bottom  of 
which  is  sometimes 
thickened  so  as  to  ap- 
pear Hke  a  humeral 
vein  (Fig.  919). 

The  larvas  of  most 
of  our  species  hve  ex- 
posed on  the  leaves  of 
trees  and  shrubs;  but 
some  of  them,  as  the 
New  Mexico  range- 
caterpillar,  feed  on 
grass.  They  are  more 
or  less  armed  with 
tubercles  and  spines 
and  are  very  conspicu- 
ous on  account  of 
their  large  size.  Most 
of  them  transform 
within  silken  cocoons, 
which  are  usually  very 
dense,  and  in  some 
cases  have  been  utiliz- 
ed by  man.  These  co- 
coons are  often  at- 
tached to  trees  and 
shrubs,  and  are  some- 
times inclosed  in  a 
leaf.  They  can  be 
easily  collected  during 
the  winter  months, 
and  the  adults  bred 
from  them.  The  lar- 
vas of  some  members 
of  the  family  as  Hemi- 

leuca  mdia  enter  the  ground  to  transform. 

The  family  Saturniidae  as  now  recognized  includes  what  were 

formerly  regarded  as  two  distinct 

families,    the    Hemileucidas   and 

the  Saturniidae.     Our  latest  list 

includes  only  34  species,  of  which 

the    following    are    the    better 

known. 

The    Maia-moth,    Hemileuca 

maia. — The  genus  Hemileuca  is 

represented  in  our  fauna  by  elev- 
en species,  but  only  one  of  these  is 

found  in  the  East.    In  this  species 

(Fig.   920)   the  wings  are  thinly  Fig.  920. — Hemileuca  maia. 


id  A 
Fig.  919. — Wings  of  Samia  cecropia 


LEPIDOPTERA 


721 


scaled,  sometimes  semi-transparent;  they  are  black  with  a  common 
white  band  near  their  middle ;  and  the  discal  veins  are  usually  white 
and  broadly  bordered  with  black.  There  are  great  variations  in  the 
width  of  the  white  band  on  the  wings.  The  larva  feeds  on  the  leaves 
of  oak;  it  is  brownish  black,  with  a  lateral  yellow  stripe;  and  is  armed 
on  each  segment  with  large,  branching,  venomous  spines.  The  larva 
almost  always  enters  the  ground  to  transform. 

The  New  Mexico  range-caterpillar,  Hemileuca  olivice. — Of  the  ten 
western  species  of  Hemileuca  this  is  doubtless  of  the  greatest  economic 
importance.  It  is  a  grass-feeding  species,  which  has  been  very  de- 
structive in  certain  sections  of  the  cattle-range  in  northeastern  New 
Mexico.  It  was  estimated  that  in  1809  the  total  infested  area  was 
at  least  15,000  square  miles,  and  that  there  were  an  average  of  10 
caterpillars  to  the  square  rod  over  this  region.  For  a  full  account  see 
U.  S.  Dept.  Agr.  Bull.  No.  85,  Part  V. 


Fig.  921. — Pseudohazis  hera. 

Pseudohdzis. — In  the  West  there  occur  two  species  of  Psetidohazis. 
These  are  P.  hera  in  which  the  ground-color  of  the  wings  is  white 
(Fig.  921),  and  P.  eglanterlna,  in  which  the  ground-color  is  buff  or 
salmon.  Both  species  are  spotted  and  striped  with  black  as  shown 
in  the  figure. 

Color ddia  panddra. — This  is  a  brownish  gray  species  found  in  the 
Rocky  Mountains.  The  wings  are  only  moderately  broad,  and  each 
is  marked  with  a  small  black  spot  at  the  end  of  the  discal  cell .  The  hind 
wings  are  semi-transparent.    The  expanse  of  the  wings  is  from  75  to 


722 


AN  INTRODUCTION  TO  ENTOMOLOGY 


loo  mm.    This  species  is  easity  recognized  by  the  fact  that  vein  M] 

of  both  fore  and  hind  wings  is  coalesced  at  its  base  with   radius. 

The  larvffi  Hve  in  the  tops  of  pines  and  are  abundant  in  alternate 

years;  they  are 
dried  and  eaten 
by  Indians. 

Thelo-moth, 
Automeris  to. — ■ 
This  is  a  com- 
mon species  in 
the  East.  The 
female  is  repre- 
sented by  Figure 
922.  In  this  sex 
the  ground-color 
of  the  fore  wings 
is  purplish  red. 
Fig.  922.—Automens  io.  The  male  differs 

greatly  in  ap- 
pearance from  the  female,  being  somewhat  smaller  and  of  a  deeper 
}'ellow  color,  but  it  can  be  easily  recognized  by  its  general  resemblance 
to  the  female  in  other  respects. 

The  larva  is  one  that  the  student  should  learn  to  recognize  in  order 
that  he  may  avoid  handling  it;  for  it  is  armed  with  spines  the  prick  of 
which  is  venomous  (Fig.  923). 
The  same  is  true  of  the  larva 
of  the  Maia-moth,  but  that  is 
much  less  common.  The  lan^a 
of  the  lo-moth  is  green,  with  a 
broad  brown  or  reddish  stripe, 
edged  below  with  white,  on 
each  side  of  the  abdomen.  The 
spines  are  tipped  with  black. 
This  lan^a  feeds  on  various  trees  and  shrubs. 

The  polyph emus-moth,  Telea  polyphemus. — This  is  a  yellowish  or 
brownish  moth  with  a  window-like  spot  in  each  wing.  There  is  a 
gray  band  on  the  costal  margin  of  the  fore  wings ;  and  near  the  outer 
margin  of  both  pairs  of  wings  there  is  a  dusky  band,  edged  without 
with  pink;  the  fore  wings  are  crossed  by  a  broken  dusky  or  reddish 
line  near  the  base,  edged  within  with  white  or  pink.  The  transparent 
spot  on  each  wing  is  divided  by  the  discal  vein,  and  encircled  by  yellow 
and  black  rings.  On  the  hind  wings  the  black  surrounding  the  trans- 
parent spot  is  much  widened,  especially  toward  the  base  of  the  wing, 
and  is  sprinkled  with  blue  scales.  The  wings  expand  from  125  to 
150  mm. 

The  larva  (Fig.  924)  feeds  on  oak,  butternut,  basswood,  elm, 
maple,  apple,  plum  and  other  trees.  When  full  grown  it  measures 
75  mm.  or  more  in  length.  It  is  of  a  light  green  color  with  an  oblique 
vellow  line  on  each  side  of  each  abdominal  segment  except  the  first 


Automeris  io,  larva. 


LEPIDOPTERA 


^23 


and  last;  the  last  segment  is  bordered  by  a  purplish-brown  V-shaped 
mark.  The  tubercles  on  the  body  are  small,  of  an  orange  color  with 
metallic  reflections.  The  cocoon  (Fig.  925)  is  dense  and  usually  en- 
closed in  a  leaf;  it  can  be  utilized  for  the  manufacture  of  silk.    When 


Telea  polyphemus,  larva. 


the  adult  is  ready  to  emerge,  it  excretes  a  fluid  which  softens  the 
cocoon  at  one  end,  and  breaking  the  threads  by  means  of  a  pair  of 
stout  spines,  one  on  each  side  of  the  thorax  at  the  base  of  the  fore 
wings,  it  makes  its  exit  through 
a  large  round  hole. 

The  Luna-moth,  Tropcea 
luna. — This  magnificent  moth 
(Fig.  926)  is  a  great  favorite 
with  amateur  collectors.  Its 
wings  are  of  a  delicate  light 
green  color,  with  a  purple- 
brown  band  on  the  costa  of 
the  fore  wings ;  there  is  an  eye- 
like spot  with  a  transparent 
center  on  the  discal  vein  of 
each  wing ;  and  the  anal  angle 

of  the  hind  wings  is  greatly  prolonged.    The  larva  feeds  on  the  leaves 
of  walnut,  hickory,  and  other  forest-trees.     It  measures  when  full 


Fig.   925. — Cocoon   of    Telea  polyphemus. 


724 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.   926. — Tropcea  lio 


Fig.  927. — Callosamia  promethea,  female. 


LEPIDOPTERA 


T2b 


grown  about  75  mm.  in  length.  It  is  pale  bluish  green  with  a  pearl- 
colored  head.  It  has  a  pale  yellow  stripe  along  each  side  of  the  body, 
and  a  transverse  yellow  line  on  the  back  between  each  two  abdominal 
segments.  The  cocoon  resembles  that  of  the  preceding  species  in  form, 
but  is  very  thin,  containing  but  little  silk. 

The  Promethea-moth,  Callosdmia  promethea.— This  is  the  most 
common  of  the  giant  silk-worms.  The  wings  of  the  female  (Fig.  927) 
are  light  reddish  brown;  the  transverse  line  crossing  the  middle  of 
the  wings  is  whitish,  bordered  within  with  black;  the  outer  margin  of 
the  wings  is  clay-colored,  and  each  wing  bears  an  angular  discal  spot. 
The  discal  spots  vary  in  size  and  distinctness  in  different  specimens. 
The  male  differs  so  greatly  from  the 
female  that  it  is  liable  to  be  mistaken 
for  a  distinct  species.  It  is  blackish, 
with  the  transverse  lines  very  faint, 
and  with  the  discal  spots  wanting  or 
very  faintly  indicated.  The  fore  wings 
also  differ  markedly  in  shape  from 
those  of  the  female,  the  apex  being 
much  more  distinctly  sickle  shaped. 
The  males  fly  by  day .  The  larva  when 
full  grown  measures  50  mm.  or  more 
in  length.  It  is  of  a  clear  pale  bluish- 
green  color;  the  legs  and  anal  shield 
are  yellowish ;  and  the  body  is  armed 
with  longitudinal  rows  of  tubercles. 
The  tubercles  are  black,  polished, 
wart-like  elevations,  excepting  two 
each  on  the  second  and  third  thoracic 
segments,  which  are  larger  and  rich 
coral-red,  and  one  similar  in  size  to 
these  but  of  a  yellow  color  on  the 
eighth  abdominal  segment.  This  lar- 
va feeds  on  the  leaves  of  a  large  pro- 
portion of  our  common  fruit  and  forest 
trees ;  but  we  have  found  it  more  fre- 
quently on  wild  cherry,  lilac,  tulip- 
tree,  and  ash  than  on  others.  The  co- 
coons can  be  easily  collected  during 
the  winter  from  these  trees.  This  is 
the  best  way  to  obtain  fresh  specimens 
of  the  moths,  which  will  emerge  from 
the  cocoons  in  the  spring  or  early 
srmimer.  The  cocoon  (Fig.  928)  is 
interesting  in  structure.  It  is  greatly 
elongated  and  is  enclosed  in  a  leaf, 
the  petiole  of  which  is  securely  fas- 
tened to  the  branch  by  a  band  of  silk  extending  from  the  cocoon; 
thus  the  leaf  and  enclosed  cocoon  hang  upon  the  tree  throughout  the 


Callosamia    promethea, 


726  ^A^  INTRODUCTION  TO  ENTOMOLOGY 

winter.  At  the  upper  end  of  the  cocoon  there  is  a  conical  valve-like 
arrangement  which  allows  the  adult  to  emerge  without  the  necessity 
of  making  a  hole  through  the  cocoon.  This  structure  is  characteristic 
of  the  cocoons  of  the  moths  of  this  and  the  following  genus.  See 
Figure  211,  page  189. 

The  angulif  era -moth,  Callosdmia  anguUfera. — This  is  a  somewhat 
rare  insect  which  closely  resembles  the  Promethea-moth.  Specimens 
of  it  are  usually  a  little  larger  than  those  of  C.  promethea,  and  the  trans- 
verse line  and"  discal  spots  are  more  angular.  The  most  important 
differences,  however,  are  presented  by  the  male,  which  quite  closely 
resembles  the  female  of  the  Promethea-moth  in  color  and  markings, 
and  thus  differs  decidedly  from  the  male  of  that  species.  The  male 
of  this  species  is  nocturnal,  differing  in  this  respect  from  C.  promethea. 
The  larva  feeds  on  the  leaves  of  the  tulip-tree  and  of  Alagnolia. 
It  make  its  cocoon  within  a  leaf  or  it  crawls  down  the  trunk  of  the 
tree  and  spins  its  cocoon  in  the  grass  or  fastens  it  to  some  object  on 
the  ground.  The  cocoon  usually  has  no  stem  and  when  made  in  a 
leaf  falls  to  the  ground  in  it  when  the  leaf  falls. 

The  Cecropia-moth,  Sdmia  cecropia.- — This  is  the  largest  of  our 
giant  silk-worais,  the  wings  of  the  adult  expanding  from  125  to  160 
mm.  The  ground  color  of  the  wings  is  a  grizzled  dusky  brown,  es- 
pecially on  the  central  area.  The  wings  are  crossed  beyond  the 
middle  by  a  white  band,  which  is  broadly  margined  without  with  red, 
and  there  is  a  red  spot  near  the  apex  of  the  fore  wing  just  outside  of  a 
zigzag  line.  Each  wing  bears  near  its  center  a  crescent-shaped  white 
spot  bordered  with  red.  The  outer  margin  of  the  wings  is  clay-colored. 
The  larva  is  known  to  feed  on  at  least  fifty  species  of  plants,  including 
apple,  plum,  and  the  more  common  forest  trees.  When  full  grown  it 
measures  from  75  mm.  to  100  mm.  in  length  and  is  dull  bluish  green 
in  color.  The  iDody  is  armed  with  six  rows  of  tubercles,  extending 
nearly  its  entire  length,  and  there  is  an  additional  short  row  on  each 
side  of  the  ventral  aspect  of  the  first  five  segments  following  the  head. 
The  tubercles  on  the  second  and  third  thoracic  segments  are  larger 
than  the  others,  and  are  coral-red.  The  other  dorsal  tubercles  are 
yellow,  excepting  those  of  the  first  thoracic  and  last  abdominal  seg- 
ments, which  with  the  lateral  tubercles  are  blue;  all  are  armed  with 
black  bristles.  The  pupa  is  represented  by  Figure  929  and  the  cocoon 
by  Figure  930. 

The    Cecropia-moth    occurs    from 
the  Atlantic  Coast  to  the  Rocky  Moun- 
tains.    In  the  North  Atlantic  States 
there  is  another  species  which  resembles 
it  in  general  appearance  but  is  much 
smaller,  expanding  from  75  to  100  mm. 
and  is  much  less  common ;  this  is  Sdmia 
-Samia  cecropia,  pupa.  Columbia.     In  the  Far  West  the  place 
of  the  Cecropia-moth  is  taken  by  two 
very  closely  allied  species.    In  these  the  ground-color  of  the  wings  is 
usually  reddish  or  dusky  brown.    Sdmia  gloveri  is  found  in  the  Rocky 


LEPIDOPTERA 


727 


Mountain  region  and  in  Arizona;  and  Samia  rubra  in  the  Pacific 
States.  In  Samia  rubra  the  crescent-shaped  white  spot  near  the 
center  of  the  hind  wings  is  more  elongate  and  pointed  than  in  the 
other  species. 

The  Ailanthus-worm,  Philosdmia  cynthia  (?).— This  is  an  Asiatic 
species  which  has  been  introduced  into  this  countrv.    It  has  become 


Fig-  930- — Samia  cecropia,  cocoon. 

a'pest  in  the  vicinity  of  New  York  City,  where  it  infests  the  Ailanthus 
shade  trees.  The  moth  differs  from  all  our  native  species  of  this 
family  in  having  rows  of  tufts  of  white  hairs  on  the  abdomen.  Its 
cocoon  resembles  that  of  the  Promethea-moth.  The  specific  identity 
of  this  species  is  in  doubt. 

Family  BOMBYCID^ 


The  Silk-Worm 

The  family  Bombycidffi  is  not  represented  in  our  fauna;  but  a 
single  species,  the  silk-worm,  is  frequently  bred  in  this  country,  and 
is  usvially  present  in  collections  of  Lepidoptera. 

The  silk-worm,  Bombyx  mori.~The  moth  (Fig.  931)  is  of  a  cream- 
color  with  two  or  three  more  or 
less  distinct  brownish  lines  across 
the  fore  wings  and  sometimes  a 
faint  double  bar  at  the  end  of 
the  discal  cell.  The  head  is  small ; 
the  antennae  are  pectinated 
broadly  in  both  sexes;  and  the 
ocelli,  palpi,  and  maxillas  are 
wanting.  A  striking  feature  of 
the  venation  of  the  wings  (Fig. 
932)  is  the  obvious  presence  of 
the  base  of  vein  Ri  in  the  hind 
wings. 

The  usual  food  of  the  silk- 
wonns  is  the  leaf  of  the  mulberry.    Our  native  species,  however  are 
not  suitable.    The  species  that  are  most  used  are  the  white  mulberr^^ 


Fig.    93 1 . — Bombyx   mori. 


728 


AN  INTRODUCTION  TO  ENTOMOLOGY 


{Morns  alba),  of  which  there  are  several  varieties,  and  the  black 
mulberry  {Moms  nigra) ;  the  former  is  the  better.  \  The  leaves  of 

osage  orange  {Madura 
f^  aurantiaca)  have   also 

r,  ^^<<'~~P=^  been  used  as  silk-worm 
'^^^  ^  ^  food  to  a  considerable 
extent.  In  case  silk- 
worins  hatch  in  the 
spring  before  either 
mulberry  or  osage- 
orange  leaves  can  be 
obtained,  they  may  be 
quite  successfully  fed, 
for  a  few  days,  upon 
lettuce-leaves. 

The  newly-hatched 
larva  is  black  or  dark- 
grav,  and  is  covered 
with  long  stiff  hairs, 
which  spring  from  pale- 
colored  tubercles.  The 
hairs  and  tubercles  are 
not  noticeable  after 
the  first  molt,  and  the 
worm  becomes  lighter 
and  lighter,  until  in 
the  last  larval  period 
it  is  of  a  cream-white 
color.  There  is  a 
prominent  tubercle  on 
the  back  of  the  eighth 
abdominal  segment, 
resembling  those 
borne  by  certain  lar- 
vae of  the  Sphingidffi. 
There  are  many  special  treatises  on  this  insect,  some  of  which 
should  be  consulted  by  any  one  intending  to  raise  silk-worms. 


Fig.  932. 


2d  A 

-Wings  of  Bombyx  mori. 


Family  LASIOCAMPID^ 

The  Lasiocampids 

The  best-known  representatives  of  this  family  are  the  tent-cater- 
pillars and  the  lappet-caterpillars.  The  adults  are  stout-bodied,  hairy 
moths  of  medium  size.  The  antennae  are  pectinated  in  both  sexes, 
and  from  one-fourth  to  one-half  as  long  as  the  front  wings;  the  teeth 
of  the  antennae  of  the  male  are  usually  much  longer  than  those  of  the 
female.  The  ocelli  and  the  maxillje  are  wanting ;  and  the  palpi  are  us- 
ually short  and  woolly.    But  the  most  distinct  characteristic  is  found 


LEPIDOPTERA 


729 


in  the  wings.  The  frenulum  is  wanting,  there  being  instead,  as  in 
the  Saturnioidea,  a  largely  expanded  humeral  angle  of  the  hind  wings. 
But  these  moths  differ  from 
the  Saturnioidea  in  having 
cubitus  apparently  four- 
branched  and  in  having  the 
humeral  angle  of  the  hind 
wings  strengthened  by  the  de- 
velopment of  some  extra  veins, 
the  humeral  veins  (Fig.  933 
h.  v.). 

The  larvcC  of  the  Lasio- 
campidae  feed  upon  the  foliage 
of  trees,  and  are  frequently 
very  destructive. 

The  family  is  a  small  one, 
less  than  thirty  North  Ameri- 
can species  are  known;  but 
these  represent  eleven  genera. 
Our  more  common  species 
represent  three  genera :  Mala- 
cosoma,  which  includes  the 
tent-caterpillars,  and  Tolype 
and  Eptcuaptera,  which  in- 
clude   the    lappet-caterpillars. 

There  are  several  species  of 
tent-caterpillars  in  this  coun- 
try. Most  of  them  belong  to 
the  Pacific  coast;  but  two  are 

common  in  the  East.  Of  these  the  most  common  one  is  the  apple- 
tree  tent-caterpillar,  Malacosoma  americdna. — This  is  the  insect  that 
builds  large  webs  in  apple  and  wild  cherry  trees  in  early  spring. 
Figure  934  represents  its  transformations.  The  moth  is  dull  reddish 
brown,  with  two  transverse  whitish  or  pale  yellowish  lines  on  the 
fore  wing.  The  figure  represents  a  male;  the  female  is  somewhat 
larger.  These  moths  appear  early  in  the  summer.  The  eggs  are  soon 
laid,  each  female  laying  all  her  eggs  in  a  single  ring-like  cluster  about 
a  twig;  and  here  they  remain  unhatched  for  about  nine  months. 
This  cluster  is  covered  with  a  substance  which  protects  it  during  the 
winter.  The  eggs  hatch  in  early  spring,  at  the  time  or  just  before 
the  leaves  appear.  The  larv«  that  hatch  early  feed  upon  the  un- 
opened buds  till  the  leaves  expand.  The  larvae  are  social,  the  entire 
brood  that  hatch  from  a  cluster  of  eggs  keeping  together  and  building 
a  tent  in  which  they  live  when  not  feeding.  The  figure  represents  a 
specimen  in  our  collection.  In  this  case  the  tent  was  begun  near  the 
cluster  of  eggs.  But  usually  the  larvae  soon  after  hatching  migrate 
down  the  branch  towards  the  trunk  of  the  tree  until  a  fork  of  consider- 
able size  is  reached  before  they  begin  their  tent.  This  is  necessary, 
as  the  completed  tent  often  measures  nearly  two  feet  in  length. 


Fig-  933- 


Wings  of  Malacosma  americana. 


730 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  larvce  leave  the  nest  daily  in  order  to  feed;  and  spin  a  silken 
thread  wherever  they  go.  The  larvae  become  full  grown  early  in 
June;  one  of  them  is  represented  on  a  partially-eaten  leaf  in  the 
figure.  When  ready  to  transform  they  leave  the  trees  and  make  their 
cocoons  in  some  sheltered  place.  These  cocoons  are  quite  pecuHar 
in  appearance,  having  a  yellowish  white  powder  mixed  with  the  silk. 
The  pupa  state  lasts  about  three  weeks.  The  easiest  way  to  fight 
this  pest  is  to  destroy  the  webs  containing  the  larvae  as  soon  as  they 
appear  in  the  spring.  This  should  be  done  early  in  the  morning,  or 
late  in  the  afternoon,  or  on  a  cold  day,  when  the  larvae  are  not  scattered 
over  the  tree  feeding. 


Fig.  934. — -Malacosma  americana,  eggs,  tent,  larva,  cocoons,  and  adult. 


Another  species  of  the  genus  Malacosoma  found  in  the  East  is  the 
so-called  forest  tent-caterpillar,  Malacosoma  disstria.  The  range  of 
this  species  extends  throughout  the  United  States  and  Canada.  It 
differs  from  the  preceding  species  in  that  the  larvae  do  not  construct 
a  true  tent.  It  feeds  on  the  leaves  of  many  forest  and  fruit  trees,  but 
maple  is  its  favorite  food -plant.  In  other  respects  its  life  history  is 
quite  similar  to  that  of  the  apple-tree  tent-caterpillar.  The  moth 
differs  from  M.  americana  in  having  the  oblique  lines  on  the  wings 
dark  instead  o^;  light;  the  larva  differs  in  having  a  row  of  spots  along 
the  back  instead  of  a  continuous  narrow  line;  the  egg-masses  differ 


LEPIDOPTERA  731 

in  ending  squarely  instead  of  being  rounded  at  each  end;  and  the 
cocoon  is  more  fragile,  with  less  powder,  and  distinctly  double. 

The  Great  Basin  tent-caterpillar,  Malacosonia  frdgilis. — This  spe- 
cies is  found  throughout  the  northern  portions  of  the  Great  Basin, 
extending  from  the  Rocky  Mountains  to  the  Cascades  and  Sierra 
Nevadas,  and  has  been  found  in  California.  It  feeds  on  Ceanothus 
and  many  other  wild  shrubs. 

The  California  tent-caterpillar,  Malacosdma  californica,  feeds 
normally  on  oak  but  also  attacks  fruit  trees.  The  caterpillars  are 
orange-colored  and  about  25  mm.  long. 

Malacosdma  constricta. — The  larva  is  somewhat  larger  than  the 
preceding  species,  and  may  be  readily  recognized  by  the  distinct  blue 
lines  along  the  sides.    It  feeds  on  oaks. 

Malacosdma  pluvidlis. — This  is  another  Pacific  Coast  species.  The 
larvae  are  buff -colored  and  usually  feed  upon  alder,  but  occasionally 
become  quite  injurious  to  apple  trees. 

The  lappet-caterpillars. ^ — The  larvae  of  the  species  of  Tolype  and 
of  Epicndptera  are  remarkable  for  having  on  each  side  of  each  segment 
a  little  lappet  or  flat  lobe;  from  these  many  long  hairs  are  given  out, 
forming  a  fringe  to  the  body.  When  at  rest  the  body  of  the  larva  is 
flattened,  and  the  fringes  on  the  sides  are  closely  applied  to  the 
surface  of  the  limb  on  which  the  insect  is.  Thus  all  appearance  of 
an  abrupt  elevation  is  obliterated;  the  colors  of  these  larvae  are  also 
protective,  resembling  those  of  the  bark.  The  following  are  our 
better-known  species. 

The  Velleda  lappet,   Tolype  velleda. — The  body  of  the  moth  is 

milk-white,  with  a  large  blackish  spot  on  the  middle  of  its  back 

(Fig.  935).    That  part  of  this  spot  which 

is   on  the  thorax   is  composed   of  erect 

scales,  the  caudal  part  of  recumbent  hairs. 

The  wings  are  dusky  gray,  crossed  by 

white  lines  as  shown  in  the  figure.     The 

figure  represents  the  male;  the  female  is 

much  larger.     The  moths  are  found  in 

August  and  September.    The  larva  feeds 

upon   the  leaves   of  apple,    poplar,   and 

syringa.     Its  bodv  is  bluish  grav,  with        „.  „  ,  ^      „  , 

r   •    .L  1         -^'j-      11-  J  Fig- 935- — Tolype  velleda. 

many  f  amt  longitudmal  Imes ;  and  across 

the  back  of  the  last  thoracic  segment  there 

is  a  narrow  velvety-black  band.  The  larva  reaches  maturity  during 
July.  The  cocoon  is  brownish  gray,  and  is  usually  attached  to  one 
of  the  branches  of  the  tree  on  which  the  larva  has  fed. 

The  larch  lappet,  Tolype  Idricis. — This  is  a  smaller  species,  the 
"females  being  about  the  size  of  the  male  of  the  preceding  species,  and 
the  males  expanding  only  about  30  mm.  The  wings  of  the  females 
are  marked  much  like  those  of  T.  velleda,  except  that  the  basal  two- 
thirds  of  the  front  wings  are  much  lighter,  and  the  dark  band  on  the 
outer  third  is  narrower  and  much  darker  than  the  other  dark  bands. 


732  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  males  are  bluish  black,  with  the  markings  indistinct.  The  larva 
feeds  upon  the  larch.  When  mature  it  is  of  a  dull  brown  color  and 
less  than  40  mm.  in  length.  When  extended,  the  front  of  the  first 
thoracic  segment  is  pale  green,  and  the  incision  between  the  second 
and  third  is  shining  black.  The  larva  matures  during  July.  The 
cocoon  is  ash-gray,  flattened  and  moulded  to  the  limb  to  which  it  is 
attached,  and  partially  surrounding  it.  The  moths  appear  in  August 
or  September.    The  winter  is  passed  in  the  egg  state. 

The  American  lappet,  Epicndptera  americdna. — This  species  is 
found  from  the  Atlantic  to  the  Pacific.  It  is  somewhat  variable, 
and  the  different  varieties  were  formerly  regarded  as  distinct  species. 
The  moth  (Fig.  936)  is  reddish  brown,  with  the  inner  angle  of  the 
front  wings  and  the  costal  margin  of  the  hind  wings  deeply  notched. 

Beyond  the  middle  of  each  wing  there  is  a 

ftl^  V  J      iinimi      P^^^  band  edged  with  zigzag,  dark  brown 

|JBfclb^S^<''^^^^P      lines.     The  larva  lives  upon  apple,  cherry, 

^^HIBb^K^H^^P'       oak,  birch,  maple  and  ash.    When  full  grown 

^^Ktj^HM^k^         it  measures  60  mm.  in  length  and  12  mm.  in 

^^RjMpi^Sp  breadth.      The    upper    side    is    slate-gray, 

""^^JHfc^^  mottled   with    black,    with   two   transverse 

pj     Q,5 Epicnaptera        scarlet  bands,  one  on  the  second  and  one  on 

americana.  the  third  thoracic  segments.     There  is  a 

black  spot  on  each  end  and  in  the  middle 
of  each  of  these  bands-  The  larva  is  found  during  July  and  August. 
It  is  said  that  the  cocoons  are  attached  to  limbs  like  those  of  Tolype; 
but  the  larvas  of  this  species  that  we  have  bred  made  their  cocoons 
between  leaves,  or  in  the  folds  of  the  muslin  bag  enclosing  the  limb 
upon  which  they  were  feeding.  The  species  passes  the  winter  in  the 
pupa  state ;  and  the  moth  appears  in  June,  when  it  lays  its  eggs  upon 
the  leaves  of  the  trees  it  infests. 

SUPERFAMILY   HESPERIOIDEA 

The  Skippers 

The  skippers  are  so-called  on  account  of  their  peculiar  mode  of 
flight.  They  fly  in  the  daytime  and  dart  suddenly  from  place  to  place. 
Wlien  at  rest  most  species  hold  the  wings  erect  in  a  vertical  position 
like  butterflies;  in  many  the  fore  wings  are  thus  held  while  the  hind 
wings  are  extended  horizontally;  and  a  few  extend  both  pairs  of 
wings  horizontally.  The  head  is  wide;  the  antennas  are  widely 
separated;  they  are  thread-like,  and  enlarged  toward  the  tip;  and 
in  most  cases  the  extreme  tip  is  pointed  and  recurved,  forming  a  hook. 
The  abdomen  is  usually  stout,  resembling  that  of  a  moth  rather  than 
that  of  a  butterfly.  The  skippers  are  most  easily  distinguished  by 
the  peculiar  venation  of  the  wings,  vein  R  of  the  fore  wings  being 
five-branched,  and  all  of  the  branches  arise  from  the  discal  cell 
(Fig.  937).  In  some  butterflies  all  of  the  branches  of  vein  R  appear 
to  arise  from  the  discal  cell ;  but  this  is  because  two  of  the  branches 


LEPIDOPTERA 


733 


In  such  butterflies  vein  R  appears 


coalesce  to  the  margin  of  the  wing, 
to  be  only  four-branched. 

The  North  American  skip- 
pers   represent    two    families. 
In  Australia  there  is  a  skipper- 
like insect,  Euschemon  rafflesice, 
which  has  a  distinct  frenulum. 
If  this  belongs  to  the  Hesperi- 
oidea,    it    represents    a    third 
family,     the     Euschemonidce. 
Our  two  families  can  be  sepa- 
rated as  follows. 
A.     Head  of  moderate  size;  club  of 
antenna  large,  neither  drawn  out 
at  the   tip  nor  recurved.     Large 
skippers,  with    wing  expanse    o^ 

40  mm.  or  more.  p.  733 

Megathymid/e 

AA.  Head  very  large;  club  of  an- 
tenna usually  drawn  out  at  the 
tip,  and  with  a  distinct  recurved 
apical  crook.  In  a  few  forms  the 
crook  of  the  antennas  is  wanting ; 
such  forms  can  be  distinguished 
from  the  Megathymidae  by  their 
smaller  size,  the  wing  expanse  be- 
ing less  than  30  mm.  p.  734.  .  . 
Hesperiid^ 

Family  MEGATHYMID^ 


The  Giant  Skippers  pig.   937.— Wings  of  Epargyreus  tityrus. 

This  family  includes  a  small  nimiber  of  large  skippers,  which  are 
found  in  the  South  and  far  West.  In  the  adult  insect  the  head  is 
of  moderate  size,  the  width,  including  the  eyes,  being  much  less 
than  that  of  the  metathorax.  The  club  of  the  antenna?  is  large; 
and,  although  the  tip  is  turned  slightly  to  one  side,  it  is  neither  drawn 
out  to  a  point  nor  recurved.  The  body  is  very  robust,  even  more  so 
than  in  the  Hesperiidas.  These  insects  fly  in  the  daytime  and  with 
a  rapid  darting,  flight.  When  at  rest  they  fold  their  wings  in  a 
vertical  position. 

So  far  as  is  known  the  larvas  in  the  later  stages  of  their  growth  are 
borers  in  the  stems  and  roots  of  various  species  of  Yucca  and  Agave 
and  the  young  larvae  spin  silken  tubes  between  the  young  and  tender 
shoots  of  these  plants. 

A  monograph  of  the  family  was  published  by  Barnes  and  Mc- 
Dunnough  ('12).  It  is  represented  in  the  United  States  by  a  single 
genus,  Megathymiis,  of  which  eight  species  have  been  found  in  the 
United  States. 

Megathymus  streckeri  (Fig.  938)  will  serve  as  an  example  of  the 
giant  skippers.     The  specimen  figured  is  a  female  of  the  variety 


734 


AN  INTRODUCTION  TO  ENTOMOLOGY 


known  as  texana. 
A  much  better  known 
species  is  the  yucca-borer, 
Megathymns  yiiccce.  The 
female  of  this  species 
differs  from  that  of  the 
preceding  in  having  much 
darker  wings,  all. of  the 
spots  being  smaller,  and 
in  having  only  one  or  two 
white  spots  on  the  lower 
surface  of  the  hind  wings. 
The  male  lacks  the  erect 
hairs  on  the  hind  wings. 

The  larva  bores  in  the  stem  and  root  of  the  Yucca  or  Spanish  bayonet. 

It  differs  greatly  in  appearance  from  the  larvas  of  the  Hesperiidas, 

having  a  small  head.    This  species  is  widels^  distributed  through  the 

southern  part  of  our  country. 


Fig-  938. — Megathymus  streckeri. 


Family  HESPERIID^ 


FJg-  939- — Epargyreiis  tityrus,  larva. 


The  Common  Skippers 

This  family  includes  all  of  our  skippers  except  the  very  small 
nimiber  that  belong  to  the  preceding  family,  the  giant  skippers.    The 
two  families  can  be  separated 
by  the  table  given  above. 

The  larvas  of  the  common 
skippers  present  a  ver\^  char- 
acteristic appearance,  having 
large  heads  and  strongly  con- 
stricted necks  (Fig.  939).  They 
usually  live  concealed  in  a 
folded  leaf  or  in  a  nest  made 

of  several  leaves  fastened  together.  The  pupae  are  rounded,  not 
angular,  resembling  those  of  moths  more  than  those  of  butterflies. 
The  pupa  state  is  passed  in  a  slight  cocoon,  which  is  generally  com- 
posed of  leaves  fastened  together  with  silk,  and  thinly  lined  with  the 
same  substance. 

A  monograph  of  the  North  American  species  was  published  by 
Lindsey  ('21);  and  the  species  of  the  Eastern  United  States  are  de- 
scribed and  figured  in  natural  colors  by  Comstock  and  Comstock  ('04). 

The  family  Hesperiidas  includes  four  subfamilies ;  but  only  three 
of  them  are  represented  in  this  country,  the  fourth  being  confined 
to  the  Old  World.    Our  forms  can  be  separated  as  follows. 

A.    Club  of  antennas  large;  the  entire  club  reflexed.  p.  735 Pyrrhopygin^ 

AA.     Club  of  antennas  variable,  but  never  with  the  entire  club  reflexed. 

B.     Vein  Mj  of  the  fore  wings  arising  nearer  to  vein  Mi  than  to  vein  M3.  p.  735. 
Hesperiin^ 


LEPIDOPTERA  735 

BB.    Vein  AL  of  the  fore  wings  arising  midway  between  veins  Mi  and  M,  or 
nearer  to  vein  M3  than  to  vein  Mi. 

C.     Vein  AL  of  the  fore  wings  arising  nearly  midway  between  veins  Mi 
and  M3. 

D.     Discal  cell  of  fore  wings  more  than  two-thirds  as  long  as  the  costa. 
Mid  tibiae  without  spines.    Males  usually  with  costal  fold  in  fore  wings 

p.  735 Hesperiin^ 

DD.     Discal  cell  of  fore  wings  less  than  two-thirds  as  long  as  the  costa. 
Mid  tibiae  spined.    Males  usually  with  a  discal  patch,  the  brand,  on  the 

for  wings,  p.  737 Pamphilin^ 

CC.    Vein  M2  of  the  fore  wings  arising  much  nearer  to  vein  M3  than  to  vein 
Mi    p.    737 Pamphilin^ 


Subfamily  PYRRHOPYGIN^ 

The  distinguishing  feature  of  this  subfamily  is  that  the  antennal 
club  is  large  and  the  entire  club  is  recurved.  In  the  other  members 
of  the  Hesperiidas  if  the  antennal  club  is  recurved  it  is  only  the 
terminal  part  of  the  club  that  is  bent  back.  This  subfamily  includes 
a  large  number  of  South  and  Central  American  species;  but  only 
one  has  been  found  north  of  Mexico.  This  is  Apyrrothrix  ardxes 
variety  artzdn<r.  This  has  been  found  only  in  Arizona.  It  is  a  large 
skipper,  having  a  wing-expanse  of  50  mm.  In  general  appearance  it 
resembles  our  common  silver-spotted  skipper,  Epargyreus  tttyrus, 
except  that  the  ground  color  is  a  darker  brown  and  the  spots  on  the 
fore  wings  and  the  lighter  parts  of  the  fringes  are  snow  white. 


Subfamily  HESPERIIN^ 
Skippers  with  a  Costal  Fold  and  their  Allies 

This  subfamily  includes  the  larger  of  the  common  skippers,  as 
well  as  some  that  are  of  moderate  size.  Most  of  the  species  are  dark 
brown,  marked  with  white  or  translucent,  angular  spots.  The  an- 
tennae usually  have  a  long  club,  which  is  bent  at  a  considerable  dis- 
tance from  the  tip  (Fig.  940)  and  vein  M2  of  the  fore  wings  retains  its 
primitive  position  nearly  midway  between  veins  Mi  and  M3  or  is 
nearer  to  vein  Mi  than  to  M3  at  base  (Fig.  937).  But  the  most  dis- 
tinctive feature  of  the  subfamily  is  exhibited 
by  the  males  alone,  and  is  lacking  in  some 
species.  It  consists  of  a  fold  in  the  fore  wing 
near  the  costal  margin,  which  forms  a  long 
slit-like  pocket,  containing  a  sort  of  silky 
down.  This  is  a  scent-organ.  When  this 
pocket  is  tightlv  closed  it  is  difficult  to  see  it.  ^. 
It  is  known  as  "the  costal  fold.  _  L/?f '         '""''  '""" 

More  than  eighty  species  belonging  to 
this  subfamily  have  been  found  in  America  north  of  Mexico.     The 
following  are  some  of  the  more  common  of  these. 


/J.       JUUL    LllC  lllUbL   Ulb- 


736 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  silver-spotted  skipper,  Epargyreus  tUyrus. — This  is  one  of  the 
larger  of  our  common  skippers,  having  a  wing-expanse  of  nearly  or 

quite  50  mm.  It  is  dark  choco- 
late brown,  with  a  row  of  yel- 
lowish spots  extending  across 
the  fore  wing  and  with  a  large 
silvery -white  spot  on  the  lower 
side  of  the  hind  wing  (Fig.  941). 
It  is  found  in  nearly  the  whole 
United  vStates  and  in  southern 
Canada.  The  larva  (Fig.  939) 
feeds  upon  various  papilionace- 
ous plants.  It  is  common  on 
locust.  It  makes  a  nest,  with- 
in which  it  remains  concealed, 
by  fastening  together,  with  silk, 
the  leaflets  of  a  compound  leaf 
(Fig.  942).     This  is  one  of  the  very  few  skippers  that  winter  in  the 


Fig.  941. — Epargyreus  tityrus;  under  surface 
at  left.     (From  Scudder.) 


Fig.  942. — Nest  of  larva  of  Epargyreus  tityrus. 

pupa  state;  most  species  winter  as  larvae,  either  partly  grown  or  in 
their  cocoons. 

The  bean  leaf-roller,  Goniurus  prdteus. — This  skipper  by  the  shape 
of  its  wings  reminds  one  of  a  swallow-tail  butterfly,  the  hind  wings 
being  furnished  with  long  tails.  It  expands  about  43  mm.  and  the 
greatest  length  of  the  hind  wings  is  about  30  mm.  The  wings  are 
very  dark  chocolate-brown.  The  front  wings  contain  several  silvery- 
white  spots ;  and  the  body  and  base  of  the  wings  bear  metallic-green 
hairs.  The  larvae  feed  upon  both  Leguminosas  and  Cruciferas.  In  the 
South  it  is  sometimes  a  pest  in  gardens,  cutting  and  rolling  the  leaves 
of  beans,  turnips,  and  cabbage,  and  feeding  within  the  rolls  thus 
formed.  It  is  found  on  the  Atlantic  border  from  New  York  southward 
into  Mexico. 

There  are  two  common  skippers  which  are  nearly  as  large  as  the 
two  described  above,  but  which  have  neither  the  yellow  band  of  the 
first  nor  the  long  tails  of  the  second ;  neither  do  they  have  the  brown 
spots  characteristic  of  the  following  genus.  These  two  skippers  belong 
to  the  genus  Thorybes.    The  wings  are  of  an  even  dark  brown ;  the  fore 


LEPIDOPTERA  737 

wings  are  flecked  with  small  or  very  small  irregular  white  spots,  and 
the  hind  wings  are  crossed  beneath  by  two  rather  narrow,  parallel, 
inconspicuous  darker  bands.  These  skippers  are  distinguished  as 
follows. 

The  northern  cloudy-wing.  Thoryhes  pylades. — In  this  species  the 
white  spots  on  the  fore  wing  are  usually  mere  points,  although  their 
number  and  size  vary.  The  species  is  found  in  nearly  all  parts  of  the 
United  States.    The  larva  commonly  feeds  on  clover. 

The  southern  cloudy-wing,  Thoryhes  daunus. — In  this  species  the 
white  spots  are  larger  than  in  the  preceding,  almost  forming  a  con- 
tinuous band.  It  differs  also  in  that  the  males  do  not  have  a  costal 
fold.  It  is  widely  distributed  over  the  Eastern  United  States,  except 
the  more  northern  portions. 

To  the  genus  Thanaos  belong  a  large  number  of  species  which  on 
account  of  their  dark  colors  have  been  named  dusky-wings.  These 
species  resemble  each  other  so  closely  in  markings  that  it  is  very 
difficult  to  separate  them  without  longer  descriptions  than  can  be 
given  here.    The  one  following  will  serve  as  an  example. 

Martial's  dusky-wing,  Thanaos  martidlis. — The  wings  are  grayish 
brown  with  many  dark  brown  spots  evenly  distributed  and  with 
several  minute  white  ones  on  the  outer  half  of  the  fore  wings  (Fig. 
940).  This  skipper  is  found  throughout  the  greater  part  of  the 
United  States  east  of  the  Rocky  Mountains,  and  in  Canada. 

Among  the  smaller  members  of  this  subfamily  are  the  skippers 
of  the  genus  Pholisora.  The  most  widely  distributed  species  of  this 
genus  is  the  sooty-wing,  Pholisora  catullus.  The  expanse  of  the  wings 
is  a  little  more  than  25  mm.  The  wings  are  nearly  black,  marked 
with  minute  white  spots,  which  vary  in  size  and  number.  This  species 
is  found  throughout  the  United  States  and  southern  Canada. 

The  genus  Hesperia  includes  a  considerable  number  of  small 
skippers,  which  are  easily  recognized  by  their  checkered  markings  of 
white  upon  a  dark  brown  ground.  Small  white  spots  on  the  wings 
are  common  in  this  subfamily,  but  in  this  genus  the  white  spots  are 
unusually  large,  so  large  in  some  cases  that  they  occupy  the  greater 
part  of  the  wing.  One  of  the  more  common  species  is  the  variegated 
tessellate,  Hesperia  tesselldta.  This  is  distributed  from  the  Atlantic 
to  the  Pacific,  and  is  the  only  one  common  in  the  Eastern  United 
States.  In  this  species  more  than  one-half  of  the  outer  two-thirds  of 
both  fore  and  hind  wings  is  white. 

Subfamily  PAMPHILIN^ 

Skippers  with  a  Brand  and  their  Allies 

This  subfamily  includes  the  greater  number  of  our  smaller  skippers . 
Some  of  the  species,  however,  surpass  in  size  many  of  the  Hesperiinae. 
To  the  Pamphilinffi  belong  all  of  our  common  tawny  skippers,  as  well 
as  some  black  or  dark  brown  species.  The  antennae  usually  have  a 
stout  club,  with  a  short,  recurved  tip;  sometimes  this  tip  is  wanting. 


'38 


^.V  INTRODUCTION  TO  ENTOMOLOGY 


Fig. 943. — Atryone  con 
spicua. 


In  the  majority  of  our  species  the  males  can  be  recognized  at  a  glance 

by  a  conspicuous  patch  crossing  the  disk  of  the  fore  wings,  which 

usually  appears  to  the  naked  eye  like  a  scorched, 

^^  ^^      oblique  streak,  and  which  on  this  account  is 

^^V/^^B      termed  the  brand  (Fig.  943).     The  brand  is  a 

^^Sg^M^^^V      complicated  organ,  composed  of  tubular  scales, 

^^^BHHj^^^      the  androconia,  that  are  the  outlets  of  scent- 

^^BMM^^B         glands,  and  of  other  scales  of  various  shapes; 

tUt    w^B^         ^^^  some  species  the  brand  is  wanting.     In  this 

w  subfamily  vein  M2  of  the  fore  wings  arises  much 

nearer  to  vein  M3  than  to  Mi,  the  base  of  the 

vein  usually  curving  noticeably  toward  vein  M3 

(Fig.  944). 

This  subfamily  is  an  exceedingly  difficult  one  to  study.     One 
hundred  and  twenty-five  species  have  been  described  from  America 
north  of  Mexico ;  and  in  many  cases  the  differences  between  allied 
species  are  not  well  marked. 
The  following   two  are 

named  merely  as  examples.  K, 

The  first  one  is  easily  recog- 
nized . 

The  least  skipper,  Ancy- 
loxipha  niimitor . — This 
skipper  is  the  smallest  of 
our  common  species,  and  is 
also  remarkable  for  lacking 
the  recur\^ed  hook  at  the 
tip  of  the  antennas.  The 
wings  are  tawny,  broadly 
margined  with  dark  brown. 
In  some  specimens  the  fore 
wings  are  almost  entirely 
brown.  The  larger  indi- 
viduals expand  about  25 
mm.  The  lar^'a  feeds  upon 
grass  in  damp  places. 

The  black-dash,  Atry- 
tone  consplciia. — The  male 
of  this  species  is  represented 
by  Figure  943.  It  is  black- 
ish brown,  with  consider- 
able yellow  on  the  basal 
half  of  the  fore  wings.  The 
brandis  velvety  black.  This 
species  is  distributed  from 
Massachusetts  to  Nebraska.         Fig.  944.— Wings  of  Pamphila  sassacus- 


LEPIDOPTERA  739 

SUPERFAMILY  PAPILIONOIDEA 

The  Butterflies 

The  butterflies  differ  from  moths  in  that  they  have  clubbed  an- 
tennae, fly  only  in  the  daytime  (except  some  species  in  the  tropics), 
hold  the  wings  erect  above  the  back  when  at  rest,  and  have  no 
frenulimi.  Some  moths  present  one  or  more  of  these  characteristics, 
but  no  moth  presents  all  of  them.  Butterflies  can  be  distinguished 
from  skippers  by  the  venation  of  the  front  wings,  as  indicated  above 
in  the  characterization  of  the  Hesperioidea. 

Among  the  many  works  treating  of  American  butterflies  the  two 
following  are  especially  useful  for  the  classification  of  our  species, 
each  of  these  works  is  illustrated  by  many  full-page  plates  representing 
the  insects  in  their  natural  colors:  "How  to  Know  the  Butterflies,  A 
Manual  of  the  Butterflies  of  the  Eastern  United  States"  by  J.  H. 
and  A.  B.  Comstock  (04),  and  "The  Butterfly  Book,  A  Popular  Guide 
to  a  Knowledge  of  the  Butterflies  of  North  America"  by  W.  J. 
Holland  ('98). 

The  butterflies  found  in  America  north  of  Mexico  represent  five 
families.  Our  representatives  of  these  families  can  be  separated  by 
the  following  table. 

A.  Butterflies  in  which  the  cubitus  is  apparently  four-branched;  and  in  which 
the  anal  area  of  the  hind  wings  is  more  reduced  than  the  anal  area  of  the  fore 
wings,  as  in  the  fore  wings  there  are  always  two  anal  veins,  and  ususally  all 
three  are  at  least  partly  preserved,  while  in  the  hind  wings  there  is  only  a  single 

anal   vein.    p.    740 Papilioxid.^ 

AA.      Butterflies  in   which   the   cubitus  is   apparently   three-branched;  and  in 
which  the  anal  area  of  the  fore  wings  is  more  reduced  than  the  anal  area  of  the 
hind  wings,  the  former  having  a  single  anal  vein  and  the  latter  two. 
B.      Palpi   much   longer  than   the   thorax    (Subfamily   Libytheinae) .   p.    766 

Nymphalid^ 

BB.     Palpi  not  as  long  as  the  thorax. 

C.  With  only  four  well-developed  legs  in  both  sexes,  the  front  legs  being 
much  shorter  than  the  others,  and  folded  on  the  breast  like  a  tippet; 
radius  of  the  fore  wings  five-branched.  To  determine  the  number  of 
branches  of  radius,  count  the  two  cubital  and  the  three  medial  branches 
first,  the  branches  left  between  vein  Mi  and  the  Subcosta  belong  to  radius. 

p.  750 NVMPHALID/E 

CC.  With  six  well-developed  legs  in  the  females  and  with  the  fore  legs  of  the 
males  more  or  less  reduced,  only  slightly  reduced  except  in  the  metal- 
marks;  radius  of  the  fore  wings  (except  in  some  orange-tips,  p.  747)  only 
three  or  four  branched. 

D.    Vein  Mi  of  the  fore  wings  arising  at  or  near  the  apex  of  the  discal  cell 
(except  in   Feniseca,  p.   772) .... 
E.     Hind  wings  with  the  costa  thickened  out  to  the  humeral  angle 

(Fig.  978)  and  with  a  humeral  vein.  p.  767 Riodimd.« 

EE.    Costa  of  hind  wings  not  thickened  at  base;  humeral  vein  absent. 

p.  768 Lyc.^nid^ 

DD.    Vein  Mi  of  the  fore  wings  united  with   a  branch   of  radius  for  a 
considerable  distance  beyond   the   apex   of  the  discal  cell    (Fig.  952). 

p.    744 PlERID.'E 


740  AN  INTRODUCTION  TO  ENTOMOLOGY 

Family  PAPILIONID^ 

The  Swallow-tails  and  the  Parnassians 

This  family  includes  the  swallow-tail  butterflies,  which  are  common 

throughout  our  country, 
/?2  and  the  parnassians, 

[/e,  which  are  found  only  on 
high  mountains  or  far 
north.  These  insects  are 
distinguished  from  all 
other  butterflies  found  in 
our  fauna  by  the  fact  that 
vein  M2  of  the  fore  wings 
appears  to  be  a  branch 
of  cubitus,  making  this 
vein  appear  to  be  four- 
branched,  and  by  the 
fact  that  the  anal  area  of 
the  hind  wings  is  more 
reduced  than  the  anal 
area  of  the  fore  wings, 
the  former  containing 
only  a  single  anal 
vein,  the  latter  two  in 
the  parnassians  and  three 
in  the  swallow-tails. 

This  family  includes 
two  well-marked  sub- 
families, which  are  dis- 
tinguished as  follows. 

A.  The  outer  margins  of  the 
hind  wings  usually  with  one 
or  more  tail-like  prolonga- 
tions; ground  color  of 
wings  black  or  yellow;  the 
base  of  the  first  anal  vein 
preserved  as  a  spur-like 
branch  of  vein  Cu  (Fig. 
945);  radius  of  the  fore 
wings  five-branched,  p.  740 

Papilionin^ 

AA.  The  outer  margin  of  the  hind  wings  rounded,  without  a  tail-like  prolonga- 
tion; ground  color  of  wings  white;  radius  of  fore  wings  four-branched;  the 
first  anal  vein  wanting  (Fig.  951),  p.  744 Parnassin^ 


Fig.  945. — Wings  of  Papilio  polyxenes. 


Subfamily  PAPILIONIN^ 


The  Swallow-tails 

These  magnificent  butterflies  are  easily  recognized  by  their  large 
size  and  usually  by  their  tail-like  prolongations  of  the  hind  wings. 


LEPIDOPTERA 


741 


The  ground  color  of  the  wings  is  black,  which 
is  usually  marked  with  yellow,  and  often 
with  metallic  blue  or  green.  The  larva?  of 
the  swallow-tails  are  never  furnished  with 
spines,  but  are  either  naked  or  clothed  with 
a  few  fine  hairs.  In  a  single  species  that  is 
widely  distributed  in  the  United  States, 
Laertias  philenor  (Fig.  946)  and  in  the  genus 
Ithobalus,  which  is  represented  in  our  fauna 
only  in  the  extreme  South,  the  body  of  the 
larva  bears  fleshy  filaments.  An  osmeterium 
is  always  present;  this  is  bright  colored, 
forked,  and  is  thrust  out  from  the  upper  part 
of  the  prothorax  when  the  caterpillar  is  dis- 
turbed. It  diffuses  a  disagreeable  odor. 
See  page  loi. 

The  chrysalids  are  thickened  in  the 
middle  and  taper  considerably  at  each  end; 
they  are  more  or  less  angulated,  and  always 
have  two  prominent  projections  at  the  an- 
terior end.  They  are  suspended  by  the  tail 
and  by  a  loose  girth  around  the  middle  (Fig. 

947)- 

There  are  about  twenty  species  of  swal- 
low-tails in  America  north  of  Mexico.  The 
following  well-known  species  will  serve  as 
illustrations. 

The  black  swallow-tail,  PapUio  polyxenes. — The  larva  of  this 
swallow-tail  (Fig.  948)  is  well-known  to  most  country  children.  It  is 
the  green  worm,  ringed  with  black  and  spotted  with  yellow,  that  eats 
the  leaves  of  caraway  in  the  back  yards  of  country  houses.  It  feeds 
also  on  parsnips  and  other  umbelliferous  plants.  The  first  instar  of 
this  larva  is  black,  banded  about  the  middle  and  caudal  end  with 
white.    There  are  two  generations  an- 

,_j^ — z — ~^^~:Z:      nually  in  the  North  and  at  least  three 

in  the  South. 

In  the  adult  the  wings  are  black, 
crossed  with  two  rows  of  yellow  spots, 
and  with  marginal  lunules  of  the  same 
color.  The  two  rows  of  spots  are  much 
more  distinct  in  the  male  than  in  the  female,  the  inner  row  on  the 
hind  wing  forming  a  continuous  band  crossed  with  black  lines  on  the 
veins.  Between  the  two  rows  of  spots  on  the  hind  wings  there  are 
many  blue  scales;  these  are  more  abundant  in  the  female.  Near  the 
anal  angle  of  the  hind  wing  there  is  an  orange  spot  with  a  black  center. 
On  the  lower  surface  of  the  wings  the  yellow  markings  become 
mostly  orange  and  are  heavier. 

This    species    is   found   throughout    the    United   States  and    in 
the  southern  parts  of  Canada.     In  California  the  black   swallow- 


Fig.  946. — Lcertias  phile- 
nor, larva.  (From  Ri- 
ley.) 


Fig.  947. —  Chrysalis  of  Papilio. 


r42 


'.N  INTRODUCTION  TO  ENTOMOLOGY 


tail  is  replaced  as  a  celery  and  parsley  pest    by   a   related  species, 

Papilio  zolicaon. 

Th  e  tiger  swallow-tail , 
Papilio     glaucus. —  The 
larva   of    this    butterfly 
(Fig.  949)  is  even  more 
striking    in    appearance 
than  that  of  the  preced- 
ing species.     When  full- 
grown  it  is  dark  green, and 
bears  on  each  side  of  the 
third  thoracic  segment  a 
large   greenish -y  e  1 1  o  w 
spot,    edged  with  black, 
and  enclosing  a  small 
purple    spot    bordered 
with  black.  This  cater- 
pillar  has   the   curious 
habit  of  weaving  upon  a 
leaf  a  carpet  of  silk, upon 
which  it  rests  when  not 
feeding;     when    nearly 
full   grown,   instead   of 
spinning  a  simple  carpet 
as  before,  it    stretches 
web   across  the  hol- 
low of  a  leaf  and  thus 
makes     a     spring    bed 
upon    which    it    sleeps 
(Fig.  949). 

The  larva  of  this 
species  feeds  on  birch, 
poplar,  ash,  wild  cherry, 
fruit-trees,  and  many 
other  trees  and  shrubs. 
In  the  adult  state 
two  distinct  forms  of  this  insect  occur.  These 
differ  so  greatly  in  appearance  that  they  were 
long  considered  distinct  species.  They  may  be 
distinguished  as  follows. 

(i)  The  turnus  form,  Papilio  glaiicns  hirnus.- — The  wings  are 
bright  straw-yellow  above,  and  pale,  faded  straw-yellow  beneath,  with 
a  very  broad  black  outer  margin,  in  which  there  is  a  row  of  vellow 
spots.  On  the  fore  wings  there  are  four  black  bars,  extending  back 
from  the  costa;  the  inner  one  of  these  crosses  the  hind  wings  also. 
This  form  is  represented  by  both  sexes,  and  is  found  in  nearly  all 
parts  of  the  United  States  and  Canada. 

(2)  The  glaucus  form,  Papilio  glaucus  glaucus. — In  this  form  the 
disk  of  the  wings  is  entirely  black,  but  the  black  bands  of  the  turnus 


Fig.    948. — Papilio 
xenes,    larva. 


poly- 


Fig.  949. — Papilio 
glaucus,  larva  upon 
its  bed. 


LEPIDOPTERA 


743 


form  are  faintly  indicated,  especially  on  the  lower  surface,  by  a  darker 
shade.  The  marginal  row  of  yellow  spots  is  present,  and  also  the 
orange  spots  and  blue  scales  of  the  hind  wings.  This  form  is  repre- 
sented only  by  the  female  sex,  and  occurs  only  in  the  more  southern 
part  of  the  range  of  the  species,  i.  e.,  from  Delaware  to  Montana  and 
southward.  It  was  the  first  of  the  two  forms  to  be  described,  hence 
the  species  bears  the  name  glaticiis. 

The  zebra  swallow-tail,  Iphiclides  marcelhis. — This  butterfly  (Fig. 
950)  differs  from  all  other  swallow-tails  found  in  the  eastern  half  of 
the  United  States  in  having  the  wings  crossed  by  several  bands  of 
greenish  white.  This  is  one 
of  the  most  interesting  of 
our  butterflies,  as  it  occurs 
under  three  distinct  forms, 
two  of  which  were  con- 
sidered for  a  long  time  dis- 
tinct species.  Without  tak- 
ing into  account  the  more 
minute  differences  these 
forms  can  be  separated  as 
follows. 

(i)  The  early-spring 
form,  Iphiclides  marcelhis 
marcellus: — This  is  the  form 
figured  here.  It  expands 
from  65  to  70  mm. ;  and  the 
tails  of  the  hind  wings  are 
about  15  mm.  in  length  and 
tipped  with  white. 

(2)  The  late-spring  form,  Iphiclides  marcellus  telanwnides. — This 
form  is  a  little  larger  than  the  early  spring  form  and  has  tails  nearly 
one-third  longer;  these  tails  are  bordered  with  white  on  each  side  of 
the  distal  half  or  two-thirds  of  their  length. 

(3)  The  Slimmer  form,  Iphiclides  marcellus  lecontci. — The  stmi- 
mer  form  is  still  larger  expanding  from  80  to  87  mm.,  and  has  tails 
nearly  two  thirds  longer  than  the  early  spring  form. 

The  life  history  of  this  species  has  been  carefully  worked  out  by 
Mr.  W.  H.  Edwards.  He  has  shown  that  there  are  several  generations 
each  year,  and  that  the  winter  is  passed  in  the  chrysalis  state.  But 
the  early-spring  form  and  the  late-spring  form  are  not  successive 
broods;  these  are  both  composed  of  individuals  that  have  wintered 
as  chrysalids,  those  that  emerge  early  developing  into  marcellus 
marcellus,  and  those  that  emerge  later  developing  into  marcellus 
telamonides.  All  of  the  butterflies  produced  from  eggs  of  the  same 
season,  and  there  are  several  successive  broods,  are  of  the  summer 
form,  marcellus  lecontei. 

The  larva  feeds  upon  papaw  {Asimina).  This  insect  is  found 
throughout  the  eastern  half  of  the  United  States  except  in  the  ex- 
treme north. 


950. — Iphiclides    marcellus. 


744 


AN  INTRODUCTION  TO  ENTOMOLOGY 


This  species  was  formerly  supposed  to  be  the  Papilio  ajax  of 
Linnaeus,  and  the  specific  name  ajax  has  been  commonly  applied  to 
it  in  this  country. 

Subfamily  PARNAvSvSIN^ 


The  Parnassians 

The  Parnassians  are  butterflies  of  medium  size  in  which  the 
ground  color  of  the  wings  is  white  shaded  with  black,  and  marked 

with  round  red  or  yellow  spots 
i^j  margined  with  black. 

In  structure  the  pamassi- 
ans  are  closely  allied  to  the 
swallow-tails;  but  in  their 
general  appearance  they  show 
little  resemblance  to  them, 
differing  in  the  ground  color 
of  the  wings,  and  in  lacking 
the  tail-like  prolongation  of 
the  hind  wings  in  all  of  our 
species. 

In  the  venation  of  the 
wings  (Fig.  951)  they  differ 
from  the  swallow-tails  in  that 
radius  of  the  fore  wings  is  only 
four-branched  and  the  first 
anal  vein  is  wanting.  They 
agree  with  the  swallow-tails 
and  differ  from  all  other  butter- 
flies in  that  the  cubitus  of  the 
fore  wings  is  apparently  four- 

^.  „-.         ,  „  .  branched. 

Fie.  QSi. — Wmgs  of  Farnassiiis.  ^r'^     ^  j.      ■ 

^   ^^  ^  The  larvffi  possess  osmeteria 

similar  to  those  of  the  larvae  of  swallow-tails.     When  about  to  pupate 

the  larva  either  draws  a  leaf  or  leaves  about  its  body  by  a  few  threads 

or  it  merely  hides  under  some  object  on  the  ground.     The  pupa  is 

cylindrical  and  rounded,  not  angulate  like  those  of  swallow-tails. 

Only  four  species  have  been  found  in  North  America;  they  all 

belong  to  the  genus  Parnassius.    Of  the  four  species,  two  are  Alaskan ; 

the  others  occur  in  the  mountains  of  the  Pacific  States,  in  Wyoming, 

and  in  the  Rocky  Mountains.     Of  each  of  the  two  latter  there  are 

several  named  varieties. 


Family  PIERID^ 

The  Pierids 

These  butterflies  are  usually  of  medium  size,  but  some  of  them 
are  small;  they  are  nearly  always  white,  yellow,  or  orange,  and  are 


LEPIDOPTERA 


74! 


usually  marked  with 
black.  They  are  the 
most  abundant  of  all 
our  butterflies,  being 
common  everywhere 
in  fields  and  roads. 
Some  species  are  so 
abundant  as  to  be  seri- 
ous pests,  the  larvae 
feeding  on  cultivated 
plants. 

The  characteristic 
features  of  the  vena- 
tion of  the  wings  are 
the  following  (Fig. 
952) :  Vein  M2  of  the 
fore  wings  is  more 
closely  connected  with 
radius  than  with  cu- 
bitus, the  latter  ap- 
pearing to  be  three- 
branched;  vein  Ml  of 
the  fore  wings  coalesces 
with  radius  for  a  con- 
siderable   distance    in 

all  of  our  species ;  and  only  three  or  four  of  the  branches  remain  dis- 
tinct except  in  some  orange-tips. 

In  this  family  the  fore  legs  are  well  developed  in  both  sexes,  there 
being  no  tendency  to  their  reduction  in  size,  as  in  the  three  following 
families. 

The  larvae  are  usually  slender  green  worms  clothed  with  short, 
fine  hairs;  the  well-known  cabbage-worms  are  typical  illustrations 
(Fig-  953)-  The  chrysalids  are  supported  by  the  tail  and  by  a  girth 
aroimd  the  middle.  They  may  be  distinguished  at  a  glance  by  the 
presence  of  a  single  pointed  projection  in  front  (Fig.  953). 

Our  genera  of  this  family  can  be  separated  into  three  groups,  which 
seem  hardly  distinct  enough  to  be  ranked  as  subfamilies.  These  are 
the  whites,  the  yellows  and  the  orange  tips. 


Fig.  952. — Wings  of  Pieris  protodice. 


I.    THE  WHITES 


The  more  common  representatives  of  this  group  are  the  well- 
known  cabbage-butterflies.  They  are  white  butterflies  more  or  less 
marked  with  black.  Occasionally  the  white  is  tinged  with  yellow; 
and  sometimes  yellow  varieties  of  our  white  species  occur.  About  a 
dozen  North  American  species  of  this  group  are  known. 


746 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  cabbage-butterfly,  Pleris  rapes.— The  wings  of  this  butterfly 
are  dull  white  above,  occasionally  tinged  with  yellowish,  especially 


Fig.  953. — Pieris  rapct,  larva  and  pupa. 


in  the  female;  below,  the  apex  of  the  fore  wings,  and  the  entire  sur- 
face of  the  hind  wings  are  pale 
lemon  yellow.  In  the  female  there 
are  two  spots  on  the  outer  part 
of  the  fore  wing  besides  the  black 
tip,  in  the  male  only  one  (Fig. 
954)- 

There  is  considerable  varia- 
tion in  the  intensity  of  the  black 
markings,  and  in  the  extent  of 
the   yellow   tinge   of  the  wings. 

The  larva  of  this  species  (Fig. 
053)  feeds  principally  on  cabbage, 
but  it  also  attacks  many  other 
cruciferous  plants.  Its  color  is  the  green  of  the  cabbage-leaf,  with  a 
narrow,  greenish,  lemon-yellow  dorsal  band,  and  a  narrow,  interrupted 
stigmatal  band  of  the  same  color.  The  body  is  clothed  with  very  fine 
short  hairs. 

P'teris  rapes  is  without  doubt  the  most  injurious  to  agriculture  of 
all  our  species  of  butterflies.  It  is  an  introduced  species,  but  has 
spread  over  the  greater  part  of  this  country.  As  it  is  three-brooded 
in  the  North  and  more  in  the  South,  it  is  present  nearly  the  entire 
season,  so  that  it  needs  to  be  fought  constantly.  The  larvs  can  be 
easily  killed  by  spraying  the  plants  with  Paris  green,  one  pound  in 


Fig.  954. — Pieris  rape 


LEPIDOPTERA  747 

fifty  gallons  of  water.  Chemical  analysis  of  sprayed  plants  has  shown 
that  there  is  practically  no  danger  from  eating  cabbages  that  have 
been  treated  in  this  way. 

The  gray-veined  white,  Pleris  ndpi. — In  the  most  common  form 
the  wings  are  white  above  and  below,  with  a  scarcely  perceptible  tinge 
of  greenish  yellow.  Sometimes  there  is  a  dark  spot  in  cell  M3  of  the 
fore  wings,  but  usuallv  the  wings  are  immaculate.  The  base  of  the 
wings,  however,  and  the  basal  half  of  the  costal  margin  of  the  front 
wings,  are  powdered  more  of  less  with  dark  scales,  and  the  veins  of 
the  wings,  especially  on  the  lower  side  are  grayish.  The  wing-expanse 
is  from  42  to  50  mm. 

This  species  occurs  throughout  Canada  and  the  more  northern 
portions  of  the  United  States.  It  appears  in  many  different  forms ; 
eleven  named  forms  arenow^  recognized  in  the  United  States,  and  still 
other  forms  are  known  in  Europe.  This  polymorphism  is  partly 
seasonal  and  partly  geographical. 

The  checkered  white,  Pleris  protodice. — The  two  sexes  of  this 
species  differ  greatly  in  appearance,  the  female  being  much  more 
darkly  marked  than  the  male.  The  wings  are  white,  marked  above 
with  grayish  brown.  There  is  a  bar  of  this  color  at  the  end  of  the 
discal  ceil;  beyond  this  there  is  in  the  male  a  row  of  three  more  or 
less  distinct  spots,  and.  in  the  female  an  almost  continuous  band  of 
spots.  Besides  these  there  is  in  the  female  a  row  of  triangular  spots 
on  the  outer  margin  of  both  fore  and  hind  wings,  and  on  the  hind  wings 
a  submarginal  zigzag  bar. 

The  larva  of  this  species  is  colored  with  alternating  stripes  of 
bright  golden  yellow  and  dark  greenish  purple,  upon  which  are  nu- 
merous black  spots.  It  feeds  upon  cabbage  and  other  cruciferous  plants, 
and  occurs  in  nearly  the  whole  of  the  United  States.  Both  this  and 
the  preceding  species  seem  to  become  greatly  lessened  in  numbers  by 
the  increase  of  the  imported  Pieris  rapcB. 


II.    THE  ORANGE-TIPS 

These,  like  the  butterflies  comprising  the  i^receding  group,  are 
white,  marked  with  black.  Their  most 
characteristic  feature  is  the  presence 
on  the  lower  surface  of  the  hind  wings 
of  a  greenish  network,  or  a  marbled 
screen  mottling.  This  usually  shows 
through  the  wing  so  as  to  appear  as  a 
dark  shade  when  the  wings  are  seen 
from  above  (Fig.  955).  Many  species 
have  a  conspicuous  orange  spot  on  the 
apical  portion  of  the  front  wings.  This 
has  suggested  the  common  name  orange-  Fig.  g^s.—Synchloe  olympia. 
tips  for  the  group.  But  it  should  be 
remembered  that  some  species  lack  this  mark,  and  that  in  some  others 


748  AN  INTRODUCTION  TO  ENTOMOLOGY 

it  is  confined  to  the  males.  Nearly  all  of  our  species  are  confined  to 
the  Far  West.    The  two  following  occur  in  the  East. 

The  falcate  orange-tip,  Anthdcharis  genutia. — In  this  species  the 
apex  of  the  fore  wings  is  hooked,  reminding  one  of  the  hook-tip  moths. 
In  the  males  there  is  a  large  apical  patch.  This  butterfly  is  found 
throughout  the  southeastern  part  of  the  United  States,  not  including 
Florida.  It  occurs  as  far  north  as  New  Haven,  Conn.  It  is  nowhere 
abundant.  The  larva  feeds  on  rock-cress,  bitter  cress,  shepherd's 
purse.  Sisymbrium,  and  other  Cruciferae  that  are  slender  in  form. 

The  olympia  orange-tip,  Synchloe  olympia.- — In  this  species  the 
orange  patch  is  wanting  in  both  sexes.  There  is  a  conspicuous  black 
bar  at  the  end  of  the  discal  cell  of  the  fore  wings,  and  the  apical 
portion  of  these  wings  is  gray  including  a  large  irregular  white  band 

(Fig-  955)- 

The  larva  is  striped  lengthwise  with  pale  slate  color  and  bright 
yellow;  the  feet,  legs,  and  head  are  grayish  green.  It  feeds  on 
hedge-mustard  and  other  Cruciferae. 

III.    THE  YELLOWS 

The  yellows  are  easily  recognized  by  their  bright  yellow  colors, 
although  in  some  species  whitish  forms  occur.  They  abound  almost 
everywhere  in  open  fields,  and  are  common  about  wet  places  in  roads. 
To  this  group  belong  the  larger  number  of  our  pierids. 

The  roadside  butterfly  or  the  clouded  sulphur,  Eurymus  philodice. 
— The  wings  above  are  rather  pale  greenish  yellow,  with  the  outer 
borders  blackish  brown.  Figure  956 
represents  the  male;  in  the  female 
the  border  on  the  fore  wings  is 
broader,  and  contains  a  sub-margin- 
al row  of  yellow  spots.  The  discal 
dot  of  the  fore  wings  is  black,  that  of 
the  hind  wings  is  orange.  The  under 
surface  is  sulphur-yellow. 

This  species  is  dimorphic.     The 
second  form  is  represented  only  by 
the  female  sex,  and  differs  in  having 
the  ground-color  of  the  wings  white        Fig-   95^.--Eurymus   philodice. 
instead  of  yellow. 

This  butterfly  often  occurs  in  large  nimibers  in  muddy  places  in 
country  roads,  for  this  reason  it  may  be  known  as  the  roadside 
butterfly.  It  is  also  known  as  the  clouded  sylphur.  Its  range  extends 
from  the  mouth  of  the  St.  Lawrence  to  South  Carolina  and  west- 
ward to  the  Rocky  Mountains.  Its  larva  feeds  upon  clover  and 
other  Leguminosffi. 

The  orange  sulphur,  Eurymus  eurytheme.- — This  species  closely  re- 
sembles the  preceding  one  in  size,  shape  and  markings.  The  typical 
form  differs  from  E.  philodice  in  being  of  an  orange  color  above  instead 
of  yellow.  This  butterfly  is  found  chiefly  in  the  Mississippi  Valley 
and  west  to  the  Pacific  Ocean;  it  is  also  found  in  the  Southwestern 


LEPIDOPTERA  749 

States,  and  occurs  ven^  rarely  north  to  Maine.  It  is  one  of  the  most 
polymorphic  of  all  butterflies;  the  forms  difi'er  so  much  in  appearance 
that  four  or  five  of  them  have  been  described  as  distinct  species.  The 
larva  feeds  on  clover  and  allied  plants,  and  is  sometimes  a  pest  in 
alfalfa  fields. 

The  dog'shead,  Zereneccosdnia. — The  wings  are  lemon-yellow  above 
bordered  on  the  outer  margin  with  black.  On  the  hind  wings  the 
border  is  narrow,  but  on  the  fore  wings  it  is  broad.  The  outline  of  the 
yellow  of  the  fore  wings  suggests  a  head  of  a  dog  or  of  a  duck,  a 
prominent  black  spot  on  the  discal  vein  serving  as  the  eye.  This  is 
an  abundant  species  in  the  Southeastern  and  Southwestern  States, 
extending  from  the  Atlantic  to  the  Pacific.    The  larva  feeds  on  clover. 

The  sleepy  yellow,  Eurema  nictppe. — The  wings  above  are  bright 
orange,  marked  with  blackish  brown  as  follows:  on  the  fore  wings  a 
narrow  bar  at  the  apex  of  the  discal  cell,  the  apical  portion  of  the 
wings,  and  the  outer  margin;  on  the  hind  wings,  the  outer  margin. 
In  the  female  the  outer  marginal  band  is  interrupted  at  the  anal 
angle  of  each  wing,  and  on  the  hind  wings  it  may  be  reduced  to  an 
apical  patch.    The  expanse  of  the  wings  is  from  40  to  47  mm. 

The  common  name,  sleepy  yellow,  was  suggested  by  the  fact  that 
the  black  spot  near  the  middle  of  each  fore  wing  is  reduced  to  a 
narrow  transverse  line,  which  looks  like  an  eye  almost  closed.  This 
species  occurs  from  southern  New  England  to  Florida  and  west  to 
Lower  California.    The  lar^^a  feeds  on  several  species  of  Cassia. 

The  little  sulphur,  Eurema  euterpe. — Although  this  species  is 
larger  than  the  following  one  it  is  considerable  below  the  average  size 
of  our  yellows,  the  larger  individuals  expanding  less  than  37  mm. 
The  wings  are  canary-yellow  above,  with  the  apex  of  the  fore  wings 
and  the  outer  margin  of  both  fore  and  hind  wings  blackish  brown. 
The  border  of  the  hind  wings  is  narrow  and  sometimes  wanting. 
There  is  a  red-brown  splash  on,  the  apex  of  the  hind  wings  below. 

The  distribution  of  this  species  is  similar  to  that  of  the  preceding 
one.    The  larva  feeds  on  Cassia. 

The  dainty  sulphur,  Nathdlis  tale.- — This  little  butterfly  can  be 
distinguished  from  all  others  described  here  by  its  small  size,  as  it 
expands  only  from  less  than  25  mm.  to  30  mm.  It  is  of  a  pale  canary- 
3-ellow  color,  with  dark  brown  markings.  There  is  a  large  apical 
patch  on  the  fore  wings,  and  a  broad  band  parallel  with  the  inner 
margin;  on  the  hind  wings  there  is  a  stripe  on  the  basal  two-thirds  of 
the  costa,  and  spots  on  the  ends  of  the  veins;  these  are  more  or  less 
connected  on  the  margin  of  the  wing,  especially  in  the  female. 

This  species  also  is  found  from  Southern  New  England  to  Florida 
and  west  to  Lower  California.     It,  too,  feeds  on  Cassia. 

The  cloudless  sulphur,  CatopsUia  eubUle. — This  large  butterfly 
differs  greatly  in  appearance  from  those  described  above.  It  expands 
62  mm.  The  wings  above  are  of  uniform  bright  canary-yellow.  In 
the  male  they  are  without  spots,  except  frequently  an  inconspicuous 
brown  dot  at  the  tip  of  each  vein,  and  a  lilac-brown  edging  of  the 
costal  border.  In  the  female  there  is  a  discal  dot  on  the  fore  wings 
and  a  marginal  row  of  brown  spots  at  the  ends  of  the  veins. 


750  AN  INTRODUCTION  TO  ENTOMOLOGY 

This  is  a  southern  species  which  occasionally  extends  as  far  north 
on  the  coast  as  New  York  City,  and  in  the  Mississippi  Valley  as  far 
as  Southern  Wisconsin.    The  larva  feeds  on  Cassia. 

Family  NYMPHALID^ 
The  Four-footed  Butterflies 

The  famih'  Nymphalidae,  includes  chiefly  butterflies  of  medium  or 
large  size,  but  a  few  of  the  species  are  small.  With  a  single  exception, 
Hypatus,  these  butterflies  differ  from  all  others  in  our  fauna  in  having 
the  fore  legs  very  greatly  reduced  in  size  in  both  sexes.  So  great  is  the 
reduction  that  these  legs  cannot  be  used  for  walking,  but  are  folded 
on  the  breast  like  a  tippet.  Dr.  W.  T.  M.  Forbes  has  observed  mem- 
bers of  this  family  use  their  reduced  fore  legs  for  cleaning  their  an- 
tennae, and  in  case  of  Basilarckia  to  make  a  sound. 

A  more  or  less  reduction  in  the  size  of  the  fore  legs  occurs  in  the 
Lycffinidas  and  Riodinidae,  but  there  it  occurs  only  in  the  males,  and 
to  a  much  less  degree  than  in  this  family.  The  N>Tnphalidae  differ 
from  these  two  families  in  retaining  all  of  the  branches  of  radius  of 
the  fore  wings,  this  vein  being  five-branched,  except  in  the  genus 
Ancea. 

This  is  the  largest  of  the  families  of  butterflies.  It  not  only  sur- 
passes the  other  families  in  nimiberof  species,  but  it  contains  a  greater 
number  and  variety  of  striking  forms,  and  also  a  larger  proportion  of 
the  species  of  butterflies  familiar  to  every  observer  of  insects.  There 
may  be  in  any  locality  one  or  two  species  of  yellows  or  of  whites  more 
abundant,  but  the  larger  number  of  species  commonly  observed  are 
four-footed  butterflies. 

Five  subfamilies  of  the  Nymphalidas  are  represented  in  our  fauna. 
These  can  be  separated  by  the  following  table.  Each  of  these  sub- 
families is  regarded  as  a  distinct  family  by  some  writers. 

A.     Palpi  much  longer  than  the  thorax,  p.   766 Libythein^ 

AA.    Palpi  not  as  long  as  the  thorax. 

B.    Vein  3d  A  of  the  fore  wings  preserved;  antennae  apparently  naked,  p.  765. 

■ Danain.-e 

BB.    Vein  3d  A  of  the  fore  wings  wanting;  antennas  abundantly  clothed  with 
scales,  at  least  above. 
C.    Discal  cell  of  the  hind  wings  closed  by  a  well-preserved  vein. 

D.     With  some  of  the  veins  of  the  fore  wings  greatly  swollen  at  the  base 

(Fig.     972).     p.      761  ... S.\TYRIN^ 

DD.    With  none  of  the  veins  of  the  fore  wings  unusually  swollen  at  base. 

P-  764 Helicoxin/E 

CC.    Discal  cell  of  the  hind  wings  either  open  or  closed  by  a  mere  vestige  of  a 
vein.    p.    750 Nymph.a.lin^ 

Subfamily  NYMPHALIN^ 

The  Nymphs 

The  nymphs  •  can  be  distinguished  from  the  other  four-footed 
butterflies  as  follows:  the  palpi  are  not  longer  than  the  thorax  as  in 


LEPIDOPTERA 


751 


the  long;-beaks;  the  veins  of  the  fore  wing;s  are  not  greatly  swollen 
at  the  base  as  in  the  meadow-browns,  except  in  the  genera  Mestra 
and  Eunica,  which  are  found  only  in  the  extreme  South ;  the  discal 
cell  of  the  hind  wings  is  not  closed  as.  in  the  heliconians;  and  the 
antennae  do  not  appear  to  be  naked  as  in  the  milkweed  butterflies. 

The  larva?  are  nearlv  or  quite  cylindrical,  and  are  clothed  to  a 
greater  or  less  extent  with  hairs  and  sometimes  with  branching  s]3ines. 

The  chyrsalids  are  usually  angular,  and  often  bear  large  projecting 
prominences;  sometimes  they  are  rounded.  They  always  hang  head 
downwards,  supported  only  by  the  tail  which  is  "fastened  to  a  button 
of  silk. 

Our  genera  of  nymphs  represent  six  quite  distinct  groups,  as 
follows. 

I.    THE  FRITILLARIES 


The  fritillaries  are  butterflies  varying  from  a  little  below  to  some- 
what above  medium  size.  The  color  of  the  wings  is  fulvous,  bordered 
and  checkered  with  black,  but  not  so  heavily  bordered  as  in  the  next 
subfamily.  The  lower  surface  of  the  wings  is  often  marked  with  curv- 
ing rows  of  silvery  spots.  The  common  name  fritillary  is  from  the 
Latin  fritillus,  a  dice  box,  and  was  suggested  by  the  spotted  coloration 
of  these  butterflies. 

In  the  larvffi  there  is  an  even  number  of  rows  of  spines  on  the 
abdomen,  due  to  the  fact  that  there  are  none  on  the  middle  of  the 
back.    The  larvae  feed  upon  the  leaves  of  violets. 

There  are  many  species  of  fritillaries.  about  fifty  occur  in  America 
north  of  Mexico,  and  it  is  difficult  to  separate  the  closely  allied  species. 

The  great  spangled  fritillary,  Argymiis  cyhele.- — This  species  (Fig. 
957)  will  serve  to  illustrate  the  appearance  of  the  larger  members  of 
this  group,  those  belonging  to  the  genus  Argymiis.     In  this  genus 
vein    R2    of   the    fore 
wings  arises  before  the 
apex  of  the  discal  cell. 

There  are  a  num- 
ber of  common  fritil- 
laries which  resemble 
the  preceding  in  color 
and  markings  but 
which  are  much  small- 
er, the  wings  expand- 
ing considerable  less 
than  50  mm.  These 
belong  to  the  genus 
Brenthis.  In  this  gen- 
us vein  R2  of  the  fore 
wings  arises  beyond 
the  apex  of  the  discal  cell. 

The  variegated  fritillary,  Euptoieta  clandia 


Fig.  957. — Argynnis  cyhele. 


-This  butterflv agrees 


752  AN  INTRODUCTION  TO  ENTOMOLOGY 

with  the  smaller  fritjllaries  (Erenthis)  in  the  origin  of  vein  R2  of  the 

fore  wing  bevond  the  apex  of 
the  discal  cell,  but  differs  from 
them  in  the  shape  of  the  fore 
wing,  the  apex  of  which  is 
much  more  produced  (Fig. 
958)  and  the  outer  margin, 
except  at  the  apex,  concave; 
it  is  also  considerably  larger. 
This  species  occurs  through- 
out the  United  States  east  of 
Fig.  95%.~Eiiptoieta  claudia.  ^he  Rocky  Mountains;  but  is 

very  rare  m  the  northern  half 

of  this  region.    The  larva  feeds  on  the  passion-flowers. 

II.    THE  CRESCENT-SPOTS 

This  group  includes  some  of  the  smaller  members  of  the  Nymph- 
alidae.  The  color  of  the  wings  is  sometimes  black,  with  red  and  yellow 
spots;  but  it  is  usually  fulvous,  with  the  fore  wings  broadly  margined, 
especially  at  the  apex,  with  black,  and  crossed  by  many  irregular  lines 
of  black. 

In  the  larva  there  is  an  odd  number  of  rows  of  spines  on  the 
abdomen,  due  to  the  presence  of  spines  on  the  middle  of  the  back  of 
some  of  the  abdominal  segments. 

Sixty-three  species  of  crescent-spots  have  been  described  from 
America  north  of  Mexico;  but  nearly  all  of  these  are  restricted  to 
the  Far  West. 

The  Baltimore,  Euphydryas  phaeton. — The  wings  are  black  above, 
with  an  outer  marginal  row  of  dark  reddish-orange  spots,  and  two 
parallel  rows  of  very  pale  yellow  spots;  on  the  fore  wings  a  third  row 
is  more  or  less  represented.     The  wings  expand  50  mm.  or  more. 

The  larvae  feed  on  a  species  of  snakehead,  Chelone  glabra;  they 
are  gregarious  in  the  fall  and  build  a  common  nest  in  w^hich  they  pass 
the  winter;  but  separate  after  hibernation.  They  are  very  striking 
in  appearance.  The  head  and  first  two  thoracic  segments  are  shining 
black  and  the  last  three  abdominal  segments  are  black  with  two 
orange  bands  around  each.  All  the  other  segments  have  a  ground 
color  of  orange  with  various  narrow  trans- 
verse lines  of  black.  This  species  occurs  in 
Ontario  and  the  northern  half  of  the 
United  States  east  of  the  Rocky  Moun- 
tains. It  is  very  local,  the  butterflies  re- 
maining near  the  bogs  or  moist  meadows 
where  the  food-plant  of  the  larva  is  found. 

The  butterflies  of  the  genus  Phycwdes  pig.  959--/^/nrzWf.  nycteis. 
and  the  allied  genera  abound  throughout 

our  country.    They  are  of  small  size,  and  of  a  fulvous  color,  heavily 
marked  with  black.    Each  species  varies  considerably  in  markings,  and 


Fig.  960. —  I,  Lyccena  argiolus;  2,  Polygonia 
faunis;  3,  Polygonia  comma.  4,  Incisalia 
niphon;  5,  Euvanessa  antiopa;  6,  Miloura 
damon;  7,  Lyccena  argiolus,  8,  Polygonia 
interrogationis. 


754 


■'-  AN  INTRODUCTION  TO  ENTOMOLOGY 


different  species  resemble  each  other  close!}-,  making  this  a  difficult 
group  for  the  beginning  student.  Figure  959  represents  a  common 
species. 

The  larvae  feed  on  asters  and  other  Composites. 

III.    THE  ANGLE-WINGS 


To  this  group  belong  many  of  our  best-known  butterflies;  there 
are  twenty-five  species  in  our  fauna.  With  these  the  outer  margin 
of  the  fore  wings  is  usually  decidedly  angular  or  notched  as  if  a  part 
had  been  cut  away.  A  large  proportion  of  the  species  hibernate  in 
the  adult  state,  and  seme  of  them  are  the  first  butterflies  to  appear 
in  the  spring.  Seme  of  the  hibernating  species,  however,  remain  in 
concealment  till  quite  late  in  the  season. 

The  red  admiral,  Vanessa  atalanta.- — The  wings  are  purplish  black 
above.  On  the  fore  wing  there  is  a  bright  orange-colored  band  begin- 
ning near  the  middle  of  the  costa,  and  extending  nearly  to  the  inner 
angle;  between  this  and  the  apex  of  the  wing  are  several  white  spots 

as  shown  in  Figure  961 ;  on 
the  hind  wing  there  is  an 
orange  band  on  the  outer 
margin  inclosing  a  row  of 
black  spots. 

The  larva  feeds  chiefly 
on  elm,  nettle,  and  hop. 
When  first  hatched  it  folds 
together  a  half-opened  leaf 
at  the  siimmit  of  the  plant ; 
when  larger  it  makes  its  nest 
of  a  lower  expanded  leaf. 
There  are  two  broods ;  both 
butterflies  and  chrysalids 
hibernate.  This  butterfly"  occurs  over  nearly  the  whole  of  the  European 
and  North  American  continents. 

The  painted  beaut \,  I'a- 
nessa  virginiensis. — Figure  962 
represents  the  upper  side  of 
this  butterfly.  The  darker 
parts  of  the  wings  are  very 
dark  brownish  black,  the  light- 
er parts  a  golden  orange,  some- 
times with  a  pinkish  tinge. 
In  the  apical  portion  of  the 
fore  wings  there  are  several 
white  spots  as  shown  in  the 
figure;     the    largest    of    these,  pig.  gb2.--Vanessa  virginiensis 

the  proximal  one,  is  salmon  or 

flesh-colored  in  the  female.     A  characteristic  feature  of  this  species 
is  the  presence  of  two  submarginal  e}'e-like  spots  on  the  lower  side 


Fig.  961. —  Vanessa  atalanta. 


LEPIDOPTERA 


of  the  hind  \vin<rs.  The  larva  feeds  on  everlasting^  {Antennaria)  and 
allied  plants.  This  species  occurs  in  Ontario  and  nearly  the  whole 
of  the  United  States,  also  in  South  America  and  the  Canary  Islands. 
The  painted  beauty  has  been  commonly  known  in  this  country  as 
Vanessa  htintera;  but  Vanessa  virginiensis  is  the  older  name. 

The  cosmoplite,  Vanessa  cdrdui. — The  Butterfly  resembles  the 
preceding  very  closely  in  color  and  markings.  There  is  however,  a 
smaller  proportion  of  orange  markings;  and  on  the  lower  surface  of 
the  hind  wings  there  is  a  submarginal  row  oifour  or  five  eye-like  spots. 
The  larva  feeds  upon  Ccmpositae,  especially  thistles.  This  species 
is  very  remarkable  for  its  wide  distribution.  Mr.  Scudder  states 
"with  the  exception  of  the  arctic  regions  and  South  America  it  is 
distributed  over  the  entire  extent  of  every  continent." 

The  American  tortoise-shell,  Aglais  milberti. — The  wingsaboveare 
brownish  black,  with  a  broad  orange-fulvous  band  between  the  middle 
and  the  outer  margin.  There  are 
two  fulvous  spots  in  the  discal 
cell  of  the  front  wings  (Fig.  963). 
The  larvce  feed  on  nettle  (Uriica) 
and  are  gregarious  in  habits. 
This  species  occurs  in  the  north- 
ern portions  of  the  United  States 
and  in  Canada. 

The  mourning-cloak,  Euva- 
nessa  antlopa. — The  wings  above 
are  purplish  brown,  with  a  broad 
yellow  border  on  the  outer  mar- 
gin sprinkled  with  brown,  and  a  submarginal  row  of  blue  spots.  The 
upper  surface  is  represented  by  Figure  964,  the  lower  by  Figure  960,  5. 

__  The   larvce 

live  on  willow, 
elm,  poplar  and 
Celtis;  they  are 
gregarious,  and 
often  strip  large 
branches  of  their 
leaves.  The  spe- 
cies is  usually 
two-brooded . 
"This  butterfly 
is  apparently  dis- 
tributed over  the 
entire  breadth  of 
the  Northern 
Hemisphere  be- 
¥{g.()6j^.—Euvaness(iantinpa.  low     the     Arctic 

Circle  as  far  as 
the  thirtieth  parallel  of  latitude."  (Scudder). 


lais   milberti. 


756  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  Compton  tortoise,  Eugonia  j-dlbum. — This  butterfly  (Fig. 
965)  resembles  in  its  general  appearance  those  of  the  genus Polygonia, 

but  it  is  sharply  distin- 
guished from  them  by  the 
inner  margin  of  the  fore 
wings  being  nearly 
straight,  by  the  heavier 
markings  of  the  fore 
wings,  and  by  the  pres- 
ence of  a  whitish  spot  on 
both  fore  and  hind  wings, 
near  the  apex,  and  be- 
tween two  larger  black 
patches.  On  the  lower 
surface  of  the  hind  wings 
there  is  a  small  L-shaped 
Fig.  965. — Eugonia  j-albh„i.  silvery  bar.    This  species- 

occurs  throughout  Cana- 
da and  the  northern  portion  of  the  United  States  east  of  the  Rocky 
Mountains.    It  is  double-brooded. 

Polygonia. — The  butterflies  of  this  genus  resemble  the  preceding 
species  in  having  a  metallic  spot  on  the  lower  surface  of  the  hind 
wings,  but  differ  in  having  the  inner  margin  of  the  fore  wings  roundly 
notched  beyond  the  middle. 

Ten  species  occur  in  this  country.  These  differ  principally  in  the 
coloring  and  markings  of  the  under  surface  of  the  hind  wings.  The 
following  are  some  of  the  more  common  ones. 

The  green  comma,  Polygonia  faunus: — The  silvery  mark  of  the 
hind  wings  is  usually  in  the  form  of  a  C  or  a  G,  the  ends  being  more 
or  less  expanded  (Fig.  960,  2 )  but  sometimes  it  is  reduced  to  the  form  of 
an  L.  The  lower  surface  of  the  wings  is  more  greatly  variegated  than 
in  any  other  species  of  this  genus;  and  there  is  a  larger  amount  of 
green  on  this  surface  than  in  any  other  of  the  eastern  species,  there 
being  two  nearly  complete  rows  of  green  spots  on  the  outer  third 
of  each  wing. 

The  larva  feeds  upon  black  birch,  willow,  currant,  and  wild  goose- 
berry. This  is  a  Canadian  species;  but  it  is  also  found  in  the  Moun- 
tains of  New  England  and  of  New  York,  and  in  the  northern  portions 
of  the  Western  States,  extending  as  far  south  as  Iowa.  It  is  single- 
brooded. 

The  hop-merchant,  Polygonia  comma. — As  in  the  preceding  species, 
the  silvery  mark  of  the  hind  wings  is  in  the  form  of  a  C  or  a  G  (Fig. 
960,  3)  but  the  general  color  of  the  lower  surface  of  the  hind  wings  is 
very  different,  being  marbled  with  light  and  dark  brown;  and  the 
green  spots  so  characteristic  oi  faunus  are  represented  here  by  a  few 
lilaceous  scales  on  a  submarginal  row  of  black  spots. 

Two  forms  of  this  species  occur.  In  one,  P.  comma  dryas,  the  hind 
wings  above  are  suffused  with  black  on  the  outer  half,  so  that  the 
submarginal  row  of  fulvous  spots  is  obsured,  and  on  the  lower  side  the 


LEPIDOPTERA  'J^'J 

wings  are  more  vellowish  than  in  the  other  form.     The  latter  is  the 
typical  form  of  P.  comma  comma. 

The  larva  feeds  upon  hop,  elm,  nettle,  and  false-nettle.  It  is 
often  abundant  in  hop-yards,  and  the  chrA^salids  are  commonly  known 
as  hop-merchants,  from  a  saying  that  the  golden  or  silvery  color  of 
the  metallic  spots  on  the  back  of  the  chrysalis  indicates  whether  the 
price  of  hops  is  to  be  high  or  low.  This  species  is  found  in  Canada  and 
the  northern  part  of  the  eastern  half  of  the  United  States;  its  range 
extends  south  to  North  Carolina,  Tennessee,  Arkansas  and  Indian 
Territory.  It  is  double-brooded  in  the  North,  and  at  least  three- 
brooded  in  the  South. 

.  The  grav  comma,  Polygdnia  progne. — In  its  general  appearance 
this  butterfly  closely  resembles  P.  .comma,  but  it  can  be  readily  dis- 
tinguished by  the  form  of  the  silvery  mark,  which  is  L-shaped  and 
tapers  towards  the  ends.  It  is  much  grayer  below  with  a  finer  striate 
pattern  in  the  male. 

The  larva  feeds  on  currant,  wild  gooseberry,  and  rarely  elm. 
This  species  occurs  in  Canada  and  in  the  northern  portion  of  the 
United  States  except  in  the  extreme  West. 

The  violet  tip,  Polygdnia  interrogatidnis. — This  butterfly  (Fig. 
960,  8.)  is  somewhat  larger  than  the  preceding  species  of  Polygonia 
and  differs  in  the  form  of  the  silvery  mark,  which  consists  of  a  dot 
and  a  crescent  resembling  a  semicolon.  It  received  its  scientific  name 
frorn  the  Greek  note  of  interrogation,  which  is  identical  with  our 
semicolon.  On  the  upper  side,  the  outer  margins  of  the  wings  and 
the  tails  of  the  hind  wings  are  tinged  with  violet,  this  fact  suggested 
its  common  name. 

This  species  is  dimorphic;  and  the  two  forms  differ  so  constantly 
and  in  such  marked  manner  that  they  were  described  as  distinct 
species.  In  P.  interrogationis  interrogationis  the  upper  surface  of  the 
hind  wings  is  not  much  darker  than  that  of  the  fore  wings,  and  there 
is  a  submarginal  row  of  fulvous  spots  in  the  broad  ferruginous  brown 
border.  In  P.  interrogationis  umbrosa  the  outer  two-thirds  of  the 
upper  surface  of  the  hind  wings  is  blackish,  and  the  submarginal 
fulvous  spots  are  obliterated,  except  sometimes  faint  traces  near  the 
costal  margin. 

This  species  is  found  in  Canada  and  throughout  the  United  States 
east  of  the  Rocky  Mountains. 

IV.    THE  SOVEREIGNS 

The  members  of  this  group  differ  from  other  N_vmphalidas  in  that 
the  first  three  veins  of  the  hind  wings  separate  at  the  same  point 
(Fig.  966);  in  the  other  nymphs  the  humeral  vein  arises  beyond 
this  point.  The  club  of  the  antennas  is  very  long,  and  increases  in  size 
so  gradually  that  it  is  difficult  to  determine  where  it  begins.  In  its 
thickest  part  it  is  hardly  more  than  twice  as  broad  as  the  stalk. 
The  palpi  are  slender,  and  the  wings  are  rounded. 

The  larvae  present  a  very  grotesque  appearance,  being  very  ir- 
regular in  form,  and  strongly  mottled  or  spotted  in  color. 


758 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  following  are  our  best-known  species. 

The  banded  purple,  Basilarchia  arthemis. — The  upper  surface  of 

the  wings  is  velvety  choco- 
late-black, marked  with  a 
conspicuous  white  bow  (Fig. 
967). 

This  is  a  Canadian  spe- 
cies which  extends  a  short 
distance  into  the  northern 
part  of  the  United  States; 
the  larva  feeds  on  birch, 
willow,  poplar,  and  many 
other  plants. 

The  red  spotted  purole, 
Basilarchia  astyanax. — The 
upTDcr  surface  of  the  wings  is 
velvetv  indigo-black,  tinged 
with  blue  or  green.  There 
are  three  rows  of  blue  or 
green  spots  on  the  outer 
third  of  the  hind  wings; 
the  spots  of  the  inner  row 
varv  greatlv  in  width  in 
different  individuals.  On 
the  lower  surface  there  is  a 
reddish  orange  spot  in  the 
discal  cell  of  the  fore  wings, 
and  one  on  the  discal  vein; 
on  the  hind  wings  there  are 
two  orange  soots  similarly 
situated,  a  third  at  the  base 
of  cell  R,  and  a  row  of  seven 
spots  just  within  a  double  row  of  submarginal  blue  or  green  spots. 

This  species  occurs 
throughout  nearly  the 
whole  of  the  Eastern 
United  States  south  of 
the  43rd  parallel  of  lati- 
tude. The  larva  feeds 
on  many  plants;  among 
them  are  plum,  apple, 
pear,  and  gooseberry. 

The  hybrid  purple, 
Basilarchia  proserpina. — 
There  is  a  form  of  Basil- 
archia which  was  de- 
scribed as  a  distinct  spe- 
cies under  the  name  pro- 
serpina, but  which  is  believed  to  be  a 


Fig.  966. — Wings  of  Basilarchia  astyanax. 


Fig.  967. — Basilarchia  arthemis. 


hybrid  between  B.  astyanax 


LEPIDOPTERA 


759 


Fief.  968. — Basilarchia  archibpus. 


and  B.  arthemis.  See  Field  ('10).  This  butterfly  has  the  coloring  of 
B.  astyanax,  with  a  portion  of  the  white  bow  of  B.  arthemis.  It  occurs 
in  a  narrow  belt  of 
country  extending 
from  southern  Wis- 
consin and  north - 
em  Illinois  east- 
ward to  the  Atlan- 
tic coast  of  New 
England.  This  is 
the  region  which 
forms  the  southern 
limit  of  the  range 
of  B.  arthemis  and 
the  northern  limit 
of  the  range  of  B. 
astyanax,  the  place 
where  the  two  spe- 
cies meet.  The  hy- 
brids vary  greatly  in  the  extent  of  the  white  band  and  the  red  spots. 
The  viceroy,  Basilarchia  arcMppus. — The  wings  vary  in  color 
from  a  dull  yellow  orange  tinged  slightly  with  brown  to  a  dark  cin- 
namon color;  they  are  bordered  with  black,  and  all  the  veins  are 
edged  with  the  same  color  (Fig.  968).  The  fringe  of  the  wings  is 
spotted  with  white,  and  the  black  border  on  the  outer  margin  contains 
a  row  of  white  spots. 

This  species  is  remarkable  for  its  resemblance  to  the  monarch 
Danaus  archippus  (Fig.  974).  But  aside  from  the  structural  charac- 
ters separating  the  two  subfamilies  which  these  butterflies  represent, 

the  viceroy  can  be 
easily  distinguished 
from  the  species  it 
mimics  by  its  smaller 
size,  and  by  the  pres- 
ence of  a  transverse 
black  band  on  the 
hind  wings.  As  Da- 
naus  archippptis  has 
been  termed  the  mon- 
arch, this  species  is 
aptly  called  the  vice- 
roy. 

"  The  larva  (Fig. 
969,  a)  when  full- 
grown  is  about  30  mm. 
in  length.  The  body 
is  humped  and  naked, 
with  many  tubercles. 
In  color  it  is  dark  brownish  yellow  or  olive  green,  with  a  pale  buff  or 


Fie.  969. — Basilarchia  archippus:  a,  larva,  b,  pupa, 
c,  nest;  d,  partly  eaten  leaf  before  rolled  to  form 
nest.      (From    Riley.) 


760 


AN  INTRODUCTION  TO  ENTOMOLOGY 


whitish  saddle  on  the  middle  segment  of  the  abdomen.  The  tubercles 
on  the  second  thoracic  segment  are  club-shaped  and  spiny. 

The  larva  of  the  vicerov  feeds  upon  willow,  poplar,  balm  of  gilead, 
aspen,  and  cottonwood.  The  species  is  two-  or  three-brooded  and 
hibernates  as  a  partially  grown  larva  in  a  nest  made  of  a  rolled  leaf. 
(Fig.  969,  c).  This  nest  is  lined  with  silk,  and  the  leaf  is  fastened  to 
the  twig  with  silk  so  that  it  cannot  fall  during  the  winter.  So  far  as 
is  known  all  of  the  species  of  the  sovereigns  hibernate  as  larvae  in 
nests  of  this  kind.  It  is  worthy  of  note  that  only  the  autumn  brood 
of  caterpillars  make  these  nests;  so  that  the  nest-building  instinct 
appears  only  in  alternate  generations,  or  even  less  frequently  when  the 
species  is  more  than  two-brooded.  B.  ar  chip  pus  is  found  over  nearly 
the  whole  of  the  United  S'^ates  as  far  west  as  the  Sierra  Nevada 
Mountains,  and  has  been  found  sparingly  even  to  the  Pacific  coast 
near  our  northern  boundaries. 

The  vice-reine,  Basilarchia  arcJnppiis  floridcnsis.- — This  is  a  variety 
of  Basilarchia  archippus  that  is  much  darker  than  the  typical  form; 
the  ground  color  of  the  wings  resembling  that  of  the  queen,  Danaus 
herenice.  As  it  is  found  in  the  same  region  as  the  queen  it  is  supposed 
to  mimic  that  species,  hence  the  popular  name  suggested  above. 


V.    THE  EMPERORS 


This  group  is  poorly  represented  in  our  fauna;  our  best-known 
species  are  the  two  following,  which  occur  in  the  South. 

The  tawny  emperor,  Chlonppe  clyton. — In  this  and  the  following 
species  the  apex  of  the  front  wings  and  the  anal  angle  of  the  hind 
wings  are  considerably  produced  in  the  males,  but  more  rounded  in 
the  females.  The 
male  is  represented 
in  Figure  970  and 
the  dotted  line  at 
the  left  indicates 
the  contour  of  the 
wings  of  the  female. 
This  excellent  fig- 
ure is  from  the  sixth 
Missouri  report  by 
C.  V.  Riley,  where 
a  detailed  account 
of  the  life-history 
of  the  species  is 
given.  The  wings 
of  this  butterfly  are 
more  or  less  ob- 
scure tawny,  mark- 
ed with  blackish  brown,  and  with  pale  spots.  There  is  a  submargi- 
nal  row  of  six  eyelike  spots  on  the  hind  wings. 


Fig.  970. — Chlonppe  clylon:  a,  eggs;  b,  larva;  c,  pupa; 
d,  upper  surface  of  male  butterfly;  the  dotted  line  at 
left  indicates  the  contour  of  the  wings  of  the  female. 
(From  Riley.) 


LEPIDOPTERA 


761 


The  species  is  dimorphic;  the  dimorphism  affects  both  sexes  and 
is  independent,  so  far  as  is  known,  of  season,  as  there  is  only  one 
brood  each  year.  It  is  the  typical  form  Chlorippe  clyton  clyton  that 
is  figured  here.  The  second  form,  Chlorippe  clyton  proserpina,  differs 
in  having  the  hind  wings  darker  and  the  submarginal  row  of  eyelike 
spots  wanting. 

The  larva  (Fig.  970,  h)  feeds  on  hackberry. 

The  gray  emperor,  Chlonppe  celtis. — In  this  species  the  wings  are 
russety  brown  marked  with  blackish  brown.  In  addition  to  the  sub- 
marginal  row  of  six  eye-like  spots  on  the  hind  wings,  there  is  one  in 
cell  Cui  of  the  fore  wings. 

The  larva  of  this  species  also  feeds  on  hackberry. 


VI.    THE  AN^AS 

The  butterflies  of  the  genus  Ancsa  are  quite  distinct  from  any  of 
the  preceding  divisions  of  the  Nymphalinas,  although  they  have  been 
classed  with  the  em- 
perors. There  are 
three  species  found 
intheUnitedStates, 
A .  portia  from  Flor- 
ida, A.  morrisonii 
from  Arizona,  and 
the  following   one. 

The  goat-weed 
butterfly,  Ancsa  dn- 
dria.- — The  female 
of  this  species  can 
be  easily  recognized 
by  Figure  971.  The 
male  is  smaller, 
with  wings  of  a  rich 

dark  orange,  margined  with  brown,  and  without  the  light-colored  band 
characteristic  of  the  female.  This  species  is  found  in  the  Mississippi 
Vallev  from  Illinois  to  Texas. 


Fig.  971. — Anaa  andria 


Subfamily  SATYRIN^ 


The  Meadow-browns 

This  subfamily  includes  chiefly  brown  butterflies  whose  markings 
consist  almost  entirely  of  eyelike  spots.  Some  western  species,  how- 
ever, are  bright-colored.  In  our  species  some  of  the  veins  of  the  fore 
wings  are  greatly  swollen  at  the  base  (Fig.  972).  This  character  is 
not  quite  distinctive;  for  in  some  species  of  the  Nymphalinas  that  are 
found  in  southern  Florida  and  in  Texas  near  the  Mexican  border  some 
of  the  veins  of  the  fore  wings  are  swollen  at  the  base. 

The  larvae  are  cylindrical,  tapering  more  or  less  towards  each  end. 
The  caudal  segment  is  bifurcated,  a   character  that   distinguishes 


762 


AN  INTRODUCTION  TO  ENTOMOLOGY 


them  from  all  other  American  butterfly  larvae  excepting  those  of  the 

emperors,  Chlorippe. 

The  pupse  are  rounded; 
in  some  cases  the  transfor- 
mation takes  place  beneath 
rubbish  on  the  ground  with- 
out any  preparation  of  cell 
or  suspension  of  the  body. 
Nearly  sixty  species  be- 
longing to  this  subfamily 
have  been  described  from 
America  north  of  Mexico. 
The  eyed  brown,  Saty- 
rddes  cdnthus. — The  upper 
surface  of  the  wings  is  soft 
mouse-brown  on  the  basal 
half  and  paler  beyond,  con- 
siderably so  in  the  female; 
each  wing  bears  a  row  of 
four  or  five  small  black  eve- 
like spots  (Fig.  973).  This 
species  is  found  in  Ontario, 
and  throughout  the  eastern 
half  of  the  United  States  in 
wet  places.  The  larva  feeds 
on  swamp  grasses ;  its  head 
and  caudal  segment  are  each 
adorned  with  a  pair  of  red 
cone-shaped  tubercles. 
The  gravling,  Cercyonis  alope. — This  species  is  found  from  the 
Atlantic  to  the  Pacific;  it  occurs  under  several  forms,  some  of  which 
have  been  described  as  distinct  spe- 
cies. The  most  common  forms  found 
East  of  the  Rocky  Mountains  are 
the  first  two  described  below  and 
intergrades  between  these.  The  ex- 
panse of  the  wings  is  from  50  to  62 
jnm.    The  larva  feeds  on  grass. 

(i)  The  blue-eyed  grayling, 
Cercyonis  alope  alope. — The  upper 
surface  of  the  wings  is  dark  brown; 
on  the  outer  half  of  the  fore  wings 
there  is  a  distinct  yellow  band,  which 
extends  from  vein  R5  to  the  anal  vein ; 
spots  with  a  white  or  bluish  center. 

small  spot  in  cell  Cui,  which  is  narrowly  rimmed  with  yellow  and 
has  a  minute  white  pupil.  The  lower  surface  of  the  hind  wings  is 
either  with  or  without  eye-like  spots,  usually  with  six  of  them. 


Fig.  972. — Wings  of  Cercyonis  alope. 


Fig.  973. — Satyrodes  canthus 

in  this  band  there  are  two  dark 
The  hind  wings  usuallv  bear  a 


LEPIDOPTERA  763 

This  is  a  Southern  form,  which  extends  into  the  southern  portions 
of  New  England,  New  York,  Michigan,  Wisconsin,  Iowa,  and  Ne- 
braska; and  into  the  northern  portions  of  IlHnois,  Indiana,  and  Ohio. 

(2)  The  dull-eved  grayhng,  Cercyonis  alope  ncphele. — In  this  form 
the  yellow  band  of  the  fore  wings  is  either  absent  or  represented  by 
a  faint  pallid  cloud.  In  other  respects  it  closely  resembles  the  blue- 
eyed  grayling. 

This  is  a  Northern  form;  the  southern  limits  of  its  range  overlap 
the  northern  limits  of  the  range  of  the  blue-eyed  grayling  as  given 
above. 

(3)  The  hybrid  graylings. — In  that  narrow  belt  where  the  ranges 
of  the  two  forms  of  Circyonis  alope  described  above  overlap,  all 
variations  between  the  two  types  occur.  In  most  of  these  intergrades 
the  eye-spots  of  the  upper  side  of  the  fore  wings  are  surrounded  by 
yellowish  rings,  or  each  of  them  is  on  a  yellowish  patch. 

(4)  The  sea-coast  grayling,  Cercyonis  alope  maritima. — In  a  nar- 
row belt  along  the  Atlantic  coast  there  occurs  a  form  which  is  smaller 
than  those  described  above,  and  of  a  dark  color;  this  form  is  easily 
recognized  by  the  color  of  the  band  bearing  the  eye-spots,  it  being 
reddish  yellow. 

The  White  Mountain  butterfly,  CEneis  semldea. — The  genus  CEneis 
is  composed  of  cold-loving  arctic  species  whose  natural  habitat  is  the 
Far  North;  but  some  members  of  this  genus  are  found  within  the 
limits  of  the  United  States.  Their  presence  here  and  their  distribution 
are  extremelv  interesting.  The  best-known  of  these  forms  is  the  White 
Mountain  butterfl}\ 

This  butterfly  is  found  only  on  the  higher  parts  (above  5,000 feet) 
of  the  White  Mountains  in  New  Hampshire,  and  on  the  highest  peaks 
of  the  Rocky  Mountains  of  Colorado,  above  12,000  feet. 

These  two  widely  separated  colonies  of  this  butterfly  are  believed 
to  be  the  remnants  of  an  arctic  fauna  which  was  forced  southward 
during  the  Ice  Age.  At  the  close  of  this  period,  as  the  arctic  animals 
followed  the  retreating  ice  northward,  the  tops  of  these  mountains 
became  colonized  by  the  cold-loving  forms.  Here  they  found  a 
congenial  resting  place,  while  the  main  body  of  their  congeners,  which 
occupied  the  intervening  region,  was  driven  northward  by  the  increas- 
ing heat  of  the  lower  land.  Here  they  remain,  clinging  to  these 
islands  of  cold  projecting  above  the  fatal  sea  of  warmth  that  fills  the 
vallevs  below. 

The  White  Mountain  butterfly  is  a  delicate-winged  species.  The 
upper  surface  of  the  wings  is  grayish  brown,  without  spots,  except 
sometimes  a  minute  one  in  cell  Mi  of  the  fore  wings;  the  fringe  of 
the  wings  is  brownish  white  interrupted  with  blackish  brown  at  the 
ends  of  the  veins.  On  the  hind  wings  the  marbling  of  the  lower  surface 
shows  through  somewhat.  On  the  lower  surface,  the  tip  of  the  fore 
wings  and  the  greater  part  of  the  hind  wings  are  beautifully  marbled 
with  blackish  brown  and  grayish  white.  The  expanse  of  the  wings  is 
43  mm. 


764  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  larv'a  feeds  on  Carex.  The  species  is  either  single-brooded  or 
requires  two  years  for  the  development  of  a  brood. 

A  closely  allied  species,  CEneis  katdhdtn,  is  found  on  Mount 
Katahdin,  Maine.    This  is  called  the  Katahdin  butterfly. 

Subfamily  HELICONIIN^ 

The  Heliconians 

This  subfamily  consists  chiefly  of  tropical  butterflies.  They  are 
of  medium  or  rather  large  size,  and  are  easily  recognized  by  their 
nariow  and  elongated  fore  wings,  which  are  usually  more  than  twice 
as  long  as  broad.  Most  of  the  species  are  striking  in  appearance, 
being  black  banded  with  yellow  or  crimson,  and  sometimes  with  blue. 
The  discal  cell  of  the  hind  wings  is  closed  by  a  well-preserved  vein. 
The  following  species  is  the  only  one  found  in  our  fauna  that  un- 
questionably belongs  to  this  subfamily. 

The  zebra,  Heliconius  charitdnius. — This  is  a  black  butterfly  with 
its  wings  banded  with  lemon  yellow.  There  are  three  bands  on  the 
fore  wings;  on  the  hind  wings  there  is  a  broad  band  parallel  with  the 
front  wings  when  the}'  are  spread,  a  submarginal  row  of  about  fifteen 
spots,  and  a  row  of  dots  on  the  outer  margin  near  the  anal  angle. 
The  wings  expand  from  62  mm.  to  100  mm.  The  larva  feeds  upon 
the  passion-flower.  This  species  is  found  in  the  hotter  portions  of 
the  Gulf  States. 

There  are  two  other  species  found  in  the  United  States  that  are 
placed  in  this  subfamily  by  some  writers;  but  in  each  of  these  the 
discal  cell  of  the  hind  wings  is  open  as  in  the  Nymphalinae.  These  are 
the  following. 

The  Julia  butterfly,  Colanis  julta. — This  butterfly  resembles  the 
true  heliconians  in  having  very  long  and  narrow  fore  wings,  these 
being  more  than  twice  as  long  as  broad.  The  upper  side  of  the  wings 
is  dark  reddish  orange,  with  the  margins  of  the  wings  black, 
and  with  a  more  or  less  distinct  black  band  cutting  off  the  outer 
third  of  the  fore  wings.  On  the  lower  surface  the  wings  are  pale  rusty- 
red,  mottled  with  a  darker  shade.  The  wings  expand  about  85  mm. 
This  is  a  very  common  species  in  the  tropics  of  America  and  is  found 
in  the  extreme  southern  part  of  the  United  States. 

The  gulf  fritillary,  Didne  vamllce. — In  this  species  the  front  wings 
are  about  twice  as  long  as  broad,  but  the  markings  of  the  wings  re- 
semble those  of  a  fritillary  more  than  those  of  an  heliconian.  The 
wings  are  reddish  fulvous  above;  the  veins  of  the  front  wings  are 
black  on  the  outer  two-thirds  of  the  wing;  the  black  expands  into 
spots  at  the  ends  of  veins  M3  to  anal;  there  are  two  white  spots  in 
the  discal  cell  and  one  at  the  apex  of  it,  each  of  these  spots  is  sur- 
rounded with  black;  cells  M3,  Cu],  and  Cu2  each  contains  a  round 
black  spot.  The  outer  margin  of  the  hind  wings  has  a  broad 
black  border,  which  contains  a  fulvous  spot  in  each  cell.  The  wings 
expand  from  55  mm.  to  75  mm. 

The  larva  feeds  on  the  passion-flower.  In  addition  to  the  six 
rows  of  thorny  spines,  which  characterize  the  caterpillars  of  many 


LEPIDOPTERA  765 

Other  fritillaries,  this  one  has  on  the  head  a  pair  of  backward  bending 
spines  branched  Hke  the  others. 

This  species  occurs  from  New  Jersey  and  Pennsylvania  southward, 
also  in  Arizona  and  California. 

Subfamily  DANAIN^ 
The  Milkweed  Butterflies 

These  butterflies  are  of  large  size,  with  .rounded  and  somewhat 
elongate  wings,  the  apical  portion  of  the  fore  wings  being  much 
produced.  The  discal  cells  of  the  wings  are  closed;  the  third  anal 
vein  of  the  fore  wings  is  preserved ;  and  the  antennae  are  apparently 
without  scales.  Only  a  very  few  species  of  this  family  occur  in  our 
fauna.  The  two  following  are  the  best-known ;  the  others  are  found 
only  in  the  extreme  South  or  in  California. 

The  monarch,  Ddnaus  archippus. — The  upper  surface  of  the  wings 
is  light  ruddy  brown,  with  the  borders  and  veins  black,  and  with  two 
rows  of  white  spots  on  the  costal  and  outer  borders  as  shown  in  Figure 


Fig.  974. — Danaus  archippus. 

974.  The  figure  represents  a  female;  in  the  male  the  veins  of  the 
wings  are  more  narrowly  margined  with  black,  and  there  is  a  black 
pouch  next  to  vein  Cu2  of  the  hind  wings,  containing  scent-scales  or 
androconia. 

The  larva  feeds  upon  different  species  of  milk-weed,  Asclepias. 
When  full  grown  it  is  lemon  or  greenish  yellow,  broadly  banded  with 
shining  black.  It  is  remarkable  for  bearing  a  pair  of  long  fleshy  fila- 
ments on  the  second  thoracic  segment,  and  a  similar  pair  on  the 
seventh  abdominal  segment  (Fig.  975).  The  chrysalis  is  a  beautiful 
object;  it  is  bright  green  dotted  with  golden  spots,  and  about  25mm. 
in  length  (Fig.  976). 


766 


^A^  INTRODUCTION  TO  ENTOMOLOGY 


This  species  occurs  throughout  the  greater  part  of  the  United 
States,  and  is  distributed  far  be\ond  our  borders.  It  is  believed, 
however,  that  the  species  dies  out  each  3-ear  in  a  large  part  of  the 
Northern  States,  and  that  those  butterflies  which  appear  first  in  this 


Fig.    976. — Danaus 
Fig.  QJS.^Danaus  archippiis,  larva.     (From  Riley.)  archippus,  chrys- 

alis.     (From  Ri- 
ley ) 

region,  in  June  or  July,  have  flown  hither  from  the  South,  where  they 
hibernate  in  the  adult  state.  In  the  extreme  South  they  fly  all  winter. 
Great  swarms,  including  many  thousands  of  individuals  of  this 
species,  are  sometimes  seen,  late  in  the  year;  and  these  swarms  appear 
to  be  migrating  southward. 

The  queen,  Danaus  berenice. — This  species  is  found  in  the  Southern 
States.  The  upper  surface  of  the  wings  is  reddish  chocolate-brown 
with  the  costal  margin  of  the  front  wings  and  the  outer  margins  of 
both  pairs  bordered  with  black.  There  are  two  partial  rows  of  white 
dots  near  the  costal  and  outer  margins  of  the  front  wings ;  and  there 
is  a  larger  white  spot  in  each  of  the  cells  R5  to  Cu.  The  male  possesses 
a  black  pouch  containing  androconia  next  to  vein  Cu  of  the  hind  wings 
as  in  the  preceding  species.    The  wings  expand  from  60  to  88  mm. 

There  is  a  well-marked  variety,  Danaus  berenice  strigosa,  in  which 
on  the  upper  surface  of  the  hind  wings  the  veins  are  narrowly  edged 
with  grayish  white. 

The  larva  of  this  species  feeds  on  milkweed.  This  larva  bears 
three  pairs  of  long,  brown,  whiplash  filaments;  these  are  on  the  second 
thoracic  and  the  second  and  eighth  abdominal  segments. 


Subfamily  LIBYTHEIN^ 

The  Long-beaks 

The  long-beaks  can  be  easily  recog- 
nized by  their  excessively  long,  beak- 
like palpi,  which  are  from  one-fourth 
to  one-half  as  long  as  the  body  and  pro- 
ject straight  forward  (Fig.  977).  The 
outer  margin  of  the  fore  wings  is  deeply 
notched ;  the  males  have  only  four  well- 
developed  legs,  while  the  females  have  six 


Fig.  977.    -Ilypatus  haclnnann 


LEPIDOPTERA 


767 


Only  two  species  are  listed  from  the  United  States,  one  from  Texas 
and  one  from  the  East;  and  these  may  be  merely  varieties  of  one 
species. 

The  snout  butterfiv,  Hypatus  bachmdnni. — The  wings  are  blackish 
brown  above,  marked  with  orange  and  white  spots.  This  species 
occurs  throughout  the  Eastern  United  States,  excepting  the  northern 
part  of  New  England  and  the  southern  part  of  Florida.  The  larva 
feeds  on  hackberry,  and  in  the  West  where  hackberry  does  not  occur, 
it  feeds  on  wolfberry. 

Family  RIODINID^ 
The  Metal-marks 


The  metal-marks  are  small  butterflies,  which  bear  some  resem- 
blance to  the  gossamer  winged  butterflies.  They  are  distinguished 
from  the  gossamer-winged  but- 


terflies by  the  presence  of  a 
humeral  vein  in  the  hind  wings, 
and  from  them  and  all  other 
butterflies  by  the  fact  that  the 
costa  of  the  hind  wings  is  thick- 
ened out  to  the  humeral  angle 
(Fig.  978).  The  fore  legs  are  re- 
duced and  brushlike  in  the  males, 
normal  in  females. 

Only  twelve  species  have  been 
found  in  our  fauna,  and  nearly  all 
of  these  are  from  the  Far  West  or 
Southwest.  The  two  following 
species  occur  in  the  East. 

The  small  metal-mark,  Cal- 
ephelis  virginiensis. — The  upper 
surface  of  the  wings  is  rust- 
colored,  and  is  crossed  by  four  or 
Ave  more  or  less  sinuous  blackish 
lines  on  the  basal  two-thirds,  and 
on  the  outer  third  by  two  lines  of 
shining  scales,  that  look  like  cut 
steel,  and  an  intermediate  row  of 
black  spots.  The  under  surface 
is  of  a  brighter  rust  color  and 
marked  as  above.  The  expanse  of 
the  wings  is  20  mm.  This  species 
occurs   in   the   Southern   States. 


R^^i 


Fig.  978. — Wings  of  Emesis  zela. 


The  large  metal-mark,  Calephelis  boredlis. — The  upper  surface  of 
the  wings  is  dull  brownish  yellow,  crossed  by  obscure  transverse 
stripes;  on  the  outer  half  of  the  wings  are  two  lead-colored  lines,  with 
a  row  of  black  dots  between  them.    The  under  surface  is  of  a  rather 


768 


AN  INTRODUCTION  TO  ENTOMOLOGY 


dark  and  a  pale  orange;  paler  and  duller  next  the  base,  marked  with 
transverse  black  lines  and  dots,  and  transverse  series  of  steel-colored 
spots.    The  wings  expand  from  25  to  30  mm. 

This  is  a  rare  butterfly;  it  has  been  taken  in  New  York,   New 
Jersey,  West  Virginia,  Michigan,  and  Illinois. 

Family  LYC^NID^ 


The  Gossamer-ivinged  Butterflies 

The  family  Lycaenidas  includes  butterflies  which  are  of  small  size 
and  delicate  structure.  In  size  they  resemble  the  smaller  Hesperiidas; 
but  they  can  be  distinguished  at  a 
glance  from  the  skippers,  as  they 
present  an  entirely  different  appear- 
ance. The  bodv  is  slender,  the  wings 
delicate  and  often  brightly  colored, 
and  the  club  of  the  antenna  straight. 
The  antennae  are  nearly  always 
ringed  with  white;  each  is  situated 
very  closely  to  the  edge  of  an  eye, 
often  flattening  it;  they  are  not  in 
pits ;  and  a  conspicuous  rim  of  white 
scales  encircles  the  eyes. 

An  easily-observed  combination 
of  characters  by  which  the  members 
of  this  family  can  be  distinguished  is 
the  absence  of  one  or  two  of  the 
branches  of  radius  of  the  fore  wings, 
this  vein  being  only  three-  or  four- 
branched,  and  the  origin  of  vein  Mi 
of  the  fore  wings  at  or  near  the  apex 
of  the  discal  cell  (Fig.  979).  In  all 
other  butterflies  occurring  in  our 
fauna  in  which  radius  is  only  three- 
or  four-branched  (except  Parnas- 
sius),Ye\n  Mi  of  the  fore  wings  coal- 
esces with  radius  for  a  considerable 

distance  beyond  the  apex  of  the  discal  cell.  An  exception  to  the 
characters  of  the  Lycaenidas  is  presented  by  Feniseca,  as  indicated  in 
the  table  of  families,  p.  739. 

A  characteristic  of  this  family  is  that  while  in  the  female  the  front 
legs  are  like  the  other  legs,  in  the  male  they  are  shorter,  without 
tarsal  claws,  and  with  the  tarsi  more  or  less  aborted. 

The  caterpillars  of  the  Lycaenidae  present  a  very  unusual  form 
being  more  or  less  slug-like,  reminding  one  of  the  larvae  of  the  Eucle- 
idas.  The  body  is  short  and  broad;  the  legs  and  prolegs  are  short 
and  small,  allowing  the  body  to  be  closely  pressed  to  the  object  upon 
which  the  insect  is  moving — in  fact  some  of  the  species  glide  rather 


dA 
Fig.  979. — Wings  of  Heodes  thoe. 


LEPIDOPTERA  769 

than  creep;  and  the  head  is  small,  and  can  be  retracted  more  or  less 
within  the  prothorax.  The  body  is  armed  with  no  conspicuous  ap- 
pendat^es ;  but  some  of  the  species  are  remarkable  for  having;  osmeteria 
which  can  be  pushed  out  from  the  seventh  and  eighth  abdominal 
segments,  and  through  which  honeydew  is  excreted  for  the  use  of 
ants.  Certain  other  species  are  remarkable  in  being  carnivorous; 
one  American  soecies  feeds  exclusively  upon  plant-lice. 

The  chrysalids  are  short,  broad,  ovate,  and  without  angulations. 
They  are  attached  b\^  the  caudal  extremity,  and  by  a  loop  passing 
over  the  body  near  its  middle.  The  ventral  aspect  of  the  body  is 
straight  and  often  closely  pressed  to  the  object  to  which  the  chrysalis 
is  attached. 

The  family  Lycaenidfe  is  represented  in  our  fauna  by  three  well- 
marked  groups  of  genera,  which  are  hardly  distinct  enough  to  be 
ranked  as  subfamilies;  these  are  known  as  the  hair-streaks,  the  cop- 
pers, and  the  blues  respectively.  In  addition  to  these  there  is  a  single 
species,  the  wanderer,  the  relationship  of  which  is  uncertain. 

I.     THE  HAIR-STREAKS 

The  hair-streaks  are  usually  dark  brown,  with  delicate  striped 
markings,  which  suggested  their  common  name;  but  some  species 
are  brilliantly  marked  with  metallic  blue,  green,  or  purple.  The  hind 
wings  are  commonly  furnished  with  delicate  tail-like  prolongations 
(Fig.  980),  and  the  eyes  are  hairy.  The  fore 
wings  of  the  male  often  bear  a  small  dull  oval 
spot  near  the  middle  of  the  costal  part  of  the 
wings,  the  discal  stigma,  which  is  filled  with  the 
peculiar  scent-scales  known  as  androconia. 
The  males  are  also  distinguished  by  having  a 
tuft  of  hair-like  scales,  the  beard,  on  the  front; 
this  is  wanting  or  very  thin  in  the  females. 
More  than  sixtv  species  occur  in  America  north 
of  ATexico;  of  these  nearly  twenty  occur  in  the 
eastern  half  of  the  United  States. 

The  banded  hair-streak,  Thecla  cdlamis. —      pig.  ggo. — Thecla  cal- 
In  the  northeastern  United  States  the  most         anus. 
common  of  the  hair-streaks  is  this  species  (Fig. 

980) .  The  upper  surface  of  the  wings  is  dark  broWn  or  blackish  brown. 
The  under  surface  is  blackish  slate-brown  nearly  as  dark  as  the  upper 
surface,  and  marked  as  shown  in  the  figure. 

The  larva  feeds  on  oak  and  hickory.  Excepting  the  southern  por- 
tion of  the  Gulf  States,  the  species  is  found  throughout  our  territory 
east  of  the  Rocky  Mountains,  and  in  the  southern  part  of  Canada. 

The  olive  hair-streak,  Mitoiira  ddmon. — The  upper  surface  of  the 
wings  is  dark  brown,  with  the  disk  more  or  less  deeply  suffused  with 
brassy  yellow  in  the  male  or  tawny  in  the  female;  the  hind  wing  has 
two  tails,  one  much  longer  than  the  other,  both  black  tipped  with 
white.  The  lower  surface  of  the  hind  wings  is  deep  green;  both  fore 
and  hind  wings  are  marked  with  white  bars  bordered  with  brown. 
(Fig.  960.  6). 


770  AN  INTRODUCTION  TO  ENTOMOLOGY 

vSouthern  individuals  have  much  longer  tails  than  the  one  shown 
in  the  figure;  and  there  is  a  variety,  patersonia,  in  which  the  upper 
surface  of  the  wings  is  all  dark  brown. 

The  larva  feeds  on  red  cedar  and  smilax.  This  species  occurs 
from  Massachusetts  to  Florida  and  westward  to  Dakota  and  Texas. 

The  banded  elfin,  Incisdlia  nlphon. — In  the  butterflies  of  the  genus 
htcisalia  the  fringe  of  the  outer  margin  of  the  hind  wings  is  slightly 
prolonged  at  the  end  of  each  vein,  giving  the  wings  a  scalloped  out- 
line; they  also  lack  tail-like  prolongations  of  the  hind  wings. 

There  are  several  species  occurring  on  both  sides  of  the  continent. 
One  of  these,  the  banded  elfin,  is  represented  in  Figure  960,  4.  In 
this  species  there  is  a  distinct  white  or  whitish  edging  near  the  base 
of  the  under  side  of  the  hind  wing  which  limits  a  darker  band  that 
occupies  the  outer  two-thirds  of  the  basal  half  of  the  wing. 

This  species  occurs  in  the  Eastern  and  Middle  States.  The  larva 
feeds  on  pine. 

The  hair-streaks  described  above  are  of  moderate  size  and  modest 
colors.  The  two  following  will  serve  to  illustrate  a  somewhat  differ- 
ent type. 

The  great  purple  hair-streak,  Atlides  halesus. — This  is  the  largest 
of  our  eastern  hair-streaks,  the  larger  individuals  expanding  50  mm. 
In  the  male  the  greater  part  of  the  upper  surface  of  the  wings  is  bright 
blue;  the  discal  stigma,  the  outer  fourth  of  the  fore  wings,  the  apex 
of  the  inner  margin  of  the  hind  wings,  and  the  tails  are  black.  In  the 
female  the  outer  half  of  the  wings  is  black. 

This  species  occurs  in  the  southern  half  of  the  United  States  and 
southward.  It  has  been  found  as  far  north  as  Illinois.  The  larva  is 
said  to  feed  on  oak. 

The  white-m  hair-streak,  Thecla  m-dlbum.- — This  is  a  smaller 
species,  expanding  about  37  mm.  The  upper  surface  of  the  disk  of 
the  wings  is  a  rich,  glossy  dark  blue,  with  green  reflections;  a  broad 
outer  border  and  costal  margin  are  black.  The  hind  wing  has  two 
tails,  and  a  bright  dark  orange  spot  preceded  by  white  at  the  anal 
angle.  The  under  surface  is  brownish  gra}',  and  on  this  surface  both 
wings  are  crossed  by  a  common,  narrow  white  stripe  which  forms  a 
large  W  or  reversed  M  on  the  hind  wings. 

This  species  occurs  in  the  southern  half  of  the  United  States.  The 
larva  feeds  on  oak  and  on  milk-vetch. 

II.     THE  COPPERS 

The  coppers,  as  a  rule,  are  easily  distinguished  from  other  gos- 
samer-winged butterflies  by  their  orange-red  and  brown  colors,  each 
with  a  coppery  tinge,  and  conspicuous  black  markings.  They  are 
the  stoutest  of  the  Lycaenidae.  Among  the  exceptions  to  the  more 
common  coloring  of  these  insects  are  the  following:  In  the  male  of 
Heodes  epixanthe,  a  small  species  which  frequents  cranberry  bogs, 
the  wings  have  a  purple  tinge;  and  in  Heodes  heteronea,  a  species 
found  from  California  to  Colorado,  the  male  is  blue. 

Eighteen  species  of  the  group  are  now  listed  in  our  fauna ;  the  two 
following  will  serve  as  examples : 


LEPIDOPTERA  771 

The  American  copper,  Heddes  hypophlceas.- — This  is  the  most 
common  of  our  coppers  in  the  Northeastern  States  and  in  Canada. 
Its  range  extends  also  along  the  boundary  between  the  United  States 
and  Canada  to  the  Pacific  Ocean,  and  southward  into  California; 
and  in  the  east  along  the  Alleghany  Mountains  south  to  Georgia. 
The  fore  wings  are  orange-red  above,  spotted  with  black,  and  with  a 
blackish  brown  outer  border;  the  hind  wings  are  coppery  brown,  with 
a  broad  orange-red  band  on  the  outer  margin;  this  band  is  indented 
by  four  black  spots. 

The  larva  feeds  on  the  common  sorrel  {Rnmex  acetosella). 

The  bronze  copper,  Heodes  thoe.- — This  is  larger  than  the  preceding 
species,  the  wings  expanding  3  7  mm.  or  more.  In  the  male  the  wings  are 
coppery  brown  above,  spotted  with  black,  and  with  a  broad  orange-red 
band  on  the  outer  margin  of  the  hind  wings.  The  female  dift'ers  in 
having  the  fore  wings  orange-red  above,  with  prominent  black  spots. 

This  species  occurs  in  the  Middle  and  Western  States  from  the 
Connecticut  Valley  to  Nebraska.  The  larva  feeds  on  curled  dock 
(Rumex  crispus) . 

III.     THE  BLUES 

The  blues  can  be  distinguished  from  the  other  gossamer-winged 
butterflies  by  the  slender  form  of  the  body,  and  the  blue  color  of  the 
upper  surface  of  the  wings  of  the  males  at  least ;  in  many  species  the 
upper  surface  of  the  wings  of  the  female  is  much  darker  than  that  of 
the  male.  Thirty -eight  North  American  species  have  been  described; 
but  most  of  these  occur  only  in  the  Far  West.  This  is  a  rather  difficult 
group  to  study  owing  to  the  fact  that  in  several  cases  a  single  species 
exists  under  two  or  more  distinct  forms,  and  also  that  the  two  sexes 
of  the  same  species  may  differ  greatly.  It  often  happens  that  two 
individuals  of  the  same  sex  but  of  different  species  resemble  each  other 
more  closely  in  the  coloring  of  the  upper  surface  than  do  the  two  sexes 
of  either  of  the  species. 

The  spring  azure,  Lyccena  arglolus. — In  this  species  the  hind  wings 
are  without  tails,  the  eyes  are  hairy,  and  the  lower  surface  of  the 
wings  is  pale  ash-gray.  This  combination  of  characters  will  distin- 
guish it  from  all  other  blues  occurring  in  the  Eastern  United  States. 
But  the  species  is  not  confined  to  this  region,  as  it  occurs  in  nearly  all 
parts  of  the  United  States,  in  a  large  part  of  Canada,  and  most  of 
the  Old  World. 

This  butterfly  exhibits  polymorphism  to  the  greatest  degree  of 
any  known  species.  In  this  country  alone  there  are  thirteen  or  more 
named  forms.  Some  of  these  are  geographical  races ;  some  are  seasonal 
forms;  and  some  are  distinct  forms  that  exist  at  the  same  time  and 
place  as  the  more  typical  form.  In  the  Old  World  many  other  forms 
of  this  species  have  been  described.  Two  forms  are  represented  in 
Figure  960,  i  and  7. 

The  larva  feeds  on  the  buds  and  flowers  of  various  plants,  es- 
pecially those  of  Cornus,  Cimicifuga,  and  Actinomeris.  They  are 
frequently  attended  by  ants  for  the  sake  of  the  honey-dew  which 


772 


AN  INTRODUCTION  TO  ENTOMOLOGY 


they  excrete  from  osmeteria  which  they  push  out  from  the  seventh 
and  eighth  abdominal  segments. 

The  tailed  blue,  Evcres  comyntas. — The  butterflies  of  the  genus 
Everes  can  be  distinguished  from  our  other  blues  by  the  presence  of  a 
small  tail-like  prolongation  of  the  hind  wing.  This  is  borne  at  the 
end  of  vein  Cu.  Our  common  species  {E.  comyntas)  is  distributed 
over  nearly  all  parts  of  North  America.  The  male  is  dark  purplish 
violet  above,  bordered  with  brown ;  the  female  is  dark  brown,  some- 
times flecked  with  bluish  scales.  In  the  Eastern  United  States  this 
is  the  only  species  of  the  genus. 

The  larva  feeds  upon  clover  and  other  leguminous  plants. 

lY.     GENUS  FENISECA 


Fig.   981. — Feniseca 
tarquinius. 


The  wanderer,  Feniseca  tarquinius. — This  is  the  onlv  known  mem- 
ber of  the  genus  Feniseca,  the  affinities  of  which  have  not  been  deter- 
mined. It  does  not  seem  to  belong  to  either  of 
the  three  groups  of  genera  mentioned  above. 
A  distinctive  feature  of  this  genus  is  the  fact 
that  vein  Mi  of  the  fore  wings  coalesces  with  a 
branch  of  radius  for  a  considerable  distance 
beyond  the  apex  of  the  discal  cell;  in  this  re- 
spect it  differs  from  all  other  members  of  the 
Lycasnidae  found  in  our  fauna. 

The  upper  surface  of  the  wings  of  this  but- 
terfly (Fig.  981)  is  dark  brown,  with  a  large 
irregular,  orange-yellow  patch  on  the  disk  of  the  fore  wing,  and  one 
of  the  same  color  next  the  anal  angle  of  the  hind  wing. 

This  species  is  of  unusual  interest,  as  the  larva 
is  carnivorous  in  its  habits.  It  feeds  on  plant-lice; 
and,  so  far  as  observed,  it  feeds  only  on  the  woolly 
aphids.  It  is  found  more  often  in  colonies  of  the 
alder  blight  {Schizoneura  tessellata)  than  in  those 
of  the  allied  species.  It  is  found  from  Maine  to 
Northern  Florida  and  westward  to  Kansas.  It  is  a 
very  local  insect,  being  found  only  in  the  neighbor- 
hood of  water  where  alder  grows. 

I  do  not  know  wh}-  the  name  the  wanderer  was 
applied  to  this  butterfly,  it  may  have  been  on  ac- 
count of  its  local  appearance  in  widely  separated 
places,  or  because  in  habits  the  larva  deviates  far 
from  the  more  usual  habits  of  caterpillars.  The 
name  is  also  appropriate  as  its  nearest  relatives  are 
found  in  Africa  and  in  Asia. 

The  chrysalis  of  Feniseca  presents  a  remarkable  appearance  (Fig. 
982);  the  anterior  half  when  viewed  from  above  bears  a  curious  re- 
semblance to  a  monkey's  face;  and  it  differs  from  all  other  lycc-enid 
pupje  in  our  fauna  in  having  on  each  side  a  row  of  small  rounded 
tubercles. 


Fig.  982. — Ch3Tsa- 
lis  of  Feniseca . 
Enlarged. 


CHAPTER  XXVIII 

ORDER  DIPTERA* 

The  winged  members  of  this  order  have  only  two  wings;  these  are 
borne  by  the  mesothorax.  The  second  pair  of  wings  is  represented  by  a 
pair  of  knobbed,  thread-like  organs,  the  halteres,  these  are  present  in 
nearly  all  flies,  even  when  the  mesothoracic  wings  are  wanting.  The 
mouth-parts  are  formed  for  sucking.     The  metamorphosis  is  complete. 

To  the  order  Diptera  belong  all  insects  that  are  properly  termed 
flies,  and  only  these.  The  word  fly  forms  a  part  of  many  compound 
names  of  insects  of  other  orders,  as  butterfly,  May-fly,  and  chalcis-fly ; 
but  when  used  alone,  it  is  correctly  applied  only  to  dipterous  insects. 
To  some  flies  other  common  names  have  been  applied,  as  mosquito, 
gnat,  and  midge. 

The  presence  of  a  single  pair  of  wings  and  of  a  pair  of  halteres  is 
sufficient  to  distinguish  members  of  this  order  from  those  of  all  other 
orders,  except  in  the  case  of  a  few  wingless  forms. 

This  is  a  large  order  both  in  number  of  species  and  of  individuals. 
Aldrich  ('95)  gives  a  list  of  about  eight-thousand  North  American 
species,  distributed  in  more  than  a  thousand  genera. 

Different  species  differ  greatly  in  habits.  Some  are  very  annoying 
to  man.  Familiar  examples  are  the  mosquitoes,  which  attack  his 
person,  the  flesh-flies,  which  infest  his  food,  the  botflies  and  the  gad- 
flies that  torment  his  cattle,  and  the  gallgnats  that  destroy  his  crops. 
Some  species  are  extremely  noxious,  being  disease  carriers,  as  for 
example  the  mosauitoes  that  transmit  malaria  and  yellow  fever. 
Other  species  are  beneficial.  Those  belonging  to  the  Syrphidffi  and 
the  Tachinidse  destroy  many  noxious  insects;  and  very  many  species, 
while  in  the  larval  state,  feed  upon  decaying  animal  and  vegetable 
matter,  thus  acting  as  scavengers. 

There  are  certain  structural  features  of  flies  that  are  used  in  the 
classification  of  these  insects  and  to  which  special  terms  have  been 
applied.  The  more  important  of  these  terms  are  defined  below ;  others 
are  defined  later  in  the  discussion  of  chgetotaxy. 

The  head  and  its  appendages. — The  head  is  very  mobile,  being  con- 
nected to  the  thorax  by  a  slender  neck.  It  is  variable  in  shape  and  in 
its  relative  size. 

The  compound  eyes  are  usually  large,  sometimes  occupying  a  large 
part  of  the  surface  of  the  head.  When  the  eyes  are  contiguous  on  the 
upper  side  of  the  head  they  are  termed  holoptic;  when  they  are  sep- 
arated more  or  less  broadly  they  are  termed  dichoptic.  In  some  flies 
each  compound  eye  is  divided  into  two  parts,  one  of  which  is  a  day- 
eye  and  the  other  a  night-eye.    See  page  144. 

The  ocelli  are  usuallv  three  in  number. 


^Diptera:  dis  (5ts),  two;  pteron  {wTepdv),  a  wing. 
(773) 


774  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  antenna  va.r\  greatly  in  form  in  the  different  famihes.     In 


Fig.  983. 


Fig.  984. 


Fig. 


Fig.  986. 


Fig.  987. 


the  more  generahzed  families  the  antennas  consist  of  many  segments, 
which,  except  the  basal  two,  are.  similar  in  form  (Fig. 
983).  Frequently  such  antennae  bear  whorls  of  long 
hairs  (Fig.  984).  In  the  more  specialized  families  there 
is  a  reduction  in  the  number  of  segments  of  the  anten- 
nae. This  is  brought  about  either  by  a  more  or  less 
complete  consolidation  of  the  segments  beyond  the 
second  into  a  single  segment  (Figs.  985  and  986),  or  by 
a  dwindling  of  the  terminal  segments,  so  that  they  form 
mereh"  a  slender  style  (Fig.  987)  or  bristle  (Fig.  988). 
Such  a  bristle  is  termed  the  arista.  In  most  cases  where 
a  style  or  arista  exists  it  is  borne  by  the  third  segment, 
and  this  segment  is  then  usually  greatly  enlarged.  When 
the  enlargement  of  this  segment  has  taken  place  evenly 
the  style  or  arista  is  terminal;  but  frequently  one  part  of  the  third 
segment  is  expanded  so  that  it  projects  beyond  the 
insertion  of  the  arista  (Fig.  989) ;  then  the  arista 
is  said  to  be  dorsal. 

The  mouth-parts  of  flies  are  formed  for  sucking, 
and  sometimes  also  for  piercing.  Their  structure 
differs  greatly  in  different  families;  and  in  some 
cases  it  is  exceedingly  difficult  to  determine  the 
homologies  of  the  different  parts.  In  the  more 
typical  forms  the  mouth-parts  consist  of  six 
bristle-like  or  lance-like  organs  enclosed  in  a 
sheath  and  a  pair  of  jointed  palpi.  There  are 
differences  of  opinion  as  to  the  homologies  of 
these  parts,  but  according  to  the  most  generally 
accepted  view  they  are  as  indicated  below.  The 
mouth-parts  of  a  mosquito  will  serve  as  an 
example   of   a    comparatively   generalized   type. 


Fig.  989- 


DIPTERA 


775 


Figure  990   represents  a  side  view  of  the  head  of  Anopheles  with  the 
bristle-Hke  organs  removed  from  the  sheath.    The  parts  are  as  follows : 


ir-e 


Fig.  990. — Head  of  Anopheles. 
explained  in  the  text. 


(After  Xuttall  and  Shipley).     The  lettering  is 


the  antenna  (a) ;  the  labrum  or  labnun-epipharynx  {Ir-e) ;  the  hypo- 
pharynx  {h) ;  the  two  mandibles 
(m) ;  the  two  maxilla  {mx) ;  the 
labium  (/) ;  and  the  maxillary 
palpi  {mp).  The  labiimi  is  the 
sheath  in  which  the  six  bristle- 
like organs  are  normally  enclosed ; 
the  maxillarv^  palpi  are  not  en- 
closed in  the  sheath.  At  the  tip 
of  the  labium  there  is  on  each 
side  a  lobe-like  appendage;  these 
are  termed  the  labella.  The  lab- 
ella  are  believed  by  some  writers 
to  be  the  labial  palpi ;  but  it  seems 
more  probable  that  they  are  the 
paraglossce.  The  labella  of  certain 
flies  are  quite  large ;  in  the  house- 
fly, for  example,  they  are  ex- 
panded into  broad  plates,  which 
are  fitted  for  rasping. 

The  frontal  lumde  (Fig.  991, 
/.  /)  is  a  small  crescent-shaped 
sclerite  immediately  above  the 
antennae,  which  is  characteristic 
of  the  second  suborder,  the 
Cyclorrapha.     In  most  members  of  this  suborder  there  is  a  suture 


Fig.  991. — Head  of  a  fly:  A,  antennae; 
ar,  arista,  E,  eye;  /.  /.,  frontal  lun- 
ule;  f.s.,  frontal  suture. 


--1-V  IXTRODL'CTIOX  TO  EXTOMOLOCY 


separating  the  frontal  lunule  from  that  part  of  the  head  above  it ;  this 
is  termed  the  frontal  suture.  Frequently  the  frontal  suture  extends 
down  on  each  side  to  near  the  mouth  (Fig.  991,  /.  s). 

The  ptilimim  is  a  large  bladder-like  organ  which  exists  in  those 
flies  that  have  a  frontal  suture.  The  ptilinum  is  pushed  out  through 
this  suture  when  the  adult  is  about  to  emerge  from  the  puparium.  In 
this  way  the  head  end  of  the  puparium  is  forced  off,  making  a  large 
opening  through  which  the  adult  escapes;  afterwards  the  ptilinirm is 

withdrawn  into  the 
head.  If  a  specimen 
is  captured  soon 
after  its  emergence 
from  the  pupariiun. 
there  may  be  seen 
instead  of  the 
frontal  suttu-e  the 
bladder-like  ptili- 
num projecting 
from  the  head,  im- 
mediately above 
the  antennae. 

The  thorax  a)id 
its  appendages. — 
The  thoracic  region 
of  the  body  con- 
sists chiefly  of  the 
mesothorax,  both 
the  prothorax  and 
the  metathorax  be- 
ing greatly  reduced 
in  size.  The  thorax 
o^f  a  crane-fly  (Fig. 
992),  will  serve  to 
illustrate  the  struc- 


Fig.  992. — Lateral  aspect  of  thorax  of  Pachyrhina  ferru- 
ginea.  (After  Young).  The  thoracic  segments  to 
which  the  sclerites  belong  are  indicated  by  the  num- 
bers I.  2,  and  3.  A,  A,  A,  first  abdominal  segment: 
aem.  anepimerum,  the  upper  part  of  the  epimerum; 
aes,  anepistemum,  the  upper  part  of  the  epistemum; 
ex.  coxa:  em.  epimerum  of  the  metathorax;  h,  halter: 
kem,  kat epimerum,  the  upper  part  of  the  epimerum: 

kes.  kat  epistemum,  the  lower  part  of  the  epistemum;    tvire  of  this  part  m 
me.    meron;  psc.    prescutum;  psl,    postscutellum;  sc,    ^i^  o-pnpral 

scutum;  si.    scutellum;  sp.    spiracle;  tr,    trachantin.    .    ^,  ™"^^    general- 
ized    members     of 
this  order,  and  will 
also  ser\x  as  a  type 
with  which  to  compare  the  thorax  of  the  more  specialized  forms. 

There  are  differences  of  opinion  among  writers  on  this  order  re- 
garding the  homologies  of  certain  thoracic  sclerities.  The  most  ex- 
tended investigation  of  this  subject  is  that  of  Yotmg  ('21)  who  studied 
and  figured  the  thorax  of  representatives  of  fifty-five  of  the  fifty-nine 
families  found  in  our  fauna.  I  have  adopted  this  writer's  conclusions 
regarding  the  homologies  of  the  sclerites  in  question. 

The  most  distinctive  feature  of  the  wings  of  the  Diptera  is  the  fact 
that  only  the  first  pair  are  developed  as  organs  of  flight ;  the  second 


DIPTERA 

pair  being  greatly  reduced  in  size. 
The  second  pair  of  wings  are 
known  as  the  halter es,  they  are 
thread-like,  enlarged  at  the  end, 
and  bear  organs  of  special  sense, 
the  function  of  which  has  not 
been  definitely  determined.  They 
are  present  in  nearly  all  mem- 
bers of  the  order,  even  when  the 
front  wings  are  wanting;  they 
can  be  easily  seen  in  a  crane-fl\' 
(Fig.  993). 

The  fore  iL'ings  are  thin,  mem- 
branous, and  usually  either  naked 
or  clothed  with  microscopic  setae ; 
but  with  mosquitoes  the  wings 
bear  a  fringe  of  scale-like  setae  on 
the  margin  and  usually  also  on 
each  of  the  wing-veins,   and  in 

the  moth-like  flies  (Psychodidae)  and  in  some  others  the  clothing  of 
setce  is  very  conspicuous. 

In  the  more  generalized  members  of  this  order  the  venation  of 
the  mesothoracic  wings  corresponds  quite  closely  to  the  hypothetical 
primitive  type.  Neither  accessor}-  nor  intercalary  veins  are  ever  de- 
veloped, and  only  the  principal  cross- veins  are  present.     The  most 


Fig-   993- — '^   crane-fly,   showing   wings 
and  halteres. 


Fig.  994. — Wing  of  .4  nisopus. 


Striking  divergence  from  this  type  is  the  fact  that  vein  M  is  only 
three-branched.  The  wing  of  ArAsopus  (Fig.  994)  is  a  good  example 
of  a  generalized  dipterous  wing  except  that  the  branches  of  radius 
have  been  reduced.  In  the  more  specialized  forms  the  typical  arrange- 
ment of  the  veins  has  been  greatly  modified  by  the  approaching  and 
coalescing  of  the  tips  of  adjacent  veins,  as  shown  later. 


778 


AN  INTRODUCTION  TO  ENTOMOLOGY 


In  many  families  there  is  a  notch  in  the  inner  margin  of  the  wing 
near  its  base  (Fig.  995,  a.  e)',  this  is  the  axillary  excision;  that  part  of 
the  wing  lying  between  the  axillary  excision  when  it  exists,  and  the 
axillary  membrane  is  the  posterior  lobe  (Fig.  995,7).  In  certain  fami- 
lies the  axillar}^  membrane,  the  membrance  of  the  wing  base,  is  ex- 
panded so  as  to  form  a  lobe  or  lobes  which  fold  beneath  the  base  of 
the  wing  when  the  wings  are  closed;  this  part  of  the  wing  is  the  alula 
or  alulet.  The  alulae  are  termed  the  squamcs  by  some  writers  and  the 
calypteres  by  others.    The  alulae  are  well  developed  in  the  common 


/?■     /?,  +  3 


Fig.  995. — Wing  of  Conops. 

House-fly.  Each  alula,  in  those  species  where  the  alute  are  well  de- 
veloped, consists  of  two  lobes  which  fold  over  each  other  when  the 
wings  are  closed.  These  two  lobes  are  designated  as  the  upper  squama 
or  squamula  alaris  and  the  lower  sqiiama  or  squamula  thoracalis  re- 
spectively. The  alulae  are  called  the  tegulae  by  many  writers  on  Dip- 
tera ;  but  the  term  tegula  was  first  used  in  insect  anatomy  for  the  cup- 
like scale  which  covers  the  base  of  the  wing  in  certain  insects,  as  most 
Hymenoptera,  and  should  be  restricted  to  that  use.  The  terms  alula 
and  alulet  are  also  often  misapplied,  being  used  to  designate  the  pos- 
terior lobe  of  the  wing. 

The  legs  vary  greatly  in  length  and  in  stoutness.     The  coxae  are 
usually  long,  and  in  most  of  the  fungus-gnats  (Mycetophilidae)  they 
are  very  long.     When  pulvilli  are  developed  they  are  membranous 
pads,  one  beneath  each  tarsal  claw.    A  third 
appendage,  the  empodium,  often  exists  be- 
tween the  two  pulvilli  of  each  tarsus.    The 
empodia  may  be  bristle-like  or  tapering  (Fig. 
996)  or  membranous,  resembling  the  pulvilli 
in  form  (Fig.  997)  in  the  last  case  they  are 
described  as  pulvilliform. 

In  descriptions  of   flies  the  ntimber  of 
tibial  spurs  borne  by  the  different  pairs  of 
legs  is  often  indicated  by  a  brief  formula,  as, 
for  example;  "Tibial  spurs  i  :2:2"  indicates  that  the  fore  tibiae  bear 
each  one  spur;  the  middle  tibiae,  two;  and  the  hind  tibas  two. 


Fig.  996. 


Fig.  997. 


DIPTERA  779 

CH^TOTAXY 

OR  THE  ARRANGEMENT  OF  THE  CHARACTERISTIC  BRISTLES  OF  DIPTERA 

In  certain  families  of  the  Diptera  some  of  the  setae  with  which  the  body  is 
clothed  are  stout  bristles,  termed  macrochcetce.  In  the  classification  of  these 
families  much  use  is  made  of  the  number,  position,  and  arrangement  of  these 
bristles.  This  has  made  necessary  the  establishment  of  a  set  of  terms  by  which  the 
different  bristles  or  sets  of  bristles  can  be  designated.  Such  a  terminology  was 
proposed  by  Osten-Sacken  in  1881,  and  is  still  in  use  with  additions. 

In  the  choice  of  terms  Osten-Sacken  and  later  writers  have  used  those  that  in- 
dicate the  places  of  insertion  of  the  bristles.  But  owing  to  the  fact  that  the  homol- 
ogies of  the  sclerites  of  the  head  and  thorax  had  not  been  definitely  determined  at 
the  time  Osten-Sacken  wrote  he  proposed  a  "purely  conventional  terminology" 
for  the  areas  upon  which  the  bristles  are  inserted;  and  in  this  he  has  been  followed 
to  the  present  time.  The  result  is  that  some  of  the  terms  are  misleading;  as  for 
example,  the  so-called  frontal  bristles  are  not  inserted  on  what  is  really  the  front 
but  on  the  vertex.  But  the  use  of  these  terms  is  so  firmly  established  that  it  is  not 
probable  that  they  will  be  changed.  In  the  following  account  I  have  endeavored 
to  indicate  the  homologies  of  the  parts  named  in  those  cases  where  the  terms 
applied  to  them  differ  from  those  used  in  accounts  of  other  orders  of  insects,  and 
which  are  defined  in  Chapter  II.  In  defining  the  special  terms  used  by  writers  on 
chaetotaxy  I  have  made  free  use  of  the  definitions  given  by  Osten-Sacken  ('81), 
Hough  ('98),  Williston,  ('08)  and  Walton  ('09). 

THE  PARTS  OF  THE  HEAD 

The  homologies  of  the  areas  of  the  head  were  determined  by  Peterson  ('16) 
who  studied  and  figured  the  heads  of  representatives  of  nearly  all  of  the  families 
of  Diptera  found  in  our  fauna,  and  who  gives  a  diagram  representing  a  hypothetical 
type  of  the  head-capsule  of  Diptera  (Fig.  998).  The  conclusions  of  Peterson  are 
based  on  comparisons  of  heads  of  the  more  generalized  Diptera  with  those  of  the 
more  generalized  members  of  other  orders  of  insects;  for  descriptions  of  the 
latter  see  above,  pages  37-40  and  96-97. 

The  more  important  landmarks  for  determining  the  homologies  of  the  areas  of 
the  cephalic  aspect  of  the  head,  the  region  in  which  the  greatest  confusion  exists, 
are  the  stem  of  the  epicranial  suture  (Fig.  998,  5.  e.  s);  the  arms  of  the  epicranial 
suture  (Fig.  998,  a.  e.  s);  and  the  positions  of  the  invaginations  of  the  dorsal  arms 
of  the  tentorium.  (Fig.  998,  i.  d.)\  and  of  the  anterior  arms  of  the  tentorium 
(Fig.  998,  i.  a.) 

In  Figure  999  is  given  a  diagram  illustrating  the  terms  applied  by  writers  on 
chaetotaxy  to  the  areas  of  the  head.    These  terms  are  defined  below. 

The  antennal  fossa,  fovea,  or  groove. — Depressed  areas  of  the  fronto-clypeus  in 
which  the  antennae  rest  (Fig.  999,  a.f.) 

The  Bucca. — That  part  of  the  wall  of  the  head  on  each  side  that  is  ventrad  of 
the  transverse  impression,  and  ventrad  of  the  eye,  extending  ventrad  to  the  edge 
of  the  mouth  opening,  cephalad  to  the  vibrissal  ridge  and  continuing  caudad  on 
the  gena  to  the  caudal  margin  of  the  head  (Fig.  999,  b.) 

The  cheeks. — This  term  is  used  differently  by  different  systematists;  by  some 
is  applied  to  the  space  on  each  side  of  the  head  that  is  between  the  lower  border  of 
the  eye  and  the  oral  margin,  differing  from  the  bucca  only  in  that  it  does  not 
extend  over  the  caudal  aspect  of  the  head;  by  others  it  is  applied  to  this  space  and 
the  so-called  gena  of  writers  on  chaetotaxy;  and  by  others  to  the  so-called  gena 
alone. 

The  cheek-grooves. — A  more  or  less  distinct  depression  on  each  side  below  the 
eye. 

The  clypeus. — See  fronto-clypeus. 

The  epistoma. — The  oral  margin  and  an  indefinite  space  immediately  con- 
tiguous thereto. 

The  face. — That  part  of  the  cephalic  aspect  of  the  head  lying  below  an  imag 
inary  horizontal  line  passing  through  the  base  of  the  antennas.   (Fig.  999,  Fa.). 


780 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  facial  depression. — See  antennal  fossa. 

The  facialia  or  facial  ridges. — See  vibrissal 
ridges. 

The  front.— {a)  The  true  front  (Fig.  998, 
fr.)  is  the  first  of  the  unpaired  sclerites  be- 
tween the  arms  of  the  epicranial  suture.  See 
above  pages  37  and  38.  This  term  has  been 
generally  applied  to  this  sclerite  since  it  was 
proposed  by  Kirby  (Kirby  and  Spence)  nearly 
a  century  ago.  (b)  The  so-called  front  of 
writers  on  chaetotaxy  is  that  part  of  the  vertex 
that  extends  from  the  base  of  the  antennae  to 
the  upper  margin  of  the  head  (Fie.  999,  Fr.). 

The  frontalia. — See  frontal  vitta. 

The  frontal  orbits. ^See  genovertical  plates. 

The  frontal  triangle. — In  holoptic  flies, 
those  in  "which  the  eyes  are  contiguous  on  the 
upper  side  of  the  head,  the  triangle  between 
the  eyes  and  the  antennae,  the  apex  of  which 
is  above,  is  termed  the  frontal  triangle.  Some 
times  this  term  is  applied  to  a  triangle  indi- 
cated by  color  or  a  depression  in  the  corre- 
sponding position  in  fhes  with  dichoptic  eyes. 

The  frontal  lunule. — See  page  775. 

The  frontal  suture. — See  page  776. 

The  frontal  vitta.  The  median  portion  of 
the  so-called  front,  extending  from  the  base  of 
the  antennae  to  the  oceUi  (Fig.  999,  f.  v.). 

The  fronto-clypeiis. — This  term  is  applied 
to  the  combined  front  and  clypeus  when  the 
suture  between  them  is  obsolete,  as  is  usually 
the  case  in  Diptera.  It  is  the  part  bounded 
above  by  the  arms  of   the   epicranial 


le   pS    gl  md 

Fig.  998. — Hypothetical  type  of 
head-capsule  of  Diptera;  a.  e. 
s,  arms  of  epicranial  suture;  a, 
/,  antennal  fossa;  ant,  antenna; 
a.  s,  antennal  sclerite;  c,  cly- 
peus; c.  e,  compound  eye;  c.  I. 
s.  clypeo-labial  suture;  /2,  fur- 
ca;  /3,  furca;  g,  galea,  ge,  gena; 
gl,  glossa;  i.  a.  and  i.  d,  invagi- 
nations of  the  tentorium;  /,  lab- 
rum;  le,  labella;  m,  membrane; 
md,  mandible;  mx.  pi,  maxilla- 
ry palpus;  oc,  ocelli;  0.  I,  oral 
lobe;  pgl,  paraglossa;  5.  e.  s, 
stem  of  epicranial  suture;  z', 
vertex.     (From  Peterson.) 


suture 
(Fig.  998,  a.  e.  s)  and  below  by  the  clypeo- 
labial  suture  (Fig.  998,  c.  I.  s.). 

The  gencE. — (a)  The  true  genae  (Fig.  48,  G,  page  39).  The  term  genae  was 
introduced  into  entomology  nearly  a  century  ago  by  Kirby  (Kirby  and  Spence) 
and  was  applied  to  the  lateral  portions  of  the  epicranium,  that  part  on  each  side  of 
the  head  lying  beneath  and  behind  the  eye;  and  has  been  generally  used  by 
writers  on  insect  morphology  in  this  sense,  (b)  The  so-called  genae  of  writers  on 
chaetotaxy  are  portions  of  the  cephalic  aspect  of  the  head,  that  part  on  each  side 
which  is  dorsad  of  the  transverse  impression,  laterad  of  the  arm  of  the  frontal 
suture  and  mesad  of  the  eye  (Fig.  999,  g).  This  region  is  "the  sides  of  the  face" 
of  older  descriptions  and  the  parafacialia  of  some  later  writers. 

The  genovertical  plates. — The  so-called  front  of  writers  on  chaetotaxy  (see 
above)  is  usually  distinctly  divided  into  three  parts,  a  median,  the  frontal  vitta  or 
frontalia,  and  two  lateral,  the  genovertical  plates  or  parafrontalia.  (Fig.  999, 
g-P-)- 

The  interfrontalia. — Specialized  stripes  on  the  middle  of  the  so-called  front, 
formed  from  the  enlarged  ocellar  triangle. 

The  occiput. — The  term  occiput  is  applied  by  writers  on  the  classification  of 
the  Diptera  to  the  caudal  aspect  of  the  head,  this  includes  the  genae  and  post- 
genas  described  on  page  39. 

The  ocellar  plate  or  ocellar  triangle. — A  triangle  indicated  by  grooves  or  de- 
pressions on  which  the  ocelli  are  situated. 

The  orbits. — That  part  of  the  epicranium  on  each  side  immediately  contiguous 
to  the  compound  eye.  The  orbit  is  sometimes  indicated  by  structural  characters, 
at  other  times  it  is  indefinite. 

The  parafacials. — The  so-called  genae  of  writers  on  chaetotaxy. 

The  parafrontals. — The  genovertical  plates. 

The  peristome. — The  region  around  the  mouth. 


DIPTERA 


ISl 


The  poslgence. — See  page  39. 

The  ptilinnm. — See  page  776. 

The  transverse  impression. — See  cheek-groves. 

The  tormcE. — A  sclerite  situated  between  the  clypeus  and  the  labrum  in  the 
more  specialized  Diptera.  It  is  composed  of  two  sclerites  which  belong  to  the 
lateral  portions  of  the  epiphar,vnx  and  are  internal  in  the  more  generalized  in- 
sects; but  they  become  exposed  and  united  on  the  middle  line  in  the  more  special- 
ized Diptera.  In  such  cases  the  tormas  are  sometimes  incorrectly  termed  the 
clypeus.     See  Peterson  ('16  p.  19). 

The  vertex. — (a)  The  term  vertex,  as  defined  by  Kirby  (Kirby  and  Spence, 
1815-1826),  is  the  dorsal  portion  of  the  epicranium;  or,  more  specifically,  that 
portion  which  is  next  the  front  and  between  the  compound  eyes  (Fig.  998,  v.  v.  v.) 
{h)  This  term  is  often  applied  merely  to  the  top  of  the  head. 


Fig.  999. — Diagram  illustrating  the  terms 
applied  by  writers  on  ch^totaxy  to  the 
areas  of  the  head:  a.  f.  antennal  fossa; 
h,  bucca;  E,  eye;  Fa,  face;  Fr,  the  so- 
called  front;  f.v,  frontal  vitta;  g,  the  so- 
called  gena;  g.p,  genovertical  plate;  v, 
vibrissa;  v.  r,  vibrissal  ridge. 


Fig.  1000. — Cephalic  bristles:  fa,  fa- 
cial, /;-,  frontal;  /.  0.,  fronto-orbital; 
g.  0,  greater  ocellar;  /.  0,  lesser  ocel- 
lar;  ve,   vertical;  vi,   vibrissae. 


The  vertical  triangle. — See  the  ocellar  plate. 

The  vibrissal  angles. — Two  prominences  at  the  lower  ends  of  the  vibrissal 
ridges  upon  which  are  borne  the  vibrissae. 

The  vibrissal  ridges. — Two  ridges,  one  on  each  side,  inside  the  arms  of  the 
frontal  suture,  constituting  the  lateral  boundaries  of  the  antennal  fossa,  and 
bearing  the  vibrissas  (Fig.  999,  v.  r).  These  are  also  termed  the  facialia  or  facial 
ridges. 

THE  CEPH.\LIC  BRISTLES 

The  ascending  frontal  bristles. — See  frontal  bristles. 

The  beard. — A  clothing  of  hair  borne  by  the  lower  part  of  the  so-called  occiput 
and  on  the  buccae. 

The  cilia  of  the  posterior  orbit. — A  row  of  bristles  along  the  posterior  orbit  of 
the  eve. 


782  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  cruciate  bristles.-^A  pair  of  bristles  on  the  lower  part  of  the  frontal  vitta, 
directed  inward  and  forward. 

The  facial  bristles. — A  series  of  bristles  on  either  side  borne  by  the  vibrissa! 
ridge,  above  the  vibrissa  (Fig.  looo,  fa.). 

The  facio-orhital  bristles. — Bristles  borne  on  that  portion  of  the  face  on  each 
side  next  to  the  orbit,  the  so-called  gena. 

The  frontal  bristles. — A  row  of  bristles  on  each  side  on  the  boundary  line  be- 
tween the  frontal  vitta  and  the  genovertical  plate.  (Fig.  lOOO,  fr.)  the  uppermost, 
of  these,  from  one  to  four  in  number,  are  termed  the  ascending  frontal  bristles; 
the  lower  ones,  which  are  often  directed  across  the  frontal  vitta,  are  termed  the 
transfrontral  bristles. 

The  fronto-orbital  bristles. — A  bristle  or  bristles  on  the  genovertical  plate,  ■ 
immediately  below  the  vertical  bristles.  (Fig.  lOOO,  fo.).  So  named  because 
they  are  on  that  part  of  the  so-called  front  next  to  the  orbit. 

The  lateral  facial  bristles. — One  or  two  bristles  sometimes  present  on  the  sides 
of  the  face  below,  towards  the  eye. 

The  lower  fronto-orbital  bristles. — These  are  situated  on  the  lower  part  of  the 
genovertical  plates  near  the  eyes  and  are  not  quite  in  line  with  the  fronto-orbitals. 
They  are  not  of  fiequent  occurrence. 

The  ocellar  bristles. — (a)  The  greater  ocellars  or  the  ocellar  pair,  a  pair  of  bristles 
on  the  ocellar  triangle  just  back  of  the  median  ocellus  (Fig.  lOOO,  g.  o.).  (b)  The 
lesser  ocellar  bristles,  from  three  to  twelve  pairs  of  bristles,  usually  inserted  in  two 
parallel  lines,  sometimes  in  four,  which  begin  very  close  to  the  insertion  of  the 
greater  ocellar  bristles  and  extend  backward  a  variable  distance  (Fig.  lOOO,  /.  o.). 

The  occipito-central  bristles. — A  pair  of  bristles  on  the  upper  part  of  the  occiput 
just  below  and  almost  in  line  with  the  inner  vertical  pair. 

The  occipito-lateral  bristles. — A  pair  of  bristles  borne,  one  on  each  side,  a 
little  back  of  the  outer  vertical  bristles. 

The  orbital  bristles. — See  fronto-orbital  bristles. 

The  postorbital  bristles. — See  cilia  of  the  posterior  orbit. 

The  postvertical  bristles. — The  hinder  pair  of  the  lesser  ocellar  bristles. 

The  preocellar  bristles. — A  pair  of  small  bristles  sometimes  found  below  the 
median  ocellus. 

The  transfrontal  bristles. — See  frontal  bristles. 

The  vertical  brisHes. — Two  pairs  of  bristles,  an  inner  and  outer  pair,  inserted 
more  or  less  behind  the  upper  and  inner  corners  of  the  eyes  (Fig.  lOOO,  ve.). 

The  vibrissce. — A  pair  of  stout  bristles,  one  on  each  side  of  the  face,  near  or  a 
little  above  the  oral  margin  (Fig.  lOoo,  vi).  These  are  the  longest  or  strongest  of 
the  bristles  borne  on  the  vibrissal  ridges. 

THE  THORACIC  SUTURES 

The  transverse  suture. — The  suture  between  the  prescutum  and  the  scutum  of 
the  mesothorax. 

The  notopleural  or  dorsopleural  suture. — The  suture  on  each  side  separating 
the  mesonotum  from  the  pleurum  of  the  mesothorax. 

The  mesopleural  suture. — The  suture  on  each  side  separating  the  episternum 
and  the  epimerum  of  the  mesothorax. 

The  sternopletcral  suture. — The  suture  on  each  side  separating  the  mesopleurum 
and  the  sternopleurum. 


THE  PLEURAL  DIVISIONS 

The  propleura. — The  pleura  of  the  prothorax  (Fig.  looi,  pr.). 

The  notopleura. — A  sclerite  on  each  side  at  the  end  of  the  transverse  suture  in 


DIPTERA 


783 


the  presutural  depression.  (Fig. 
looi,  np.). 

The  mesopleura. — The  upper 
part  of  the  episterna  (anepis- 
terna)  of  the  mesothorax  (Fig. 
looi  mes.). 

The  sternopleura. — The  lower 
part  of  the  episterna  (katepi- 
stema)  of  the  mesothorax  (Fig. 

lOOI,  St.). 

The  pteropleura. — The  upper 
part  of  the  epimera  (anepimera) 
of  the  mesothorax,  (Fig.  lOOi, 
pt.). 

The  hypopleura. — The  lower 
part  of  the  epimera  (katepimera) 
of  the  mesothorax  (Fig.  lOOi, 
hy.). 

The  metapleura. — The  pleura 
of  the  metathorax. 


OTHER  TERMS  FOR  PARTS 
OF  THE  THORAX 


Fig.  lOOi. — Diagram  of  the  thorax  of  a  fly 
illustrating  the  terms  applied  by  writers  on 
chaetotaxy  to  the  areas  of  the  thorax.  The 
positions  of  the  more  important  bristles 
are  indicated  by  dots:  ex,  ex,  ex,  coxs;  h. 
c,  humeral  callus;  h,  halter;  hy,  hypo- 
pleura;  mes,  mesopleura;  np,  notopleiu"a 
or  presutural  depression;  po.  c,  postalar 
callus;  pr,  propleura;  pt,  pteropleura;  s, 
scutellum;  sq,  sq,  squamas  or  calypteres; 
St,  sternopleura;  w.  b.  wing-base.  (After 
Riley  and  Johannsen.) 


The  alar  frenum. — A  little 
ligament  dividing  the  supraalar 
cavity  into  an  anterior  and  a 
posterior  part. 

The  humeral  callus. — Each  of 
the  anterior  lateral  angles  of  the 
prescutum  of  the  mesothorax, 
usually  a  more  or  less  rounded 
tubercle.     (Fig.  lOOi,  h.  c.). 

The    prealar    callus. — A    not 
very  prominent  projection,  situ- 
ated before  the  root  of  the  wing,  on  each  side  of  the  mesonotum,  just  back  of  the 
outer  end  of  the  transverse  suture. 

The  postalar  callus. — A  more  or  less  distinct  rounded  swelling  on  each  side, 
situated  between  the  root  of  the  wing  and  the  scutellum.     (Fig.  looi,  po.  c). 

The  presutural  depression. — A  depression,  usually  triangular  in  shape,  at  the 
outer  end  of  the  transverse  suture,  near  the  notopleural  suture  (Fig.  lOOi,  np). 

The  supraalar  groove  or  cavity. — A  groove  on  the  mesothorax  immediately 
above  the  root  of  the  wing. 

The  scutellar  bridge. — A  small  ridge  on  either  side  of  the  scutellum  connecting' 
it  with  the  scutum,  crossing  the  intervening  suture. 


THE  THORACIC  BRISTLES 


The  acrostichal  bristles. — Two  rows  of  bristles,  one  on  each  side  of  the  median 
line  of  the  mesonotum,  the  two  rows  nearest  to  the  median  line  (Fig.  1002,  a). 
Those  in  front  of  the  transverse  suture  are  termed  the  anterior  acrostichals  or 
preacrostichals;  those  behind  this  suture,  the  posterior  acrostichals  or  pos'acrosti- 
chals. 

The  anterior  acrostichals. — See  the  acrostichal  bristles. 

The  discal  scutellar  bristles. — See  the  scutellar  bristles. 

The  dorsocentral  bristles. — ^A  row  of  bristles  on  each  side  next  to  and  parallel 
with  the  acrostichals  bristles  (Fig.  1002,  dc).  Those  before  the  transverse  suture 
are  termed  the  anterior,  those  behind,  the  posterior,  or  postsutural  dorsocentrals. 

The  humeral  bristles. — One  or  more  bristles  inserted  on  the  humeral  callus. 
(Fig.  1002,  h  m). 


•84 


AN  INTRODUCTION  TO  ENTOMOLOGY 


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The  hypopleiiral  row. — A  row  of  bristles  extending  in  a  more  or  less  vertical 
direction  on  the  hypopleura,  usually  directly  above  the  hind  coxae.  The}'  are 
sometimes  grouped  into  a  tuft.     (Fig.  looi). 

The  inner  dorsocentral  bristles. — These  are  the  acrostichal  bristles. 
The  intraalar  bristles. — A  row  of  two  of  three  bristles  between  the  supraalar 

group   and   the  dorsocentral 
bristles  (Fig.  1002,  i.  a). 

The  int rah  lime ral  bristles. 
— These  are  the  same  as  the 
presutural  bristles. 

The  marginal  scutellar 
bristles. — See  the  scutellai' 
bristles. 

The  mesopleural  row. — A 
row  of  bristles  inserted  on  the 
mesopleurum,  near  its  dorso- 
caudal  angle,  or  along  its 
caudal  margin.  (Fig.  lOOi). 
The  metapleural  bristles. — 
A  fan  like  row  on  the  meta- 
pleurum  conspicuous  in  some 
families  but  not  found  in  the 
Calypteratse. 

The  notopleiiral  bristles. — 
Usually  two  bristles,  inserted 
immediately  above  the  dorso- 
pleural  suture,  between  the 
humeral  callus  and  the  root 
of  the  wing,  on  the  noto- 
pleura.     (Fig.  1002,  n  p  I  ). 

The  postacrostichals. — See 
the  acrostichal  bristles. 

The  postalar  bristles. — 
Bristles  on  the  postalar  callus 
back  of  the  supraalar  bris- 
tles.    (Fig.  1002,  pa). 

The  posthumeral  bristles. 
— One  or  more  bristles  situated  on  the  prescutum  near  the  inner  margin  of  the 
humeral  callus.     (Fig.  1002,  ph.) 

The  preacrostichals. — See  acrostichal  bristles. 

The  prealar  bristle. — A  bristle  found  in  the  Anthomyiidse  inserted  just  back  of 
the  transverse  suture  in  line  with  the  supraalar  bristles.     (Fig.  1002,  pra). 

The  prescutellar  row. — A  row  of  bristles  in  front  of  the  scutellum  consisting  of 
the  hindermost  dorsocentral  and  the  acrostichal  bristles. 

The  presutural  bristles. — One  or  more  bristles  situated  immediately  in  front  of 
the  transverse  suture,  above  the  presutural  depression.     (Fig.  1002,  pr.). 

The  propleural  bristles. — A  bristle  or  bristles  inserted  on  the  lower  part  of  the 
pleurum  of  the  prothorax,  immediately  above  the  front  coxa. 
The  prothoracic  bristle. — The  same  as  the  propleural  bristle. 
The  pteropleural  bristles. — Bristles  inserted  on  the  pteropleura. 
The  scutellar  bristles. — (a).    The  dorso-scutellar  bristles.,  usually  a  single  pair  of 
bristles,  borne  on  the  dorsal  portion  of  the  scutellum,  one  on  each  side  of  the 
median  line,  slightly  behind  its  middle.     (Fig.  1002,  ds).     {b)  The  marginal  scu- 
tellar bristles,  usually  a  distinct  row  of  large  bristles  borne  on  the  margin  of  the 
scutellum  (Fig.  1002,  ms). 

The  sternopleural  bristles. — One  or  several  bristles  on  each  sternopleurum 
below  the  sternopleural  suture  and  near  it. 

The  supraalar  bristles. — Usually  one  to  four  bristles  above  the  root  of  the  wing, 
between  the  notopleural  and  the  postalar  bristles.     (Fig.  1002,  sa). 
The  trichostichal  bristles. — The  same  as  the  metapleural  bristles. 


Fig.  1002. — Thoracic  bristles:  a,  acrostichal; 
dc,  dorsocentral;  ds.  dorsoscutellar;  hm,  hum- 
eral; ia,  intraalar;  ms,  marginal  scutellar; 
npl,  notopleural;  pa,  postalar;  ph,  posthum- 
eral; pr.  presutural;  sa,  supraalar;  /.  sq., 
lower  squama  or  calypter;  u.  sq.  upper  squama 
or  calypter;  w.  b,  wing-base.  (After  Riley 
and  Johannsen.) 


DIPTERA  785 

THE  BRISTLES  OF  THE  LEGS 

The  extensor  row. — A  row  of  bristles  on  the  upper  surface  of  femur. 

The  flexor  row. — One  or  more  rows  of  bristles  placed  along  the  lower  surface  of 
the  femur. 

The  preapical  bristle. — A  large  bristle  found  on  the  extensor  side  on  the  distal 
third  of  the  tibia  in  some  families  of  the  Acalyptratas ;  it  is  quite  distinct  from  the 
tibial  spurs.     This  term  is  sometimes  used  for  a  bristle  on  the  femur. 

The  tibial  spurs. — One  or  more  bristly  spurs  placed  at  the  distal  end  of  the 
tibia. 

THE  ABDOMINAL  BRISTLES 

The  discal  bristles. — Usually  one  or  more  pairs  of  bristles  inserted  near  the 
middle  of  the  dorsal  wall  of  the  abdominal  segments  before  the  hind  margin. 

The  lateral  bristles. — One  or  more  bristles  situated  on  or  near  the  lateral 
margins  of  the  abdominal  segments,  above. 

The  marginal  bristles. — Bristles  inserted  on  the  posterior  margin  of  the  ab- 
dominal segments,  above. 

Flies  undergo  a  complete  metamorphosis.  The  larvfe  are  com- 
monly called  maggots.  These  are  usually  cylindrical  and  are  footless. 
In  the  more  generalized  families  the  larvse  possess  a  distinct  head ;  but 
in  the  more  specialized  Diptera  there  is  an  anomalous  retarding  of  the 
development  of  the  head;  with  these  the  rudiments  of  the  head  are 
invaginated  within  the  body  of  the  larva  and  the  head  does  not  be- 
come exposed  until  the  pupal  stage  is  reached.  The  development  of 
the  head  in  these  insects  is  described  in  Chapter  IV.  The  pupae  are 
usually  either  naked  or  enclosed  in  the  last  or  the  next  to  the  last 
larval  skin.  A  few  are  enclosed  in  cocoons.  When  the  pupa  state  is 
passed  within  the  last  larval  skin  the  body  of  the  pupa  separates  from 
the  larval  skin  more  or  less  completely;  but  the  larval  skin  is  not 
broken  till  the  adult  fly  is  ready  to  emerge.  In  this  case  the  larval 
skin,  which  serves  as  a  cocoon,  is  termed  a  pupariiim.  In  some  fam- 
ilies the  puparium  retains  the  form  of  the  larva;  in  others  the  body 
of  the  larva  shortens,  assuming  a  more  or  less  barrel-shaped  form 
before  the  change  to  a  pupa  takes  place. 

SYNOPSIS  OF  THE  DIPTERA 

Suborder  Orthorrhapha.     The  Straight-seamed  Flies,     p.  794. 
Series  I. — Nemocera.     The  Long-horned- Orthorrhapha.  p.  795. 
Subseries  A. — The  True  Nemocera. 

The  Crane-flies,  p.  795.    vSuperfamily  Tipuloidea 

The  Primitive  Crane-flies,  p.  796.    Family  Tanyderid.e 
The    Phantom    Crane-fly    Family,  p.  796.      Family    Ptychopterid.^ 
The  So-called  False  Crane-flies,  p.  797.     Family  Anisopid^ 
The  Typical  Crane-flies,  p.   798.     Family  Tipulid.e 
The  Dixa  midges,  p.  800.     Family  DixiD.« 
The  Moth-like  Flies,  p.   801.     Family  Psychodid.« 
The  Midges,  p.  802.     Family  Chironomid^ 
The  Mosquitoes,   p.   804.      Family   Culicid^ 
The    Fungus-gnats,    p.    810.      Family    Mycetophilid^ 
The  Gall-gnats,  p.   813.     Family  Cecidomyiid.e 
Subseries  B. — The  Anomalous  Nemocera. 
The  March-flies,  p.  820.     Family  Bibionid.^ 
The  Scatopsids.  p.  821.     Family  Scatopsid.« 


786  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  Black-flies,  p.  821.     Family  Simuliid^ 
The  Net-winged  Midges,  p.  824.     Family  Blepharocerid^ 
The  Solitary-midge,  p.   828.     Family  Thaumaleid^ 
Series  II. — Brachycera.    The  Short-horned  Orthorrhapha.  p.  828. 
Subseries  A. — The  Anomalous  Brachycera. 
The  Horse-flies,  p.  829.     Family  TabaniD/E 
The  Soldier- flies,  p.  830.    Family  Stratiomyiid.'E 
The  Xjdomyiids.  p.  832.    Family  Xylomyiid^ 
The  XVlophagids.  p.  833.     Family  Xylophagid/E 
The  Coenomyiids.  p.  834.     Family  Ccenomyiid^ 
Subseries  B. — The  True  Brachycer^a.. 

The  Snipe-flies,  p.  834.     Family  Rhagionid^ 
The  Tangle-veined  Flies,  p.  836.     Family  Nemestrinid^ 
The  Small-headed  Flies,  p.   837.     Family  Acrocerid^ 
The  Bee-flies,  p.  838.     Family  Bombyliid^ 
The  Stiletto-flies,  p.  839.    Family  Therevid^ 
The  Window-flies,  p.  839.     Family  vScenopinid/E 
The  Robber-flies,  p.  840.     Family  AsiliDvE 
The  Mydas-flies.  p.  842.     Family  Mydaid^ 
The  Apiocerids.  p.  842.     Family  Apiocerid^ 
The  Long-legged  Flies,  p.  843.     Family  Dolichopodid^ 
The  Dance-flies,  p.  845.     Family  Empidid/E 
The  Spear-winged  Flies,  p.  846.     Family  LoNCHOPTERiDiE 
Suborder  Cyclorrhapha.     The  Circular-  seamed  Flies. 
Series  I. — Aschiza.    Cyclorrhapha  without  a  frontal  suture. 
The  Humpbacked  Flies,  p.  847.     Family  Phorid^ 
The  Flat-footed  Flies,  p.  848.     Family  Platypezid^ 
The  Big-eyed  Flies,  o.  849.    Family  Pipunculid^ 
The  Syrphus-flies.  p.  850.    Family  Syrphid.« 
Series  II. — Schizophora.     Cyclorrhapha  with  a  frontal  suture. 
Section  I. — Myodaria.     The  Muscids. 

Subsection  I. — Acalyptrat^.     The  Acalyptrate  Muscids. 
The  Thick-headed  Flies,  p.  853.     Family  Conopid^ 
The  Dung-flies,   p.   854.     Family  Cordylurid^ 
The  Clusiids.  p.  854.     Family  Clusiid^ 
The  Helomyzids.  p.  854.     Family  Helomyzid^ 
The  Borborids.  p.  855.    Family  Borborid^ 
The  Phycodromids.  p.  855.    Family  Phycodromid^ 
The  Sciomyzids.  p.  855.    Family  SciomyziD/E 
The  Sapromyzids.  p.  856.    Family  Sapromyzid/e 
The  Lonchasids.  p.  856.     Family  Lonch^id^e 
The  Ortalids.  p.  856.     Family  OrtaliD/E 
The  Trypetids.  p.  858.     Family  Trypetid^ 
The  Tanypezids.  p.  858.     Family  Tanypezid.!: 
The  Micropezids.  p.  858.     Family  Micropezid^ 
The  vSeosids.  p.  858.    Family  Sepsid^ 
The  Piophilids.  p.  858.     Family  Piophilid.'E 
The  PsiHds.  p.  859.    Family  Psilid/E 
The  Diopsids.  p.  859.     Family  Diopsid^ 
The  Canaceids.  p.  859.     Family  Can.\ceid^ 
The  Ephydrids.  p.  859.    Family  Ephydrid/E 
The  Chloropids.  p.  860.     Family  Chloropid^ 
The  Asteiids.  p.  860.    Family  Asteiid^ 
The  Drosophilids.  p.  860.     Family  Drosophilid^e 
The  Geomyzids.  p.  861.     Family  Geomyzid.^ 
The  Agromyzids.  p.  861.     Family  Agromyzid/E 
The  Mihchiids.   o.   862.     Family  Milichiid^ 
The  Ochthiphilids.   p.   862.     Family  Ochthiphilid/E 
Subsection  II.     Calyptr.\t^.     The  Calyptrate  Muscids. 
Superfamily   Axthomyioidea 

The  Anthomyiids.  p.  863.     Family  Anthomyiid^ 


DIPT  ERA  787 

Superfamily  Muscoidea. 

The  Bot-flies  of  Horses,  p.  864.     Family  Gastrophilid.« 
The  Oistrids.  p.  866.     Family  CEstrid^ 
The  Phasiids.  p.   868.     Family  Phasiid^ 
The  Megaprosopids.  p.  869.     Family  Megaprosopid^ 
The  Blow-fly  Family  p.  869.     Family  Calliphorid.^ 
The  Sarcopiiagids.  p.   870.     Family  Sarcophagid.-e 
The   Tachina-flies.   p.    871.     Family   Tachinid^ 
The  Typical  Muscids.  p.  872.    Family  Muscid/E 
Section  II.     Pupipara. 

The  Louse-flies,  p.  874.     Family  Hippoboscid^ 

The  Bat-ticks  in  part.  p.  875.     Family  Streblid^ 

The  Bat-ticks  in  part.  p.  875.     Family  Nycteribiid^ 

The  Bee-lice.  p.  876.    Family  Braulid^ 

TABLES  FOR  DETERMINING  THE  FAMILIES 

OF  THE  DIPTERA 

Table  A.— DIPTERA  WITH  WELL  DEVELOPED  WINGS. 

A.  Flies  in  which  the  abdomen  is  distinctly  segmented,  and  the  two  legs  of  each 
thoracic  segment  are  not  widely  separated.  Habits  various,  but  the  adults  do 
not  live  parasitically  upon  either  birds  or  mammals. 

B.     Antennae  consisting  of  more  than  three  segments.     (Note  that  a  style  or 

arista  borne  by  the  third  segment  is  not  counted  as  a  segment.) 

C.     Antennae  consisting  of  inore  than  five  distinct  segments,  the  segments 

beyond  the  second  not  consolidated;  cell  ist  A  of  the  wings  but  slightly 

narrowed  at  the  margin  of  the  wing,  if  at  all;  palpi  usually  elongate,  and 

composed  of  from  three  to  five  segments. 

D.  Small  moth-like  flies,  with  the  body  and  wings  densely  clothed  with 
hairs  and  scales.  Wings  with  from  nine  to  eleven  longitudinal  veins 
but  with  no  cross-veins  except  sometimes  near  the  base  of  the  wings. 

(Fig.      IOI4).      p.      801 PSYCHODID^ 

DD.    Flies  that  do  not  resemble  moths  in  appearance. 

E.     Mesonotum  with  a  distinct  V-shaped  transverse  suture. 

F.     The  radial  sector  four-branched,  p.  796 Tanyderid/E 

FF.      The   radial   sector   with   less   than   four   branches. 

G.     With  only  one  anal  vein.  p.  796 Ptychopterid/E 

GG.     With  two  anal  veins,  p.   798 Tipulid^ 

EE.     Mesonotum  without  a  distinct  V-shaped  suture. 

F.      Media    three-branched    {Anisopus    and    Trichocera).  p.    797.. 

AnISOPID/E 

FF.    Media  simple,  two-branched,  or  wanting;  cell  M2  is  not  divided 
by  a  cross-vein. 
G.     Wings  with  a  network  of  fine  lines  near  the  outer  and  inner 

margins  in  addition  to  the  veins    (Fig.    1048).   p.   824 

Blepharocerid/e 

GG.     Wings  without  a  network  of  fine  lines. 

H.     The  margin  of  the  wings  and  each  of  the  wing- veins  fringed 

with    scales    (Fig.    1019).    p.    804 Culicid^ 

HH.     The  wing-veins  with  or  without  a  fringe  of  hairs,   but 
without  a  fringe  of  flat  scales. 

I.  Anal  veins  entirely  wanting;  vein  M  wanting  or  at  most 

represented    by    a    single    unbranched    fold.    p.    813 

Cecidomyiid^ 

II.  Anal  veins  usually  present  or  represented  by  folds ;  vein  M 
present  or  at  least  represented  by  a  fold  which  is  usually 
branched. 

J.    Ocelli  present. 

K.      Antennas   shorter   than    the   thorax;  coxae   not    un- 
usually long. 


788  AN  INTRODUCTION  TO  ENTOMOLOGY 

L.  Cross-vein  m-cu  present,  p.  820. .  .Bibionid^ 
LL.  Cross-vein  m-cu  wanting,  p.  821 .  Scatopsid^. 
KK.  Antennae  usually  longer  than  the  thorax;  legs 
slender  and  usually  with  greatly  elongate  coxas. 
L.  Vein  m-cu  present,  the  first  branch  of  the  radial 
sector,   vein   R2  -I-  3,   arising    slightly     proximad   of 

vein      m-cu.        {Mycetohia)      p.  797 ANisopiDiE 

LL.     Vein  m-cu  present  or  absent,  when  present  the 

forking  of  the  radial  sector  is  distad  of  it. 

M.     Eyes  rounded  or  oval.   p.  Sio.Mycetophilid^ 

MM.     Each  eye  with  a  narrow  expansion,  the   two 

expansions  extending  behind  the  antennae  and  in 

front  of  the  ocelli,  and  meeting  on  the  middle  line 

of  the  head  or  nearly  so. 

N.     With  tibial  spurs;  larvae  with  well-developed 

head     (Sciarinae)     p.     812 Mvcetophilid^ 

NN.     Without  tibial  spurs,  larvae  with  a  poorly 

developed    head     (Lestremiinae).    p.    816 

CeCIDOMYIID/E 

JJ.     Ocelli  absent. 

K.  Antennas  short,  not  clothed  with  long  hairs,  and  with 
most   of   the   segments   wider   than   long;  wings   very 

broad,     p.     821 Simuliid^ 

KK.  Antenns  either  bushy,  being  densely  clothed  with 
long  hairs,  or  slender  with  narrow  segments;  wings 
narrow  or  moderately  broad. 

L.    Wing-veins  well-developed  on  all  parts  of  the  wing. 

M.    Vein  Ri  ending  at  or  near  the  end  of  the  second 

third  of  the  costal  margin,  p.  828.  Thaumaleid^ 

MM.     Vein  Ri  ending  on  the  outer  margin  of  the 

wing.   p.   800 DixiD.^ 

LL.     Wing  veins  much  stouter  near  the  costal  margin 
of  the  wing  than  elsewhere,   p.   8o2.Chironomid^ 
CC.    Antenna  either  consisting  of  four  or  five  distinct  segments  or  consisting 
of  five  or  more  segments,  with  those  beyond  the  second  more  or  less  closely 
consolidated  so  as  to  appear  as  a  single  segment  consisting  of  several  sub- 
segments.     (Figs.  985,  986);  cell  1st  A  closed  by  the  coalescence  of  the 
tips  of  veins  Cu,  and  2nd  A,  or  greatly  narrowed  at  the  margin  of  the 
wing;  palpi  rarely  elongate,  and  composed  of  from  one  to  three  segments. 
D.      Antennae    consisting    of    four  or  five   distinct   segments,    empodia 
wanting  or  bristle-like. 
E.     The  first  branch  of  media  terminating  at  or  before  the  apex  of  the 

wing.  p.  842 MvDAiD^ 

EE.     The  first  branch  of  media  terminating  on  the  outer  border  of  the 
wing. 

F.     The  vertex  of  the  head  sunken,  the  eyes,  bulging  and  never  con- 
tiguous, p.  840 ASII.ID^. 

FF.    The  vertex  of  the  head  plane  or  convex,  the  eyes  not  bulging; 

eyes  of  males  often  contiguous,  p.   838 BombvliiD/E. 

DD.  Antennae  consisting  of  five  or  more  segments  but  with  those  beyond 
the  second  more  or  less  closely  consoHdated;  empodia  resembling 
pulvilli  in  form. 

E.      The   alulets   large,    p.    829 Tabanid.^ 

EE.    The  alulets  small  or  vestigial. 

F.    The  branches  of  radius  crowded  together  near  the  costal. margin; 

tibiae    without    spurs,    p.     830 Stratiomyiid^ 

FF.     The  branches  of  radius  not  crowded  together  near  the  costal 
margin;  at  least  some  of  the  tibiae  with  spurs. 

G.     Cell  M3  closed,  p.  832 Xvlomyiid^ 

GG.    Cell  AI3  open. 


DIPTERA  789 

H.      Scutellum    without    spinous    protuberances,    p.    833 

Xylophagid^ 

HH.      Scutellum   with    two   spinous   protuberances,    p.    834.  .  . 

CCENOMYIID/E 

BB.    Antennae  consisting  of  not  more  than  three  segments;  the  third  segment 

either  with  or  without  a  style  or  an  arista,  but  not  divided  into  subsegments. 

C.     Antennag  consisting  apparently  of  a  single  globular  segment  bearing  a 

long  arista;  wings  with  some  stout  veins  near  the  costal  margin  and  other 

weaker   veins    extending    across    the   wing   unconnected   by    cross-veins 

(Fig.    1099) .  p.   847 Phorid.« 

CC.     Flies  that  do  not  present  the  type  of  wing-venation  represented  by 
Figure  1099.  p,  847. 

D.    Cells  M  and  ist  AL  not  separated.   (See  Figures  1094  and  1095,  p.  844 
for  examples  of  this  type  of  wing-venation). 

E.     Vein  R  with  a  knot-shaped  swelling  at  the  point  of  separation  of 
veins  R2  +  .,  and  R4  -|-  5;  the  cross-vein  r-m  at  or  near  this  swelhng 

when  present;  frontal  suture  absent,  p.  843 Dolichopodid.^ 

EE.     Vein  R  with  or  without  a  swelling  at  the  point  of  separation  of 
veins  R>  +  j  and  R4  -f  ,;  the  cross- vein  r-m  more  remote   from  the 
base  of  the  wing;  the  frontal  suture  present.     (Muscoidea).     Pass  to 
Table  B. 
DD.    Cells  M  (or  2d  M)  and  1st  M2  separate. 
E.    Radial  sector  three-branched. 

F.     Venation  intricate  due  to  an  unusual  anastomosing  of  the  veins 

(Fig.    1077)    p.    836 Nemestrinid^ 

FF.    Venation  not  of  the  type  represented  by  Figure  1077. 

G.     Vertex  of  the  head  distinctly  hollowed  out  between  the  eyes; 

eyes    never    contiguous,    p.     840 Asilid^ 

GG.    Vertex  of  the  head  not  hollowed  out  between  the  eyes;  eyes 
often  contiguous  in  males. 

H.      Alulets    very    large,    p.    837 Acrocerid.e 

HH.    Alulets  small  or  rudimentary. 

I.  Cell  M3  present. 

J.     Vein  Rj  ending  before  the  apex  of  the   wing.   p.  842.. 
Apiocerid^ 

JJ.    Vein  R5  not  ending  before  the  apex  of  the  wing. 

K.       Empodia     pulvilliform.     p.     834 Rhagionid^ 

KK.       Empodia     wanting,     p.      839 THEREViDiE 

II.  Cell  M3  obliterated  by  the  coalescence  of  veins  M3  and  Cuj. 
J.     Third  segment  of  the  antennas  without  a  style  or  an 

arista;  vein  Mi  ending  at  or  before  the  apex  of  the  wing. 

p.  839 SCENOPINID^ 

JJ.    Third  segment  of  the  antennae  usually  with  a  style  or  an 

arista;  Vein   Mi   ending   beyond   the   apex   of  the   wing. 

K.    Vein  Cu2  extending  free  to  the  margin  of  the  wing  or 

coalesced  with  vein  2d  A  for  a  short  distance  at  the 

margin    of    the    wing.    p.    838 Bombylid^ 

KK.     Vein  Cui  joinine  vein  2d  A  far  from  the  margin  of 
the  wing,  often  extending  towards  the  base  of  the  wing 

p.  845 Empidid.e 

EE.    Radial  sector  with  not  more  than  two  branches. 

F.     Wings  lanceolate  and  with  no  cross- veins  except  at  the  base. 

(Fig.      1097)      p.      846 LONCHOPTERID/E 

FF.     Wings  not  of  the  type  represented  by  Figure  1097. 

G.      Empodia    pulvilliform.    p.    837 Acrocerid^ 

GG.     Empodia  not  pulvilliform. 

H.    Vein  Cui  not  coalesced  with  vein  2d  A  to  such  an  extent  as  to 
cause  the  free  part  to  appear  like  a  cross-vein. 
I.    Antenna  with  a  terminal  style  or  arista. 
J.     Antennae  with  a  terminal  arista,   p.   848.  Platypezid^ 
J  J.    Antennae  with  a  terminal  style. 


790  AN  INTRODUCTION  TO  ENTOMOLOGY 

K.      Front   with   grooves   or   a   depression   beneath   the 

antennas,  p.  853 Conopid^ 

KK.        Front    convex   beneath    the   antennse.    p.     850. . 

Syrphid^ 

II.    Antennae  with  a  dorsal  arista. 

J.    Head  extremely  large,  and  with  nearly  the  entire  surface 

occupied  by  the  eyes.     (Fig.   1103).   p.  849.  Pipunculid^ 

JJ.      Head  not   of  the  type  represented  by   Figure    1103. 

K.    Wings  with  a  vein-like  thickening,  the  spurious  vein, 

between    veins    R    and    M.    p.    850 Syrphid^ 

KK.     Wings  without  a  spurious  vein. 
L.     Front  with  grooves  or  a  depression  beneath  the 

antennas,    p.    853 Conopid/E 

LL.      Front    convex   beneath   the    antennae,    p.     850. 

Syrphid^ 

HH.    Vein  Cuj  appearing  as  a  cross-vein  or  curved  back  towards 
the  base  of  the  wing  (Figs.  1096  and  11 15). 
1.     Antennas  with  a  terminal  style  or  arista,  p.  845.Empidid^ 
n.    Antennse  with  a  dorsal  arista. 

J.    Proboscis  vestigial ;  mouth  opening  small ;  palpi  wanting 

(Bot-fiies)  Pass  to  Table  B. 
JJ.      Probscis   not   vestigial;  palpi  present   in  most   cases. 
K.    Frontal  suture  present  (Myodaria).    Pass  to  Table  B. 

KK.      Frontal    suture    absent,    p.    845 Empidid^ 

AA.  Flies  in  which  the  abdomen  is  indistinctly  segmented,  and  the  two  legs  of 
each  thoracic  segment  are  widely  separated  by  the  broad  sternum.  The 
adults  live  parasitically  upon  birds,  or  mammals. 

B.  Head  sunk  in  an  emargination  of  the  thorax;  eyes  round  or  oval;  palpi 
forming  a  sheath  for  the  probscis,  not  projecting  in  front  of  the  head.  p.  874. 

• HiPPOBOSCID/E 

BB.  Head  with  a  fleshy  movable  neck;  eyes  wanting  or  vestigial;  palpi  pro- 
jecting leaf-like  in  front  of  the  head.  p.  875 Streblid^e 

TABLE  B.— THE  FAMILIES  OF  THE  AIYODARIA 

A.  The  alulae  or  calypteres  small  or  rudimentary;  the  subcostal  vein  often  in- 
distinct or  vestigial,  but  sometimes  well-preserved;  vein  Ri  shortened  and 
often  very  short;  thorax  without  a  complete  transverse  suture;  postalar 
callus  usually  absent.     (Subsection  1 — Acalyptratae). 

B.  Subcosta  distinctly  separated  from  vein  Ri  and  ending  in  the  costa  notice- 
ably before  Ri,  the  latter  ending  near  or  beyond  the  middle  of  the  wing  in 
most  cases. 

C.     Oral  vibrissae  present  and  distinctly  differentiated  from  the  hairs  of  the 
peristome. 

D.     A  distinct  costal  break  or  scar  proximad  of  the  tip  of  Rt  near  the 
apex  of  Sc. 

E.      The  post  vertical   bristles   are   divergent   or  parallel   or   wanting. 

F.     The  frontals  are  convergent  (lacking  in  Hydromyza)  and  stand 

nearer    the    median    line    than    the    fronto-orbitals.      Abdominal 

spiracles  in  most  cases  in  the  chitin.  p.  854 Cordylurid.-e 

FF.  The  fontals  absent,  or  if  present  and  convergent  stand  in  line  or 
laterad  of  the  line  of  the  fronto-orbitals;  transverse  suture  in- 
terrupted in  the  middle;  anal  vein  does  not  reach  the  wing-margin; 
cross  veins  in  most  cases  approximated;  abdominal  spiracles  in  the 

conjunctivas,    p.    854 Clusiid^ 

EE.     Postvertical  bristles  convergent,  costa  of  wing  in  nearly  all  cases 

with  a  row  of  spines  projecting  beyond  the  ciliation.  p.   854 

•  -i^ Helomyzid^ 

D\J.     Costa  without  a  sign  of  a  break,  palpi  vestigial  in  most  species. 

E.     Palpi  vestigial;  "front"  never  bristly  near  the  antennas;  anal  vein 

not  produced  to  the  wing  margin,   p.   858 Sepsid^e 


DIPTERA  791 

EE.     Palpi  well-developed;  "front"  and  face  bristly;  anal  vein  pro- 
duced to  the  wing-margin.     Seashore  flies,  p.  855 .  .  .  Phycodromid^ 
CC.    Oral  vibrissas  not  differentiated  from  the  peristomal  hairs. 

D.    Legs  very  long  and  stilt-like,  tibiae  usually  without  preapical  bristle; 
cell  Rs  constricted  at  the  wing-margin. 

E.      Proboscis   greatly   elongate   and   folding   near   its   middle;  arista 
terminal;  ovipositor    very    long    (Stylogaster)    p.    853.  .  .Conopid^* 
EE.    Proboscis  short ;  arista  dorsal;  ovipositor  not  lengthened. 

F.      Buccag   and   posterior   orbits   narrow,    p.    858 ....  Tanypezid^ 

FF.       Buccae    broad,     p.     858 Micropezid^ 

DD.    Legs  not  long  and  stilt-like. 

E.     Preapical  tibial  bristles  present;   "ovipositor"  membranous  and  re- 
tractile. 
F.    Postvertical  bristles  well -developed  and  converging. 

G.     Anal  vein  produced  to  the  wing  margin;  last  tarsal  segment 

enlarged  and  fiat.   p.   855 Phycodromid^ 

GG.     Anal  vein   not   produced   to   the   wing  margin;  last   tarsal 

segment    normal,    p.    856 Sapromyzid^ 

FF.     Postvertical  bristles  parallel  or  diverging,  rarely  lacking,  p.  855. 

Sciomyzid^ 

EE.    Preapical  tibial  bristles  absent,  if  present  in  exceptional  cases,  the 

ovipositor  horny  and  not  wholly  retractible,  or  the  cell  1st  A  of  the 

wing  drawn  out  into  a  lobe,  or  vein  Ri  bristly  above. 

F.     Ovipositor  membranous,  retractile;  vein  Ri  bare  above;  cell  ist 

A  without  acute  process  or  lobe. 

G.       Palpi    well-developed;  postvertical    bristles    converging    or 

wanting,     p.     862 Ochthiphilid^ 

GG.     Palpi  vestigial;  postvertical  bristles  divergent;  the  "front" 

not  bristly  except  at  the  vertex,  p.  858 Sepsid^ 

FF.     Ovipositor  horny,  not  wholly  retractible;  postvertical  bristles 
not  converging;  palpi  present. 

G.  The  costal  break  or  scar  is  located  just  proximad  of  the  tip  of 
vein  Sc;  cell  M  and  the  cell  ist  A  small,  the  latter  with  rounded 

apex;  only   one  fronto-orbital  bristle,   p.   856 Lonch^id^ 

GG.  Costa  either  unbroken  or  if  broken  there  is  also  a  trace  of  a 
break  basally,  indicated  by  a  dark  or  light  scar  or  constriction; 
cell  M  and  cell  ist  A  large,  the  latter  in  many  cases  with  a  sharp 
angle  or  prolonged  into  a  lobe;  or  the  costa  with  a  strongly 
marked  stigma  due  to  an  abrupt  double  curve  in  vein  Ri  near  its 
tip  and  the  second  tergite  of  the  abdomen  with  at  least  one  long 

bristle  on  each  side.  p.  856 Ort.\lid^ 

BE.  Subcosta  absent,  or  vestigial,  or  running  very  close  to  vein  Ri  and  ending 
with  it  in  the  costa  before  the  middle  of  the  wing,  or  evanescent  at  the  tip  _ 
C.    Head  produced  on  each  side  into  a  lateral  process  bearing  the  eye.  p.  859. 

DlOPSID^ 

CC.     The  eyes  not  stalked. 

D.    First  segment  of  hind  tarsi  swollen  and  in  most  cases  shorter  than  the 

second  segment;  oral  vibrissas  present,  p.  855 Borborid^ 

DD.    First  segment  of  hind  tarsi  normal. 

E.  Subcostal  vein  evanescent  at  the  tip,  where  it  turns  sharply  forward 
at  some  distance  before  the  tip  of  vein  Ri;  wings  nearly  always  pic- 
tvu-ed;  cell  ist  A  angular  or  drawn  out  into  an  acute  lobe;  no  pre- 
apical tibial  bristle,  p.  856 Trypetid.^ 

EE.'    The  subcosta  runs  very  close  to  Ri  or  is  fused  with  it  either  wholly 
or  in  part  but  only  in  a  few  cases  suddenly  interrupted  at  the  tip,  in 
which  case  the  wing  with  a  fold  extending  across  from  the  costal 
fracture  to  the  tip  of  cell  M. 
F.    Cell  1st  A  wanting. 


*See  Table  A  for  distinctive  characters  of  those  Conopidae  in  which  the  free 
part  of  vein  Cu^  does  not  appear  like  a  cross-vine. 


792  AN  INTRODUCTION  TO  ENTOMOLOGY 

G.  Subcosta  vestigial  or  only  basally  indicated  as  a  fold;  costa 
fractured  but  once;  cell  M  and  anal  vein  wanting;  ocellar  tri- 
angle large  and  conspicuous;  head  bristles  but  feebly  developed. 

p.  860 Chloropid.^ 

GG.    Subcosta  developed  basally  at  least;  ocellar  triangle  in  most 
cases  not   conspicuous;  head  bristles  well-developed. 
H.    Costa  twice  fractured,  basally  and  near  the  tip  of  Ri;  arista 

never   feathered   below,    p.   859 Ephydrid.-e 

HH.     Basal  fracture  of  the  costa  indistinct;  cell  R5  very  long, 

the    bounding    veins    converging,    p.    860 Asteiid.« 

FF.    Cell  1st  A  present  though  in  some  cases  quite  small. 

G.  Basal  cells  M  and  ist  A  large;  wings  with  a  fold  extending 
across  from  the  costal  fracture  to  the  tip   of  cell  M;  frontal 

triangle    conspicuous,    p.    859 Psilid.e 

GG.    Basal  cells  M  and  ist  A  small;  wings  without  a  fold. 

H.    Arista  plumose,  in  rare  cases  pectinate;  wing  with  two  costal 

fractures;  vibrissas  present,   p.   860 Drosophilid.-e 

HH.  Arista  bare  or  pubescent;  if  in  a  few  cases  plumose  then 
costa  of  wing  with  but  one  fracture  which  is  situated  dis- 
tinctly before  the  tip  of  Ri. 

I.  Tormse  large  and  distinctly  projecting;  vein  Sc  distinctly 
isolated  at  its  extremity;  ocellar  triangle  large  nearly  attain- 
ing the  base  of  the   antennae;    costal  fracture  close  to  the 

tip     of     Ri.     p.     859 C.\NACEID/E 

II.  Tormas  small  and  not  projecting,  or  differing  in  other 
characters. 

J.     Anterior  part  of  the   "front"  not  bristly;  post  vertical 
bristles  not  converging;  cells  M  and  1st  M2  not  confluent; 
Sc  distinct  to  the  tip;  arista  bare.  p.  858.  .  .Piofhilid.^ 
JJ.    Not  such  flies. 

K.  Costa  broken  twice;  proboscis  in  most  cases  genicu- 
late; postvertical  bristles  converging,  rarely  parallel  or 
wanting;  anal  vein  in  most  cases  vestigial  or  wanting. 

p.  862 MlLICHIID.^ 

KK.    Costa  broken  but  once  or  proboscis  not  geniculate. 

L.     Postvertical  bristles  divergent,  in  exceptional  cases 

wanting;  basal  segment  of  the  arista  minute,  shorter 

than  broad;  the  so-called  genae  narrower  than  the 

buccae,  except  in  Phytomyza  in  which  cell  ist  JVL  is 

open   distally.   p.   861 Agromyzid.e 

LL.    Postvertical  bristles  converging,  or  if  wanting  Cell 
R5  long  and  narrowed  in  the  margin  of  the  wing; 
or  cells  M  and  1st  M2  confluent,  or  proboscis  genicu- 
late,    or    arista    plumose;    basal    segment    of    arista 
longer  than  wide;  the  so-called  genae  as  broad  as  or 
broader    than    the    buccse.    p.    86i .  .  .  .Geomyzid^ 
AA.    At  least  the  lower  lobe  of  the  alulae  or  calypteres  well-developed;  the  sub- 
costal vein  distinct  in  its  whole  course;  vem  Ri  never  very  short;  thorax 
with  a  complete  transverse  suture;  and  the  postalar  callus  present.      (Sub- 
section II. — Calyptratae) . 

B.    Proboscis  usually  much  reduced  or  vestigial,  not  functional;  mouth-open- 
ing small.    (Bot-flies). 

C.     Costa  ends  at  or  slightly  beyond  the  tip  of  vein   R^  +  5;  •vein  Mi  +  2 
extends  in  a  nearly  straight  line  toward  the  outer  margin  of  the  wing 

p.  864 Gastrophilid^ 

CC.    Costa  extends  to  the  tip  of  vein  Mi  -\-  2]    vein  Mi  -|-  2  with  a  bend  so 
that  cell  Rs  is  much  narrowed  or  closed  at  the  margin  of  the  wing.  p.  866. 

LEstrid^ 

BB.    Alouth-opening  normal;  mouth-parts  functional. 


DIPTERA  793 

C.    Both  hypopleural  and  pteropleural  bristles  absent.    Cell  R^  very  slightly 
or  not  at  all  narrowed  at  the  margin  of  the  wing.    (Anthomyioida).  p.  86,^. 

Anthomyiid^ 

CC.     Either  the  hypopleural  or  the  pteropleural  bristles  or  both  present. 
Cell  R;  narrowed  or  closed.     (Muscoidea). 
D.     Both  hypopleural  and  pteropleural  bristles  present. 

E.  Clypeus  more  or  less  produced  below  the  vibrissal  angles.  Like  the 
bridge  of  a  nose.  Abdomen  not  armed  with  stout  bristles.  The  con- 
junctivae of  the  ventral  sclerites  of  the  abdomen   present,   p.    868. 

Phasiid^ 

EE.  Clypeus  flattened,  at  most  slightly  produced.  Abdomen  bearing 
some  stout  bristles.  The  conjunctivae  of  the  ventral  sclerites  of  the  ab- 
domen not  visible. 

F.  Clypeus  receding  and  short;  the  cheeks  very  broad;  vibrissae 
located  near  the  middle  of  the  face;  antennae  short,  p.  869..  .  . 

MEGAPROSOPIDiE 

FP.  Clypeus  long  and  never  conspicuously  receding ;  the  oral  margin 
more  or  less  prominent;  vibrissal  angles  near  the  oral  margin; 
antennae  usually  long. 

G.  Second  ventral  sclerite  of  the  abdomen  lying  with  its  edges 
either  upon  or  in  contact  with  the  ventral  edges  of  the  corre- 
sponding dorsal  sclerite. 

H.     Hindermost  posthumeral  bristle  almost  always  lower  (more 

ventrad)  in  position  than  the  presutural  bristle;  body  color  very 

frequently  metallic  green  or  blue,  or  yellow;  arista  plumose. 

p.  869 Calliphorid^ 

HH.  Hindermost  posthumeral  bristle  on  a  level  with  or  higher 
(more  dorsad)  than  the  presutural  bristle;  arista  bare,  pubes- 
cent, or  plumose  only  on  the  basal  two-thirds;  body  coloring 
gray  or  silvery,  tessellated  or  changeable  pollinose. 

I.  Fifth  ventral  abdominal  sclerite  of  the  male  either  wanting 
or  with  the  caudal  margin  straight,  presutural  intraalar 
bristle    rarely    present,    p.    870 Sarcophagid^ 

II.  Fifth  ventral  abdominal  sclerite  of  the  male  cleft  to  beyond 

the  middle,  p.  871 Tachinid^ 

GG.  Second  ventral  abdominal  sclerite,  as  well  as  the  others,  more 
or  less  covered,  sometimes  wholly,  by  the  edges  of  the  dorsal 

sclerites.   p.   871 Tachinid/e 

DD.  Either  the  hypopleural  or  the  pteropleural  bristles  present;  basal 
bristles  of  the  abdomen  reduced;  arista  plumose  to  the  tip.  p.  872. 
MusciD^ 

TABLE  C— DIPTERA  IN  WHICH  THE  WINGS  ARE 
WANTING  OR  VESTIGIAL 

A.     Mesonotum  with  a  complete  V-shaped  transverse  suture  (Chionea)  p.  798. 

Family  Tipulid^ 

AA.    Mesonotum  without  a  V-shaped  transverse  .suture. 

B.  Flies  in  which  the  abdomen  is  distinctly  segmented  and  the  two  legs  of  each 
thoracic  segment  are  not  widely  separated.  The  adults  do  not  live  parasitic- 
ally  upon  either  birds,  mammals  or  the  honey-bee. 

C.    Nematocerous  flies;  antennae  more  or  less  thread-like  and  consisting  of. 
six  or  more  segments. 
D.     Wings  short,  strap-like,  thickened,  and  without  distinct  venation 

(Eretmoptera).    p.    802 Chironomid^ 

DD.     Wings  and  halteres  wholly  wanting   {Pnyxa,     female)   p.  810.  .  . 

Mycetophilid^ 

CC.    Brachycerous  flies. 

D.  Antennas  consisting  apparently  of  a  single  segment,  which  bears  a 
long,   three-jointed  arista,   p.   847    Phorid/E 


794  AN  INTRODUCTION  TO  ENTOMOLOGY 

DD.    Antennae  three-jointed,  third  joint  with  an  arista. 

E.     Hind  metatarsi  shorter  than  the  second  segment  and  more  or  less 

thickened,   p.   855 Borborid^ 

EE.    Hind   metatarsi   longer  than   the   second   segment   and   slender. 

p.  859 Ephydrid^ 

BB.     Flies  in  which  the  abdomen  is  indistinctly  segmented  (except  Braula), 
and  the  two  legs  of  each  thoracic  segment  are  widely  separated  by  the  broad 
sternum.     The  adults  are  parasites. 
C.    Flies  parasitic  upon  birds  or  mammals. 

D.    Head  folded  back  on  the  dorsum  of  the  thoiax.  p.  875 .  .  .  Nycteribiid^ 
DD.     Head  not  folded  back  on  the  thorax. 

EE.    Head  sunk  in  an  emargination  of  the  thorax;  eyes  round  or  oval; 
palpi  forming  a  sheath  for  the  proboscis,   not  projecting  in   front  of 

the     head.     p.      874 HiPPOeosciDyE 

EE.     Head  with  a  fleshy  movable  neck;  eyes  wanting  or   vestigial; 

palpi  projecting  leaf-like  in  front  of  the  head.  p.   875.  Streblid^ 

CC.     Flies  parasitic  upon   the  honey-bee.   p.   876 Braulid^ 


MEIGEN'S  FIRST  PAPER  ON  DIPTERA 

In  the  year  1800,  J.  A.  Meigen  published  a  paper  on  the  classifi- 
cation of  the  Diptera,  in  which  many  generic  names  were  proposed. 
This  was  followed  by  a  second  paper  published  in  1803,  in  which 
nearly  all  of  the  generic  names  used  in  his  first  paper  were  discarded 
and  new  names  proposed.  The  first  paper  was  evidently  not  widely 
distributed  for  it  was  practically  unknown  for  more  than  one  hundred 
years.  Attention  was  called  to  it  by  Mr.  Fr.  Hendel  in  1908,  and 
since  then  an  effort  has  been  made  to  substitute  the  generic  names 
proposed  by  Meigen  in  1800  for  those  used  by  him  in  1803.  If  this 
were  done,  not  only  would  these  generic  names  be  changed  but  the 
well-known  names  of  many  families  based  on  these  generic  names 
would  need  to  be  changed  also.  Fortunately  this  revolution  in  nomen- 
clature is  not  necessary,  even  according  to  the  law  of  priority;  for  the 
names  published  by  IVIeigen  in  1800  were  not  adequately  defined  and 
no  type  species  were  indicated. 

Suborder  ORTHORRHAPHA.* 

The  Straight-seamed  Flies 

This  suborder  includes  those  flies  in  which  the  pupa  escapes  from 
the  larval  skin  through  a  T-shaped  opening,  which  is  formed  by  a 
lengthwise  split  on  the  back  near'  the  head  and  a  crosswise  split 
at  the  front  end  of  this  (Fig.  1003),  or  rarely 
through  a  crosswise  split  between  the 
seventh  and  eighth  abdominal  segments. 
The  adults  do  not  have  a  frontal  lunule.        ^%  ioo3.--Pupanum  with 

The  families   included  in  this  suborder       ^-s^^Ped  openmg. 
are  commonly  grouped  in  two  series :  the  Nemocera  and  the  Brachy- 
cera. 


*0rth6rrhapha ;  orthos  {op6s),  straight;  rhaphe  (pacpri), 


DIPTERA  795 

Series  I.— NEMOCEA* 

The  Long-horned  Orthorrhapha 

This  series  of  families  is  termed  the  Nemocera  from  the  fact  that 
in  the  more  typical  forms  the  antenna  are  elongate  and  slender;  but 
in  some  families  placed  at  the  end  of  the  series,  the  Anomalous  Nemo- 
cera, the  antennae  are  shorter  and  less  thread-like  than  in  the  more 
typical  forms.  The  antennae  are  composed  of  from  six  to  thirty-nine 
segments,  usually  from  eight  to  sixteen.  The  palpi  are  pendulous 
and  consist  of  from  one  to  five  segments,  usually  of  four.  Except  in 
a  few  genera,  cell  ist  A  is  not  narrowed  towards  the  margin  of  the 
wing.  In  those  cases  where  the  radial  sector  is  three-branched,  it  is 
veins  R4  and  R5  that  have  coalesced;  in  the  Brachycera  veins  R2  and 
R3  are  the  first  to  coalesce. 

SUBSERIES    A.' — THE    TRUE    NEMOCERA 

In  this  subseries  the  antennae  are  usually  long  and  frequently  bear 
whorls  of  long  hairs,  especially  in  the  males.     The  legs  are  long  and 
slender,     and    the    abdomen    is 
usually  long  and  slender. 


SUPERFAMILY    TIPULOIDEA 

The  Crane-flies 

The  crane-flies  are  mosquito- 
like in  form;  but  they  are  usually 
very  much  larger  than  mosqui- 
toes. The  body  is  long  and 
slender,  the  wings  narrow,  and 
the  legs  very  long  (Fig.  1004). 
This  family  includes  the  larger 
members  of  that  series  of  families 
in  which  the  antennee  are  thread- 
like, the  Nemocera;  but  it  also  ^'^-  1004.-A  crane-fly. 
includes  some  species  that  are  not 
larger  than  certain  mosquitoes. 

Most  crane-flies  differ  from  all  other  Nemocera  in  that  the  trans- 
verse suture  of  the  mesonotum  is  V-shaped;  but  one  small  family 
the  Anisopidffi,  lack  the  V-shaped  suture. 

This  superfamily  includes  the  four  following  families;  these  can 
be  separated  by  the  characters  indicated  in  the  table  of  families 
page  787- 

*Nem6cera:  nema  {vrjfxa),  thread;  ceras  (K^pas),  horn. 


796  AN  INTRODUCTION  TO  ENTOMOLOGY 

Family  TANYDERID^ 

The  Primitive  Crane-flies 

This  family  is  of  especial  interest  as  it  includes  the  most  general- 
ized of  living  crane-flies.  It  is  a  small  family,  only  ten  species  repre- 
senting three  genera  being  known.  Of  these  a  single  genus,  Proto- 
plasa,  represented  by  three  species,  has  been  found  in  North  America. 
Protoplasa  vipio  and  Protoplasa  vanduzeei  are  found  in  the  West  and 
Protoplasa  JUchii,  in  the  East. 

The  life-history  of  no  member  of  this  family  is  known.  Alexander 
('20)  described  what  is  probably  the  larva  of  Protoplasa  fitchii.  It 
was  found  in  a  much  decayed  maple  log  in  Fairfax  County,  Virginia. 


2d  A     Cu2  ^"' 

Fig.  1005. — -Wing  of  Protoplasa  fitchii. 

The  venation  of  a  wing  of  Protoplasa  fitchii  is  represented  by 
figure  1005.  The  generalized  condition  of  this  wing  is  shown  by  the 
following  features ;  both  branches  of  vein  Sc  are  preserved ;  the  forking 
of  the  other  branched  veins  is  nearer  the  base  of  the  wing  than  in  the 
typical  crane-flies;  and  all  of  the  branches  of  vein  R  are  distinct. 


Family  PTYCHOPTERID^ 

The  Phantom  Crane-fly  Family 

This  is  a  small  family  of  which  only  six  or  seven  species  have  been 
found  in  our  fauna;  and  of  these  only  three  are  found  in  the  East. 
These  flies  differ  from  the  typical  crane-flies  in  having  only  one  anal 
vein  preserved,  and  the  transverse  suture  of  the  mesonotum  is  rather 
poorly  defined. 

The  larvffi  are  found  in  decaying  vegetable  matter  rich  in  organic 
mud,  usually  in  swamps,  swales,  or  wet  meadows,  but  sometimes  in 
shaded  woods.  They  feed  on  decaying  vegetable  matter,  diatoms, 
and  the  organic  mud  in  which  thev  live. 


DIPTERA 


797 


The  phantom  crane-fly,  Bittacomorpha  cldvipes. — This  remarkable 
insect  is  the  member  of  this  family  that  is  most  likely  to  attract  atten- 
tion. Its  long  legs  are  banded  with  black  and  white  and  themetatarsi 
are  conspicuously  enlarged  and  swollen.  In  its  progress  through  the 
air  the  legs  are  held  outspread  like  the  spokes  of  a  wheel  with  the 
metatarsi  hanging  vertically.  It  uses  its  wings  but  little  in  flight  but 
is  borne  along  by  currents  in  the  air.  The  black  and  white  banding 
of  its  legs  makes  it  a  very  conspicuous  object  as  it  drifts  phantom- 
like through  the  air. 

Family  ANISOPID^* 

The  So-called  False  Crane-Flies 

The  family  Anisopidas  has  not  been  classed  with  the  crane-flies 
till  recently;  the  presence  of  ocilli  and  the  lack  of  a  V-shaped  trans- 
verse mesonotal  suture  in  this  family  having  been  regarded  as  charac- 
ters excluding  it  from  the  Tipuloidea.  On  the  other  hand  the  members 
of  this  family  resemble  crane-flies  in  certain  features  of  the  venation 
of  the  wings;  for  this  reason  they  have  been  known  as  false  crane-flies. 
•But  a  study  of  the  larvae  and  pupas  of  members  of  this  family  has 
shown  that  it  should  be  regarded  as  one  of  the  families  of  the  Tipu- 
loidea. 

This  family  is  represented  in  our  fauna  by  three  genera,  Anisopus 
Trichocera,  and  Mycetobia;  of  these  the  last  two  have  been  commonly 
classed  in  other  families;  but  the  immature  stages  of  the  three  genera 
are  very  similar. 

Anisopus. — The  adults  are  mosquito-like  insects  with  spotted 
wings,  which  often  enter  houses,  where  they  are  found  on  windows.   I 


/?,    R^^ 


Fig.  1006. — Wing  of  Anisopus. 


have  also  observed  them  in  considerable  numbers  just  at  nightfall, 
feeding  on  sugar  which  had  been  placed  on  trees  to  attract  moths. 

*This  family  has  been  known  as  the  Rhyphidae. 


'98 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  1007 


They  feed  on  over-ripe  fruit,  the  exuding  sap  of  trees,  and  upon  the 
nectar  of  flowers.  Figure  1006  represents  the  venation  of  the  wings 
and  Figure  1007  the  form  of  the  antennae.  Only  four 
species  of  this  genus  are  recorded  from  the  United 
States. 

The  lar\'ae  are  found  in  decaying  vegetable  matter, 
in  manure,  in  sewage,  and  in  similar  material. 

Trichocera. — The  members  of  this  genus  often  at- 
tract attention  by  appearing  in  swarms  in  the  autumn 
and  early  spring,  and  sometimes  on  warm,  sunny  days 
in  winter.  The  swarms  vary  greatly  in  size,  sometimes 
one  includes  thousands  of  individuals.  They  are  usually 
from  five  to  twenty-five  feet  above  ground;  and  all  members  of  a 
swarm  face  the  wind. 

These  flies  are  often  found  during  the  winter  months  in  cellars, 
resting  on  the  windows.  Nine  species  have  been  described  from  our 
fauna.  In  this  genus  the  radial  sector  is  three-branched  and  there 
are  two  distinct  anal  veins. 

The  larvse  are  found  in  decaying  vegetable  matter,  beneath  dead 
or  decaying  leaves,  and  in  fungi.  They  have  also  been  found  in 
stored  roots  and  tubers,  especially  potatoes. 

Mycetohia. — A  single  species  of  these  genus,  M.  divergens  is  found 
in  North  America.  This  is  a  small  fly  measuring  from  three  to  four 
millimeters  in  length  and  resembling  superficially  a  fungus-gnat  more 
than  a  crane-fly.  For  this  reason  it  has  been  commonly  classed  in 
the  MycetophiiidcC.  In  this  genus  cell  ist  M2  is  lacking,  the  radial 
sector  and  media  are  each  two-branched,  and  there  is  only  one  distinct 
anal  vein. 

The  lar\'£e  are  common  in  wounds  on  trees  from  which  sap  is 
exuding,  and  in  decaying  wood. 

Family  TIPULID.'E 

The  Typical  Crane-Flies 

To  this  family  belong  the  far  greater  number  of  the 
crane-flies,  the  other  three  families  of  the  Tipuloidea 
including  but  few  species.  The  typical  crane-flies  dift>r 
from  the  Anisopidae  in  having  a  \"-shaped  transverse 
mesonotal  suture  (Fig.  1008),  ^^rom  the  Tanyderids  in 
that  the  radial  sector  has  less  than  four  branches,  and 
from  the  Ptychopteridse  in  having  two  distinct  anal 
veins. 

Figure  1009  represents  the  venation  of  a  wing  of  a 
member  of  this  family.     The  most  striking  feature  of 
this    venation    is    the    fact    that  the    forking   of    the 
eins  is  near  the  distal  end  of  the  wing.     This  gives  the 
wing  a  ver\-  distinctive  appearance. 

Crane-flies  are  seen  most  often  in  damp  localities,  especially  where 
there  is  a  rank  growth  of  vegetation;  but  sometimes  thev  occur  in 


DIPTERA 


799 


great  numbers  flying  over  meadows  and  pastures.  In  most  cases 
their  power  of  flight  does  not  seem  to  be  well  developed  for  they  fly 
slowly,  and  only  a  short  distance  at  a  time.  Some  species,  however, 
sustain  themselves  in  the  air  for  long  periods.  This  is  especially  true 
of  some  of  the  smaller  species ;  which  often  collect  in  swarms  at  twi- 


Fig.  1009. — Wing  of  Tipula  abdominalus. 

light,  forming  a  small  cloud,  and  dancing  up  and  down  like  some  of 
the  midges.  Their  ability  to  walk  is  also  poor,  for  they  use  their  long 
legs  awkwardly,  as  if  they  were  in  the  way.  Little  is  known  regarding 
the  feeding  habits  of  the  adult  crane-flies;  but  some  species  have 
been  observed  to  feed  on  the  nectar  of  flowers.  Many  species  are 
attracted  to  lights. 

The  larvse  of  crane-flies  vary  greatly  in  habits  both  as  to  the 
situations  in  which  they  live  and  as  to  the  nature  of  their  food.  Some 
are  aquatic;  Antocha  lives  in  silken  cases  on  rocks  in  swiftly  flowing 
streams;  and  members  of  several  other  genera  live  on  submerged 
plants.  Some  live  in  or  beneath  damp  cushions  of  moss.  Many  live 
in  mud  or  sand  along  the  margins  of  streams,  in  swamps,  or  in  shaded 
woods,  while  others  are  strictly  terrestrial,  burrowing  in  the  soil  of 
meadows  and  pastures. 

The  larvae  of  most  species  are  scavengers  feeding  on  decaying 
vegetable  matter,  but  some  feed  on  living  vegetable  tissue,  and  still 
others  are  carnivorous.  For  a  detailed  account  of  the  life-histories 
and  the  structural  characteristics  of  the  early  stages  of  the  different 
groups  of  crane-flies  see  Alexander  ('20). 

The  Tipulidffi  is  a  large  family;  nearly  3000  species  are  known  and 
about  500  species  have  been  described  from  North  America  alone. 
Among  those  that  are  of  especial  interest  are  the  following : 

The  snow-flies,  Chionea. — To  the  genus  Chionea  belong  several 
species  of  crane-flies  in  which  the  wings  are  vestigial,  being  reduced 
to  mere  knobs,  much  smaller  than  the  halteres.  These  flies  are  most 
often  seen  in  winter  crawling  about  on  the  snow;  but  they  are  occa- 
sionally found  in  the  spring  and  fall  in  leaf-mold. 

The  meadow-maggots  or  leather-jackets. — The  larva?  of  some 
species  of  crane-flies,  most  of  which  belong  to  the  genus  Tipula,  often 
do  considerable  damage  in  meadows,  pastures,  and  grain  fields  by 
devouring  the  roots  of  the  plants.  The  full-grown  larvae  are  about 
25  mm.  long  and  of  a  dirty-grayish  color.  As  the  body-wall  is  of  a 
tough  leathery  texture  these  larvae  are  commonly  known  as  leather- 


800 


AN  INTRODUCTION  TO  ENTOMOLOGY 


jackets.  Serious  outbreaks  of  these  pests  have  occurred  at  various 
times  in  Ohio,  Indiana,  Ilhnois,  and  CaHfomia.  In  the  case  of  the 
species  infesting  ranges,  pastures,  and  grain  and  alfalfa  fields  in 
California  it  was  found  that  the  larvae  usually  come  out  upon  the 
surface  of  the  ground  during  the  night  and  could  be  destroyed  by  the 
use  of  poisoned-bran  bait,  made  by  mixing  one  pound  of  Paris  green, 
twenty-five  pounds  of  bran,  and  sufficient  water  to  make  a  flaky 
mash.    The  bait  is  applied  with  a  broadcast  giain  seeder. 


Family  DIXID^ 
The  Dixa-Midges 

These  midges  closely  resemble  mosquitoes  in  size  and  form;  but 
they  are  easily  distinguished  by  the  venation  of  their  wings,  (Fig. 
loio). 


Fig.  loio. — Wing  of  Dixa. 

The  wing-veins  are  not  furnished  with  scales,  and  are  distinct 
over  the  entire  surface  of  the  wing;  the  costa  is  prolonged  into  an 
ambient  vein,  the  subcosta  is  well  de- 
veloped, but  is  short,  ending  in  the 
margin  of  the  wing  near  its  middle,  and 
before  the  first  fork  of  the  radius;  the 
radius  is  four-branched, 
the  vein  R]  extends  par- 
allel to  the  margin  of  the 
wing  to  a  point  on  the 
outer  end  of  the  wing; 
the  media  is  two-branch- 
ed; and  the  medial  cross- 
vein  is  wanting.  The  an- 
tennae (Fig.  loii)  are 
sixteen-jointed,  and  dif- 
fer but  slightly  in  the  two 
sexes;  the  legs  are  long 
and  slender;  and  the  cau- 
dal end  of  the  abdomen  Fig.  ioi2.-Larva  of  Dixa, 
of  the  male  is  enlarged.  (After  Needham  and  Lloyd.) 


DIPTERA 


801 


The  family  includes  only  a  single  genus,  Dixa,  of  which  eight 
species  have  been  found  in  North  America. 

The  adult  midges  occur  in  the  vicinity  of  streams  and  in  swam- 
py places. 

The  larv£e  are  aquatic,  living  in  ponds  or  slowly  running  water; 
they  resemble  somewhat  those  of  Anopheles  but  the  body  is  almost 
always  bent  so  that  the  head  and  tail  come  close  together.  They 
progress  by  alternate  thrusts  of  the  two  ends  of  the  body,  the  bent 
portion  traveling  foremost  (Fig.  1012).  The  first  and  second  ab- 
donimal  segments  each  bear  a  pair  of  pseudopods  on  the  ventral 
surface.    These  larva?  feed  on  algae. 


Family  PSYCHODID^ 
The  Moth-like  Flies 

There  may  be  foimd  frequently  upon  windows  and  on  the  lower 
surface  of  the  foliage  of  trees  small  flies  which  have  the  body  and 
wings  densely  clothed  with  hair  and  which  resemble  tiny  moths  in 
appearance.  The  wings  are  broad,  and  when  at  rest  slope  at  the 
sides  in  a  roof-like  manner  or  are  held  horizontally  in  such  a  way  as 
to  give  the  insect  a  triangular  outline  (Fig.  1013). 

The  moth-like  appearance  of  these  insects  is  suffi- 
cient to  distinguish  them  from  all  other  flies.  The  ven- 
ation of  the  wings,  (Fig.  10 14)  is  also  ver^^  peculiar. 
All  of  the  longitudinal  veins  separate  near  the  base 
of  the  wing  except  veins  Ro  and  R3  and  veins  Mi  and 
M2-  In  some  forms  veins  R4  and  R5  are  distinct,  as 
shown  in  the  figure,  in  others  they  coalesce  complete- 
ly, so  that  radius  is  only  four-branched.  Cross-veins 
are  wanting  in  most  cases. 

The  antennae  are  long  and  slender,  and  are  clothed  with  whorls  of 


Fig.  1 013. —A 
moth -like 
fly- 


Fig.   1014. — Wing  of  a  moth-like  fly. 

hairs  (Fig.  1015).  Those  of  the  male  are  longer;  and  in  the  species 
figured  the  two  basal  segments  are  clothed  with  scales  like  those  of 
theLepidoptera.  Scales  of  this  form  occur  also  on  the  wings,  palpi, 
and  legs  of  certain  species. 


802 


^A^  INTRODUCTION  TO  ENTOMOLOGY 


The  moth-like  flies  are  often  very  minute  and  rarely  exceed  4  mm. 
in  lens:th.  Most  of  the  species,  so  far  as  is  known,  feed  on  nectar 
or  other  fluid  matter  other  than  blood ;  but  the  species  of  the  genus 
Phlehotcnnus  are  blood-suckers,  feeding  upon  the  blood  of  various  rep- 
tiles, amphibians  and  mammals,  including  man;  and  it  has  been  found 
that  some  exotic  species  transmit  certain  diseases  of  man,  as  the  Euro- 
pean pappatici  fever,  or  three  day  fever,  and  the  Peruvian  veruga  (Riley 
and  Johannsen  '15).  A  single  species  of  this  genus,  Phlebotomus 
vexdtor,  has  been  found  in  the  United  States;  this  is  a  minute  species, 
measuring  1.5  mm.  in  length.  It  was  taken  on  Plimimer's  Island^ 
Maryland. 

The  lar\^se  of  members  of  this  family  are  fotmd  in  various  situ- 
ations;   in    decaying   vegetable   matter,    in 
sewage,  in  cow  dung,  in  exuding  sap  on  tree- 
trunks,  and  in  streams. 

About    thirty    species    have    been    de- 
scribed from  the  United  States. 


Family  CHIRONOMID^ 


The  Midges 


Fig.  1015. — Antennae  of 
Psychoda:  m,  antenna  of 
male  and  the  second  seg- 
ment of  the  same  more 
enlarged;  /.  antenna  of 
female  and  the  tip  en- 
larged. 


The  members  of  this  famih'  are  more  or 
less  mosquito-like  in  form,  but  are  usually 
more  delicate  than  mosquitoes.  The  ab- 
domen is  usually  long  and  slender;  the 
wings  narrow;  the  legs  long  and  delicate;  and  the  antennas,  especially 
in  the  males,  strongly  plumose  (Fig.  1016).  In  fact  many  of  these 
insects  are  commonly  mistaken  for  mosquitoes;  but  only  a  few  of 
them  can  bite,  the  greater  number  being  harmless. 

The  midges  are  most  easily  distinguished  from  mosquitoes  by 
the  structure  of  the  wings  (Fig.   1017).     These  are  furnished  with 
fewer  and  usually  less  distinct  veins;  and  the  veins,  although  some- 
times  hairy,    are   not   fringed  with   scale-like 
hairs.     There  is  a  marked  contrast  between  «^" 

the  stouter  and  darker  colored  veins  near  the 
costal  border  of  the  wing  and  those  on  the 
other  parts  of  the  wing,  which  seem  to  be 
fading  out.  The  costal  vein  is  not  prolonged 
into  an  ambient  vein,  beyond  the  apex  of  the 
wing. 

In  several  genera  of  this  family  the  wings 
are  either  absetit  or  vestigial;  of  these  a  single 
species  has  been  found  in  our  fauna.  This  is 
Eretmoptera  browni,  a  species  described  by  Pro- 
fessor Kellogg  from  tide-pools  on  the  Pacific  Coast.  In  this  species 
the  wings  are  short,  strap-like,  thickened,  and  without  distinct  ve- 
nation. 

The  name  midge  has  been  used  in  an  indefinite  way,  some  writers 
applying  it  to  any  minute  fly.    It  is  much  better,  however,  to  restrict 


Fig 


016. — Antennae 
of  Chironomus.  f,  fe- 
male; w,  male. 


DIPTERA 


803 


it  to  members  of  this  family  except  where  it  has  become  firmly  estab- 
lished as  a  part  of  a  specific  name.  The  wheat-midge  and  the  clover- 
seed  midge  are  examples  of  names  of  this  kind ;  it  would  not  be  wise 
to  attempt  to  change  these  names,  although  the  insects  they  represent 
belong  to  the  gall-gnat  family,  and  hence  are  not  true  midges. 


/?,      R..y 


Fig.    1 017. — Wing  of  Chironomus. 


Midges  often  appear  in  large  swarms,  dancing  in  the  air,  especialh' 
towards  the  close  of  day.  Professor  Williston  states  that,  over  mead- 
ows in  the  Rocky  Mountains,  he  has  seen  them  rise  at  nightfall  in  most 
incredible  numbers,  producing  a  buzzing  or  humming  noise  like  that 
of  a  distant  waterfall,  and  audible  for  a  considerable  distance. 

Most  larvae  of  midges  are  aquatic;  but  some  live  either  in  manure, 
in  decaying  vegetable  matter,  under  bark,  or  in  the  ground.  Some  of 
the  pupag  are  free  and  active,  others  are  quiescent;  some  of  the  latter 
remain  partly  enclosed  in  the  split  larval  skin.  The  larvae  and  pupae 
of  the  aquatic  species  are  of  much  importance  as  fish-food. 

Many  of  the  aquatic  larvae  live  in  tubes  which  they  build  of  bits  of 
dead  leaves  and  particles  of  sand  fastened  together  with  viscid 
threads.  These  tubes  are  frequently  seen  upon  the  surface  of  dead 
leaves,  stones,  and  sticks ;  and  they  are  often  made  in  the  mud  of  the 
bottom  of  a  pool,  in  which  case  they  open  at  the  surface  of  the  mud. 
Many  of  the  species  are  blood-red  in  color,  and  hence  are  frequently 
known  as  blood-worms . 

The  aquatic  larvae  feed  on  algae,  decaying  vegetable  matter,  di- 
atoms, and  small  Crustacea;  the  terrestrial  species,  on  manure  or  de- 
caying vegetable  matter.  There  are  a  few  cases  reported  of  the  larvae 
of  midges  infesting  living  plants. 

To  the  genus  Culicoides  belong  the  small  midges  commonly  known 
as  sandflies  or  punkies.  Certain  minute  species  are  sometimes  very 
abundant,  and  extremely  annoying  on  account  of  their  bites.  They 
are  exceedingly  troublesome  in  the  Adirondack  Mountains,  in  the 
White  Mountains,  and  along  mountain  streams  generally;  they  are 
also  abundant  in  some  places  at  the  seashore. 

More  than  200  species  of  the  Chironomidae  have  been  described 
from  our  fauna.  The  family  was  monographed  by  Professor  Johannsen 
('05  and  '08). 


804 


AN  INTRODUCTION  TO  ENTOMOLOGY 
Family  CULICID^ 


The  Mosquitoes 

The  form  of  mosquitoes  is  so  well  known  that  it  would  be  un- 
necessary to  characterize  the  Culicidae  were  it  not  that  there  are 
certain  mosquito-like  insects  that  are  liable  to  be  mistaken  for  mem- 
bers of  this  family. 

The  mosquitoes  are  small  flies,  with  the  ab- 
domen long  and  slender,  the  wings  narrow,  the 
antennas  pliimose  in  the  males,  (Fig.  1018),  and 
usually  with  a  long,  slender,  but  firm  proboscis. 
The  thorax  lacks  the  transverse  V-shaped  suture 
characteristic  of  the  crane-flies ;  and  vein  M  of  the 
wings  is  only  two-branched.  But  the  most  dis- 
tinctive feature  of  mosquitoes  is  the  fringe  of 
scale-like  setae  on  the  margin  of  the  wings  and  also 
in  most  cases  on  each  of  thewing-veins  (Fig.1019). 

The  eyes  are  large,  occupying  a  large  part  of 
the  surface  of  the  head.  The  ocelli  are  wanting. 
The  antennae  are  composed  of  fifteen  segments,  of 
which  the  first  segment,  the  scape,  is  concealed  by  the  large  globular 
pedicel  (Fig.  173.  p.  153)  and  has  been  over-looked  by  many  describ- 
ers  of  mosquitoes.  The  pedicel  contains  the  Johnston's  organ  de- 
scribed on  pages  152  to  154.  The  form  of  the  mouth-parts  differs  in 
the  two  subfamilies;  those  of  Anopheles  are  represented  by  Figure 


Fig.  1 01 8. — Antennee 
of  mosquitoes,  m, 
male;    /,     female. 


'"2d  A 
Fig.   1019. — Wing  of  a  mosquito. 

990  on  page  775 ;  in  the  Corethrinae  they  are  short  and  not  adapted  for 
piercing. 

The  larvae  of  mosquitoes  are  all  aquatic.  They  are  well  known 
and  are  commonly  called  "wigglers,"  a  name  suggested  by  their 
wriggling  motion  as  they  swim  through  the  water.  They  vary  in 
details  of  structure  but  the  larva  of  Culex  will  serve  to  illustrate  the 
general  form  of  the  body  (Fig.  1020).  The  head  and  thorax  are 
large  and  the  abdomen  is  slender.  The  next  to  the  last  abdominal 
segment,  the  eighth,  bears  a  breathing-tube;  and  when  the  larva  is  at 
rest  it  hangs  head  downward  in  the  water,  with  the  opening  of  this 


DIPTERA 


805 


tube  at  the  surface.     (Fig.  102 1).    At  the  end  of  this  tube  there  is  a 
rosette  of  plate-Hke  lobes  (Fig.  1022,  a)  which  resting  on  the  surface 


Fig.  1020. — Larva  of  Culex  showing 
details  of  external  structure.  (From 
Riley   and   Johannsen.) 


Fig.  1021. — ^A  glass  of  water  containing  eggs, 
larvae,   and   pupae   of  mosquitoes. 


film,  keeps  the  larva  in  position.  At  the  end  of  the  last  abdominal 
segment  there  are  one  or  two  pairs  of  tracheal  gills.  About  the  mouth, 
on  the  antennfe,  and  on  the  caudal  segments  of  the  abdomen  are 
tufts  of  setcc  that  afford  characters  much  used  in  the  classification  of 
mosquito  larvae.  These  various  tufts  have  received 
special  names  as  indicated  in  Figure  1020. 

The  food  of  mosquito  larvae  varies  with  the 
different  species,  with  most  of  them  it  consists  of 
organic  matter  in  suspension  in  the  water,  or 
floating  upon  the  surface,  or  settled  or  growing 
upon  the  bottom.  Some  mosquito  larvae  are  can-  ^|^ 
nibalistic ;  those  of  the  Corethin^e  are  all  preda-  ^ 
cious  and  seize  their  prev  with  the  antennas.  Fig.  1022. — a,  end  of 

So  far  as  is  known,  there  are  four  larval  instars      \l^^^^'l%^^^^l^^l 
in  all  species  of  mosquitoes,  with  the  fourth  molt       ^ube  of' pupa, 
the  larva  becomes  a  pupa. 

The  pupae  of  mosquitoes  like  the  larvae  are  aquatic,  but  they  differ 
greatly  in  form  from  the  larvae.     (Fig.  1023).     The  head  and  thorax 


806  AN  INTRODUCTION  TO  ENTOMOLOGY 

are  greatly  enlarged  and  are  not  distinctly  separated,  while  the 
abdomen  is  slender  and  flexible.  With  the  change  to  the  pupa  state 
a  remarkable  change  takes  place  in  the  re- 
spiratory system.  There  are  now  two  breath- 
ing tubes,  and  these  are  borne  on  the  thorax. 
One  of  these  is  represented  greatly  enlarged 
by  Figure  1022,  b.  At  the  tail-end  of  the 
body  there  is  a  pair  of  leaf-like  appendages, 
with  which  the  insect  swims,  for  the  pupae  of 
mosquitoes,  and  also  of  certain  midges,  differ 
from  the  pupae  of  most  other  insects  in  being 
active;  but  the  pupae  take  no  food.  The 
duration  of  the  pupal  stage  is  brief,  usually 

^'a      lan'a^Y°^^u  ^a""^'       ^°^  "^°^^  ^^^^  ^^^'°  °^  ^^^^^  '^^^^'^  ^^^^  ^^^ 
'  .      ,        p  •         gj^-^  splits  down  the  back,  and  the  winged 

mosquito    carefully    works    itself    out    and 

cautiously  balances  itself  on  the  cast  skin,  using  it  as  a  raft,  until  its 

wings  are  hardened  so  that  it  can  fly  away. 

All  adult  mosquitoes  are  commonly  regarded  as  blood-sucking 
insects  and  are  feared  on  that  account;  but  there  are  many  species 
that  never  suck  blood  at  all,  and  of  the  blood-sucking  species  many 
attack  by  choice  birds  and  mammals  other  than  man.  It  is  only  the 
females  that  suck  blood ;  the  mouth-parts  of  males  are  not  fitted  for 
piercing  the  skin  of  animals.  The  males  feed  on  nectar,  the  juices  of 
ripe  fruits,  and  other  sweet  substances;  this  is  also  true  to  a  certain 
extent  of  females. 

The  different  species  of  mosquitoes  differ  greatl}'  in  their  manner 
of  oviposition.  Those  most  often  observed  about  water-barrels, 
Cttlex,  lay  their  long,  slender  eggs  side  by  side  in  a  boat-shaped  mass, 
on  the  surface  of  the  water  (Fig.  1021) ;  species  of  Anopheles  deposit 
their  eggs  separately  upon  the  surface  of  the  water;  and  many  Aedes 
lay  their  eggs  on  the  ground  after  the  pools  in  which  they  were  de-' 
veloped  have  dried  out.  In  this  case  the  eggs  remain  unhatched  until 
later  rains  or  melting  snow  refill  the  pools.  The  eggs  of  some  mosqui- 
toes hatch  very  soon  after  they  are  laid;  but  with  the  majority  of 
species  the  winter  is  passed  in  the  egg  state ;  and  in  the  case  of  certain 
species  it  is  believed  that  the  eggs  may  remain  on  dry  ground  several 
years  awaiting  rain  and  then  hatch. 

The  family  Culicidce  is  divided  into  two  subfamilies,  the  Coreth- 
rinae  and  the  CuHcinae. 

Subfamily  CORETHRIN^ 

This  is  a  small  group  of  mosquitoes  including  but  few  species.  It 
is  distinguished  from  the  Culicinas  by  the  comparative  shortness  of 
the  proboscis,  which  is  not  much  longer  than  the  head  and  is  not 
fitted  for  sucking  blood. 

The  larvae  of  members  of  this  subfamily  are  transparent;  they 
are  predacious  and  capture  their  prey  with  their  antennae;  they 
feed  on  infusoria,  small  crustacea,  and  small  larvae,  including  those 


DIPTERA 


807 


of  mosquitoes;  they  are  free-swimming  and  are  found  most  abun- 
dantly beyond  the  hne  of  shore  vegetation.  The  ]3tipa?  are  also  trans- 
parent at  first  but  become  darker  colored  just  before  transforming. 
The  females  of  Corethra  plmnicornis,  as  observed  by  Professor  Need- 
ham,  deposit  their  eggs  on  the  surface  of  the  water,  laying  them  down 
flatwise,  in  a  spiral  held  together  by  scanty  gelatine. 

A  monograph  of  this  subfamily  was  published  by  Johannsen  ('03). 


Subfamily  CULICIN^ 

To  this  subfamily  belong  by  far  the  greater  number  of  mosquitoes. 
With  these  the  proboscis  is  longer  than  the  head  and  thorax  taken 
together;  this  character  is  sufficient  to  distinguish  them  from  the 
Corethrinae. 

The  CulicincC  have  received  much  attention  in  recent  3-ears.  Since 
the  discovery  that  certain  species  are  carriers  of  diseases  of  man  many 
investigators  have  studied  mosquitoes,  and  thousands  of  papers  have 
been  published  regarding  them.  Fortunately  the  more  important 
results  of  these  investigations  have  been  summarized  by  several 
writers  and  published  in  easil}^  available  books.  The  most  important 
contribution  to  this  subject  is  the  monograph  by  Howard,  Dyar,  and 
Knab  ('  1 2-' 1 7) .  This  is  a  large  work  in  four  volumes.  A  more  avail- 
able and  more  recent  monograph  is  that  of  Dyar  published  in  1922. 

It  has  been  demonstrated  that  malaria,  yellow  fever,  filariasis,  and 
dengue  are  each  caused  by  a  parasitic  organism,  which  has  a  complex 
life-cycle,  part  of  which  is  passed  in  man  and  part  in 
certain  mosquitoes;  and  that  it  is  only  by  being 
bitten  by  an  infected  mosquito  that  one  contracts 
any  of  these  diseases.  There  are  also  diseases  of 
other  mammals  and  of  birds  that  are  transmitted 
in  a  similar  way. 

In  each  case  the  parasitic  organism  is  restricted 
in  host  relations,  infecting  in  turn  only  certain 
species  of  Vertebrates  and  certain  species  of  mosqui- 
toes. 

Representatives  of  eleven  genera  of  the  Culicinffi 
have  been  found  in  the  United  States.  Some  of  these 
occur  only  in  the  extreme  South  and  others  are  either 
rare  or  rarely  attack  man.  The  species  that  are  our 
most  serious  pests  are  included  in  the  genera  Culex, 
Anopheles,  and  Aedes. 

Culex. — To  this  genus  belong  our  common  house 
mosquitoes  that  have  unspotted  wings  and  short 
palpi  in  the  females  and  which  when  at  rest  on  a 
vertical  wall  hold  the  body  parallel  with  the  wall  or 
with  the  tip  of  the  abdomen  inclined  toward  it  (Fig. 
1024).  These  are  very  annoying  pests;  but  although 
many  of  the  species  of  this  genus  transmit  blood 
diseases  of  birds  and  animals  they  do  not  play  an  important  role  in 
human  diseases. 


Fig.  1024. — Nor- 
mal position 
of  Culex  and 
Anopheles  on 
a  wall ;  Culex 
above,  Ano- 
pheles below. 
(From  Riley 
and  Johann- 
sen.) 


808  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  eggs  are  laid  in  boat-shaped  masses  or  "rafts"  on  the  surface 
of  the  water  of  ponds  of  a  permanent  nature  and  on  water  of  artificial 
containers,  as  water-barrels.  A  larva  of  Culex  is  described  and  figured 
above  (Fig.  1020). 

Anopheles. — To  this  genus  belong  those  mosquitoes  that  have 
been  found  to  be  the  carriers  of  malaria.  Nine  species  oi  Anopheles  have 
been  found  in  the  United  States,  of  which  four  are  known  to  be  carriers 
of  this  disease.  In  this  genus  the  palpi  of  both  sexes  are  nearly  or 
quite  as  long  as  the  proboscis  and  the  wings  are  frequently  spotted. 
When  at  rest  on  a  vertical  wall  the  body  is  usually  held  at  an  angle 
with  the  vertical  (Fig.  1024).  Some  species  often  enter  houses.  They 
hibernate  in  the  adult  state  and  can  be  found  during  the  winter  in 

cellars. 

The  eggs  are  laid  singly  in 
small  numbers  upon  the  sur- 
face of  water.  The  larva 
when  at  rest  floats  in  a  hori- 
zontal position  beneath  the 
surface  film  (Fig.  1025).  There 
is  no  respiratory  tube  but  in- 
stead a  flattened  area  on  the 
Fig.  1025.— Normal  position  of  the  larvae  eighth  abdominal  segment  into 
of  Culex  and  Anopheles  when  at  rest.  ^--^  ^^^  ^^^  spiracles  open. 

Culex,    left,    Anopheles,    middle;  Culex  ^r   ^     ■       ■  n  1 

pupa,  right  hand  figure.  Malaria    IS   a   well-known 

and  widely  distributed  disease. 
It  is  most  common  in  the 
vicinity  of  swamps,  and  is  more  virulent  in  the  South  than  in  the 
cooler  parts  of  the  country.  It  is  caused  by  unicellular  parasites  in 
the  blood  which  feed  upon  the  red  blood  corpuscles.  These  parasites 
belong  to  the  genus  Plasmodium  of  the  Protozoa.  Three  species  of 
these  malarial  parasites  are  now  recognized,  each  of  which  causes  a 
distinct  type  of  malaria. 

The  life-cycle  of  the  malarial  parasites  is  an  exceedingly  com- 
plicated one.  Our  knowledge  of  it  is  the  result  of  extended  investi- 
gations by  several  workers.  The  history  of  these  investigations  is  a 
most  interesting  one;  but  space  can  not  be  taken  to  narrate  it  here. 
Accounts  of  these  investigations,  with  details  of  the  results  obtained 
are  given  by  Howard,  Dyar,  and  Knab  ('12)  and  Riley  and  Johannsen 
('15).  The  following  summary  of  the  life-cycle  is  condensed  from  the 
accounts  by  these  writers. 

The  malarial  infection  is  introduced  into  the  blood  circulation  of  man  by 
the  bite  of  a  mosquito  that  has  previously  bitten  a  person  having  this  disease. 
It  is  onl}^  certain  species  of  mosquitoes  of  the  genus  Anopheles  that  transmit  this 
disease  to  man.  The  infecting  organism,  which  in  that  stage  of  its  development  is 
known  as  a  sporozoite,  penetrates  a  red  blood  corpuscle  and  becomes  an  amoeboid 
schizont.  This  lives  at  the  expense  of  the  blood  corpuscle  and  as  it  develops  there 
are  deposited  in  its  body  scattered  black  or  reddish  black  particles.  These  are 
generally  called  melanin  granules,  but  are  much  better  referred  to  as  hcemozoin, 
as  they  are  not  related  to  melanin.  The  haemozoin  is  the  most  conspicuous  part  of 
the  parasite,  a  feature  of  advantage  in  diagnosing  from  unstained  preprations. 
As  the  schizont  matures,  its  nucleus  breaks  up  into  a  number  of  daughter  nuclei, 


DIPTERA  809 

each  with  a  rounded  mass  of  protoplasm  about  it,  and  finally  the  corpuscles  are 
broken  down  and  these  rounded  bodies  are  liberated  in  the  plasma  as  spores  which 
are  known  as  merozoits.  These  spores  infect  new  corpuscles,  where  they  again 
go  through  the  stages  of  schizonts  and  merozoits,  and  thus  the  asexual  cycle 
is  continued.    The  malarial  paroxysm  is  coincident  with  sporulation. 

Parallel  with  the  asexual  cycle  sexual  elements  or  gametes  are  produced  by 
schizonts.  These  sexual  elements,  however,  can  not  copulate  within  the  human 
organism  on  account  of  the  unfavorable  temperature.  To  enable  them  to  carry 
out  this  function,  and  to  develop  further  they  must  be  transferred  to  the  ahment- 
ary  canal  of  an  Anopheles,  which  is  done  when  one  of  these  mosquitoes  sucks  the 
blood  in  which  they  are.  Here  the  union  of  the  male  and  female  gametes  takes 
place  and  there  results  a  stage  known  as  the  migratory  ookinete.  The  ookinete 
penetrates  the  wall  of  the  midintestine  of  the  mosquito  and  there  transforms  to 
the  oocyst.  In  the  process  of  growth  of  the  oocyst  further  stages  occur,  first  by  its 
division  the  sporoblasts,  and  from  these,  by  further  division,  the  sporozoits,  when 
the  oocyst  is  mature  it  bursts,  liberating  the  sporozoits  which  thus  pass  into  the 
general  body  cavity  of  the  host.  The  sporozoits  now  find  their  way  into  the  sali- 
vary glands  of  the  host  and  there  remain  until  the  mosquito,  in  biting,  forces 
them  along  with  the  saliva,  through  its  proboscis  into  a  human  being.  Then  the 
asexual  cycle  begins  in  the  blood  of  a  new  host. 

Aedes .—This,  is  a  very  large  genus  of  world-wide  distribution 
Dyar  ('22)  describes  73  species  that  have  been  found  in  the  United 
States.  The  species  vary  greatly  in  habits;  but  with  most  of  them 
the  larvffi  develop  from  over-wintering  eggs  in  early  spring  pools. 
Some  species,  however,  breed  in  water-barrels,  and  other  artificial 
containers ;  one  of  these  is  the  carrier  of  yellow  fever. 

The  yellow-fever  mosquito,  Aedes  CBgypti,  is  distributed  through- 
out all  tropical  regions  of  the  world  and  is  often  carried  by  commerce 
into  temperate  regions.  But  as  it  is  destroyed  by  frost  it  can  not 
become  established  where  frosts  occur.  Hence  outbreaks  of  yellow 
fever  in  the  North  are  checked  naturally  as  winter  approaches,  and 
with  our  present  knowledge  of  the  methods  of  control  of  this  disease 
it  is  not  probable  that  it  will  be  permitted  to  become  epidemic  again 
in  the  United  States. 

When  yellow  fever  appears  the  patients  should  be  kept  in  mosqui- 
to-proof rooms,  so  that  they  may  not  serve  as  centers  of  distribution 
of  the  disease ;  and  the  breeding  places  of  mosquitoes  should  be  drained 
or  screened,  or  oiled. 

The  yellow  fever  mosquito  breeds  in  cisterns,  water-barrels, 
fiower-vases,  and  in  the  various  water  receptacles  about  houses.  The 
life-cycle  imder  favorable  conditions  is  completed  in  from  twelve  to 
fifteen  davs.  This  is  essentially  a  domesticated  species.  It  is  rarely 
found  far  from  the  habitations  of  man. 

The  fact  that  yellow  fever  is  transmitted  by  this  mosquito  has 
been  definitely  established;  but  it  is  not  certain  that  the  causative 
organism  is  known,  although  some  investigators  claim  to  have  found 
it. 

The  yellow  fever  mosquito  was  first  described  by  Linnasns  in  1762  under  the 
name  Culex  cegypti.  But  the  Linnasan  genus  Culex  has  been  divided  and  this 
species  pertains  to  the  genus  Aedes  established  by  Meigen  in  18 18;  hence  its 
correct  name  is  Aedes  cegypti.  Unfortunately  a  score  of  other  names  have  been 
applied  to  it;  those  most  commonly  found  are  Aedes  calopus,  Stegomyia  fascidta, 
and  Stegomyia  calopus. 


810 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Other  mosquito-borne  diseases  of  man. — In  tropical  countries  there 
are,  in  addition  to  malaria  and  yellow  fever,  two  other  diseases  of 
man  that  have  been  found  to  be  transmitted  by  mosquitoes ;  these  are 
dengue  and  filariasis.  The  causative  organism  of  dengue  has  not  been 
discovered;  but  it  is  believed  to  be  a  protozoan  of  ultra-microscopic 
size.  Filariasis  is  due  to  the  presence  in  the  blood,  the  lymphatics, 
the  mesentery,  and  subcutaneous  connective  tissue  of  nemotode 
worms  belonging  to  the  family  Filariidae,  and  which  pass  part  of 
their  life-cycle  in  the  bodies  of  mosquitoes.  One  of  these  parasites, 
Filaria  hancrofti,  is  the  cause  of  the  extraordinary  deformities  of 
different  parts  of  the  human  body  known  as  elephantiasis. 

Mansdnia: — In  this  genus  "the  larvee  are  peculiar  in  having  the 
air  tube  adapted  for  piercing  the  vascular  roots  of  certain  aquatic 
plants,  from  which  they  get  their  supply  of  air.  The  eggs  are  de- 
posited in  rafts  in  swamps  where  suitable  plants  grow,  and  the  young 
larvae  descend  to  the  roots,  never  coming  to  the  surface  again." 
(Dyar,  '22).  Mansdnia  pertUrbans  is  widely  distributed  in  the  United 
States  and  Canada.  Its  larva  lives  attached  to  the  roots  of  a  species 
of  Carex  growing  in  marshes  or  the  edges  of  ponds.  The  winter  is 
passed  as  half-grown  larva. 

Wyeomyia  smtthii. — This  species  is  remarkable  on  account  of  its 
habits.  "The  larvae  live  in  the  water  in  the  leaves  of  pitcher  plants 
{Sarracenia  purpurea),  passing  the  winter  frozen  up  in  the  ice  cores. 
The  eggs  are  laid  on  the  still,  dry,  newly  opened  leaves  and  hatch 
when  water  collects  in  them"  (Dyar  '22).  The  adult  can  be  distin- 
guished from  all  other  Culi- 
cinse  found  north  of  Southern 
Florida  by  the  presence  of  a 
tuft  of  setae  on  the  metonotum. 

Family  MYCETOPHILID^ 
The  Fungus-Gnats 


These 
flies  are  of 
medium  or 
small  size 
and  more  or 
less  mos- 
quito-like in 
form.  They 
are  most 
easily  recog- 
nized by  the 
length  of  the 
coxae  (Fig. 
1026).  The 
ocelli      are 


Fig.  1026.- — Mycetophila  punctata. 
Johannsen.) 


(After 


Fig.   1027. 


DIPT ERA 


811 

7)  and 


present;  the  antennae,  as  a  rule,  lack  whorls  of  hairs  (Fig.  102 
all  the  tibiae  are  furnished  with  spurs. 

At  first  sight  considerable  variation  seems  to  exist  in  the  venation 
of  the  wings  as  shown  in  the  three  wings  represented  in  Figure  1028; 
but  in  reality  the  variations  are  comparatively  slight.  The  costa 
extends  along  the  margin  of  the  wing  to  the  end  of  the  radial  sector. 
Radius  preser\^es  three  branches  in  the  more  generalized  forms  (Fig. 
1028,  a) ;  in  some  genera  veins  Ri  and  R2+3  coalesce  from  the  apex  of 
the  wing  backward  for  a  greater  or  less  distance  so  that  the  basal  part 
of  vein  R2+3  appears  like  a  cross-vein  (Fig.  1028,  h)\  in  some  genera 


CU^        CU, 


/?,...3 


C«,      Cu. 


Fig.    1028. — Wings  of  fungus-gnats.      (The  drawings  are  after  Winnertz;  the 
lettering  is  original.) 

radius  is  only  two-branched,  this  condition  may  have  been  brought 
about  by  the  complete  coalescence  of  veins  Ri  and  R2+3  or  by  the 
coalescence  of  veins  R2-1-3  and  R1+5,  whichever  may  be  the  case  the 
two  branches  are  commonly  designated  as  Ri  and  Rs  respectively 
(Fig.  1028,  c).  ' 

The  fungus  gnats  are  exceedingly  numerous  both  in  number  of 
individuals  and  in  number  of  species.  They  are  often  found  in  great 
nimibers  on  fungi  and  in  damp  places  where  there  is  decaying  vege- 
table matter.    They  are  active  and  leap  as  well  as  fly. 

A  monograph  of  the  known  species  of  the  world,  not  including  the 
Sciarinas,  was  published  by  Professor  Johannsen  ('09a) ;  and  in  a  later 


812 


AN  INTRODUCTION  TO  ENTOMOLOGY 


series  of  papers  he  published  a  synopsis  of  the  species  of  North  Amer- 
ica, including  the  Sciarinae  (Johannsen  '09-' 12). 

The  larvae  of  most  species  live  upon  and  destroy  mushrooms, 
usually  the  wild  plants,  but  sometimes  they  are  pests  in  mushroom 
cellars;  other  species  are  found  in 
decaying  wood;  and  certain  species  of 
the  subfamily  Sciarinae  are  sometimes 
pests  of  cultivated  plants,  destroying 
seed  corn,  seed  potatoes,  and  the  roots 
of  other  plants. 

In  this  family  the  larva  is  more  or 
less  cylindrical,  smooth,  soft,  whitish  in 
color,  and  with  a  small  strongly  chiti- 
nized  head,  which  is  usually  brown  or 
black,  and  is  provided  with  mandibles 
and  maxillae.  There  are  usually  eight 
pairs  of  spiracles. 

The  pupa  is  not  enclosed  in  the  skin 
of  the  larva;  but  in  some  genera  the 
transformations  are  undergone  in  a 
delicate  cocoon. 

The  subfamily  Sciarince. —  The 
family  Mycetophilidas  is  divided  into 
nine  subfamilies,  eight  of  which  are 
One  of  these  subfamilies,  the  Sciaringe, 
merits  special  mention  in  this  place.  The  members  of  this  subfamily 
differ  from  the  more  typical  fungus-gnats  as  follows ;  the  coxae  are  not 
so  greatly  elongated;  the  eyes  differ  in  shape,  there  being  a  narrow  ex- 


Fig.   1029. — Eyes  of  Sciara. 
represented  in  our  fauna. 


A/i+2 


Fig.  1030. — Wing  of  Sciara.     (After  Enderlein.) 

pansion  of  each  eye  extending  above  the  base  of  the  antennae  and 
meeting  or  nearly  meeting  the  expansion  of  the  other  eye,  (Fig.  1029), 
while  in  other  fungus-gnats  the  eyes  are  either  round,  oval,  or  kidney- 
shaped,  but  not  markedly  narrowed  above;  and  the  cross- vein  r-m  is 
in  the  same  right  line  with  the  second  section  of  the  radial  sector  (Fig. 
1030). 


DIPTERA 


813 


The  larvae  of  some  species  of  the  genus  Sclara  often  attract  atten- 
tion on  account  of  a  strange  habit  they  have  of  sticking  together  in 
dense  patches.  Such  assemblages  of  larvae  are  frequently  found  under 
the  bark  of  trees.  But  what  is  more  remarkable  is  the  fact  that  when 
the  larvce  are  about  to  change  to  pupae  an  assemblage  of  this  kind 
will  march  over  the  surface  of  the  ground,  presenting  the  appearance 
of  a  serpent-like  animal.  Such  a  congregation  is  commonly  spoken 
of  as  a  wSciara-army-worm.  Examples  have  been  described  that  were 
four  or  five  inches  wide  and  ten  or  twelve  feet  long,  and  in  which  the 
larvae  were  piled  up  from  four  to  six  deep.  The  larvae  crawl  over 
each  other  so  that  the  column  advances  about  an  inch  a  minute. 

THE  FAMILY 'SCIARID^  OF  ENDERLEIN 

The  establishment  of  a  family  to  be  known  as  the  Sciaridse  was  proposed  by 
Enderlein  ('ii  &  '12  a).  The  proposed  family  includes  the  subfamily  Sciarinae  of 
the  Mycetophilidas  and  the  subfamily  Lestremiins  of  the  Cecidomyiidae  and  is 
characterized  by  the  form  of  the  eyes;  the  two  subfamilies  agreeing  in  having  the 
type  of  eyes  described  above  (Fig.  1029)  and  differing  in  this  respect  from  other 
fungus-gnats  and  gall-gnats. 

This  proposed  grouping  of  these  two  subfamilies  has  not  been  generally  ac- 
cepted. While  they  agree  in  the  shape  of  their  eyes,  they  diflfer  in  the  presence  of 
tibial  spurs  in  the  Sciarinae  and  the  absence  of  these  sptirs  in  the  Lestrenainas; 
and  they  diflfer  markedly  in  the  form  of  their  larvae.  The  larvas  of  the  Lestremiinae 
have,  like  those  of  other  Cecidomyiidae,  an  undeveloped  head,  indistinct  mouth- 
parts,  and  a  well-developed  sternal  spatula;  the  larvae  of  the  vScarinae  have, 
on  the  contrary  like  other  Mycetophilidae,  a  well-developed  head  which  is  strongly 
chitinized,  and  strong,  toothed  mandibles,  and  do  not  have  a  sternal  spatula. 

Family  CECIDOMYIID^* 
The  Gall-Gnats 

The  gall-gnats  are  minute  flies  which  are  ex- 
tremely delicate  in  structure.  The  body  and  wings 
are  clothed  with  long  hairs,  which  are  easily  rubbed 
off.  The  antennge  are  usually  long  and  clothed  with 
whorls  of  hairs  (Fig.  103 1) ;  but  they  vary  greatly  in 
length,  in  the  number  of  their  segments,  in  the  form 
of  the  segments  of  the  f^agellum,  and  in  the  nature  of 
their  clothing.  Except  in  the  first  subfamily,  the 
ocelli  are  wanting.  The  legs  are  slender  and  quite 
long,  but  the  coxae  are  not  greatly  elongated  and  the 
tibiae  are  without  spurs.  Except  in  the  first  sub- 
family, the  wing-veins  are  greatly  reduced  in  num- 
ber (Fig.  1032),  the  anal  veins  being  entirely  want- 
ing, and  the  media  wanting  or  merely  represented  by 
a  slight,  unbranched  fold;  in  the  first  subfamily,  the 
Lestremiinse,  vein  AI  is  well  preserved. 

A  striking  feature  of  this  family  is  the  presence 
in  most  species  (/.  e.  in  all  except  the  first  two  small 
subfamilies)  of  what  have  been  generally  known  as  arched  filaments 

*This  family  is  named  the  Itonididae  by  some  writers,  those  who  recognize 
the  names  published  by  Meigen  in  1800;  seepage  794  for  a  discussion  of  these 
names. 


m  f 
Fig.  1 03 1. — An"- 
tennas  of  gall- 
gnats:  m,  male; 
/,  female,  en- 
larged more 
than  that  of 
the  male. 


814 


AN  INTRODUCTION  TO  ENTOMOLOGY 


on  the  antennae  (Fig.  1033).  These  filaments  occur  in  series,  and 
there  may  be  one,  two  or  three  of  these  series  on  each  segment  of  the 
flagellum.     As  each  of  these  series  has  the  appearance  of  a  looped 


Fie.  1032. — Wing  of  a  eall-enat. 

thread  extending  around  the  segment  of  the  antenna  the>'  are  termed 
circumfili  by  Dr.  Felt,  who  has  described  and  figured  many  forms  of 
them  in  his  series  of  papers  on  this  famih'. 


Fie.  1033. — Antennal  segments  with  circumfili:  a,  fifth  segment  of  antenna  of 
Karschomyia  viburni,  male;  b,  fifth  antennal  segment  of  a  Rhopalomyia, 
female;  c,  sixth  antennal  segment  of  Winnertzia  calciequina,  female.  (From 
Felt.) 

To  this  family  belong  the  smallest  of  the  midge-like  flies.     On 
account  of  their  minute  size  the  adult  flies  are  not  apt  to  attract  the 


DIPTERA  815 

attention  of  the  young  student.    But  the  larvae  of  many  species  cause 
the  growth  of  galls  on  plants,  some  of  which  are  sure  to  be  found  by 
any   close   observer.      Other   species   arrest   the 
growth  of  the  plants  they  infest,  and  cause  very  -.^^jk 

.serious  injur\\  y^iQJP^ 

The  larva?  are  small  maggots,  with  nine  pairs       £  "^        ""'"^X 

of  spiracles.  The  head  is  small,  poorly  developed,       f       — ^*- 

and  without  mandibles;  between  the  head  and  the 
first  thoracic  segment  there  is  a  large  neck-seg-  Fig-  1034.— Head 
.■,■■,-.■,  1  4.U  j:        end  of  larva  show- 

ment,  which  gives  these  larvae  the  appearance  of  -^g  the  breast- 
having  an  extra  segment.  Many  species  are  bone. 
brightly  colored,  being  red,  pink,  yellow,  or 
orange,  and  many  species  possess  in  the  last  larval  instar  a  peculia.r 
chitinous  organ  on  the  ventral  aspect  of  the  prothorax ;  this  organ  is 
known  as  the  breast-bone  or  sternal  spatula,  or  anchor  process  (Fig. 
1034).  It  varies  in  form  in  different  species;  different  views  are  held 
regarding  its  function,  none  of  which  seems  well  established. 

The  larval  mouth-parts  are  fitted  only  for  taking  liquid  food;  but 
the  nature  of  this  food  differs  greatly  in  different  members  of  the 
family.  Some  species  are  parasitic  in  the  bodies  of  aphids  and  other 
Homoptera;  some  are  predacious  feeding  on  either  aphids,  coccids, 
mites,  or  larvae  and  pupae  of  other  Diptera,  especially  those  of  other 
species  of  gall-gnats;  some  feed  on  the  excrement  of  other  larvae  or 
that  of  cattle  and  of  birds;  but  most  species  are  vegetable  feeders. 
Among  those  that  feed  on  plants  many  species  produce  galls.  The 
larvae  of  several  genera  of  the  second  subfamily,  the  Heteropezinae 
give  birth  to  living  young,  as  described  later. 

Different  modes  of  pupation  have  been  observed  among  the  gall- 
gnats;  in  some  the  pupa  is  naked;  in  others  the  change  to  the  pupa 
state  takes  place  within  a  puparium,  but  this  puparium  differs  from 
that  of  most  Diptera  in  being  formed  by  the  next  to  the  last  larval 
skin,  the  last  larval  molt  taking  place  within  it;  in  some  species  as  the 
wheat-midge,  the  puparium  consists  only  of  the  peunltimate  larval 
skin,  in  others  as  the  Hessian  fly,  it  is  lined  with  a  delicate  silken 
layer  (Marchal  '97);  and  in  still  others  the  pupa  is  enclosed  in  a 
delicate  cocoon  instead  of  in  a  puparium. 

The  literature  regarding  this  family  is  very  extensive;  hundreds 
of  articles  have  been  written  about  those  species  that  are  of  economic 
importance,  and  very  many  papers  have  been  published  on  the  classi- 
fication of  these  insects;  A  monograph  of  the  species  of  the  world  was 
published  by  Kieffer  in  18 13  and  a  review  of  the  American  species  is 
being  published  by  Dr.  Felt  in  his  annual  reports  as  State  Ento- 
mologist of  New  York.  Ses  also  Felt  ('18)  for  descriptions  and  figures 
of  the  galls  produced  by  members  of  this  family. 

The  family  Cecidomyiidae  is  separated  into  three  subfamilies, 
which  can  be  separated  by  the  following  table: 

A.    Ocelli  present;  vein  M,  preserved  either  simple  or  forked,  p.  816.  Lestremun^ 
AA.    Ocelli  wanting;  vein  M  wanting  or  represented  merely  by  a  fold. 

B.     Antennae  without  either  circumfili  or  horseshoelike  appendages;  the  first 
segment  of  the  tarsi  usually  longer  than  the  second  p.  816.  Heteropezinae 


816 


AN  INTRODUCTION  TO  ENTOMOLOGY 


BB.    Antennae  with  circumfili  or  {Winnertzia)  with  horseshoelike  appendages; 
the  first  segment  of  the  tarsi  shorter  than  the  second   p.  817.  Cecidomyiin.^ 

Subfamily  LEvSTRE:MIIN^ 

The  members  of  this  subfamily  differ  from  other  gall-gnats  in 
having  ocelli,  in  the  shape  of  their  eyes,  these  resembling  those  of 
Sciara  (Fig.  1029),  and  in  the  less  reduced  venation  of  their  wings, 
vein  AI  being  preserved ;  in  some  genera  this  vein  is  forked  (Fig.  1035) 
in  others  it  is  unbranched. 


M.^2 


Cm  Ctt^ 

Fig.   1035. — Wing  of  Lestremia.     (After  Kieffer.) 

Most  of  the  known  lar\-ae  of  this  subfamily  live  in  decaying  vege- 
table matter,  especially  in  rotten  wood  under  bark. 


SuBF.\MiLY  HETEROPEZIN^ 

This  subfamily  includes  comparatively  few  species,  none  of  which 
is  known  to  be  of  economic  importance.  The  known  lar\^ae  live  in  the 
decaying  bark  of  trees.  Some  of  them  are  remarkable  for  the  fact 
that  they  give  birth  to  living  young. 

This  type  o^  reproduction  is  termed  psedogenesis  (See  page  192). 
It  was  first  discovered  by  Nicholas  Wagner  in  1862  and  has  been  in- 
vestigated by  several  other  Europeans.  It  has  also  been  studied  in 
this  country  by  Dr.  Felt  ('11)  who  gives  an  extended  account  of  it  as 
observed  by  him  in  Miastor  atnericdna,  and  by  Professor  Hegner  ('12 
and  '14)  who  gives  the  history  of  the  germ  cells  in  the  paedogenetic 
larva  of  this  species. 

The  larva  of  Miastor  americdna  possesses  two  ovaries,  one  on 
either  side  of  the  body  in  the  tenth  or  eleventh  segments.  Each  ovary 
consists  of  typically  thirty-two  oocytes,  each  of  which  is  accompanied 
by  a  group  of  nurse-cells,  and  with  them  is  surrounded  by  a  folicular 
epithelitun.  The  nuise-cells  furnish  nutrition  to  the  growing  o6c}i;es, 
gradually  becoming  reduced  as  the  oocytes  increase  in  size.  Finally 
the  oocyte  with  accompanying  nurse-cells,  still  surrounded  by  the 
follicular  epithelium,  becomes  separated  from  the  rest  of  the  ovary  and 


DIPTERA 


817 


is  forced  by  the  movements  of  the  larva  into  some  other  part  of  its 
body.  Here  it  continues  its  growth  and  development  at  the  expense 
of  the  tissues  of  the  mother-larva.  Not  all  of  the  oocytes  complete 
their  development,  since  usually  only  from  five  to  seventeen  young 
are  produced  by  a  single  mother-larva  (Hegner). 

When  the  tissues  of  the  mother-larva  are  consum,ed,  the  voung 
larvae  break  forth  from  the  skin  of  their  parent  and  continue  their 
growth.  These  lar^^ffi  may  in  turn  produce  another  generation  of 
larvae  in  the  same  manner.  It  is  believed  that  this  asexual,  paedo- 
genetic  reproduction  may  continue  through  many  generations  cover- 
ing a  period  of  two  or  three  years.  Finally  a  generation  of  lar^-ae  are 
produced  which  do  not  reproduce  in  this  manner,  but  which  when 
full  grown  transform  first  to  pupag  and  then  to  adults,  which  repro- 
duce sexually.  According  to  the  observations  of  Kieifer  ('13)  the 
adult  females  of  those  species  in  which  pasdogenesis  occurs  produce 
each  only  four  or  five  eggs,  while  other  gall-gnats  produce  a  large 
number  of  eggs. 

Subfamily  CECIDOAIYIIN^ 

This  subfamily  includes  the  larger  ntimber  of  the  gall-gnats ;  to  it 
belong  those  species  that  have  attracted  attention  on  account  of 
their  economic  importance,  and  others  that  are  well  known  on  ac- 
count of  the  conspicuous  galls  produced  by  them.  Much  has  been 
published  regarding  some  of  these  species ;  but  unfortunately  they  are 
discussed  under  different  generic  names  by  different  writers.  For 
this  reason  the  common  names 
will  be  found  more  useful  when 
one  is  attempting  to  learn  what 
has  been  published  regarding 
these  species. 

The  pine-cone  willow-gall. 
— One  of  the  most  common 
and  conspicuous  of  the  galls 
made  by  gall-gnats  is  the  pine- 
cone  willow-gall  (Fig.  1036). 
This  often  occurs  in  great 
abundance  on  the  tips  of  twigs 
of  the  heart-leaved  willow, 
Salix  cordata.  The  gnat  that 
causes  the  growth  of  this  gall 
is  Rhabdophaga  strohiloides. 
The  larva  remains  in  the  heart 
of  the  gall  throughout  the 
summer  and  winter,  changing 
to  a  pupa  early  in  the  spring. 
The  adult  emerges  soon  after- 
ward, and  lays  its  eggs  in  the  newh'-started  buds  of  the  willow. 

The  pine-cone  willow-gall  guest,  Cecidomyia  alhovittdta. — This 
species  breeds  in  large  numbers  between  the  leaves  composing  the 


The  pine-cone  willow-gall. 


818  AN  INTRODUCTION  TO  ENTOMOLOGY 

pine-cone  willow -gall.  The  larvae  of  this  gnat  do  not  seem  to  interfere 
in  any  way  with  the  development  of  their  host,  there  being  abundant 
food  in  the  gall  both  for  the  owner  of  the  gall  and  for  its  numerous 
guests. 

The  clover-leaf  midge,  Dasyneura  trifolii: — The  leaflets  of  white 
clover  are  sometimes  infested  by  white  or  orange-colored  maggots 
which  fold  the  two  halves  of  the  leaflet  together.  From  one  to  twenty 

of  these  larvse  may  be  found 
in  a  single  leaflet.  When  full 
grown  the  larvae  make  cocoons, 
and  undergo  their  transforma- 
tions within  the  folded  leaflet. 
In  Figure  1037  an  infested  leaf 

r.^       ^-—1     ^^^1         ^     containing    cocoons    is    repre- 
\     %r^     W^.^  sented    natural    size,    also    a 

\    I     ^P  ^    -^      '*  larva     and     an     adult     gnat, 

I       ;■,]  ff  greatly  enlarged. 

/  Iv  The    clover-flower    midge, 

Fig.  1037.  -The  clover-leaf  midge.  Dasyneura  le gum inicola -This 

is  a  very  serious  pest.  Ihe 
larvae  live  in  the  heads  of 
clover  and  destroy  the  immature  seed.  Different  kinds  of  clover  are 
infested  by  this  pest;  but  red  clover  is  its  chief  food  plant;  and  in 
some  parts  of  this  country  it  has  seemed  impossible  to  raise  clover- 
seed  on  account  of  this  insect. 

The  larva  of  the  clover-flower  midge  passes  the  winter  on  or 
slightly  below  the  surface  of  the  ground,  usually  but  not  always,  in  a 
cocoon;  it  changes  to  a  pupa  early  in  the  spring,  and  emerges  an 
adult  in  late  April  or  early  May.  The  eggs  are  laid  in  the  small  green 
clover  heads,  many  eggs  in  a  single  head,  as  each  larva  infests  a 
single  floret.  The  larvae  mature  in  about  four  weeks,  and  then  drop 
to  the  ground  to  transform.  Two  or  three  weeks  later  a  second  gen- 
eration of  midges  appear  and  lay  their  eggs. 

The  most  efficient  method  of  combating  this  pest  is  to  make  the 
first  cutting  of  clover  early,  before  the  first  generation  of  midges 
have  matured,  that  is,  early  in  June;  the  drying  of  the  clover  heads 
will  result  in  the  destruction  of  the  larvae  in  them ;  and  thus  the  second 
crop  of  clover  will  not  be  infested.  Care  should  be  taken  to  cut  at 
the  same  time  any  clover  that  may  be  growing  wild  in  fence-corners 
by  roadsides,  or  elsewhere. 

The  Hessian-fly,  Phytophaga  destructor. — This  is  the  most  serious 
pest  infesting  wheat  in  this  country.  The  larvae  live  at  the  base  of  a 
leaf  between  it  and  the  main  stalk,  where  they  draw  their  nourish- 
ment from  the  plant.  There  are  two  or  three  broods  of  this  insect  in 
the  course  of  the  year.  The  larvae  of  the  fall  brood  infest  the  young 
wheat-plants  near  the  surface  of  the  ground.  When  full-grown  each 
changes  to  a  pupa  within  a  brown  puparium,  which  resembles  a  flax- 
seed. Here  they  remain  throughout  the  winter.  In  the  spring  the 
adult  gnats  emerge  and  lay  their  eggs  in  the  sheaths  of  leaves  some 
distance  above  the  ground.    The  infested  plants  are  so  weakened  by 


DIPTERA 


819 


the  larva?  that  they  produce  but  little  if  any  seed,  and  often  bend  or 
even  break  off  at  the  weakened  spot. 

There  is  no  method  by  which  a  crop  of  wheat  can  be  saved  from 
the  ravages  of  this  pest  after  it  is  infested  by  it;  the  only  means  of 
control  are  those  that  prevent  infestation.  Where  practicable  all  in- 
fested stubble  should  be  plowed  under  immediately  after  harvest  and 
the  soil  rolled  or  lightly  harrowed,  thus  preventing  the  emergence  of 
the  fall  brood  of  gnats;  but  this  can  not  be  done  where  clover  or 
grasses  are  sown  with  the  wheat.  The  most  available  means  of  con- 
trol is  to  sow  wheat  moderately  late,  that  is,  after  the  fall  generation 
of  gnats  has  disajDpeared,  but  early  enough  to  secure  the  maximum 
yield  of  grain.  This  safe  date  varies  with  the  latitude,  longitude,  and 
elevation  above  sea  level.  This  date  has  been  carefully  determined 
for  the  different  parts  of  the  country  and  can  be  ascertained  for  any 
locality  by  application  to  a  State  or  Federal  Entomologist.  Dr.  A.  D. 
Hopkins,  who  has  made  a  very  extended  investigation  of  this  subject 
states  that  the  first  general  coloring  of  the  foliage,  especially  on  the 
hickories,  dogwood,  birch,  ash,  etc.,  is,  as  a  rule,  coincident  with  the 
safest  and  best  time  to  begin  sowing  wheat  on  any  farm  within  the 
range  of  winter  wheat  culture. 

The  wheat-midge,  Thecodipldsis  moselldna. — This  gnat  is  also  a 
very  serious  enemy  of  wheat.  It  deposits  its  eggs  in  the  opening 
flowers  of  wheat.  The  larvae  feed  on  the  pollen  and  the  milky  juice 
of  the  immature  seeds,  causing  them  to  shrivel  up  and  become  com- 
paratively worthless.  When  full-grown  the  larvae  drop  to  the  ground, 
where  the  transformations  are  undergone  near  the  surface.  The 
adults  appear  in  May  or  June.  No  effective  method  of  control  of  this 
pest  has  been  devised. 

Until  recently  our  common  wheat-midge  was  supposed  to  be  the 
same  as  the  European  species  the  specific  name  of  which  is  tritici,  and 
which  has  been  placed  successively  in  the  following  genera;  Tipula, 

Cecidomyia,  Diplosis,  and 
Contarinia.  But  it  has 
been  found  to  be  another 
European  species,  the 
Thecodiplosis  mosellana. 
The  resin-gnat,  Re- 
tinodiplosis  resinlcola. — 
This  species  infests  the 
branches  of  various 
species  of  pine.  I  have 
found  it  throughout  the 
Atlantic  region  from  New 
York  to  Florida.  The 
larvae  live  together  in 
considerable  numbers 
within  a  Itunp  of  resin. 
They  derive  their  nourishment  from  the  abraded  bark  of  the  twig; 
and    the  resin  exuding  from  the  wound  completely  surrounds  and 


Fig.   1038. — The  resin-gnat. 


820  A  N  INTROD  UCTION  TO  ENTOMOLOG  Y 

protects  them.  The  transformations  are  undergone  ^yithin  the 
lump  of  resin.  After  the  gnats  emerge  the  empty  pupa-skins  project 
from  the  limip  of  resin  as  shown  at  the  right  in  Figure  1038.  In 
this  figure  the  gnat,  a  single  wing,  and  a  part  of  the  antenna  of  each 
sex  are  represented,  all  greatly  enlarged. 

The  pear-midge,  Contannia  pynvora.— The  female  of  this  species 
deposits  her  eggs  by  means  of  her  long  ovipositor,  in  the  interior  of 
the  unopened  blossoms  of  pear.  The  young  fruit  is  destroyed  by  the 
larvae.  There  is  a  single  annual  generation .  The  winter  is  passed  in  the 
ground,  usually  as  pupae  but  sometimes  as  larvae.  This  is  an  intro- 
duced European  species,  which  has  not  yet  become  a  serious  pest  in 
this  country. 

The  chrysanthemum  gall-midge,  Diarthronomyia  hypogcea. — This 
species  causes  the  growth  of  galls  on  the  leaf,  stem,  and  flower-head 
of  the  chrysanthemtmi  plant,  and  is  sometimes  a  serious  pest  in  green- 
houses. A  detailed  account  of  it  is  given  in  Bulletin  No.  833  of  the 
U.  S.  Department  of  Agriculture. 

SUBSERIES    B. — -THE    ANOMOLOUS    NEMOCERA 

In  this  subseries  the  antennae  are  composed  of  many  segments- 
but  are  shorter  than  the  head  and  thorax,  and  are  without  whorls  of 
long  hairs.  The  segments  of  the  flagellum  of  the  antennas  are  short 
and  broad  and  are  closely  pressed  together.  The  abdomen  is  com- 
paratively stout,  and  the  legs  are  shorter  and  stouter  than  in  the 
True  Nemocera. 

Family  BIBIONID^ 

The  March-Flies 

In  this  family  the  abdomen  is  often  comparativeh'  robust,  and 
the  legs  shorter  and  stouter  than  in  most  of  the  families  with  thread- 
like antennae  (Fig.  1039).  The  antennas  are  rarely  longer  than  the 
head  and  thorax,  and  composed  of  short,  broad,  and  closely-pressed- 
together  segments  (Fig.  1040).  These  insects  resemble  the  fungus- 
gnats  in  having  ocelli ;  but  they  differ  from  them  in  the  shortness  of 
^        ^  the  antennas,  in  the  fact  that  the 

coxas  are  not  greatly  elongate, 
and  that  tibial  spurs  of  any 
magnitude  are  confined  to  the 
front  tib ice.     The  venation  of  the 

p.  .        wings   of    the    typical    genus   is 

^'^'"-  tenna-of^-ito.''"  represented  by  Figure  1 04 1 .  The 
cross-vein  m-cu  is  present,  and 
vein  Cu  forks  at  a  considerable  distance  from  the  base  of  the  wing. 
The  adult  flies  are  generally  black  and  red,  sometimes  yellow. 
They  are  most  common  in  early  spring ;  which  has  suggested  the  name 
March-flies;  but  some  occur  later  in  the  season,  and  even  in  the  au- 
tumn. 


DIPTERA 


821 


The  larvcC  \-ar\'  in  habits ;  some  species  feed  on  decaying  matter, 
while  others  attack  the  roots  of  growing  plants,  especially  of  grass. 


Fig.  1 041. — ^Wing  of  Bibio. 
They  have  ten'pairs  of  spiracles,  which  is  an  unusually  large  number, 
as  but  few  insects  have  more  than  nine  pairs.    The  pupa?  are  usually 
free. 

For  descriptions  of  our  species  of  bibionid  flies  see  McAfee  ('21), 


Family  SCATOPSID^ 

This  family  includes  minute  black  flies ;  our  known  species  measure 
in  length  from  less  than  one  millimeter  to  three  millimeters.  Formerly 
these  flies  were  included  in  the  Bibionidse;  but  they  differ  markedly 
in  the  venation  of  their  wings  from  members  of  that  family.  In  the 
ScatopsidaeveinCu  forks 
at  or  very  near  the  base 
of  the  wing  (Fig.  1042) 
and  the  cross-vein  m-cu 
is  wanting.  In  some 
species  there  is  a  vestige 
of  an  anal  vein  but 
usually  there  is  none. 

This  is  a  small  family, 
only  about  a  score  of 
species  are  known  from 
our  fauna;  these  are  de- 
scribedby  Melander  (' 1 6) . 

Most  of  the  known  larvae  live  in  excrement.  One  species,  Cobol- 
dia  fonnicdrium,  is  believed  to  be  myrmecophilous,  for  the  adult  was 
taken  as  it  crawled  from  a  populous  nest  of  the  carpenter  ant. 
In  this  species  the  wings  are  vestigial. 

Family  SIMULIID^ 

The  Black-Flies 

The  common  name,  black-flies  given  to  the  members  of  this  family 
is  not  distinctive,  for  there  are  many  species  of  other  families  that  are 
of  this  color;  but  like  many  other  names  that  are  descriptive  in  form, 


Fig. 

Melander.) 


Wing  of  Reichertella  collaris.     (After 


822 


AN  INTRODUCTION  TO  ENTOMOLOGY 


it  has  come  to  have  a  specific  meaning  distinct  from  its  original  one. 
It  is  Hke  the  word  blackberry;  some  blackberries  are  white,  and  not 
all  berries  that  are  black  are  blackberries. 

In  this  family  the  body  is  short  and  stout;  the  thorax  is  much 
arched,  giving  the  fly  a  humpbacked  appearance  (Fig.  1043)  i  ^-^d  the 
legs  are  comparatively  short.     The  antennse 
are   scarcely   longer   than   the   head   and   are 
eleven  jointed;  the  segments  of  the  flagellum 
are  short  and  closely  pressed  together   (Fig. 
1044),  they  are  clothed  with  fine  hairs,  but  do 
not  bear  whorls  of  long  hairs.     The  ocelli  are 
absent.     In  the  male  the  eyes  are  very  large 
and  contiguous,  and  divided ;  the  upper  half  of 
each  has  the  facets  very  much  larger  than  the  Fig.  1044. 
lower,  from  which  they  are  distinctly  divided 
by  a  horizontal  line.    The  upper  half  of  each  is  doubtless  a  night-eye, 
while  the  lower  half  is  a  day-eye.    In  the  female,  the  eye  facets  are  of 
almost  uniform  size ;  and  the  "^wo  eyes  are  widely  separated.    The  pro- 
boscis is  not  elongated,  the  small  labella  are  homy,  and  the  palpi  are 


^^.^. 


2d  A 
Fig.  1045. — Wing  of  Simuliiim. 


four-jointed.  The  wings  are  broad,  iridescent,  and  not  clothed  witli 
hairs.  The  veins  near  the  costal  border  are  stout;  those  on  the  other 
parts  of  the  wing  are  vestigial  (Fig.  1045),  and  are  usually  represented 
merely  by  folds.* 

The  females  of  many  species  suck  blood  and  are  well-known 
pests.  Unlike  mosquitoes  and  midges,  the  black-flies  like  heat  and 
strong  light.  They  are  often  seen  in  large  numbers  disporting  them- 
selves in  the  brightest  sunshine. 


*The  forked  fold  that  I  believe  to  be  a  vestige  of  vein  Cu  is  not  so  regarded  by 
some  writers,  who  refer  to  it  as  the  fold  between  media  and  cubitus  and  label  two 
folds  of  the  anal  area  as  cubitus.  I  can  see  no  reason  for  this  conclusion ;  in  no 
other  flies  that  I  have  studied  is  there  a  fold  between  media  and  cubitus. 


/ 


DIPTERA  S23 

The  larvae  are  aquatic;  and  usually  live  in  swiftly-flowing  streams, 
clinging  to  the  surface  of  rocks  in  rapids  or  on  the  brinks  of  falls. 
They  sometimes  occur  in  such  large  numbers  as  to  form  a  moss-like 
coating  over  the  rocks.  There  is  a  disk-like  sucker  fringed  with 
little  hooks  at  the  caudal  end  of  the  body  by  means  of  which  the  larva 
clings  to  the  rocks;  and  just  back  of  the  head  there  is  a  fleshy  proleg 
which  ends  in  a  similar  sucker  fringed  with  hooks  (Fig.  1046).  By 
means  of  these  two  organs  the  larva  is  able  to  walk  with  a  looping 
gait  similar  to  that  of  a  measuring-worm.  It  has  also 
the  power  of  spinning  silk  from  its  mouth,  which  it 
uses  in  locomotion.  The  hooks  on  the  caudal  sucker 
and  at  the  end  of  the  proleg  are  well  adapted  to 
clinging  to  a  thread  or  to  a  film  of  silk  spun  upon  the 
rock  to  which  the  larva  is  clinging.  Respiration  is 
accomplished  by  means  of  blood-gills,  which  appear 
on  the  dorsal  side  of  the  last  abdominal  segment. 
but  are  evaginations  of  the  ventral  wall  of  the  rec- 
tum, and  lie,  when  retracted  completely  within  the  Fig  ^^46  — 
rectal  cavity  (Headlee  '06).  The  head  bears  two  Head  of  larva, 
large  fan-shaped  organs,  which  aid  in  procuring 
food.    The  food  consists  chiefly  of  algae  and  diatoms. 

When  full-grown  the  larva  spins  a  boot-shaped  cocoon  within 
which  the  pupal  state  is  passed  (Fig.  1047).  This  cocoon  is  firmly 
fastened  to  the  rock  upon  which  the  larva  has  lived  or  to  other  co- 
coons, for  they  occur  in  dense  masses,  forming  a  carpet -like  covering 
on  the  rocks.  The  pupa  breathes  by  tracheal  gills  which  are  borne 
on  the  prothorax. 

The  adult  fly,  on  emerging  from  the  pupa-skin,  rises  to  the  surface 

of  the  water  and  takes  flight  at  once.     Soon  after  this  the  eggs  are 

laid.     I  have  often  watched  Simtdimn  putipes 

hovering  over  the  brink  of  a  fall  where  there 

was  a  thin  sheet  of  swiftly-flowing  water,  and 

have  seen  the  flies  dart  into  the  water  and  out 

again.    At  such  times  I  have  always  found  the 

surface  of  the  rock  more  or  less  thickly  coated 

with  eggs,  and  have  no  doubt  that  an  egg  is 

fastened  to  the  rock  each  time  a  fly  darts  into 

the  water.     Alalloch  ('14)  states  that  the  eggs 

are  deposited  in  many  cases  on  blades  of  grass. 

Fig.  1047.— Cocoon       twigs,  or  leaves  of  trees  which  are  dipping  in 

and  larva.  running  water. 

Until  recently  all  members  of  this  family 
were  included  in  the  genus  Simulium;  consequently  in  nearlv  all  of 
the  published  accounts  of  these  insects  the  various  species  are  placed 
in  this  genus.  But  later  writers  have  divided  the  old  genus  Simulium 
into  several  genera,  Enderlein  ('21)  now  recognizes  fifteen  genera  of 
which  seven  are  represented  in  North  America. 

Alonographic  papers  on  the  North  American  species  of  this  family 
have  been  published  bv  Coauillett  ('98),  Johannsen  ('03)  and  Alalloch 
('14). 


824  A  N  INTROD  UCTION  TO  ENTOMOLOG  Y 

This  is  a  comparatively  small  family.  Malloch  ('14)  in  his 
"Catalogue  of  North  American  and  Central  American  Simuliidae" 
lists  38  species.  The  species  that  have  attracted  most  attention  in  the 
United  States  are  the  following. 

The  Adirondack  black-fly  Prosimulium  htrtipes. — This  is  a  widely 
distributed  species  but  it  has  attracted  most  attention  in  the  moun- 
tains of  the  Northeastern  States,  where  fishermen  find  it  to  be  a 
scourge  in  Ma>'  and  June.  In  this  species  the  radial  sector  is  dis- 
tinctly forked. 

The  southern  buffalo-gnat,  Cnephia  pecudrum. — This  is  the 
"Buffalo-gnat"  of  the  Mississippi  Valley,  which  in  the  past  has  been 
a  terrible  pest  of  mules  and  other  domestic  animals,  sometimes  caus- 
ing their  death ;  but  it  seems  to  be  much  less  common  now  than  in 
former  years.  In  this  species  the  radial  sector  is  very  indistinctly 
forked  at  the  apex.  The  popular  name  of  this  insect  refers  to  a  fancied 
resemblance  in  the  shape  of  the  insect  when  viewed  from  one  side  to 
that  of  a  buffalo. 

The  turkey-gnat,  Simulium  meridiondle. — This  species  closely 
resembles  the  preceding  in  habits,  infesting  all  kinds  of  domestic 
animals,  especially  in  the  Mississippi  Valley.  As  it  appears  at  the 
time  that  turkeys  are  setting  and  causes  great  injury  to  this  fowl,  it 
is  commonly  known  as  the  turkey-gnat.  In  this  species  the  radial 
sector  is  not  forked. 

The  white-stockinged  black-fly,  Simulium  venUstum. — This 
species  is  widely  distributed  and  is  one  of  the  more  common  species 
of  the  genus.  It  can  be  distinguished  from  the  other  species  men- 
tioned here  by  the  fact  that  the  tibiae  are  silvery  white  above.  In  the 
Adirondacks  it  appears  later  than  Prosimulium  hirtipes  and  is  not  so 
serious  a  pest.  Professor  Needham  writes:  "Guides  have  a  saying, 
that,  when  the  black-flies  put  on  their  white  stockings  in  June,  the 
trouble  is  about  over.    This  species  has  the  white  stockings". 

The  innoxious  black-fly,  Simulium  ptctipes .—This  black-fly  is 
very  widely  distributed  and  at  Ithaca  it  is  our  most  common  species. 
Although  it  may  abound  where  during  many  summers  I  have  taken 
my  classes  for  study  of  aquatic  insects,  I  have  never  known  it  to  bite. 

Family  BLEPHAROCERIDyE 

The  Net-winged  Midges 

The  net-winged  midges  are  extremely  remarkable  insects;  for  in 
certain  respects  the  structure  of  the  adults  is  very  peculiar,  and  the 
larvEe  appear  much  more  like  crustaceans  than  like  insects. 

The  adults  are  mosquito-like  in  form;  but  they  differ  from  all 
other  insects  in  having  the  wings  marked  by  a  net -work  of  fine  lines 
which  extend  in  various  directions  and  are  not  influenced  at  all  by 
the  veins  of  the  wing  (Fig.  1048).  They  are,  however,  quite  constant 
in  their  position  in  the  species  that  I  have  studied. 

When  a  wing  is  examined  with  a  microscope,  the  flne  lines  are 
seen  to  be  slender  thickenings  extending  along  the  courses  of  slight 


DIPTERA 


825 


folds  in  the  wing.    The  significance  of  these  folds  is  evident  when  a 
net-winged  midge  is  observed  in  the  act  of  issuing  from  its  pupa-skin. 


'^A     Cu 

Fig.  1048. — Wing  of  Blepharocera  tenuipes. 
When  the  wing  is  first  pulled  out  of  the  wing-sheath  of  the  pupa,  that 
part  of  it  which  is  crossed  by  the  fine  lines  is  plaited  somewhat  like  a 
fan  and  folded  over  the  other  portion.  By  this  means  the  wing, 
which  is  fully  developed  before  the  adult  emerges,  is  packed  within 
the  wing-sheath  of  the  pupa,  which  is  much  shorter  and  narrower 
than  the  wing.  When  the  wing  is  finally  unfolded,  it  does  not  become 
perfectly  flat,  but  slight,  alternating  elevations  and  depressions 
remain,  showing  the  positions  of  the  former  folds,  a  permanent  record 
of  the  unique  history  of  the  wings  of  these  insects. 

Ordinarily  the  wings  of  insects,  while  still  in  the  wing-sheaths  of 
the  pupa,  are  neither  longer  nor  wider  than  the  wing-sheaths,  but 
expand  after  the  adult  emerges  from  the  pupa  skin.  Usually  it  takes 
considerable  time  for  the  wings  to  expand  and  become  fit  for  flight 
and  during  this  interval  the  insect  is  in  an  almost  helpless  condition. 
In  certain  caddice-flies 
that  emerge  from 
swiftly-flowing  water, 
the  time  required  for 
the  expansion  of  the 
wings  has  been  re- 
duced to  the  mini- 
mum. In  the  net- 
winged  midges,  which 
also  emerge  from 
swiftly-flowing  water 
the  difficulty  is  met  by 
the  wings  reaching 
their  full  develop- 
ment before  the  adult 
leaves  the  pupa-skin. 
It    is    only   necessary 

when  the  adult  emerges  from  the  water  that  it  should  unfold  its 
wings  to  be  ready  for  flight. 

The  members  of  this  family  have  three  ocelli.     The  compound 


050. 


Fig.  1049. — Section  of  head  through  the  eyes 
of  Blepharocera  tenuipes:  0,  ocelH;  br, 
brain;  /./,  large  facets;  5./,  small  facets, 
o.  I,   optic  lobes.      (From  Kellogg.) 


826 


AN  INTRODUCTION  TO  ENTOMOLOGY 


eyes  are  usually  divided  in  both  sexes;  the  upper  part  of  each  eye 
being  composed  of  large  facets,  characteristic  of  night-eyes,  and  the 
lower  part,  of  smaller  facets,  characteristic  of  day-eyes,  in  a  few 

species  the  eyes  are  divided  only 
in  the  males.  Figure  1049  repre- 
sents a  section  of  the  head  of  the 
Blepharocera  ten  ui  pes  through 
the  eyes.  The  antennas  are 
thread-like,  but  are  not  furnished 
with  whorls  of  long  hairs  (Fig. 
1050).  The  mouth  parts  are 
elongate;  the  females  have 
slender  flattened  elongate  man- 
dibles (Fig.  105 1 )  the  males  are 
without  mandibles.  The  legs  are 
very  long.  On  the  dorsum  of  the 
mesothorax  there  is  on  each  side, 
beginning  just  in  front  of  the  base 
of  the  wing,  a  well-marked  suture 
like  that  of  the  crane-flies;  but 
the  two  do  not  meet  so  as  to  form 
a  continuous  V-shaped  suture  as 
in  the  Tipulidte. 

In  some  species  at  least  there 
are  two  kinds  of  females,  which 
differ  somewhat  in  the  shape  of 
the  head.  These  two  forms  also 
differ  in  habits,  one  being  blood- 
sucking, the  other  feeding  upon 
nectar.  The  adults  may  be  found 
resting  on  the  foliage  of  shrubs 
or  trees  on  the  margins  of  mountain-brooks,  or  dancing  in  the  spray 
of  waterfalls. 

The  immature  forms  of  these  in- 
sects are  even  more  wonderful  than  are 
the  adults.  The  larvae  live  in  water, 
in  swiftly-flowing  streams,  where  the 
water  flows  swiftest.  I  have  observed 
the  transformations  of  Blepharocera 
tenuipes,  which  is  abundant  in  some  of 
the  ravines  near  Ithaca,  N.  Y. 

The  larvae  of  this  species  are  readih' 
seen  on  account  of  their  black  color, 
and  are  apt  to  attract  attention  on 
account  of  their  strange  form.  (Fig. 
1052,  a).  At  first  sight  the  body  ap- 
pears to  consist  of  only  seven  segments, 
but  careful  examination  reveals  the 
presence  of  smaller  segments  alterna- 
ting with  these.    Each  of  the  larger  segments  except  the  last  bears  a 


Fig.  1 05 1. — Mouth-parts  of  female  of 
Bibiocephala  doanei:  I.  ep,  labrum- 
epipharynx;  md,  mandibles;  mx.  I, 
maxillary  lobe;  mx.  p,  maxillary  pal- 
pus; hyp.  hypopharynx;  N,  labium; 
pg,    paraglossa.       (From     Kellogg.) 


Fig.  1052. — Blepharocera:  a,  larva, 
dorsal  view;  h,  larva,  ventral 
view;    c,   puparium,    side   view. 


DIPTERA  S27 

pair  of  conical,  leg-like  appendages.  On  the  ventral  side  oi  the  body 
(Fig.  1052,  b)  each  of  the  seven  larger  segments  except  the  last  bears 
a  sucker,  the  cavity  of  which  extends  far  into  the  bodv,  and  each  of 
these  segments  except  the  first  bears  two  tufts  of  tracheal  gills;  but 
those  of  the  last  segment  are  united.  The  head,  which  forms  the 
front  end  of  the  first  of  the  seven  larger  divisions,  bears  a  pair  of 
slender  antenna?,  each  of  these  consists  of  a  very  short  basal  segment 
and  two  long  segments;  at  the  tip  of  the  last  of  these  there  is  a  pair 
of  minute  appendages  and  a  bristle.  The  suture  between  the  head 
and  the  remaining  parts  of  the  first  division  is  best  seen  on  the  ventral 
side  of  the  body.  On  the  dorsal  side  a  suture  may  be  seen  dividing 
the  last  division  into  two  segments. 

The  pupa-stage  is  passed  in  the  same  place  as  the  larval.  Like 
the  larvae  the  pupcE  are  very  conspicuous  on  account  of  their  black 
color,  and  are  apt  to  occur  like  the  larvae  closelv  clustered  together. 
The  pupa  is  not  enclosed  in  the  larval  skin,  and  differs  greatly  in  form 
from  the  larva.  On  the  dorsal  side  the  skin  is  hard,  forming  a  convex 
scale  over  the  body  (Fig.  1052,  c);  and  the  thorax  bears  a  pair  of 
breathing  organs,  each  composed  of  four  flattened  leaves,  two  of 
them  delicate  tracheal  gills,  and  the  other  two  protecting  chitinized 
plates;  on  the  ventral  side  the  skin  is  very  delicate,  soft,  and  trans- 
parent; so  that  the  developing  legs  and  wings  may  be  easily  seen 
when  the  insect  is  removed  from  the  rock.  The  pupae  cling  to  the 
rock  by  means  of  six  suckers,  three  on  each  side  near  the  edge  of  the 
lower  surface  of  the  abdomen ;  and  so  firmly  do  they  cling  that  it  is 
difficult  to  remove  specimens  without  breaking  them. 

I  have  watched  the  midges  emerge  from  their  pupa-skins  and 
escape  from  the  water.  The  pupae  occuiTed  in  groups  so  as  to  form 
black  patches  on  the  rocks.  Each  one  was  resting  with  its  head  down 
stream.  Each  midge  on  emerging  forced  its  way  out  through  a  trans- 
verse rent  between  the  thorax  and  abdomen.  It  then  worked  its 
body  out  slowly  and  in  spite  of  the  swift  current  held  it  vertical.  The 
water  covering  the  patch  of  pupae  varied  from  6  mm.  to  25  mm.  in 
depth.  In  the  shallower  parts  the  adult  had  no  trouble  in  working 
its  way  to  the  surface  still  clinging  to  the  pupa-skin  by  its  very  long 
hind  legs. 

While  still  anchored  by  its  legs  the  midge  rests  on  the  surface  of 
the  water  for  one  or  two  seconds  and  unfolds  its  wings*  then  freeing 
its  legs  it  takes  flight.  The  adults  emerging  from  the  deeper  water 
were  swept  awa}-  by  the  current  before  they  had  a  chance  to  take 
wing.  The  time  required  for  a  midge  to  work  its  way  out  of  the  pupa- 
skin  and  take  flight  varied  from  three  to  five  minutes. 

The  larvae  of  the  net-winged  midges  live  only  in  swift-flowing 
streams;  they  are  found,  therefore,  only  in  mountainous  or  at  least 
hilly  regions.  It  is  believed  that  they  feed  chiefly  on  algae  and  di- 
atoms. It  does  not  seem  probable  that  these  delicate  midges  can 
deposit  their  eggs  on  the  rocks  in  the  swift -running  water  where  the 
larvae  live,  as  do  the  females  of  Simulium.  It  is  more  likely  that  the 
eggs  are  deposited  on  the  wet  rocks  at  the  margins  of  the  stream  and 
that  the  larvae  migrate  to  the  center  of  the  stream. 


828 


AN  INTRODUCTION  TO  ENTOMOLOGY 


This  family  is  a  small  one;  but  it  is  world-wide  in  distribution. 
Representatives  of  it  have  been  found  in  both  North  and  South 
America,  in  Europe,  and  in  Australia  and  New  Zealand.  A  mono- 
graph of  the  North  American  species  was  published  by  Kellogg  ('03) 
and  one  of  those  of  the  world  by  the  same  author  ('07),  a  table  of  the 
North  American  species  is  given  by  Kellogg  in  Williston  ('08). 

Family  THAUMALEID^ 

The  Solitary-Midge 

Only  a  single  species  of  this  famih'  is  known  to  occur  in  North 
America;  this  is  Thaumalea  americdna.  It  is  a  small  fly  measuring 
about  8  mm.  in  length,  and  is  found  on  the  banks  of  streams. 

The  antennae  are  short,  about  as  long  as  the  head,  and  nearly  of 
the  same  structure  in  the  two  sexes ;  the  segments  of  the  antenna;  ex- 
cept those  at 
^  the  base   are 

slender  and 
are  clothed 
with  a  few 
short  hairs. 
The  ocelli 
are  wanting. 
The  eyes  are 
large  and 
meet  in  front 
in  both  sexes. 
The  venation 
of  the  wings 
is  illustrated  by  Fig.  1053  vein  Ri  ends  at  or  near  the  end  of  the 
second  third  of  the  costal  margin ;  the  radial  sector  is  two-branched ; 
media  is  simple;  and  there  are  no  anal  veins. 

The  larva;  live  in  streams  and  resemble  those  of  Chironomidas. 
This  family  has  been  commonly  known  as  the  Orphnephilidse ; 
but  it  has  been  shown  by  Bezzi  ('13)  that  the  typical  genus  was  first 
described  under  the  name  Thaumalea. 


Fig.  1053. — Wing  of  Thaumalea  americana. 


Series  II— BRACHYCERA* 
The  Short-horned  Orthorrhapha 

In  most  of  the  families  included  in  this  division  of  the  Orthorrhapha 
the  antenna  are  short  and  three-jointed,  the  flagellimi  being  reduced 
to  a  single  segment,  with  or  without  a  style  or  arista;  but  in  the  first 
subseries,  the  Anomalous  Biachycera,  the  flagellum  is  more  or  less 
distinctly  segmented.  In  all  of  the  Brachycera  the  palpi  are  porrect 
and  one-  or  two-jointed;  and  the  first  anal  cell  is  either  closed  or 
narrowed  towards  the  margin  of  the  wing. 

*Brachjf-cera:  brachy,  short;  ceras  (xepas),  a  horn. 


DIPTERA 


829 


SUBSERIES    A — THE    ANOMALOUS   BRACHYCERA 

In  the  families  constituting  this  subseries  the  antennae  consist  of 
five  or  more  segments;  but  those  beyond  the  second,  the  fiagellum, 
are.usualty  more  or  less  consolidated.  In  some  cases  the  antennae  do 
not  differ  markedly  in  form  from  those  of  certain  Anomalous  Ne- 
mocera;  but  the  Brachycera  are  sharply  distinguished  from  the  Ne- 
mocerabythe  palpi  being  porrect  and  only  one  or  two-jointed  and  by 
the  fact  that  the  anal  cell  is  either  closed  or  narrowed  towards  the 
margin  of  the  wing.  In  this  subseries  the  head  and  thorax  are  not 
furnished  with  strong  bristles  and  the  empodia  are  pulvilli-form. 

Family  TABANID^ 

TJie  Horse-Flies 


The    horse-flies    are   well-known    pests    of 
stock,   and  are  often  extremely  annoying  to 
man.     They  appear  in  summer,  are  common 
in  woods,  and  are  most  abundant  in  the  hottest         Wi 
weather.  ■>  Vj 

In  this  family  the  flagellimi  of  the  antennas 
A  ^?^'^'     is  composed  of  from  four  to  eight,  more  or  less 
of  rai)a- <^^osely   consolidated   segments   and   is   never  Fig.  1055.-- 
nus.  furnished  with  a  distinct  style  or  arista  (Figs.      Antenna 

1054,   1055).     The  wing-veins  (Fig.  1056)  are      oi  Chry- 
evenly    distributed    over    the    wing,    as    the 
branches  of  vein  R  are  not  crowded  together  as  in  the  following 
family ;  the  costal  vein  is  continued  as  an  ambient  vein  which  extends 


Fig.  1056. — Wing  of  Tabanns. 

completely  around  the  wing;  the  alulets  are  large,  in  other  Anomalous 
Brachycera  they  are  small  or  vestigial. 

The  flight  of  these  flies  is  very  powerful,  they  are  able  to  outstrip 
the  swiftest  horse.  The  males  feed  on  the  nectar  of  flowers  and  on 
sweet  sap.    The  mouth-parts  of  the  female  are  fitted  for  piercing  the 


830 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  IOC8.- 
C  hr  y  - 
sops  ni- 
ger. 


skin  and  sucking  the  blood  of  men  and  quadrupeds;   the  females, 
however,  also  feed  on  sweets  of  plants  when  the}^  cannot  obtain  blood. 
The  larger  species,  as  well  as  some 
v.    Ny^^        of  moderate  size,  belong  to  the  genus 
1^^^/  Tabanus  of  which  nearly  two  hundred 

^^'sJmHLyr-^     species  are  listed  from  North  America. 
j^HBr^  One  of  the  most  common  of  these  is 

^^Hj^^  the  mourning  horse-fiv,    Tabanus  at- 

^^^^^H  rdtus.    This  insect  is  of  uniform  black 

^^^^^H  color    throughout,    except    that    the 

^^^S|^^         body  may  have  a  bluish  tinge  (Fig. 
^^         ^H  1057)-  The  species  of  this  genus  attack 

^  ^F          cattle  and  other  farm  animals  almost  exclusively. 

Fig.    1057.   -Taba-  To  the  genus  Chrysops  belong  the  smaller  and 

nns  at  rat  us.  more  common  horse-flies  with  banded  wings  (Fig. 

1058).     The  species  of  this  genus  attack  man  as 
well  as  other  animals.    To  this  genus  belong  the  well-known  deer-flies 
familiar  to  fishermen  and  hunters.    Sixty- 
three    North    American    species    of   this 
genus  are  listed  by  Aldrich. 

The  eggs  are  deposited  in  large  masses 
on  plants  or  on  exposed  stones  in  the  bed 
of  a  stream. 

The  larvae  are  aquatic  or  semi-aquatic. 
As  far  as  known,  they  are  predacious, 
feeding  on  various  small  animals,  some 
upon  snails,  others  upon  the  larvae  of 
insects.  In  most  cases  they  have  a  single 
pair  of  spiracles,  which  is  situated  at  the 
hind  end  of  the  body;  some  have  a  pair 
of  spiracles  at  each  end  of  the  body. 
Figure  1059  represents  a  larva  of  Tab- 
anus. 

The  pupa  is  not  enclosed  in  the  skin 
of  the  larva. 

Hine  ('03)  redescribes  all  Ohio  Species 
and  gives  a  table  of  the  North  American 
genera. 

Family  STRATIOMYIID^ 
The  Soldier-Flies 

Fig-  1059.   -Larva  of  Tabanus.         The  soldier-flies  are  so  called  on  ac- 

kndT'  '^"'  ^^'  ^''  ^^'"^'''■"  count  of  the  bright-colored  stripes  with 

which  some  of  the  species  are  marked. 

In   the   more   typical   members   of   this 

family  the  abdomen  is  broad  and  greatly  flattened  (Fig.  1060)  and 

the  wings  when  at  rest  lie  parallel  upon  each  other  over  the  abdomen. 

But  in  some  genera  the  abdomen  is  narrow  and  considerably  elongate. 


DIPT ERA 


831 


The  antennae  vary  greatly  in  form,  in  some  genera  the  flagellum 
is  long  and  consists  of  several  quite  distinct  segments  (Fig.  loiSi)  in 
others  it  is  short  with  but  few  indis- 

#tinctly  separated  segments  and  with 
an  arista  (Fig.  1062)  as  in  the  True 
Brachycera. 
The  most  distinctive  characteris- 
tic is  the  pecuhar  venation  of  the 
wings  (Fig.  1063).  The  branches  of 
vein  R  are  crowded  together  near  the 
costal  border  of  the  wing ;  and  the  first 
cell  M2  is  unusually  short  and  broad ; 
the  branches  of  vein  M  and  vein  Cui 
are  comparatively  weak,  and  the  tibias  are  with- 
out spurs. 

These  flies  are  found  on  flowers  and  leaves,  especially  in  the  vi- 
cinity of  water,  and  in  bogs  and  marshes,  but  some  species  are 
found  far  from  water. 

The  larvae  occur  in  various  situations;  some  are  aquatic  and 
feed  upon  algee,  decaying  vegetable  matter,  and  small  Crus- 
tacea; some  live  in  privies,   in  cow-dung,    and    in    other   decaying 


Fig.  1060. 
Strati 
omvia. 


062. 


o  63. — Wing  of  Stratiomyia. 


matter;  some  are  found  under  bark  of  trees  that  has  become  slightly 
loosened  and  feed  upon  sap  and  upon  insect  larvae;  and  some  have 
been  found  in  nests  of  Hymenoptera  and  in  those  of  rodents,  where 
they  act  as  scavengers. 

The  larvae  are  spindle-form  or  elliptical  and  flattened,  and  with 
the  surface  of  the  body  finely  shagreened.  The  posterior  pair  of 
spiracles  is  situated  in  a  cleft  or  chamber  at  the  end  or  near  the  end 
of  the  body.  In  the  aquatic  forms  the  apical  respiratory  chamber  is 
furnished  along  its  margins  with  long  plumose  hairs.  When  the  larva 
is  at  rest  hanging  from  the  surface  of  the 
water  these  hairs  are  spread  radiatingly  upon 
the  surface  film ;  they  thus  form  a  means  of 
support  and  prevent  the  water  from  enter- 
ing the  respiratory  chamber.  Fig.     1064.   -Pupariuni    of 

The  aquatic  species  leave  the  water  to       Odontomyia. 


832 


AN  INTRODUCTION  TO  ENTOMOLOGY 


transform.  The  pupae  of  the  Stratiomy  iidas  are  enclosed  within  the  last 
larval  skin,  differing  in  this  respect  from  other  Brachycera  (Fig.  1064). 
This  is  a  large  family;  more  than  three  hundred  species,  represent- 
ing more  than  forty  genera,  have  been  described  from  North  America. 

Family  XYLOMYIID^ 
I  group  together  here,  provisionally,  two  genera,  as  representing 

/^'  ^' 


Fig.   1065. — Wing  of  Xylomyia.     (After  Verrall.) 

a  separate  family,  that  have  been  placed  by  seme  writers 
in  the  Stratiomyiidae  and  by  others  in  the  Rhagionidae. 
These  genera  are  Xylomyia  and  Rhachlcerns .  Both  differ 
from  the  Rhagionidse,  as  restricted  here,  in  the  form  of 
the  antennae,  they  clearly  belong  with  the  Anomalous 
Brachycera.  They  differ  from  the  Stratiomyiidae  in  that 
the  branches  of  radius  are  not  crowded  together  near  the 
costal  border  of  the  wing  and  in  the  possession  of  tibial 
spurs.  They  agree  with  each  other  and  differ  from  all 
other  Anomalous  Brachycera  found  in  our  fauna  in  that 
cell  M3  is  closed  (Fig.  1065). 

Xyldmia. — This  genus  includes  rather  elongate  flies, 
somewhat  Ichnenmon-like  in  appearance,  which  are  mainly 
of  black  coloration  with  more  or  less  yellow  markings. 
The  flagellum  of  the  antennae  consists  of  eight  closely  con- 
solidated segments,  the  last  of  which  usually  bears  a  tiny 
style  (Fig.  1066).     Six  species  have  been  described  from 

our  fauna.  -fig-  lo*^"^-- 

The  larva,  of  Xylo-  ^I'^^f^; 
niyia  pdllipes  have  been  m  y  i  a  . 
found  under  the  bark  of  (After 
fallen  trees  and  are  pre-  Verrall.) 
dacious. 

RhacJncerus. — The  members  of 
this  genus  resemble  Xylomyia  in  the 
form  of  the  body  but  differ  mark- 
edly in  the  structure  of  the  antennas. 
In  Rhachicerus  the  flagellum  of  the 
antennas  consists  of  from  twenty  to  thirty-five  segments.  The  seg- 
ments of  the  flagellum  are  more  or  less  cup-shaped ;  and  in  some  species 


Fig.  1067.— Antenna  of  Rhachicerus. 
(From  Williston.) 


DIPTERA 


833 


one  edge  of  each  segment  is  prolonged  so  that  the  antennae  are  pecti- 
nate (Fig.  1067).  Four  species  of  this  genus  have  been  found  in  America 
north  of  Mexico. 

The  larva  of  Rhachicerns  mtidus  has  been  found  in  a  decayed  log. 

Family  XYLOPHAGID^ 

This  family,  like  the  preceding  one,  includes  slender  flies,  which 
are  Ichneumon-like  in  appearance.  It  is  distinguished  from  other 
Anomalous  Brachycera  as  follows:  from  the  vStratomyiidae  in  that 
the  branches  of  radius  are  not  crowded  together  near  the  costal  border 
of  the  wing  (Fig.  1068)  and  in  the  possession  of  tibial  spurs;  from  the 


Oi,  +  2d  A 
Fie.  1068. — Wine  of  Xylophagus. 


Xylomj/iidffi  in  that  cell  M3  is  open;  and  from  the  Coenomyiidae  in  the 
absence  of  spinous  protuberances  on  the  scutellum.  The  flagelltim  of 
the  antennae  consists  of  several  closely  consolidated  segments;  the 
antenna  of  a  member  of  the  typical  genus  is  represented  in  Figure 
1069. 

This  family  is  represented  in  our  fauna  by  the  following  genera: 


Fig.  1070. — Wing  of  Canoniyia  Jerruginea.     (After  Verrall.) 

Xylophagus,  Glutops,  Arthoceras,  Arthropeas,  and  Misgomia.    These 
genera  include  sixteen  species  described  from  our  fauna. 


834  A  N  IXTROD  UCTION  TO  ENTOMOLOG  Y 

The  larvse  that  are  known  Hve  in  earth  or  under  the  bark  of  rotten 
trees  and  feed  upon  the  larvae  of  other  insects. 

Family  CCENOMYIID^ 

The  members  of  this  family  differ  from  the  Stratiomyiidae  in  that 
the  branches  of  radius  are  not  crowded  together  near  the  costal 
border  of  the  wing  (Fig.  1070)  and  in  the  possession  of 
tibial  spurs;  and  they  differ  from  all  other  Anomalous 
Brachycera  in  that  the  scutellum  is  armed  with  two  spinous 
protuberances.  The  eyes  are  pubescent;  the  fiagellum  of 
the  antennae  consists  of  eight  closely  consolidated  seg- 
ments (Fig.  107 1);  veins  M3  and  Cui  anastomose  for  a 
considerable  distance ;  and  the  tips  of  veins  Cu2  and  2nd 
A  are  narrowly  separated  or,  rarely,  united  for  a  short 
distance. 

This  family  is  represented  in  our  fauna  by  a  single 
species,  Coenoniyia  Jerruglnea.  This  is  a  large  thick- 
bodied  fly,  often  measuring  25  mm.  in  length;  but  it 
varies  greatly  in  size.  It  is  of  a  pale  yellowish  brown 
color. 

^Antenna  The  larvas  are  usually  found  in  the  ground,  but  they  are 
oi  Cceno-  sometimes  found  in  decaying  wood ;  they  are  predacious, 
myia.         feeding  upon  insect  lar^-^e. 

SUBSERIES  B — THE  TRUE  BRACHYCERA 

In  the  families  constituting  this  subseries  the  antennas  are  usualh' 
three-jointed,  but  in  some  cases  they  are  four-  or  five-jointed;  the 
third  segment  is  not  ringed,  but  usually  bears  a  style  or  an  arista.  A 
similar  type  of  antenna  is  possessed  by  the  Cyclorrhapa,  which  were 
formerh-  on  this  account  included  in  the  Brachycera;  but  this  term 
is  now  restricted  to  the  Short -horned  Orthorrapha. 

In  the  first  three  families  the  head  and  thorax  are  not  furnished 
with  strong  bristles  and  the  empodia  are  pulvilliform. 

Family  RHAGIONID^* 

The  Snipe-Flies 

These  trim-appearing  flies  have  rather  long  legs, 
a  cone-shaped  abdomen  tapering  towards  the  hind 
end  (Fig.  1072)  and  sometimes  a  downward-projecting 
proboscis,  which  with  the  form  of  the  body  and  legs 
has  suggested  the  name  snipe-flies.  "  ^-  __ 

The  body  is  naked  or  hairy,  but  it  is  not  clothed  Chryso- 
with  strong  bristles.  Frequently  the  hairy  covering,  pi  I  a  tho- 
though  short,  is  very  dense  and  is  of  strongly-contrasting         racica. 

*This  family  has  been  commonly  known  as  the  Leptidse,  but  Rhagionidae 
is  the  older  name  and  is  now  coming  into  use. 


DIPTERA 


835 


colors.  Three  ocelli  are  present.  The  antennas  are  only  three- 
jointed  and  the  third  segment  bears  a  style  or  an  arista  (Fig.  1073). 
The  proboscis  is  usually  short,  only  a  few 
members  of  the  family  having  it  long  like 
the  bill  of  a  snipe.  The  wings  are  broad, 
and  when  at  rest  are  held  half  open.  The 
empodia  are  pulvilliform  (Fig.  1074). 

The  venation  of  the  wings  is  compara- 
tively generalized .  Figure  1075  represen ts 
the  venation  of  a  wing  of  the  typical 
genus. 

The  flies  are  usually  of  moderate  size. 
The}'  may  be  found  about  low  bushes  and 
on  tall  grass.  They  are  sometimes  slug- 
gish and,  therefore,  easily  caught.  They 
are   sometimes    predacious   upon    other 


Fig.  1073.— 
Antenna 
of  Chryso- 
pila. 


Fig.   1074. 


msects,  and  the  species  of  Symphoromyia  suck  blood  as  do  horseflies. 

The  females  of  the  genus  Atherix  have  the  remarkable  habit  of 
clustering  in  large  numbers  on  branches  or  rocks  overhanging  water, 
where  they  deposit  their  eggs  in  common,  and  d}-ing  as  they  do  so, 
add  their  bodies  to  the  common  mass,  which  may  contain  thousands 


Fig.   1075. — Wing  of  Rhagio. 

of  individuals.  Figure  1076,  copied  from  Sharp  ('99)  represents  a 
European  species,  Atherix  ibis,  natural  size,  and  a  mass  of  dead  flies, 
much  reduced.  It  is  said  that  the  larvae  feed  upon  the  bodies  of  the 
dead  mothers  until  the  mass  is  loosened  and  falls  into  the  water, 
where  the  larvas  complete  their  growth.  Other  writers  state  that  the 
larvce  drop  into  the  water  when  hatched. 

_  Large  masses  of  these  flies  have  been  observed  in  various  parts  of 
this  country;  and  formerly,  in  the  Far  West,  they  were  collected  by 
the  Indians  and  used  for  food  after  being  cooked'  It  is  said  that  as 
many  as  a  hundred  bushels  of  flies  could  be  collected  in  a  single  day. 
For  an  account  of  the  methods  of  collecting  the  flies  and  of  preparing 
them  for  food  practiced  by  the  Indians  see  Aldrich  ('12). 


836 


AN  INTROD  UCTION  TO  ENTOMOLOGY 


The  larvae  of  this  family  are  found  in  various  situations;  some 
as  those  of  Atherix  live  in  water,  but  a  larger  number  live  in  earth, 

in  decaying  wood,  or  in  sand. 
The  larvae  of  Vermileo  resemble 
ant-lions  in  habits,  digging  pit- 
falls in  sand  for  trapping  their 
prey.  Only  one  species,  VermUeo 
comstocki,  has  been  found  in 
America;  this  lives  in  the  moun- 
tains of  California ;  other  species 
are  well-known  in  Europe.  I  pro- 
pose the  common  name  ant-tigers 
for  the  larvae  of  this  genus. 


^^^p  ^i^Y^m 


Family  NEMESTRINID^ 

The  Tangle-veined  Flies 


Fig.  1076. — Antherix  ibis:  A.  The  fly, 
natural  size;  B,  mass  of  dead  flies 
overhanging  water,  much  reduced. 
(From  Sharp.) 


The  members  of  this  family 
are  of  mediimi  size ;  some  of  them 
resemble  horse-flies,  and  others 
bee-flies.  They  can  be  recognized 
by  the  peculiar  venation  of  the 
wings,  there  being  an  unusual  amount  of  anastomosing  of  the  veins 
(Fig.  1077),  which  gives  the  wings  a  very  characteristic  appearance. 

The  antennae  are  small  and  short;  the  third  segment  is  simple 
and  furnished  with  a  slender,  jointed,  terminal  style.  The  proboscis 
is  usually  long,  sometimes  very  long  and  fitted  for  sucking  nectar 


Fig.  1077. — Wing  of  Parasymmicius  claiisa. 


from  flowers.    The  head  and  thorax  are  not  armed  with  strong  bristles, 
and  the  empodia  are  pulvilliform. 

But  little  is  known  regarding  the  habits  of  the  larvae;  one  species 
has  been  found  to  be  an  internal  parasite  of  coleopterous  larvae. 
Only  six  species  have  been  found  in  America  north  of  Mexico. 


DIPTERA 
Family  ACROCERID^^ 


837 


The  Small-headed  Flies 

These  flies  are  easily  recognized  by  the  unusuahy  smah  head,  the 
large  humpbacked  thorax,  the  inflated  abdomen,  and  the  very  large 
alulets  (Fig.  1078).  The  body  is  devoid  of  bristles 
and  the  empodia  are  pulvilliform. 

The  head  is  composed  almost  entirely  of  eyes, 
and  in  some  genera  is  minute.  The  eyes  are  contig- 
uous in  both  sexes  or  nearly  so.  The  antennas  are 
three-jointed,  and  are  furnished  with  a  style  or  an 
arista  in  some  genera,  in  others  not.  Sometimes  the 
antennae  are  apparently  two-jointed,  the  first  seg- 
ment being  sunken  in  the  head.  The  venation  of 
the  wings  varies  greatly  in  the  different  genera.  The  accompanying 
figure  (Fig.  1079)  represents  a  single  genus  rather  than  the  family. 

The  flies  are  generally  slow  and  feeble  in  their  movements.     In 
some  species  that  feed  upon  flowers  the  proboscis  is  very  long,  some- 


^1^ 


Fig.  1078.— 
Pterodontia 
misella. 


Fig.  1079. — ^Wing  of  Eidonchus. 


times  exceeding  the  body  in  length.    Other  species  take  no  nourish- 
ment in  the  adult  state,  and  have  no  proboscis. 

The  larvae  of  only  a  few  members  of  this  family  have  been  ob- 
served; these  are  parasitic  in  the  egg-sacs  or  in  the  bodies  of  spiders. 
The  life-history  of  an  American  species,  Pterodontia  fldvipes  has  been 
described  by  King  ('16).  The  females  of  this  species  deposit  their 
eggs  on  the  bark  of  trees ;  they  produce  a  large  nimiber  of  eggs ;  in  one 
of  the  cases  observed  these  numbered  3,977.  This  production  of  many 
eggs  is  doubtless  an  adaptation  made  necessan,^  by  the  fact  that  many 
of  the  young  larvae  will  fail  to  find  spiders  to'  attack  and  will  conse- 
quently perish.  A  larva  that  succeeds  in  finding  a  spider  bores  into 
its  body  and  there  lives  till  fully  grown ;  it  leaves  the  body  of  its  host 
to  transform. 


*This  is  the  family  Cyrtidae  of  some  authors ;  but  Acroceridae  is  the  older  1 


838 


AN  INTRODUCTION  TO  ENTOMOLOGY 


A  monograph  of  the  North  American  species  of  this  family  was 
pubhshed  by  Cole  ('19). 

Family  BOAIBYLIID^ 

The  Bee-Flies 


These  flies  are  mostly  of  mediimi  size,  some  are  small,  others  are 
rather  large.  In  some  the  body  is  short  and  broad  and  densely 
-._  clothed  with  long,  delicate  hair  (Fig.  1080). 
Other  species  resemble  the  horse-flies  somewhat 
in  appearance,  especially  in  the  dark  color  or 
markings  of  the  wings;  but  these  can  be  dis- 
tinguished from  the  horse-flies  by  the  form  of 
the  antenna  and  the  venation  of  the  wings. 

The  antennae  are  usually  short;  they  are 
three-jointed  with  or  without  a  style;  in  some 
genera  the  style  is  so  large  that  it  may  be  con- 
sidered a  fourth  segment.    The  ocelli  are  pres- 
ent.    The  proboscis  is  sometimes  very  long  and  slender,  and  some- 
times short  and  furnished  with  fleshy  lips  at  the  extremity. 

The  radial  sector  is  three-branched ;  cell  R3  is  sometimes  divided 
by  a  sectorial  cross-vein  (Fig.  1081,  s);  cell  M3  is  obliterated  by  the 
coalescence  of  veins  M3  and  Cui ;  in  a  few  genera  cell  Mi  is  also  oblit- 
erated bv  the  coalescence  of  veins  Mi  and  Mo;  cell  ist  A  is  narrowlv 


Fig.  1080. — Bojnhylius. 


2d  A  Cu, 

Fig.   1 08 1. — Wing  of  Pantarbes  capilo. 

Open,  or  is  closed  at  or  near  the  border  of  the  wing.  The  alulets  are 
small  or  of  moderate  size.    The  empodia  are  pulvilliform. 

The  adult  flies  feed  on  pollen  and  nectar,  and  are  found  hovering 
over  blossoms,  or  resting  on  sunny  paths,  sticks  or  stones;  the\'  rareh- 
alight  on  leaves. 

The  larvae  are  parasitic,  infesting  hymenopterous  and  lepidopter- 
ous  larvffi  and  pupae  and  the  egg-sacs  of  Orthoptera.  The  pupae  are 
free. 

The  family  is  a  largCi  one ;  more  than  four  hundred  and  fifty  North 
American  species,  representing  forty-one  genera  are  listed  by  Aldrich 
('05). 


DIPTERA 

Family  THEREVID^ 

The  Stiletto-Flies 


839 


With  the  flies  of  this  family  the  head  is  transverse,  being  nearly 
as  wide  as  the  thorax;  and  the  abdomen  is  long  and  tapering,  suggest- 
ing the  name  stiletto-flies.  These  flies  are  small  or  of  mediimi  size; 
they  are  hairy  or  bristly.  The  antennae  are  three-jointed;  the  third 
segment  is  simple,  and  usually  bears  a  terminal  style;  but  this  is  some- 
times wanting.  Three  ocelli  are  present.  The  legs  are  slender  and 
bristly;  the  empodia  are  wanting. 

The  radial  sector  is  three-branched,  (Fig.  1082)  and  the  last 
branch,  vein  R5,  terminates  beyond  the  apex  of  the  wing;  the  three 
branches  of  media  are  separate;  the  cross-vein  m-cu  is  present;  and 
the  first  anal  cell  is  usually  closed. 


Fig.   1082. — -Wing  of  Thereva. 

The  adult  flies  are  predacious;  they  conceal  themselves  among 
the  leaves  of  low  bushes  or  settle  on  the  ground  in  sandy  spots,  wait- 
ing for  other  insects,  chiefly  Diptera,  upon  which  they  prey. 

The  larvae  are  long  and  slender,  and  the  body  is  apparently  com- 
posed of  nineteen  segments.  They  are  found  in  "earth,  fungi,  and  de- 
caying wood.  They  feed  on  decaying  animal  and  vegetable  matter 
and  are  said  to  be  predacious  also.    The  pupfe  are  free. 

The  family  is  a  comparatively  small  one,  including  but  few  genera 
and  species. 

Family  SCENOPINID^ 

The  Window-Flies 

The  window-flies  are  so-called  because  the  best-known  species 
are  found  almost  exclusively  on  windows;  but  the  conclusion  that 
these  are  the  most  common  flies  found  on  windows  should  not  be 
drawn  from  this  name;  for  such  is  not  the  case. 


840 


AN  INTRODUCTION  TO  ENTOMOLOGY 


These  flies  are  of  mediiim  size,  our  most  common  species  measuring 
6  mm.  in  length.    They  are  usually  black,  and  are  not  clothed  with 
bristles.    The  thorax  is  prominent,  and  the  abdo- 
men is  flattened  and  somewhat  bent  down,  so 
'^gM^  I  '\      that  the  body  when  viewed  from  the  side  presents 

j^^  I    \     a  hump-backed  appearance  (Fig.  1083).    When  at 

*^^  fc'  •'    rest,  the  wings  lie  parallel,  one  over  the  other,  on 

the  abdomen;  when  in  this  position  they  are  very 
inconspicuous.  There  are  three  ocelli.  The  an- 
tennas are  three- jointed;  the  first  and  second  seg- 
ments aie  short,  the  third  is  long  and  bears  neither 
a  style  nor  an  arista  (Fig.  1084). 
The  venation  of  the  wings  is  represented  by  Figure  1085.  The 
radial  sector  is  three-branched;  cells  Mi  and  M3  are  both  obliterated 
by  the  coalescence  of  the  veins  that  bound  them;  the  first  anal  cell  is 
closed  at  a  considerable  distance  before  the  margin ;  and  cell  R  is  much 
longer  than  cell  2d  M. 

The  larvce,  which  are  sometimes  found  in  dwellings  under  carpets 
or  in  furniture,  are  very  slender,  and  are  remarkable  for  the  appar- 
ently large  number  of  the  segments  of  the  body,  each  of  the  abdom- 


Fig.   1083.— 

Scenopi-      ^. 

nus.  Fig- 

1084 


A/,  +  . 


Wing  of  Scenopini 


mal  segments  except  the  last  being  divided  by  a  strong  constriction. 
They  are  also  found  in  decaying  wood,  and  are  supposed  to  be  carniv- 
orous. 


The  family  is  a  very  small  one. 
Scenopinus  Jenestrdlis. 


The  most  common  species  is 


Family  ASILID^E 
The  Robber-Flies 


These  are  mostly  large  flies,  and  some  of  them  are  very  large.  The 
body  is  usually  elongate,  with  a  very  long,  slender  abdomen  (Fig. 
1086);  but  some  species  are  quite  stout,  resembling  bumblebees  in 


DIPTERA 


841 


a  dense  clothing  of 


form.     This  resemblance  is  often  increased  by 
black  and  yellow  hairs. 

In  this  and  the  following  family  the  vertex  of  the  head  is  hollowed 
out  between  the  eyes  (Fig.  1087).  In  this  family  the  proboscis  is 
pointed  and  does  not  bear  fleshy  lips  at  the  tip.  The  antennee  project 
forward  in  a  prominent  manner.    They  are  three-jointed,  and  with  or 


Fig.  1086. — Erax  api- 
calis  destroying  a 
cotton   worm. 


[088. 


Fig.    1087.— Head  of 
a  robber-flv. 


without  a  terminal  style.  The  style  when  present  sometimes  appears 
like  one  or  two  additional  segments  (Fig.  1088). 

Vein  Ml  (Fig.  1089)  does  not  terminate  at  or  before  the  apex  of 
the  wing  as  in  the  following  family.  Cell  M3  is  present,  but  is  usually 
closed  by  the  coalescence  of  the  tips  of  veins  M3  and  Cui.  The  tips 
of  veins  Cu2  and  2d  A  may  or  may  not  coalesce  for  a  short  distance. 

The  robber-flies  are  extremely  predacious.  They  not  only  destroy 
other  flies,  but  powerful  insects,  as  bumblebees,  tiger-beetles,  and 
dragon-flies,  fall  prey  to  them;  they  will  also  feed  upon  larvee.  They 
are  common  in  open  fields  and  are  as  apt  to  alight  on  the  ground  as  on 
elevated  objects. 


Fig.  1089. — Wing  of  Erax. 

The  larvse  live  chiefly  in  the  ground  or  in  decaying  wood,  where 
they  prey  upon  the  larvae  of  beetles;  some,  however,  are  supposed  to 
feed  upon  the  roots  of  plants.    The  pupae  are  free. 

More  than  five  hundred  North  American  species  of  this  family, 
representing  seventy-five  genera,  have  been  described. 


842  AN  INTRODUCTION  TO  ENTOMOLOGY 

Family  MYDAID^ 

The  Mydas-Flies 

The  Mydas-flies  rival  the  robber-flies  in  size,  and  quite  closely 
resemble  them  in  appearance.  As  in  that  family,  the  vertex  of  the 
head  is  hollowed  out  between  the  eyes;  but  these  flies  can  be 
distinguished  by  the  form  of  the  proboscis,  which  bears  a  pair 
of  fleshy  lobes  at  the  tip,  by  the  form  of  the  antennae,  which 
are  four-jointed,  long  and  more  or  less  clubbed  at  the  tip 
(Fig.  1090),  and  by  the  peculiar  venation  of  the  wings  (Fig. 
109 1),  vein  Ml  terminating  at  or  before  the  apex  of  the  wing, 
and  the  branches  of  vein  R  coalescing  near  the  apex  of  the 
wing  in  an  unusual  way. 

The  adults  are  said  to  be  predacious.    The  larvae  of  some 
species,  at  least,  live  in  decaying  wood,  and  some  are  known 
^1090!      ^o  P^^y  upon  the  larvae  of  beetles. 

The  family  is  a  small  one,  there  being  only  about  one 
hundred  known  species,  of  these  nearly  fifty  have  been  foiuid  in 


M,+C«, 


Fig.  1091 


—Wing  of  My  das. 


North  America,  but  most  of  these  occur  south  of  the  United  States. 
The  family  includes  the  largest  known  Diptera. 


Family  APIOCERID^ 
The  Apiocerids 

This  family  includes  only  a  small  number  of  species,  which  are 
rare  and  occur  in  the  Far  West.  They  are  rather  large  and  elongate, 
and  are  found  upon  flowers. 

The  head  is  not  hollowed  out  between  the  eyes;  the  ocelli  are 
present;  the  antennae  are  three-jointed,  with  or  without  a  short  simple 
style ;  the  proboscis  is  not  adapted  for  piercing.  The  radial  sector  is 
usually  three-branched,  but  sometimes  it  is  only  two-branched;  all 
of  the  branches  of  vein  R  end  before  the  apex  of  the  wing  (Fig.  1092) ; 


DIPTERA  843 

cell  AI3  is  present  but  closed  by  the  coalescence  of  veins  M3  and  Cui 

Sc  A>,    R,,, 


Fig.  1092. 


^Wing  of  Apiocera. 


at  the  margin  of  the  wing;  and  the  medial  cross-vein  is  present. 
empodia  are  wanting.    The  larvee  are  unknown. 


The 


Fig.  1093.— Z>o- 
lichopus  lo- 
batus. 


Family  DOLICHOPODID^ 

The  Long-legged  Flies 

These  flies  are  of  small  or  mediimi  size  and  usually  bright  metallic 
green  or  blue  in  color.  The  legs  are  much  longer  than  is  usual  in  the 
families  belonging  to  the  series  of  short -horned  flies 
(Fig.  1093).  This  suggested  the  name  Doltchopus, 
which  means  long-footed,  for  the  typical  genus;  and 
from  this  the  family  name  is  derived.  It  should  be 
remembered  however,  that  these  flies  are  long-legged 
in  comparison  with  the  allied  families,  and  not  in 
comparison  with  crane-flies  and  midges. 

The  members  of  this  family  are  easily  distin- 
guished as  such  by  the  peculiar  venation  of  the  wings, 
the  most  characteristic  features  of  which  are  the 
following:  cells  M  and  ist  Mo  are  rarely  if  ever  separated  by  a  com- 
plete vein;  the  basal  part  of  vein  M3  being  either  atrophied  Fig. 
1094)  or  represented  by  a  short  spur  (Fig.  1095) ;  veins  R2+3  andR4+5 
separate  near  the  base  of  the  wing,  and  there  is  usually  at  the  point 
of  separation  a  more  or  less  knot-shaped  swelling;  the  cross-vein  r-m, 
when  present,  is  near  this  swelling,  so  that  cell  R  is  very  short. 

The  members  of  this  family  have  three  ocelli;  the  antennae  are 
three-jointed;  the  second  segment  of  the  antennas  is  sometimes  ves- 
tigial and  the  third  segment  bears  an  arista;  the  palpi  are  one-jointed; 
and  the  empodia  are  not  pulvilliform. 

The  adults  are  predacious  and  hunt  for  smaller  flies  and  other 
soft -bodied  insects.  They  are  usually  found  in  damp  places,  covered 
with  rank  vegetation.  Some  species  occur  chiefly  on  the  leaves  of 
aquatic  plants,  and  about  dams  and  waterfalls;  and  some  are  able  to 
run  over  the  surface  of  water.    Others  occur  in  dry  places. 


844 


AN  INTRODUCTION  TO  ENTOMOLOGY 


In  the  genus  Melanderia,  of  which  two  species  have  been  found 
on  the  Pacific  Coast,  the  outer  lobe  of  the  labella  is  mandible-like, 


Fig. 


Mi+Cu, 
1094. — Wing  of  Dolichopus  coquilletti. 


and  doubtless  functions  as  a  mandible.  For  descriptions  of  these 
remarkable  flies  see  Aldrich  ('22). 

The  males  of  some  species  have  the  fore  tarsi  exceedingly  elon- 
gated and  slender,  with  the  last  segment  in  the  shape  of  a  compara- 
tively large,  oval,  black  disk,  as  shown  in  Figure  1093 ;  in  others  the 
front  tarsi  are  plain  but  the  middle  ones  are  elongated,  thickened,  and 
very  black;  and  in  still  others  the  first  two  segments  of  the  antennae 
are  ornartiented  with  coarse  black  hair  and  the  arista  covered  with  a 
black  pubescence.  In  several  cases  the  males  have  been  observed  to 
display  these  ornaments  before  the  female  when  courting.  Detailed 
accounts  of  these  observations  are  given  by  Professor  Aldrich  in  the 
monograph  of  Dolichopus  by  Van  Duzee,  Cole,  and  Aldrich  ('21). 

The  larvae  live  in  a  variety  of  situations,  some  in  earth  or  decom- 
posing vegetable  matter,  some  in  the  burrows  of  wood-boring  larvas 


Fig.   1095. — Wing  of  Psilopodius  sipho. 

and  also  under  bark;  some  in  the  stems  of  plants;  and  many  are 
aquatic.  But  little  is  known  regarding  the  habits  of  the  larvae;  it  is 
said  that  some  species  feed  on  decaying  vegetation,  while  others  are 
believed  to  be  predacious. 


DIPT ERA 


845 


This  is  a  ^'ery  large  family;  and  representatives  of  it  are  common 
everywhere  in  the  United  States  and  Canada. 


Family  EMPIDID^ 
The  Dance-Flies 

The  dance-flies  are  of  mediiim  or  small  size;  they  are  often  seen 
in  swarms  flying  with  an  up  and  down  movement  under  trees  or  near 
shrubs  and  over  the  surface  of  water.  These  flies  are  predacious,  like 
the  robber-flies,  but  they  also  frequent  flowers.  The  family  is  a 
rather  difficult  one  to  characterize  owing  to  great  variations  in  the 
form  of  the  antennas  and  in  the  venation  of  the  wings. 

The  branches  of  vein  Cu  coalesce  with  the  adjacent  veins  (vein 
Cui  with  vein  M3  and  vein  Cu2  with  vein  2d  A)  from  the  margin  of 
the  wing  towards  the  base  for  a  considerable  distance  (Fig.  1096). 
In  most  genera  this  coalescence  is  carried  so  far  that  the  free  parts  of 
the  branches  of  vein  Cu  appear  like  cross-veins.     The  only  other 


Fig.  1096. — Wing  of  Rhamphomyia. 


families  of  the  suborder  Orthorrhapha  in  which  this  occurs  are  the 
Dolichopodidae  and  the  Lonchopteridee,  and  the  venation  of  the 
wings  in  each  of  these  is  very  different  from  that  of  the  Empididse. 

The  antennae  are  three-jointed,  the  first  and  second  segments  are 
often  very  small,  and  then  appear  like  a  single  segment,  the  third 
segment  may  or  may  not  bear  a  style  or  an  arista.  The  mouth-parts 
are  in  many  cases  long,  and  extend  at  right  angles  to  the  body  or  are 
bent  back  upon  the  breast. 

The  larvae  live  in  various  situations,  some  in  the  ground  or  in 
decaying  wood,  and  some  species  are  aquatic;  they  are  believed  to  be 
either  predacious  or  scavengers.    The  pupte  are  free. 

This  family  is  a  large  one.  It  was  monographed  by  Coquillett 
('96)  and  by  Melander  ('02). 


846  AN  INTRODUCTION  TO  ENTOMOLOGY 

Family  LON'CHOPTERID^ 

The  Spear-winged  Flies 

These  are  minute  flies,  which  measure  from  2  mm.  to  4  mm.  in 
length,  and  are  usually  brownish  or  yellowish  but  never  green  nor 
metallic  in  color.  When  at  rest  the  wings  are  folded  fiat,  one  over 
the  other,  on  the  abdomen.  The  apex  of  the  wing  is  pointed,  and  the 
wing  as  a  whole  is  shaped  somewhat  like  the  head  of  a  spear  (Fig. 
1097).    This  suggested  the  family  name. 

The  venation  of  the  wings  is  very  characteristic,  and  is  sufficient 
to  distinguish  these  flies  from  all  others.  The  cross-veins  r-m  and 
m-cu  are  oblique,  and  near  the  base  of  the  wing.  Vein  Cua  is  very 
short,  and  extends  towards  the  base   of  the  wing.     In  the  females 


Fig.  1097. — Wing  oi  Lonchoptera,  female. 

vein  Cu)  coalesces  with  vein  AI3  as  shown  in  the  figure,  but  in  the 
males  the  tip  of  vein  Cui  is  free.    The  posterior  lobe  is  wanting. 

Three  ocelli  are  present.  The  antennee  are  three-jointed;  the 
third  segment  is  globular,  and  bears  a  long  arista. 

These  flies  are  common  from  spring  till  autumn,  in  damp  grassy 
places.  They  frequent  the  shores  of  shady  brooks,  where  the  atmos- 
phere is  moist.  The  males  are  very  rare  in  this  countn-.  Professor 
Aldrich  examined  over  2,000  specimens  and  found  only  two  males 
among  them. 

"The  larvae  live  un'^er  leaves  and  decomposed  vegetable  matter. 
The  larva  transforms  into  a  sort  of  semipupa  within  the  last  larval 
skin,  and  later  into  a  true  pupa"  (WilHston  '08). 

The  family  includes  a  single  genus,  Lonchoptera,  of  which  only 
three  North  American  species  are  known. 

Suborder  CYCLORRHAPHA* 

The  Circular-seamed  Flies 

To  this  suborder  belong  those  famihes  of  fhes  in  which  the  pupa  is 
always  enclosed  in  a  puparium  from  which  the  adult  escapes  through 


*Cycl6iThapha:  cyclos.     {icukKos),  a  circle;  rhaphe,  (pa(pv), 


a  seam. 


DIPTERA  S47 

a  round  openinf;:  made  by  pushing  off  the  head-end  of  it.  (Fig. 
logS);  the  cap  thus  pushed  off  is  often  spHt  lengthwise, 
as  shown  in  the  figure.  The  adult  flies  possess  a  frontal 
lunule  and  except  in  the  first  four  families  a  frontal  suture, 
through  which  the  ptilinum  is  pushed  out,  when  the  adult 
is  about  to  emerge  from  the  puparium. 

The  antennae  are  three-jointed,  with  a  terminal  or 
dorsal  arista,  rarely  with  a  terminal  style;  in  the  Pupipara 
the  antenna?  are  apparently  only  one-  or  two-jointed  and 
sometimes  lack  the  arista.  The  radius  is  not  more  than 
three-branched;  cells  Mi  and  M3  are  wanting.  The 
empodia  are  never  pulvilliform. 

SERIES  I— ASCHIZA* 

Cyclorrhapha  without  a  frontal  suture 

In  most  of  the  Cyclorrhapha  the  head  end  of  the  puparium  is 
forced  off  by  the  expansion  of  the  bladder-like  ptilinum,  which  is 
pushed  out  through  the  frontal  suture  when  the  adult  is  ready  to 
emerge;  but  in  four  families  this  is  not  the  case,  there  being  no  frontal 
suture  present.  These  families  are  grouped  together  as  the  Series 
Aschiza.  They  are  the  Phoridae,  Platypezidae,  PipunculidcC,  and 
Syrphidae. 

Family  PHORID/E 

The  Htintp-backed  Flies 

These  are  minute,  dark-colored,  usually  black  flies,  which  can 
be  easily  recognized  by  their  hiimpbacked  form,  their  peculiar  an- 
tennae, and  the  peculiar  venation  of  the  wings.  Certain  species  are 
often  foimd  tunning  about  rapidly  on  windows,  others  on  fallen 
leaves.  Sometimes  they  are  seen  in  swarms  dancing  up  and  down  in 
the  air.  Many  species  measure  less  than  2  mm.  in  length,  and  some 
less  than  i  mm. 

The  head  is  small ;  the  thorax  large  and  humped;  and  the  abdomen 
rather  short.  The  antennae  are  three-jointed;  but  the  first  segment 
is  exceedingly  small,  and  the  second  is  enclosed  in  the  third,  so  that 
they  appear  as  single-jointed.  The  third  segment  bears  an  arista, 
composed  of  two  short  basal  segments  and  a  long,  usually  more  or 
less  pltmiose  third  segment.  The  legs  are  large  and  strong  and  well 
adapted  to  jimiping.  The  femora,  especially  of  the  hind  legs  are 
often  very  stout  and  flattened.  The  wings  (Fig.  1099)  are  large,  and 
are  furnished  with  a  series  of  strong  veins  near  the  costal  border, 
which  extend  but  a  short  distance  beyond  the  middle  of  the  wing. 
From  these  strong  veins  from  three  to  five  weak  ones  extend  across 
the  wing. 

In  the  females  of  some  species  that  live  in  the  nests  of  ants  and 
termites  the  wings  are  absent  or  very  much  reduced  in  size. 

*Aschiza:  a  (d),  without;  schizo  ((rx^fw),  a  cleft. 


848 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  lar\'ae  of  the  different  species  differ  greatly  in  habits,  some 
feed  on  decaying  vegetable  matter,  dead  insects,  snails,  etc. ;  some  are 
common  in  mushrooms,  and  are  sometimes  a  pest  in  mushroom  cel- 
lars; some  are  internal  parasites  of  other  insects,  as  bees,  wasps,  ants, 
saw-flies,  etc. ;  several  species  are  known  to  live  in  the  nests  of  ants, 
some  as  parasites  and  others  as  commensals.    One  of  these  Metopina 


iW,+, 


Fig.   1099. — Wing  of  Phora. 

pachycondyle  lives  curled  about  the  neck  of  its  host  ant-larva,  par- 
taking of  the  food  given  the  latter  by  the  attendant  worker  ants; 
and  one  has  been  bred  from  an  egg-sac  of  a  spider. 

A  monograph  of  the  North  American  species  of  this  family  was 
published  by  Brues  ('03)  and  one  by  Malloch  ('13).  About  150 
species  have  been  described  from  this  region. 

The  Phoridae  are  classed  among  the  Brachycera  by  some  writers 
and  among  the  Cyclorrhapha  by  others.  Morris  ('22)  states  that 
when  the  adult  fly  of  a  species  studied  by  him,  Hypocera  incrassdta, 
emerges  from  the  puparium  a  circular  cap,  consisting  of  the  skin  of 
the  cephalic  region  and  thoracic  segments  of  the  larva,  is  split  off  by 
means  of  a  fissure  passing  round  the  body  between  the  third  thoracic 
and  first  abdominal  segments.  This  confirms  the  opinion  that  this 
family  should  be  placed  in  the  Cyclorrhapha. 

Family  PLATYPEZID^ 
The  Flat-footed  Flies 

These  flies  resemble  the  house-fly  somewhat  in  appearance  but 
are  very  much  smaller.  They  hover  in  the  air  in  shady  places  and 
alight  frequently  on  the  leaves  of  low  plants,  where  they  run  about 
in  circles  with  great  rapidity. 

The  head  is  hemispherical  or  spherical,  and  as  broad  as  or  broader 
than  the  thorax.  The  antennas  are  three-jointed  with  a  terminal 
arista.  The  legs  are  short  and  stout,  and  the  tarsi  of  the  hinder  pair 
are  often  very  broad  and  flat  (Fig.  11 00);  but  they  vary  greatly  in 
form  in  different  genera.     The  wings  are  rather  large,  and  when  at 


DIPTERA 


849 


rest  lie  parallel  upon  the  abdomen ;  the  axillary 
excision  is  prominent,  but  the  posterior  lobe  of 
the  wing  is  small  (Fig^.  iioi);  the  alulets  are 
minute. 

The  radial  sector  is  two-branched;  veins 
Ml  and  M2  either  coalesce  throughout  or  sep- 
arate near  the  margin  of  the  wing;  the  medial 
cross  vein  is  present  in  some  members  of  the 
family  and  absent  in  others;  cells  2d  R,  M, 
and  I  St  A  are  short. 

This  family  is  represented  in  North  Amer- 
ica by  about  twenty-five  species,  and  these  are 
usually  rare.  The  larvee  live  in  mushrooms, 
the  puparia  are  not  very  different  from  the 
larvas  in  form. 


Fig.  1 100. — LegofP/a- 
typeza,  a,  forked 
hairs  of  leg  greatly- 
enlarged. 


Cu,^  2d  A 

Fig.   IIOI. — Wing  of  Platypeza. 


Family  PIPUNCULID^ 
The  Big-eyed  Flies 

The  members  of  this  family  are  small  flies  with  very  large  heads 
composed  almost  entirely  of  eyes  (Fig.  1102).  The 
head  is  nearly  spherical  and  broader  than  the  thorax. 
The  antennae  are  small,  short,  three-jointed,  with  a 
dorsal  arista .  The  ocelli  are  present .  The  abdomen  is 
somewhat  elongate  with  the  sides  nearly  parallel. 
The  body  is  thinh^  clothed  with  hair  or  nearly  naked. 
The  wings  are  much  longer  than  the  abdomen,  and 
when  at  rest  they  lie  parallel  to  each  other  upon  it. 
The  venation  of  the  wings  (Fig.  11 03)  closely  re- 
sembles that  of  the  Conopidae.  The  radial  sector  is 
two-branched.  Veins  R4+5  and  Mi +2  approach  each 
other  at  their  tips.    Vein  M3  coalesces  with  vein  Cui  for  nearly  its 


Fig.    1102.- 
piinculiis. 


-Pi- 


850 


AN  INTRODUCTION  TO  ENTOMOLOGY 


entire  length.  Veins  Cuo  and  2d  A  coalesce  at  their  tips,  except  in 
Chalarus.  In  this  genus  vein  Mi +2  is  atrophied  and  the  medial  cross- 
vein  absent.    Cells  R  and  M  are  long. 

The  flies  hover  in  shady  places.    They  are  sometimes  found  on 
flowers,  and  may  be  swept  from  low  plants ;  our  most  common  species 


Fig.  1 103. — Wing  of  Pipimculus. 

measure  about  3  mm.  in  length,  not  including  the  wings.    The  larvae 
so  far  as  known  are  parasitic  upon  bugs. 

This  small  family  is  represented  in  North  America  by   about 
thirty  species,  nearly  all  of  which  belong  to  the  genus  Pipunculus. 


Family  SYRPHID^ 
The  Syrphus-Flies 

The  family  Syrphidae  includes  many  of  our  common  flies ;  but  the 
different  species  vary  so  much  in  form  that  no  general  description  of 
their  appearance  can  be  given.  Many  of  them  mimic  hymenopterous 
insects,  thus  some  species  resemble  bumblebees,  others  the  honey- 
bee, and  still  others  wasps;  while  some  present  but  little  resemblance 
to  any  of  these. 

The  most  distinctive  characteristic  of  the  family  is  the  presence 
of  a  thickening  of  the  membrance  of  the  wing,  which  appears  like  a 
longitudinal  vein  between  veins  R  and  M.  This  is  termed  the  spu- 
rious vein,  and  is  lacking  in  only  a  few  members  of  the  family; it  is 
represented  in  Figure  11 04  by  a  band  of  stippling.  Vein  R4+5  is 
never  forked;  the  tips  of  vein  R4+5  and  Mi +2  coalesce;  and  the  first 
anal  cell  is  closed. 

The  antennae  are  three-jointed;  the  third  segment  usually  bears 
a  dorsal  arista,  but  sometimes  it  is  furnished  with  a  thickened  style. 
The  face  is  not  furnished  with  longitudinal  furrows  to  receive  the 
antennas  as  in  the  Muscidas.  The  frontal  lunule  is  present,  but  the 
frontal  suture  is  wanting. 

The  adults  frequent  flowers  and  feed  upon  nectar  and  pollen. 
vSome  fly  with  a  loud  humming  sound  like  that  of  a  bee,  others  hover 
motionless  except  as  to  their  wings  for  a  time,  and  then  dart  away 
suddenly  for  a  short  distance,  and  then  resimie  their  hovering. 


DIPTERA 


851 


The  larv«  vary  greatly  in  form  and  habits.  Some  prey  upon  plant 
lice,  and  are  often  found  in  the  midst  of  colonies  of  these  insects;  some 
feed  in  the  stems  of  plants  and  in  bulbs ;  others  feed  on  decaying  vege- 
table matter,  and  live  in  rotten  wood,  in  mud  and  in  water;  and  others 
live  in  ordure  or  in  decomposing  animal  remains.  Some  are  found  in 
the  nests  of  ants;  and  some  in  the  nests  of  bumblebees  and  wasps. 

Among  the  common  representatives  of  this  family  there  is  one 
that  so  closely  resembles  a  male  honey-bee  as  to  be  often  mistaken 
for  it.     This  is  the  Drone-fl\',  Enstalis  tenax.     It  is  common  about 


/?,   R.. 


Fig.  1 104. — Wing  of  Eristalus. 

flowers.  The  larva  lives  in  foul  water,  where  it  feeds  on  decaying 
vegetable  matter;  it  is  of  the  form  known  as  "rat-tailed,"  which  is 
described  below. 

The  larvse  of  the  genus  Volucella  live  as  scavengers  in  the  nests 
of  bimiblebees  and  of  wasps  {Vespa).  Some  of  the  species  in  the 
adult  state  very  closely  resemble  btmiblebees. 

The  larvffi  of  the  genus  Murodon  are  hemispherical,  slug-like 
creatures  (Fig.  1105),  which  resemble  mollusks  more  than  ordinary 
maggots;  they  are  common  in  ants'  nests. 

The  larvee  of  several  species  that  live  in  water  as  well  as  some 
that  live  in  rotten  wood  are  known  as  rat-tailed  maggots  on  account 
of  the  long,  tail-like,  appendage,  with  which  the  hind  end  of  the  body 
is  furnished.  This  is  a  tube,  like  that  of  a  diver,  which  enables  the 
insect  to  obtain  air  when  its  body  is  submerged  beneath  several  inches 
of  water  or  decaying  matter.  This 
tube  being  telescopic  can  be  length- 
ened or  shortened  as  the  insect  may 
need  it ;  and  at  its  tip  there  is  a  ros- 
ette of  hairs,  which,  floating  on  tlir 
surface  of  the  water,  keeps  the  tiij  /:. 
Fig.iios.-Microdon,  adult ^om  being  submerged.  The  larva  ^' 
and  larva.  has  on  the  ventral  side  of  its  body  Fig.  11 06.-- 

several  pairs  of  tubercles  armed  with     Syrphus. 
spines,  which  serve  as  prolegs. 
Among  the  more  common  members  of  this  family  are  the  yellow- 
banded  species  belonging  to  the  genus  Syrphus  (Fig.  1 106).    The  larvae 


• 


^% 


852  AN  INTRODUCTION  TO  ENTOMOLOGY 

of  these  live  in  colonies  of  aphids,  and  do  much  good  by  destroying 
these  pests. 

This  family  is  a  very  large  one;  more  than  300  species  represent- 
ing about  60  genera  have  been  described  from  America  north  of 
Mexico.  Williston  ('86)  published  an  extended  monograph  of  our 
species. 


SERIES  II— SCHIZOPHORA* 

Cydorrhapha  with  a  frontal  suture 

This  series  of  families  includes  all  of  the  Cydorrhapha  except  the 
four  preceding  families  in  which  the  frontal  suture  is  wanting.  In 
this  series,  the  Schizophora,  there  is  a  frontal  suture  through  which 
the  ptilinimi  is  extruded  in  order  to  force  off  the  head  end  of  the  pu- 
parium  when  the  adult  is  ready  to  emerge. 

This  series  is  divided  into  two  quite  distinct  sections,  the  Myodaria 
and  the  Pupipara. 


SECTION  I— MYODARIA 

The  Muscids 

This  section  of  the  order  Diptera  is  a  very  large  group,  including 
many  families  and  probably  more  than  half  of  all  the  living  species 
of  this  order.  As  many  of  the  species  are  very  common,  it  usually 
happens  that  a  large  portion  of  the  flies  in  a  collection  belong  to  the 
families  included  in  this  section. 

Excepting  the  first  family,  the  Conopidse,  the  families  included 
in  the  Myodaria  differ  from  all  of  the  preceding  families  in  that  vein 
Cu2  coalesces  with  vein  2d  A  to  such  an  extent  that  it  appears  like  a 
cross-vein  or  is  curved  back  towards  the  base  of  the  wing ;  and  the}' 
differ  from  the  following  families,  the  Pupipara,  in  having  the  ab- 
domen distinctly  segmented  and  the  two  legs  of  each  thoracic  seg- 
ment not  widely  separated. 

The  antenna  are  three-jointed;  the  third  segment  bears  an  arista 
which  is  almost  always  dorsal  in  position.  The  radial  sector  is  not 
more  than  two-branched;  cells  Mi  and  M3  are  wanting;  and  the  two 
branches  of  cubitus  coalesce  with  the  adjacent  veins  (Vein  Cui  with 
M3  and  Cu2  with  2d  A)  for  nearly  their  entire  length,  except  in  the 
Conopidae. 

The  families  included  in  this  section  are  grouped  in  two  subsec- 
tions, the  Acalyptratae  and  the  Calyptratas. 

*Schiz6phora:  schizo  ((^x^fw),  a  deft;  phoros  ((popdt),  bearing. 


DIPTERA  853 

Subsection  I— THE  ACALYPTRATvE* 

The  Acalpptrate  Miiscids 

In  the  families  included  in  this  subsection  of  the  Myodaria  the 
alulce  or  calypteres  are  always  small  or  rudimentary;  the  subcostal 
vein  is  often  indistinct  or  vestigial,  but  well  preserved  in  some  forms; 
vein  Ri  is  shortened  and  is  often  very  short ;  the  thorax  is  without  a 
complete  transverse  suture;  the  posterior  callus  is  usually  absent; 
and  the  abdominal  spiracles,  with  some  exceptions,  are  in  the  con- 
junctivae. The  flies  are  usually  small  or  very  small,  they  are  never 
large. 

The  subsection  Acalyptrata  includes  many  families,  twenty- 
three  of  which  are  represented  in  our  fauna.  Some  of  these  families 
include  well-known  species  that  have  attracted  attention  on  account 
of  their  economic  importance  or  for  other  reasons;  but  most  of  the 
families  have  been  studied  comparatively  little  in  this  country. 


Family  CONOPID^ 
The  Thick-headed  Flies 

With  the  members  of  this  family  the  head  is  large,  being  broader 
than  the  thorax.  The  body  is  more  or  less  elongate ;  it  may  be  naked 
or  thinly  clothed  with  fine  hair,  but  it  is  rarely  bristly. 

The  ocelli  may  be  either  present  or  absent.  The  antennas  are 
prominent  and  project  forward;  they  are  three-jointed;  and  the  third 


Fig.   1 1 07. — Wing  of  Physocephala  affinis. 

segment  bears  either  a  dorsal  arista  or  a  terminal  style.  The  radial 
sector  is  only  two-branched  (Fig.  1107);  veins  'Ri+f>  and  M1+2  end 
near  together  or  coalesce  at  their  tips.  The  medial  cross-vein  is 
present.  Vein  M3  coalesces  with  vein  Cui  for  nearly  its  entire  length. 
Veins  Cu2  and  2d  A  coalesce  at  their  tips,  and  sometimes  for  nearly 
the  entire  length  of  vein  Cu2. 


*Acalyptratse :  a  (d);  without;  calypter  (KaXv/rrrip)^  a  sheath. 


854  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  adult  flies  are  found  on  flowers.    In  some  genera  the  abdomen 

is  long,  with  a  slender,  wasp-like  pedicel   (Fig. 

\    ^    /  1108).    In  others  the  abdomen  is  of  the  more  usual 

ydb/  form.      The    larvae    are    parasitic,    chiefly   upon 

^8!^^||$^^^        bumblebees  and  wasps,  but  some  species  infest 

>^T\v  locusts.     The  eggs  are  deposited  by  the  female, 

//  m\\  in  some  cases  at  least,  directly  upon  the  bodies  of 

'         *  the   bees   or  wasps   during  flight.     The  newly 

Fig.  1108.— Conops.      hatched   larvfe    burrow    within    the    abdominal 

cavity  of  their  host. 

Nearly  one  hundred  North  American  species  have  been  described. 

Family  CORDYLURID^ 

The  D wig-Flies 

The  members  of  this  family  are  often  of  considerable  size  for 
Acalyptratae,  they  are  never  very  small.  The  subcostal  vein  is  dis- 
tinctly separated  from  vein  Ri  and  ends  in  the  costa ;  vein  Ri  is  nearly 
half  as  long  as  the  wing,  cell  M  is  not  minute;  the  frontal  vitta  is 
usually  well  differentiated  from  the  orbits;  and  the  vibrissse  are 
present. 

Although  members  of  several  families  of  flies  frequent  excrement 
certain  species  of  this  family  and  of  the  Borboridas  are  so  commonly 
observed  about  dung  and  refuse  that  they  have  received  the  common 
names  of  dung-flies.  Among  these  are  those  of  the  genus  Scatophaga; 
these  are  rather  slender  flies,  which  have  the  body  clothed  with 
yellowish  hair,  and  which  are  often  abundant  especially  about  fresh 
cow-dung.  Other  members  of  this  family  are  found  in  meadows  and 
in  moist  places;  some  feed  on  other  insects  which  they  capture. 

The  larvae  of  some  species  have  been  bred  from  excrement ;  some 
live  in  the  stems  of  plants;  and  some  are  said  to  be  parasitic  in  cater- 
pillars. 

This  family  is  named  the  Scatophagidae  by  some  writers,  and  by 
some  it  is  classed  with  the  Calyptratae. 

The  family  CLUvSIID^  is  a  small  family  of  rather  small  flies;  only 
a  few  representatives  of  which  are  found  in  our  fauna.  In  this  family 
the  subcostal  vein  is  distinctly  separated  from  vein  Ri  and  ends  in 
the  costa;  vein  Ri  is  less  than  one-third  as  long  as  the  wing;  the  so- 
called  front  is  broad  and  bristly  to  or  nearly  to  the  base  of  the  an- 
tennae; the  frontal  vitta  is  not  differentiated  from  the  orbits;  the 
ocellar  bristles  are  usually  present;  the  postvertical  bristles  are  di- 
vergent; and  the  vibrissae  are  present.  Larvae  of  this  family  have 
been  found  in  decaying  wood  and  under  the  bark  of  trees. 

This  family  is  named  the  Heteroneuridae  by  some  writers. 

Family  HELOMYZID^ 

The  rnembers  of  the  Helomyzidae  can  be  recognized  by  the  follow- 
ing combination  of  characters;  the  wings  are  armed  with  a  row  of 


DIPTERA  855 

spines  along  the  costa  (Fig.  1109);  the  subcostal  vein  is  distinct;  the 
oral  vibrissas  are  present;  the  postvertical  bristles,  which  are  located 
on  the  back  of  the  head  somewhat  behind  the  ocelli,  are  convergent; 
and  the  tibife  are  armed  with  spurs  and  with  preapical  bristles. 

The  flies  are  found  in  shad}^  and  damp  places;  many  of  them  have 
been  found  in  caves;  and  some  species  on  windows. 


^^  +  C/(i  Cit2  +2d  A 

Fig.  1 109. — Wing  of  Lena.     (After  Williston.) 

"The  larvae  of  Leria  have  been  bred  from  bat  and  rabbit  dung; 
those  of  Helomyza  from  truffles,  decaying  wood,  etc."  (Williston) 

The  family  was  monographed  by  Aldrich  and  Darlington  ('08) ; 
they  recognized  ten  genera  and  about  two  score  species  found  in  the 
United  States. 

The  family  BORBORID^  is  composed  of  rather  small  or  very 
small  black,  brown  or  obscurely  }'ellowish  flies,  having  a  quick  short 
flight.  Some  of  the  species  are  very  common,  occurring  in  great  nimi- 
bers  about  excrement  or  near  water.  These  "dung-flies"  differ  from 
those  of  the  CordyluridcC  in  that  the  subcostal  vein  of  the  wings  is 
wanting  or  indistinct  and  in  having  the  hind  metatarsi  dilated  and 
usually  shorter  than  the  following  segment. 

The  larvae  of  some  of  the  species,  at  least,  live  in  excrement. 

The  family  PHYCODROMID^  includes  only  a  few  species  of 
flies  that  are  found  among  sea-weeds  along  the  sea-shore.  Two  species 
are  listed  from  Alaska  and  one  from  California.  This  family  is  named 
the  Coelopid^e  by  Hendel  ('22). 

Family  SCIOMYZID.^ 

The  members  of  this  family  are  usually  brown  or  brownish  yellow 
in  color;  and  in  many  species  the  wings  are  spotted  or  infumated. 
They  are  usually  found  in  moist  situations,  as  along  the  banks  of 
streams.    The  larvae  are  aquatic. 

These  flies  lack  vibrissas.  The  face  in  profile  forms  a  sharp  often 
very  acute  angle  with  that  of  the  oral  margin.  The  postvertical 
bristles  are  divergent  when  present. 

This  family  is  represented  in  this  country  by  more  than  twenty 
genera  and  by  nearly  one  hundred  described  species.     It  has  been 


856  AN  INTRODUCTION  TO  ENTOMOLOGY 

monographed  by  Cresson  ('20)  and  also  by  Melander  ('20a)  under 
the  name  Tetanoceridae. 

Family  SAPROMYZID^ 

The  head  is  as  broad  as  or  a  Httle  broader  than  the  thorax;  the 
legs  are  of  moderate  length ;  the  hind  tibise  bear  a  preapical  bristle ; 
the  abdomen  is  short ;  the  ovipositor  is  neither  flat  nor  drawn  out ;  the 
subcostal  vein  is  distinctly  separated  from  vein  Ri  and  ends  in  the 
costa;  vein  2d  A  does  not  reach  the  margin  of  the  wing;  the  oral  vi- 
brissa) are  absent;  the  second  antennal  segment  bears  a  dorsal  bristle ; 
the  postvertical  bristles  are  convergent ;  and  one  or  more  stemopleural 
and  a  mesopleural  bristle  are  present. 

This  family  is  composed  of  small  flies,  which  are  seldom  more  than 
7  mjm.  in  length.  Nearly  one  hundred  species  have  been  described 
from  America  north  of  Mexico.  A  synopsis  of  the  family  was  pub- 
lished by  Melander  ('13  a). 

The  larvae  of  Sapromyza  live  in  decaying  vegetable  matter. 

This  family  is  named  the  Lauxanidse  by  some  writers. 

The  family  LONCH^ID^  includes  the  genera  Lonckcea  and 
Palloptera,  which  are  included  in  the  Sapromyzidae  by  some  writers. 
These  genera  differ  from  the  Sapromyzidae  in  that  the  hind  tibiae  are 
without  a  preapical  bristle;  and  the  ovipositor  is  flattened  and  more 
or  less  projecting.  A  svnopsis  of  our  species  is  included  in  Melander 
('13a). 

Lonchcea  pohta  has  been  reared  from  a  decaying  fungus  iPolyporus) 
and  from  human  excrement. 

Family  ORTALID^ 

This  family  like  the  Trypetidae  is  a  large  one  and  contains  many 
common  species  which  have  the  wings  beautifully  marked  with  dark 
spots  or  bands.  The  members  of  this  family  differ  from  the  Trypetidae 
in  that  the  subcostal  vein  extends  to  the  margin  of  the  wing  in  the 
usual  way  and  in  that  the  lower  fronto-orbital  bristles  are  wanting. 

Comparati\'ely  few  species  of  the  Ortalidas  have  been  bred  and 
these  differ  greatly  in  habits.  The  larvag  of  some  have  been  found 
under  bark  of  dead  trees,  others  in  excrement,  some  are  parasitic  on 
lepidopterous  larvae,  and  several  infest  growing  plants.  Among  the 
latter  are  Chcetopsis  asnea  and  Tritoxa  flexa  which  sometimes  infest 
onions;  but  the  most  important  onion  maggot  is  Hylemyia  antiqua 
of  the  family  Anthomyiidas. 

The  family  includes  six  subfamilies  each  of  which  is  given  famih' 
rank  by  Hendel  ('22). 

Family  TRYPETID^ 

This  is  a  very  large  family  including  many  common  species 
with  pictured  wings,  in  which  it  resembles  the  preceding  family,  the 


DIPTERA 


857 


OrtalidcTe.    These  two  families  can  be  separated  by  differences  in  the 

subcostal  vein;  in  the  Trypetidae  the  distal  part  of  the  subcostal  vein 

is  abruptly  turned  forward  and  usually  becomes  very  weak.     In  this 

family  the  vibrissas  are  wanting; 

the    fronto-orbital    bristles    are 

numerous  and   extend  down   to 

the  antenna^;  cells  M  and  ist  M2 

are  separated  b}^  a  cross-vein ;  the 

legs    are    moderately    long;    the 

tibia?  lack  preapical  bristles;  and 

the   ovipositor   is   flattened   and 

more  or  less  projecting. 

The  larvae  of  the  species  that 
haxe  been  bred  infest  living 
plants.  Some  are  leaf-miners, 
some  live  in  the  stems  of  plants, 
some  make  galls,  and  some  are 
pests  that  infest  fruit.  Among 
the  better-known  species  are  the 
following. 

The  apple-maggot,  Rhagoletis 
pomonella. — The  adult  is  blackish 
with  the  head  and  legs  yellowish ; 
the  abdomen  is  crossed  by  three 
or  four  white  bands  (Fig.  mo) 
and  the  wings  are  crossed  by  four 
dark  confluent  bands.  The  fe- 
male punctures  the  skin  of  the 
apple  with  her  ovipositor  and 
lays  her  eggs  in  the  pulp.  The 
larvae  bores  tunnels  in  all  direc- 
tions through  the  fruit.  Early 
maturing  varieties  of  apples  are 
especially  attacked.  When  full-grown  the  larva  goes  into  the  ground 
to  transform  where  it  hibernates  in  a  brownish  pupariimi.  This  is  a 
serious  pest  in  the  Eastern  States  and  in  Canada.  This  is  a  native 
species,  originally  feeding  in  the  fruit  of  wild  thorn.  It  has  been 
found  that  most  of  the  flies  can  be  destroyed  before  they  lay  their 
eggs  by  applying  a  spray  of  arsenate  of  lead,  four  pounds  in  one  hun- 
dred gallons  of  water,  during  the  first  week  of  July.  The  flies  lap  up 
drops  of  moisture  from  the  fruit  and  foliage  and  are  thus  poisoned. 
The  fallen  apples  should  be  collected  or  hogs  allowed  to  run  in  the 
orchard. 

The  cherry  fruit-flies,  Rhagoletis  cingulata  and  Rhagoletis  fausta. 
These  two  species,  which  are  closely  allied  to  the  apple-maggot,  infest 
cherries,  but  not  so  commonly  as  does  the  plum  curculio.  The  cherry 
fruit-flies  can  be  destroyed  by  the  use  of  the  arsenate  of  lead  spray 
early  in  June. 


Fig.  mo. — The  apple-maggot:  7,  lar- 
va; 2,  puparium;  j,  adult;  la.  head 
of  larva  from  side  showing  the  oral 
hooks  and  spiracle;  ib,  head  of  lar- 
va from  below;  ic,  caudal  soiracle  of 
larva. 


858  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  currant  fruit-fly,   Epochra  canadensis. — The  larva  of  this 
species  is  a  small  white  maggot  which  feeds  within  currants  and  goose- 
berries.    The  infested  fruit  colors  prema- 
♦  I  turely  and  usually  falls  to  the  ground.    No 

^^Jfcj^       practicable  method  of  controlling  this  pest 
jflHM        has  been  suggested. 
^EElfl  ^^^  round  goldenrod  gall. — One  of  the 

^W»fe        most    familiar    of    abnormal    growths    on 
^Hr  plants  is  a  ball-like  enlargement  of  the  stem 

1p  of  goldenrod  (Fig.  nil).    This  is  caused  by 

Fig.    nil.— The    round      a  maggot,  which  lives  within  it,  and  which 
goldenrod  gall.  develops    into    a    pretty    fly    with    banded 

wings ;  this  is  Eurosta  soliddginis.  The  larva 
hibernates  in  the  gall;  the  adult  emerges  in  May.  The  gall  of  this 
species  is  easily  distinguished  from  that  of  the  solidago  gall-moth, 
described  in  the  preceding  chapter,  by  its  rounded  form. 

The  family  MICROPEZID^  is  represented  in  America  north  of 
Mexico  by  a  few  species ;  most  of  the  species  of  this  family  occur  in 
wSouth  America.  In  our  representatives  of  the  family,  the  subcostal 
vein  is  distinctly  separated  from  vein  Ri ;  cell  R5  is  closed  or  narrowed 
at  the  margin;  the  head  is  subspherical ;  the  buccse  are  broad;  the 
face  is  retreating;  the  vibrissae  are  wanting;  and  the  proboscis  is 
short. 

The  familv  TANYPEZID^  includes  the  genus  Tanypesa,  which 
differs  from  the  preceding  family  in  that  the  buccse  and  the  posterior 
orbits  are  narrow.  The  described  species  are  chiefly  from  South  and 
Central  America.    These  flies  are  rare  in  the  United  States. 

The  family  SEPSID^  includes  only  a  few  species.  These  are 
small  slender  flies,  which  are  principally  scavengers,  feeding  and 
breeding  in  decaying  organic  matter.  They  are  not  rare,  and  can  be 
obtained  by  sweeping  grass  in  meadows  and  pastures,  especially 
where  there  are  droppings  of  horses  and  cattle.  "Species  of  Sepsis 
are  particularly  abundant  and  can  be  found  on  fresh  dung,  where 
they  run  about  with  vibrating  wings  pirouetting  in  a  unique  and 
pretty  dance." 

The  family  has  been  monographed  by  Melander  and  Spuler  ('17). 

Family  PIOPHILID^ 

This  family  includes  only  a  few  species  of  small  flies,  rarely  ex- 
ceeding 5  mm.  in  length .  They  are  usually  glistening  black  or  slightly 
bluish  metallic  in  luster.  They  are  found  about  either  decaying 
organic  matter,  preserved  meats,  or  cheese.  The  best  known  species 
is  the  following. 

The  cheese-maggot,  Piophila  cdsei.- — This  fly  lays  its  eggs  on 
cheese,  ham,  and  bacon.  The  larvae  live  in  these  substances  and  are 
often  serious  pests.  They  are  commonly  known  as  "skippers"  on 
account  of  the  remarkable  leaps  they  can  make.  This  is  accomplished 
by  first  bringing  the  head  and  tail  ends  together  and  then  suddenly 
straightening  the  body;  in  this  way  they  can  leap  several  inches. 


DIPTERA  859 

The  members  of  this  family  were  formerly  included  in  the  Sepsidas. 
The  family  Piophilidtc  was  monographed  by  Melander  and  Spu- 
ler  C17).  " 

Family  PSILID^ 

The  flies  of  this  family  are  of  moderate  size  and  slender.  In  many 
of  the  species  the  antenna  are  very  long  and  decumbent,  but  in  others 
they  are  of  moderate  length.  The  vibrissa?  are  wanting;  the  costa  is 
interrupted  near  the  end  of  vein  Rr,  and  cells  ist  A  and  M  are  com- 
plete and  relatively  large.  Five  genera  including  thirty-three  species 
have  been  described  from  our  fauna.  For  a  synopsis  of  the  family 
see  Melander  ('20  b).    The  following  is  our  best -known  species. 

The  carrot  rust-fly,  Psila  rosce.—The  larva  of  this  species  infests 
carrots,  celery,  parsnips,  and  parslev.  In  the  case  of  carrots  and  pars- 
nips the  larvae  perforate  the  roots  in  all  directions ;  their  burrows  are 
of  a  rusty  color,  hence  the  common  name  of  the  insect.  When  celery 
is  attacked  the  fibrous  roots  are  eaten  off  and  destroyed. 

The  family  DIOPSID^  is  represented  in  North  America  only  by 
the  following  species. 

The  stem-eyed  fly,  Sphyraccphala  brevicornis .- — This  is  a  very 
singular  fly,  which  is  found  on  the  leaves  of  skunk-cabbage  and  the 
foliage  of  other  plants  in  shady  glens.  On  each  side  of  the  head  there 
is  a  lateral  process,  upon  which  the  eye  is  situated.  The  life -history 
of  the  species  is  unknown. 

The  family  CANACEID^  is  represented  in  our  fauna  by  a  single 
described  species,  Canace  snodgrdssi,  recorded  from  New  Jersey. 

Family  EPHYDRID^ 

These  are  small  or  very  small,  black  or  dark-colored  flies,  that 
live  in  wet  places.  The  subcostal  vein  is  coalescent  for  the  greater 
part  of  the  length  with  vein  Ri,  being  distinct  only  at  its  proximal 
end;  cells  M  and  ist  M2  are  not  separated  by  a  cross-vein;  the  hind 
metatarsi  are  not  thickened  and  are  longer  than  the  following  seg- 
ment; the  vibrissae  are  wanting;  and  in  some  species  the  mouth  cavity 
is  very  large. 

Most  of  the  species  live  about  fresh  water;  but  to  this  family 
belong  the  "Brine-flies"  the  larvae  of  which  live  in  salt  or  strongly 
alkaline  waters.  These  are  common  in  pools  about  salt-works ;  and  in 
the  far  West  and  in  Mexico  these  larvae  occur  in  the  alkaline  lakes  in 
countless  niimbers,  and  are  washed  ashore  in  such  quantities  that 
bushels  of  them  can  be  collected.  They  are  gathered  by  the  Indians, 
who  dry  them  and  use  them  for  food,  which  they  call  koo-tsabe, 
accented  on  the  first  syllable.  The  best-known  "brine-flies"  belong 
to  the  genus  Ephydra. 

Still  more  remarkable  are  the  habits  of  the  larva  of  the  petroleum- 
fly,  Psilopa  petrolei,  which  lives,  feeds,  and  swims  about  in  the  pools 
of  crude  petroleum,  which  are  numerous  in  the  various  oil-fields  of 


860  AN  INTRODUCTION  TO  ENTOMOLOGY 

California.    For  an  account  of  the  structure  and  habits  of  this  larva 
see  Crawford  ('12). 

Family  CHLOROPID^ 

This  family  includes  a  considerable  number  of  species  that  are 
common  in  meadows  and  other  places  where  there  is  rank  growing 
grass,  in  such  situations  they  can  be  collected  in  large  numbers  by  a 
sweep-net. 

The  members  of  this  family  are  small  bare  species;  with  moder- 
ately short  or  very  short  wings ;  the  subcostal  vein  is  vestigial  cells  M 
and  ist  M2  are  not  separated  by  a  cross-vein;  the  antennae  are  usually 
short  and  w4th  the  third  joint  rounded  ;  the  vibriss^e  are  rarely  present ; 
and  the  postvertical  bristles  are  convergent. 

The  larva?  of  the  different  species  differ  in  their  habits;  many 
species  infest  the  stems  of  wheat,  oats,  rye,  clover,  and  grasses;  some 
live  in  burrows  or  cavities  in  plants  made  by  other  insects ;  a  few  feed 
upon  the  egg-shells  and  cast-off  skins  of  insects;  some  live  in  excre- 
ment; and  species  of  Gaurax  develop  in  the  egg-sacs  of  spiders. 
Among  the  more  important  members  of  this  family  is  the  following 
species. 

The  European  frit-fly,  Oscinis  frit. — This  is  a  minute  black 
species,  measuring  from  i .  i  to  2  rmn.  in  length.  It  was  first  described 
by  Linnseus  in  Sweden,  where  it  was  a  very  serious  pest  of  barley,  the 
larvae  feeding  upon  the  immature  kernels.  The  light  and  worthless 
kernels  resulting  from  this  the  Swedes  called  "frits",  hence  the  com- 
mon name  of  the  species.  There  are  several  generations  annually. 
The  larvae  of  the  late  fall  generation  winter  as  stem  miners  in  winter 
grain;  and  spring  grain  is  attacked  in  the  same  way  by  the  spring 
generation.  In  this  country  the  commonest  form  of  injury  is  to  the 
stems  of  wheat  close  to  the  ground.  The  larva  of  this  species  can  be 
easily  distinguished  from  the  larva  of  the  hessian  fly  by  the  fact  that 
it  works  in  the  center  of  the  stem  and  crawls  actively  when  removed. 
For  a  detailed  account  of  this  species  see  Aldrich  ('20). 

This  family  is  named  the  Oscinidae  by  some  writers. 

The  family  ASTEIID^^E  includes  a  few  genera,  mostly  exotic, 
that  were  formerly  classed  in  the  Drosophilidae  by  some  writers  and 
in  the  Chloropidae  (Oscinidae)  by  others;  it  can  be  separated  from 
these  families  by  the  characters  given  in  Table  B .  The  best-known 
representative  of  the  family  in  our  fauna  is  Sigaloessa  flaveola,  which 
is  widely  distributed  in  the  Atlantic  states. 

Family  DROSOPHILIDAE 

The  Pomace-flies  and  their  Allies. 

There  are  certain  small  yellowish  flies  from  three  to  four  milli- 
meters in  length  which  are  very  common  about  the  refuse  of  cider- 
mills,  decaying  fruit,  and  fermenting  vats  of  grape  pomace;  these  are 
the  pomace-flies  (Fig.  11 12);  their  larvae  live  in  the  decaying  fruit. 


DIPTERA 


861 


1 1 12. — A   pomace-fly. 


The  pomace-flies  and  their  alHes  constitute  the  family  Drosophil- 
idae.  In  this  family  the  costa  is  microscopically  broken  twice,  once 
just  beyond  the  htmieral  cross-vein 
and  again  just  before  the  end  of  vein 
Ri ;  the  subcostal  vein  is  vestigial ;  the 
arista  are  almost  invariably  plu- 
mose; the  vibrissa;  are  present;  the 
postvertical  bristles  are  convergent ; 
and  the  foremost  fronto-orbital 
bristles  are  proclinate. 

The  larvae  of  most  species  6f  this 
family,  so  far  as  is  known,  live  in 
decaying  fruit  or  in  fungi ;  a  few  are 
leaf-miners;  and  some  exotic  species  have  been  found  feeding   on 
other  insects,  Aleurodes  and  Clastoptera. 

One  of  the  pomace-flies,  Drosophila  melanogdster,  which  is  easily 
bred  and  which  has  a  short  life-cycle,  is  widely  used  in  laboratories  in 
the  study  of  heredity.  This  species  has  been  commonly  known  as 
Drosophila  ampelophila;  but  melanogaster  is  the  older  specific  name. 

A  monograph  of  this  family  was  published  by  Sturtevant  ('21). 

The  family  GEOMYZID^  is  a  group  of  small  flies  of  which 
nearly  fifty  species  have  been  described  from  our  fauna.  In  these 
flies  the  postvertical  bristles  are  convergent  when  present ;  the  clypeus 
is  large,  the  foremost  fronto-orbital  bristles  are  directed  backward; 
and  the  fringe  of  the  calypteres  is  not  dense. 

The  larvae  of  the  few  species  of  which  the  habits  are  known  live 
in  the  stems  of  plants  or  mine  in  leaves. 

The  family  was  monographed  by  Melander  ('13  b). 


Family  AGROMYZID^ 


Fig.  1 1 13. — ]\Iine  of  Phytomyza  aquil- 
egia. 

sites  of  the  cotton v-cush ion  scale. 


This  family  includes  small  or 
minute  flies  in  which  the  costa  is 
broken  only  at  the  end  of  the 
subcostal  vein;  the  oral  vibrissee 
are  present,  the  arista  of  the  an- 
tenna? is  closely  short-pubescent, 
the  post-vertical  bristles  are  di- 
vergent, and  the  lower  fronto- 
orbital  bristles  are  convergent. 

The  genus  Cryptochcetum  dif- 
fers from  the  typical  members  of 
this  family  in  having  the  costa 
twice  broken  and  in  that  the  an- 
tennae lack  the  arista.  One  or 
two  species  of  this  genus  have 
been  introduced  into  California 
from  Australia,  as  they  are  para- 


862  AN  INTRODUCTION  TO  ENTOMOLOGY 

About  one  hundred  species  of  the  Agromyzidae  as  restricted  here 
have  been  described  from  our  fauna.  See  monograph  of  the  family 
by  Melander  ('13  6). 

vSo  far  as  is  known  the  larvae  of  most  members  of  this  family  feed 
on  living  plants  by  forming  burrows  or  mines  in  various  parts  of 
them,  but  principally  in  the  leaves.  A  common  species,  Phyiomyza 
aquilegicB,  makes  serpentine  mines  in  the  leaves  of  wild  columbine. 
Aquilegia  canadensis.     (Fig.  11 13). 

^  The  family  MILICHIID^  is  a  small  group  of  flies  that  is  often 
classed  with  the  Agromyzidae.  The  members  of  this  family  differ 
from  the  agromyzids  in  that  the  costa  is  broken  twice,  once  be- 
yond the  humeral  cross-vein  at  which  place  there  is  usually  a 
stronger  costal  bristle,  and  again  just  before  the  end  of  vein  Ri,  and 
the  postvertical  bristles  are  convergent.  See  monograph  of  this 
family  by  Melander  ('13  h). 

The  family  OCHTHIPHILID^E  is  also  a  small  group  of  flies 
which  is  often  classed  with  the  Agromyzidae.  In  this  family  the 
oral  vibrissae  are  wanting  or  not  differentiated;  the  postvertical 
bristles  convergent,  the  subcostal  vein  ends  in  the  costa;  and  the 
clypeus  is  small.  See  monograph  of  the  familv  bv  Melander 
('13  h). 

Only  thirteen  species,  representing  three  genera,  are  recognized 
by  Melander  from  our  fauna. 

Larvae  of  species  of  Leucopis  prey  upon  aphids  and  upon  coccids. 

This  family  is  named  the  Chamasyidse  by  Hendel  ('22). 

SUBSECTION  II.— CALYPTRAT^ 

The  Calyptrate  Muscids 

To  this  subsection  belong  our  most  familiar  representatives  of  the 
muscid  flies,  of  which  the  house-fly  and  the  flesh-flies  are  good  illus- 
trations. In  the  families  included  here  the  alulae  or  clypteres  are 
well  developed  or  of  moderate  size,  not  rudimentary;  the  subcostal 
vein  is  always  distinct  in  its  whole  course ;  vein  Ri  is  never  very  short ; 
there  is  a  complete  transverse  suture  on  the  thorax;  the  postalar 
callus  is  present  and  separated  by  a  distinct  suture  from  the  dorsum 
of  the  thorax;  and  the  abdominal  spiracles,  with  but  few  exceptions, 
are  in  the  chitin.  The  flies  are  usually  of  moderate  or  considerable 
size,  never  very  small. 

The  subsection  Cahptrats  includes  a  series  of  families  that 
are  exceedingly  difficult  to  differentiate.  In  fact  no  two  of  the  author- 
ities on  this  group  of  flies  agree  either  as  to  the  number  of  families 
that  should  be  recognized  or  as  to  the  limits  of  certain  families  that 
are  generally  recognized.  This  is  believed  to  be  due  to  the  fact  that 
this  group  of  flies  is  of  recent  origin  and  the  different  types  included 
in  it  have  not  become  segregated  by  the  dropping  out  of  intermediate 
forms.  It  is  the  dominant  group  of  flies,  including  an  immense  num- 
ber of  species. 


DIPTERA 


863 


Family  ANTHOMYIID^ 

The  Anthomyiids 

The  anthomyiids  are  very  common  flies  of  which  about  five  hun- 
dred species  have  been  described  from  North  America.  They  are 
somewhat  similar  to  the  house-fly  in  appearance  but  structurally 
distinct. 

In  this  family  cell  R5  of  the  wings  is  very  slightly  or  not  at  all 
narrowed,  vein  Mi +2  extending  in  a  nearly  straight  line  to  the  margin 
of  the  wing  (Fig.1114)  and  not  bent  in  its  outer  part  towards  the  tip 
of  the  vein  R4+5  as  in  the  house-fly.  Both  the  hypopleural  and  the 
pteropleural  bristles  are  absent ;  and  the  proboscis  is  never  adapted 


Fig. 


[4. — Wing  of  Lis  pa. 


for  bloodsucking.  The  adult  flies  are  found  on  leaves  and  flowers, 
and  are  also  often  found  on  windows  in  our  dwellings. 

The  larval  habits  are  variable.  Most  species  live  in  decaying 
vegetable  matter;  many  live  in  excrement,  and  doubtless  are  convey- 
ers of  typhoid  fever,  like  the  house-fly  or  typhoid-fly.  Several  species 
have  been  found  to  be  the  cause  of  internal  myiasis,  having  been 
taken  into  the  alimentary  canal  with  vegetables  and  continuing  to 
live  there.  A  few  species  are  parasitic  within  living  insects.  And 
some  attack  growing  plants.  Among  the  latter  are  certain  well- 
known  pests  of  garden  crops.  The  more  important  of  these  are  the 
following. 

The  cabbage-root  maggot,  Hylemyia  brassicce.- — This  insect  in  its 
larval  state  feeds  on  the  roots  of  cabbage,  radish,  turnip,  and  cauli- 
flower; it  also  attacks  the  roots  of  various  weeds  belonging  to  the 
same  family  of  plants.  There  are  two  or  more  generations  of  this 
pest  each  year.  The  first  generation  infests  the  young  plants;  the 
eggs  of  the  second  generation  are  laid  late  in  June  or  in  July;  later 
generations,  if  they  occur,  do  but  little  harm. 

The  most  practicable  methods  of  control  of  this  pest  are  to  protect 
the  seed-beds  with  a  covering  of  cheesecloth  in  order  to  exclude  the 


864  AN  INTRODUCTION  TO  ENTOMOLOGY 

flies;  to  protect  the  plants  when  they  are  set  out  by  fitting  around  the 
stem  of  each  next  to  the  ground  a  tarred  paper  card,  these  cards  can 
be  obtained  from  seedsmen  and  dealers  in  garden  supplies;  and  by 
the  use  of  a  solution  of  corrosive  sublimate  crystals,  one  ounce  dis 
solved  in  ten  gallons  of  water.  Two  applications  of  one-half  cupful 
to  a  plant  are  made,  one,  three  or  four  days  after  the  plants  are  set, 
and  another  eight  or  ten  days  later.  The  solution  is  poured  on  the 
stem  and  at  the  base  of  the"  plant.  Great  care  should  be  taken  to 
keep  the  supply  of  this  poison  where  children  or  animals  can  not 
get  it. 

The  or).\onm.a.ggot,  Hylemyia  antlqua.— The  larva  of  this  species  is 
often  exceedingly  destructive  to  onions,  destroying  young  plants  in 
the  spring,  and  when  the  plants  are  older,  burrowing  into  the  bulb 
and  causing  decay.  This  species  is  difficult  to  control.  As  the  flies 
require  from  ten  days  to  two  weeks  after  emergence  in  which  to 
mature  their  eggs,  many  of  them  can  be  destroyed  before  they  are 
ready  to  oviposit  by  a  poisoned  bait  spray  composed  of  one-fifth  ounce 
sodium  arsenite,  one  pint  molasses,  and  one  gallon  water.  There  are 
two  or  three  generations  annually  of  this  pest. 

The  raspberry-cane  maggot,  Hylemyia  rulnvora. — The  larva  of 
this  species  burrows  in  the  new  canes  of  black  and  red  raspberries  and 
blackberries  and  kills  them.  The  eggs  are  laid  on  the  young  shoots  in 
the  spring.  The  lar\^a  bores  into  the  pith  of  the  shoot,  and  tunnels 
downward;  when  about  half  way  to  the  groimd  it  girdles  the  wood 
beneath  the  bark.  The  part  of  the  shoot  above  the  girdle  soon  wilts, 
shrinks  in  size  and  droops  over.  The  larva  continues  its  burrow 
downward  in  the  pith  to  the  surface  of  the  ground,  transforms  to  a 
pupa  without  leaving  its  burrow  in  late  June  or  early  July;  but  the 
adult  does  not  emerge  till  the  following  April.  To  check  the  ravages 
of  this  pest,  cut  off  and  burn  the  wilting  canes  as  soon  as  observed. 

The  beet  or  spinach  leaf-miner,  Pegomyia  hyoscyami. — -This  leaf 
miner  infests  the  leaves  of  beets,  sugar-beets,  spinach,  orach,  mangels, 
and  chard.  The  mine  at  first  is  thread-like  but  is  soon  enlarged  to 
form  a  blotch.  Several  larvae  usually  occupy  the  same  leaf  and  their 
mines  usually  coalesce.  There  are  several  generations  each  year,  and 
the  winter  is  passed  in  the  pupal  state  under  fallen  leaves  in  the  soil. 
Where  practicable  the  infested  leaves  should  be  picked  and  burned. 
By  plowing  the  field  deeply  as  soon  as  the  crop  is  removed  the  over- 
wintering pupae  can  be  buried . 

The  kelp-flies,  Fncellia. — The  larvae  of  these  flies  live  in  brown 
sea-weeds,  cast  up  by  waves  along  ocean  beaches.  The  adults  can  be 
found  all  simimer  long  on  the  masses  of  these  weeds  often  in  immense 
numbers.  The  North  American  species,  of  which  thirteen  are  known, 
were  monographed  by  Aldrich  ('i8). 

Family  GAvSTROPHILID^ 

The  Bot-flies  of  Horses 
This  family  includes  the  well-known  pests  the  larvae  of  which 
infest  the  alimentary  canal  of  horses  and  which  are  commonly  known 


DIPTERA 


865 


as  bots.  These  insects  constitute  the  genus  Gastrophilus,  three  species 
of  which  are  now  well  established  in  the  United  States  and  Canada. 
In  the  adult  flies  the  oral  opening  is  small  and  the  proboscis  vestigial. 
The  members  of  this  genus  can  be  distinguished  from  those  of  the 
following  family  by  the  venation  of  the  wings ;  the  most  striking  fea- 
ture of  which  is  that  vein  Ml +2  extends  in  a  nearly  straight  line  towards 
the  margin  of  the  wing  (Fig.  1115). 


Fig.  1 1 15. — Wing  of  Gastrophilus. 


The  genus  Gastrophilus  has  been  commonly  included  in  the  family 
CEstridag  but  it  is  now  believed  to  represent  a  distinct  line  of  develop- 
ment. The  three  species  that  are  established  in  this  countr}^  are  the 
following. 

The  common  bot-fly  or  the  stomach  bot,  Gastrophilus  intestindlis . 
— The  adult  fly  closely  resembles  the  honey-bee  in  fonn  except  that 
the  female  (Fig.  11 16)  has  the  end  of  the  abdomen 
elongate  and  bent  forward  under  the  body.  The  wings 
are  transparent  with  dark  spots,  those  near  the  center 
form  an  irregular,  transverse  band.  This  fly  is  most 
often  seen  flying  about  horses,  which  have  an  instinctive 
fear  of  it.  The  eggs  are  laid  on  different  parts  of  the 
host,  but  preferably  on  the  long  hairs  investing  the 
inside  of  the  forelegs.  The  eggs  rarely  hatch  when  left 
untouched;  but  the  horse  by  scratching  the  forelegs 
with  the  teeth  removes  the  small  cap  of  the  egg-shell  and  inadvert- 
ently takes  the  larva  into  its  mouth.  The  larvae  thus  taken  into  the 
mouth  are  carried  with  the  food  or  water  to  the  stomach.  When  the 
larvae  reach  the  stomach  they  fasten  themselves  to  the  inner  coat  of 
it,  and  remain  there  until  full-grown.  Then  they  pass  from  the 
animal  with  the  dung,  and  crawl  into  some  protected  place,  where 
they  transform  within  a  puparium.  The  adult  fly  measures  about 
18  mm.  in  length.  This  species  is  found  throughout  the  United 
States  and  Canada  where  horses  are  present.  It  has  been  commonly 
known  as  Gastrophilus  equi,  but  intestinalis  is  the  older  specific  name. 


866  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  chin-fly  or  the  throat-bot,  Gastrophilus  nasdlis. — This  species 
is  smaller  than  the  common  bot-fly  and  the  wings  are  not  marked 
with  dark  spots  as  in  that  species.  The  female  usually  deposits  its 
eggs  upon  hairs  under  the  jaws,  and  for  this  reason  is  commonly 
known  as  the  chin-fly ;  but  sometimes  the  eggs  are  laid  upon  the  flanks 
or  forelegs  of  the  host.  The  manner  in  which  the  larv«  reach  the 
mouth  of  the  horse  has  not  been  definitely  determined;  but  having 
reached  the  mouth  they  are  carried  down  the  alimentary  canal.  In 
some  cases  the  larvas  attach  themselves  to  the  pharynx,  and  as  this 
is  the  only  species  that  is  known  to  do  this,  the  larva  is  known  as 
the  throat-bot.  But  this  species  is  sometimes  found  in  the  stomach, 
and  it  attaches  by  preference  in  the  duodenimi.  When  the  larvag 
are  matured  they  pass  out  from  the  horse  and  burrow  in  the  manure 
or  soil  to  transform. 

This  species  is  widely  distributed  in  the  United  States  and  Canada. 

The  red-tailed  bot-fly  or  the  nose-fly,  Gastrophihis  hceniorrhoiddlis . 
■ — The  adult  fly  is  easily  distinguished  by  the  bright  orange-red  tip  of 
the  abdomen.  The  wings  are  unspotted  as  in  the  chin-fly  but  differ 
from  those  of  both  of  the  preceding  species  in  that  the  cross-vein 
m-cu  is  much  farther  from  the  base  of  the  wing  than  is  cross-vein  r-m. 
The  female  oviposits  on  the  lips  of  the  horse;  the  flight  of  the  fly 
about  the  nose  of  the  horse  when  attempting  to  oviposit  on  its  lips, 
suggested  the  common  name,  the  nose-fly.  The  larvae  of  this  species 
attach  themselves  during  their  early  stages  within  the  stomach ;  but 
later  loosen  themselves  and  reattach  in  the  rectum,  from  which  they 
gradually  move  to  the  anus,  where  they  remain  for  a  short  time  before 
dropping  to  the  ground  to  transform. 

This  species  is  found  in  the  North-Central  and  Northern  Rocky 
Mountain  vStates  and  in  the  western  provinces  of  Canada. 

Family  CESTRID^ 
Bot-Flies  {except  Gastrophilus)  and  Warble-Flies 

This  family  includes  flies  that  are  large  or  of  mediimi  size ;  most 
of  the  species  resemble  bees  in  appearance;  some,  the  honey-bee, 
others,  bimiblebees.  The  mouth-opening  is  small,  and  the  mouth- 
parts  are  usually  vestigial.  The  venation  of  the  wings  differs  from 
that  of  the  preceding  family  in  that  vein  Mi +2  is  bent  so  that  cell  R5 
is  much  narrowed  or  closed  at  the  margin  of  the  wing. 

The  larvce  are  parasitic  upon  mammals ;  some  develop  in  tumors 
under  the  skin  and  others,  in  the  pharyngeal  and  nasal  cavities  of 
their  hosts.  As  a  rule  each  species  infests  a  single  species  of  mammal ; 
and  closely  alHed  oestrids  are  parasitic,  in  a  similar  manner,  upon 
closely  allied  mammals.  In  addition  to  the  species  that  infest  our 
domestic  animals,  other  species  infest  rabbits,  squirrels,  deer,  and 
reindeer.  One  that  lives  beneath  the  skin  of  the  neck  of  rabbits  is 
very  common  in  the  South. 


DIPTERA  867 

The  sheep  bot-fly,  Oestrus  ovis. — This  species  is  viviparous;  the 
female  fly  deposits  larvae,  which  have  hatched  within  her  body,  in 
the  nostrils  of  sheep.  The  larvse  pass  up  into  the  frontal  sinuses  and 
into  the  horns  when  they  are  present.  Here  they  feed  upon  the  mucus. 
They  are  very  injurious  to  sheep,  causing  vertigo  or  the  disease  known 
as  "staggers."  When  full-grown  they  pass  out  through  the  nostrils 
and  undergo  their  transformations  beneath  the  surface  of  the  ground. 

The  ox-warble-flies,  Hypoderma  bovis  and  Hypoderma  Unedtum.- — • 
If  during  the  later  winter  months  the  backs  of  cattle  be  examined  by 
rubbing  the  hand  over  them,  there  will  be  found  present  in  many 
cases  small  limips  or  swellings  in  each  of  which  there  is  an  opening 
through  the  skin;  these  swellings  are  known  as  warbles,  and  each 
contains  a  maggot,  which  when  full  grown  measures  nearly  or  quite 
25  mm.  in  length. 

The  maggots  that  produce  these  warbles  are  the  larvae  of  flies, 
which  for  this  reason  are  known  as  warble-flies.  Two  species  of 
warble-flies  both  of  which  were  introduced  from  Europe,  infest  cat- 
tle in  this  country,  and  are  very  serious  pests. 

The  warble-flies  when  attempting  to  oviposit  annoy  cattle, 
which  have  an  instinctive  fear  of  them  and  run  about  in  an  effort  to 
escape  them ;  this  leads  to  decreased  milk  yield.  The  larvse  as  para- 
sites injuriously  affect  the  health  of  the  cattle.  And  the  holes  in  the  skin 
through  which  the  larvae  escape  from  the  warbles  very  seriously 
reduce  the  value  of  the  hide  when  made  into  leather.  A  careful 
estimate  made  by  the  Department  of  Agriculture  of  Canada  showed 
that  the  annual  loss  in  value  of  hides  in  Canada  due  to  warbles  is 
between  25  and  30  per  cent,  of  the  total  value  of  the  hides. 

Our  two  species  of  warble -flies  have  much  in  common.  The 
adults  measure  from  12  to  14  mm.  in  length  and  are  bumblebee-like 
in  appearance.  They  attach  their  eggs  to  hairs  of  cattle,  usually  on 
the  hind  legs,  more  rarely  on  the  flanks.  The  newly  hatched  larva 
crawls  down  to  the  hair  follicle  where  it  penetrates  the  skin.  Later 
the  second  instar  of  the  larva  is  found  in  the  wall  of  the  oesophagus. 
The  exact  course  of  the  migration  from  the  hind  legs  to  the  oesophagus 
has  not  been  determined;  but  it  is  believed  that  the  larvae  travel  in 
the  loose  connective  tissues  under  the  skin  to  the  region  of  the 
throat  and  into  the  oesophagus  where  the  muscles  bifurcate.  This 
part  of  their  migration  occupies  about  four  months.  They  remain 
in  the  oesophagus  about  three  months,  and  then  migrate  to  the 
lumbar  region.  This  part  of  the  migrations  of  the  larv£e  is  better- 
known  than  the  earlier  part.  Hadwen  ('19)  states  as  follows:  "The 
last  larvae  to  leave  the  oesophagus  are  at  the  paunch  end.  They  pass 
out  under  the  pleura  and  go  to  the  neural  canal,  either  up  the  crura 
of  the  diaphragm,  or  up  the  posterior  border  of  the  ribs  entering  the 
canal  by  the  posterior  foreamen.  The  larva  evidently  makes  use  of 
the  canal  as  an  easy  means  of  access  to  the  lumbar  region,  the  part  of 
of  the  animal  which  is  best  suited  for  passing  its  last  stages  within  the 
host.  The  larvae  follow  connective  tissue  exclusively , no  larva}  have  been 
discovered  in  muscular  tissue." 


S68  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  larvae  complete  their  growth  in  the  lumbar  region,  causing  as 
they  increase  in  size  the  formation  of  the  warbles.  The  hole  through 
the  skin  into  the  cavity  of  the  warble  serves  as  a  breathing  hole  for 
the  larva  and  as  a  means  of  escape  when  it  is  full-grown.  The  mature 
larvae  leave  the  warbles  and  drop  to  the  ground  to  transform.  This 
takes  place  during  the  first  half  of  the  year.  The  average  pupal 
period  is  about  one  month.  The  adults  live  only  a  short  time  as 
they  are  unable  to  feed. 

The  above  account  refers  to  both  of  our  species  of  warble-fiies ; 
the  following  details  chiefly  compiled  from  Hadwen  ('19)  will  serve 
to  distinguish  the  two. 

The  bomb-fly,  Hypoderma  hovis. —  The  adult  fly  measures  14  mm. 
in  length;  there  is  yellow  hair  on  the  anterior  part  of  the  thorax; 
the  alulae  are  bordered  with  reddish  brown;  and  the  tail  end  of  the 
abdomen  is  orange-yellow.  As  a  rule  the  flies  lay  their  eggs  while 
the  cattle  are  running;  the  eggs  are  laid  singly  at  the  roots  of  the 
hairs ;  the  flies  are  clumsy  insects  and  strike  at  the  animals  blunder- 
ingly. The  presence  of  one  of  these  flies  in  a  herd  of  cattle  causes 
them  to  scatter  and  stampede  just  as  a  crowd  of  people  would  do  if 
a  bomb  were  thrown  in  their  midst.  For  this  reason  Mr.  R.  C.  Shan- 
non ('22)  has  suggested  "bomb-fly"  as  a  common  name  for  this 
species.  The  name  "European  warble-fly"  that  is  often  applied  to 
it  is  not  distinctive,  as  both  of  our  species  are  of  European  origin. 
The  eggs  are  laid  mostly  on  the  outside  of  the  hind  quarters  and  on 
the  legs  above  the  fetlocks;  they  are  laid  during  June  and  July.  In 
the  larva  the  segment  in  front  of  the  spiracular  segment  is  unarmed. 

The  heel-fly,  Hypoderma  linedtum.- — The  adult  fly  is  12.7  mm.  in 
length ;  the  anterior  part  of  the  thorax  is  black  and  shining ;  the  alulae 
are  uniformly  white;  and  the  tail  end  of  the  abdomen  is  reddish- 
orange.  The  eggs  are  laid  mostly  when  the  animals  are  recumbent 
and  on  all  parts  which  the  fly  can  reach  when  it  is  resting  on  the 
ground.  Even  when  the  animals  are  standing  the  fly  is  able  to  lay 
eggs  on  those  hairs  which  are  close  to  the  ground,  namely  on  the 
heels.  The  frequency  with  which  this  species  lays  its  eggs  in  this 
place  has  caused  it  to  be  known  as  the  heel-fly.  This  species  irritates 
the  cattle  much  less  than  does  Hypoderma  hovis,  and  consequently 
is  able  to  lay  several  eggs  on  a  single  hair.  The  eggs  are  usually  laid 
during  May.  In  the  larva  the  segment  in  front  of  the  spiracular  seg- 
ment is  spinose. 

Family  PHASIID^ 

The  Phasiids 

This  is  a  comparatively  small  family,  which  is  composed  of  certain 
genera  that  were  formerly  included  in  the  Tachinidae  but  which  are 
now  regarded  as  representatives  of  a  distinct  branch  of  the  Muscoidea. 

In  this  family  the  clypeus  is  more  or  less  produced  below  the 
vibrissal  angles,  like  the  bridge  of  a  nose.     The  conjunctivae  of  the 


DIPTERA  SG9 

ventral  scleritcs  of  the  abdomen  are  present,  and  frequently  well- 
developed,  surroimding  the  sclerites.  Vein  M1+2  is  bent  so  that  cell 
R5  is  narrowed  or  closed  at  the  margin  of  the  wing;  in  some  genera 
vein  Ml +2  joins  R^+r.  at  a  considerable  distance  before  the  margin  of 
the  wing.    The  abdomen  is  not  armed  with  macrocha?ta\ 

There  are  only  a  few  records  regarding  the  habits  of  members  of 
this  family.  Some  species  are  parasitic  on  adult  Coleoptera,  and 
other  on  n}TTiphs  and  adults  of  Hemiptera. 

Family  MEGAPROSOPID/E 

This  is  a  small  group  of  flies  the  rank  of  which  is  in  question ;  some 
authorities  regard  it  as  a  distinct  family  and  others,  as  a  subfamily 
of  the  Tachinidce.  With  these  flies  the  clypeus  is  receding  and  short; 
the  cheeks  are  very  broad;  the  vibrissa?  are  located  near  the  middle 
of  the  face;  and  the  antenna?  are  short. 

This  family  is  represented  in  our  fauna  by  two  genera,  Mega- 
prosdpus  and  Microphthdhna.  Microphthabna  disjuncta  has  been  bred 
from  the  larva  of  Phyllophaga  arciidta. 

Family  CALLIPHORID^ 

The  Blow-fly  Family 

Certain  members  of  this  family  are  very  familiar  objects  and  are 
commonly  known  as  blow-flies,  bluebottle-flies,  or  greenbottle-fiies. 
With  these,  and  with  most  other  members  of  the  family  as  well,  the 
body,  especially  the  abdomen,  is  metallic  blue  or  green  in  color. 
This  fact  has  suggested  the  common  names  bluebottle-flies  and 
greenbottle-flies,  that  have  been  applied  to  certain  species.  These 
names,  however,  merely  indicate  in  each  case  the  more  usual  color  of 
the  species;  for  in  all  of  the  metallic  colored  species  of  this  family 
the  color  varies;  it  may  be  either  violet,  green,  blue,  or  copper  color. 

In  this  family  the  arista  of  the  antennas  is  plirmose ;  both  the  hypo- 
pleural  and  the  i^teropleural  bristles  are  present;  the  hindermost 
posthumeral  bristle  is  almost  always  more  ventrad  in  position  than 
the  presutural  bristle ;  and  the  second  ventral  sclerite  of  the  abdomen 
lies  with  its  edges  upon  or  in  contact  with  the  ventral  edges  of  the 
corresponding  dorsal  sclerites. 

The  larvae  of  the  different  species  vary  in  habits;  some  have  been 
bred  from  cow-dung;  some  feed  on  fresh  or  decaying  meat  and  on 
the  bodies  of  dead  animals;  one  frequently  infests  wounds  on  animals, 
and  two  are  blood-sucking  parasites  of  nestling  birds.  The  following 
are  our  best-known  species. 

The  blow-flies  Calllphora. — The  blow-flies  normally  live -out-of- 
doors,  but  they  often  enter  houses  in  search  of  material  upon  which 
to  deposit  their  eggs.  They  then  attract  attention  by  their  large 
size,  much  larger  than  that  of  the  house-fly,  and  by  the  buzzing  noise 
that  they  make.    They  lay  their  eggs  upon  meat,  cheese,  and  other 


870  AN  INTRODUCTION  TO  ENTOMOLOGY 

provisions.  The  eggs  soon  hatch  and  the  larvee  develop  rapidly. 
There  are  several  species  of  this  genus  in  our  fauna ;  all  of  them  have 
reddish  palpi;  bluish  black,  opaque  thorax;  metallic  blue  or  green, 
more  or  less  whitish  pollinose  abdomen;  two  or  three  posthimieral 
bristles;  and  black  legs.  There  are  two  common  species  Calltphora 
erythrocephala,  in  which  the  bucca  is  reddish  brown  and  the  beard 
black ;  and  Calltphora  vomitdra,  in  which  the  bucca  is  black  and  the 
beard  reddish. 

The  large  bluebottle-fly,  Cynomyia  cadaverlna. — This  is  a  com- 
mon species  which  resembles  the  blow-flies  in  size  and  in  habits;  it 
differs  from  them  in  that  the  abdomen  is  without  silvery  pruinosity, 
and  there  is  only  one  posthumeral  bristle  on  each  side. 

The  greenbottle-fly,  Luctlia  ccBsar. — This  also  is  a  common  species, 
which  resembles  the  blow-flies  in  habits;  but  it  is  smaller  and  its 
cheeks  are  bare.  The  abdomen  is  sometimes  bluish  but  more  often 
greenish. 

The  screw-worm  fly,  Chrysomyia  macelldria.- — This  is  a  bright 
metallic-green  fly,  with  "three  black  stripes  on  the  thorax,  and  a  yellow 
face.  It  measures  from  8  to  lo  mm.  in  length.  It  lays  its  eggs  on 
decaying  animal  matter  and  also  in  wounds,  sores,  and  the  nostrils 
and  ears  of  men  and  cattle.  The  larvse  living  in  these  situations  often 
cause  serious  sickness,  and  sometimes  even  death.  This  is  a  widely 
distributed  species ;  but  it  has  attracted  most  attention  in  the  South- 
western States  where  it  is  a  serious  pest  of  stock. 

The  cluster-fly,  Pollenia  rudis: — The  cluster-fly  is  so-called  be- 
cause of  its  habit  of  entering  houses  in  the  autumn  and  hiding  away 
in  protected  nooks  in  large  groups  or  clusters.  It  is  a  dark  colored, 
slow-moving  species,  slightly  larger  than  the  house-fly.  The  thorax 
is  thickly  beset  with  soft  woolly  hair  in  addition  to  the  bristles;  the 
abdomen  is  brown  with  white  pollinose  spots. 

The  calliphorid  parasites  of  nestling  birds,  ProtocalUphora.- — Two 
species  of  this  genus  occur  in  our  fauna,  P.  aziirea  and  P.  chrysorrhea. 
Both  of  these  have  been  found  to  be  external  blood-sucking  parasites 
of  nestling  birds,  often  causing  the  death  of  the  nestlings.  Plath  ('19) 
found  that  of  63  nests  of  five  species  of  birds  studied  by  him  39  were 
infested,  chiefly  by  P.  azurea. 

Family  SARCOPHAGID.^ 

The  Sarcophagids 

This  family  has  been  commonly  known  as  the  flesh-flies  because 
some  of  them  lay  their  eggs  in  bodies  of  dead  animals,  resembling  in 
habits  the  blow-fly,  which  belongs  to  the  family  Calliphorid^ ;  but 
a  wider  knowledge  of  the  habits  of  various  members  of  this  familv 
shows  that  this  name  is  misleading. 

The  Sarcophagida?  as  limited  by  Aldrich  ('16)  in  his  monograph 
of  the  North  American  species  includes  all  of  the  Muscoidea  that 
agree  in  having  the  following  characteristics :  The  coloration  is  gray 


DIPTERA  871 

or  silvery,  tessellated  or  changeable  pollinose ;  vein  Mi +2  has  an  almost 
angular  bend  and  ends  considerably  before  the  apex  of  the  wing; 
the  sides  of  the  face  are  hairy ;  and  the  arista  of  the  antennre  is  plumose 
above  and  below  for  nearly  half  its  length  or  a  little  more.  None  of 
the  species  has  discal  machrochaetas  on  the  abdominal  segments, 
hairy  eyes,  long  proboscis,  rudimentary  palpi,  or  more  than  a  single 
pair  of  discal  scutellar  bristles. 

So  far  as  is  known  all  species  of  this  family  are  larviparous.  The 
different  species  show  a  wide  range  in  larval  habits;  but  by  far  the 
greater  nimiber  of  the  species  that  have  been  bred  are  parasitic  in 
other  arthropods.  They  have  been  bred  from  various  insects,  from 
scorpions,  and  from  the  egg-sacs  of  spiders.  Several  species  have 
been  bred  from  dead  fish ;  and  a  considerable  number  from  the  excre- 
ment of  mammals.  Five  or  six  species  live  only  in  the  tubular  cups 
of  pitcher-plants  (Sarracenia),  feeding  on  the  dead  insects  found 
there.  It  has  been  found  that  Sarcophaga  hmnorrhoiddlis  is  some- 
times the  source  of  intestinal  myiasis  in  man,  and  several  cases  of 
cutaneous  myiasis  caused  by  larv«  of  Wohljdhrtia  vigil  have  been 
described  by  Walker  ('22  a). 

For  the  determination  of  species  of  this  family  one  should  consult 
the  monograph  by  Aldrich  ('16). 

Family  TACHINID^ 
The  Tachina-Flies 

The  tachina-fiies  are  often  found  about  flowers  and  rank  vege- 
tation. They  are  usually  short,  stout  and  bristly  (Fig.  11 17).  They 
differ  from  the  following  family,  the  Mus- 
cidse,  in  that  with  the  tachina-flies  both 
the  hypopleural  and  the  pteropleural 
bristles  are  present ;  and  they  differ  from 
the  two  preceding  families,  the  Calliphor- 
idae  and  the  Sarcophagidee,  in  that  in  this 
family  the  second  ventral  abdominal 
sclerite,  as  well  as  the  others,  is  more  or 
less  covered,  sometimes  wholly,  by  the 
edges  of  the  dorsal  sclerites. 

This  is  a  very  large  family,  more  than      p.  ^ \     t    i  • 

fourteen  hundred  species  are  listed  from  'Lrva,'' adult,  puparium; 
North  America  alone;  and  from  the  and  eggs  upon  the  fore 
standpoint  of  the  agriculturist  it  is  the  part  of  an  army-worm. 
most  beneficial  family  of  the  Diptera. 

This  family  includes  two  subfamilies;  the  Dexiinas,  and  the 
Tachininae,  each  of  which  is  regarded  as  a  separate  family  by  some 
writers. 

The  larvae  are  parasitic,  chiefly  within  caterpillars,  but  they  have 
been  bred  from  members  of  several  other  orders  of  insects.  An  ex- 
tended list  of  tachinid  parasites  and  their  hosts  is  given  by  Coquillett 


872  AN  INTRODUCTION  TO  ENTOMOLOGY 

('97).  The  manner  in  which  the  larva  finds  its  way  into  the  body  of 
its  host  differs  greatly  in  different  species  of  tachinids.  Many  obser- 
vations on  this  have  been  made  at  the  Gipsy  Moth  Laboratory  and  re- 
ported by  Townsend  ('08  b).  In  many  species  the  female  fastens 
her  eggs  to  the  skin  of  the  caterpillar  "(Fig.  11 17);  when  the  larvae 
hatch  they  bore  their  way  into  their  host  and  live  there  till  they  are 
full-grown.  In  some  of  the  viviparous  species  the  female  punctures 
the  skin  of  the  caterpillar  with  the  sheath  of  her  ovipositor  and  de- 
posits the  larva  within  the  body  of  the  host.  Some  species  deposit 
their  eggs  on  the  leaves  of  the  food-plant  of  their  host ;  these  eggs  are 
swallowed  when  the  leaves  are  eaten.  But  most  remarkable  of  all  is 
the  method  practiced  by  Eupeleteria  magnicornis ;  this  is  a  viviparous 
species  which  infests  the  larva  of  the  brown-tail  moth.  It  attaches 
its  larvae  to  the  surface  of  stems  and  leaves  by  a  thin  membranous 
case,  which  is  cup-shaped  and  surrounds  the  anal  end  of  the  larva. 
Attached  to  the  stem  or  leaf  by  this  base,  the  maggot  is  able  to  reach 
out  in  all  directions  as  far  as  its  length  will  permit.  As  the  maggot 
is  deposited  on  the  silken  thread  with  which  the  caterpillar  marks 
its  trail  as  it  leaves  its  nest,  it  is  in  a  position  where  it  can  attach  itself 
to  the  caterpillar  when  it  is  on  its  way  back  to  the  nest. 

Family  MUSCID^ 
The  Typical  Muscids 

To  this  family  belong  the  house-fly  and  many  other  well-known 
members  of  the  Muscoidea.  In  this  family  either  the  hypopleural 
or  the  pteropleural  bristles  are  present,  the  basal  bristles  of  the  ab- 
domen are  reduced,  and  the  arista  of  the  antennae  are  plimiose  to  the 
tip.    Among  the  more  important  species  are  the  following. 

The  house-fly  or  typhoid-fly,  Musca  domestica.- — This  is  the  most 
familiar  representative  of  the  order  Diptera,  as  it  abounds  in  our 
dwellings.  The  flies  lay  their  eggs  preferably  on  horse-manure,  but 
will  oviposit  on  other  decaying  vegetable  matter,  when  horse-manure 
is  not  available.  A  single  female  may  deposit  from  120  to  160  eggs 
at  one  laying,  and  they  have  been  observed  to  make  as  many  as  four 
layings.  The  larvas  become  full-grown  in  from  five  to  seven  days; 
the  pupa  state  lasts  from  five  to  seven  days;  and  in  about  fourteen 
days  after  the  flies  emerge  they  are  ready  to  oviposit.  Hence  there 
mav  be  at  least  a  generation  a  month  during  the  warm  season;  and 
from  a  few  overwintering  flies  an  immense  number  may  be  developed. 
The  house-fly  is  not  only  an  exceedingly  annoying  pest  in  our  dwel- 
lings, but  as  it  will  breed  in  human  excrement,  especially  where  there 
are  open  closets,  it  is  doubtless  often  a  carrier  of  the  germs  of  typhoid 
fever,  dysentery,  and  other  enteric  diseases.  For  these  reasons  Dr. 
Howard  has  suggested  that  this  species  be  known  as  the  typhoid-fly 
and  the  "Swat-the-fly"  crusades  have  been  urged.  Various  means  of 
protection  from  this  pest,  as  window-screens  and  different  kinds  of 
traps,  are  well-known;  but  as  Howard  has  so  well  put  it,  "the  truest 


DIPTERA  873 

and  simplest  way  of  attacking  the  fly  problem  is  to  prevent  them  from 
breeding,  by  the  treatment  or  abolition  of  all  places  in  which  the\' 
can  breed."  Garbage  cans  should  be  kep^  tightly  closed  and  emptied 
at  least  once  a  week.  Manure  should  be  stored  in  tight  receptacles 
or  treated  with  borax,  one-half  pound  of  borax  to  eight  bushels  of 
manure.  The  borax  should  be  applied  immediately  after  the  removal 
of  the  manure  from  the  barn.  Apply  the  borax  particularly  around 
the  edges  of  the  pile  with  a  flour  sifter  or  any  fine  sieve,  and  sprinkle 
two  or  three  gallons  of  water  over  the  borax  treated  manure.  It  is 
estimated  that  the  cost  of  the  borax  will  be  about  one  cent  per  horse 
per  day,  (Cook,  Hutchison,  and  Scales  '14). 

The  stable-fly,  Stomoxys  cdlcitrans. — This  species  resembles  the 
house-fly  in  appearance,  but  it  is  a  trifle  larger  and  has  its  mouth- 
parts  fitted  for  piercing  and  for  sucking  blood.  It  annoys  cattle 
greatly ;  and  before  storms  and  in  the  autumn  it  enters  our  dwellings 
and  attacks  us.  The  popular  belief  that  the  house-fly  bites  more 
viciously  just  before  a  rain  is  due  to  invasions  of  this  species  at  such 
times.  The  mouth-parts  of  the  true  house-fly  are  not  fitted  for  pierc- 
ing. The  stable-fly  is  especially  common  in  barns.  It  breeds  in 
vegetable  refuse,  manure  and  excrement. 

The  horn-fly,  Hcematdbia  trritans. — This  is  an  exceedingly  annoy- 
ing pest  of  horned  cattle.  It  resembles  the  house-fly  in  appearance, 
but  is  less  than  half  as  large.  These  flies  cluster  in  great  numbers 
around  the  base  of  the  horns;  they  also  settle  upon  the  back.  The 
larva2  live  in  fresh  cow-manure.  The  flies  can  be  killed  by  spraying 
the  cattle  with  kerosene  emulsion  or  with  crude  petroleum. 

The  tsetse-fly,  Glasslna  monstans.- — This  species,  which  is  closely 
allied  to  the  stable-fly,  is  widely  distributed  in  Africa  and  is  the  carrier 
of  the  blood  parasite  that  causes  the  disease  of  cattle  known  as 
nagana  and  the  sleeping  sickness  of  man. 

SECTION  II— PUPIPARA 

Under  this  head  are  classed  several  families  of  flies  that  are  para- 
sitic in  the  adult  state.  In  most  cases  the  adults  live  like  lice  on  the 
bodies  of  birds  or  of  mammals ;  but  two  species  are  parasites  of  the 
honev-bee.  The  name  Pupipara  was  suggested  by  the  fact  that  in 
the  best -known  forms  the  larva?  attain  their  full  growth  within  the 
body  of  the  female  fly,  where  they  are  nourished  by  the  product  of 
glands  specialized  for  this  purpose.  It  was  formerly  believed  that 
the  young  are  born  as  pupse;  but  it  is  now  known  that  the  change  to 
the  pupa  state  does  not  take  place  until  after  the  larva  is  born.  It  is 
also  known  that  this  remarkable  manner  of  development  is  not  re- 
stricted to  this  group  of  families  as  it  is  characteristic  also  of  the 
tsetse-fly.  But  the  name  Pupipara  has  been  so  generally  used  for  this 
group  of  families  that  it  seems  best  to  retain  it. 

In  the  Pupipara  the  eyes  are  never  large  and  in  some  forms  they 
are  either  vestigial  or  wanting;  the  ocelli  are  present  in  some  genera 
in  others  thev  are  wanting.    The  antenna?  are  apparently  only  one-  or 


874 


AN  INTRODUCTION  TO  ENTOMOLOGY 


two-jointed,  and  in  some  genera  lack  the  arista;  the  mouth-parts  are 
short  and  not  at  all  retractile ;  the  wings  are  well  developed  in  some 
forms,  in  others  they  are  vestigial  or  wanting;  the  abdomen  is  indis- 
tinctly segmented  in  most  cases  and  leathery  in  appearance. 

Family  HIPPOBOSCIDyE 

The  Louse-Flies 

The  louse-flies  are  ver>^  abnormal  flies  that,  in  the  adult  state, 
live  like  lice,  parasitically,  upon  the  bodies  of  birds  and  mammals. 
Some  species  are  winged,  others  are  wingless,  and  still  others  are 
winged  for  a  time  and  then  lose  their  wings. 

The  body  is  depressed ;  the  head  is  closely  attached  to  the  thorax 
which  is  notched  to  receive  it.  The  antennae  are  apparently  one- 
jointed,  with  a  terminal  arista  or  style;  they  are  situated  in  depressions 


M. 


2dA 


M,+Cu, 


Fig.   II18. — Wing  of  Olfersia. 

near  the  mouth.  The  legs  are  broadly  separated  by  the  sternimi; 
they  are  comparatively  short  and  stout;  the  tarsal  claws  are  strong 
and  are  often  furnished  with  teeth.  The  winged  forms  vary  greatly 
in  the  venation  of  the  wings.  The  veins  near  the  costal  border  are 
usually  strong  while  the  others  are  weak.  Figure  1 1 18  represents  the 
venation  of  Olfersia. 

The  sheep-tick,  Melophagus  ovinns.- — This  well-known  pest  of 
sheep  is  the  most  common  member  of  the  Hippoboscidee  found  in  this 
country.  It  is  wingless  and  its  halteres  are  vestigial 
(Fig.  1 1 19).  It  is  about  6  mm.  in  length,  of  a  reddish 
or  gray-brown  color,  and  with  the  entire  body  covered 
with  long  bristly  hairs.  This  pest  is  often  very  injurious, 
especially  to  lambs  after  shearing  time,  as  it  tends  to 
migrate  from  the  old  sheep  to  the  lambs  at  this  period. 

The  life-histor}^  of  this  species  illustrates  well  that 
type  of  development  which  suggested  the  name  Pupi- 
para  for  the  Hippoboscidse  and  allied  flies.    The  struc- 
ture of  the  female  genital  tract  is  described  by  Pratt  ('99) .    A  striking 
feature  of  it  is  the  presence  of  two  pairs  of  much  branched  glands, 


DIPTERA  875 

the  "milk-glands",  which  secrete  a  fluid  for  the  nourishment  of  the 
larva.  The  larvae  become  full-grown  in  the  uterus  of  the  female  and 
are  bom  one  at  a  time  at  intervals  of  several  weeks.  In  about  twelve 
hours  after  the  larva  is  born  the  pupariiun  is  completed;  and  the 
adult  emerges  in  from  nineteen  to  twenty-four  davs  later. 

To  control  this  pest  the  sheep  should  be  dipped  twice  after  shear- 
ing, in  some  good  "dip"  of  which  several  kinds  are  on  the  market 
(See  Farmers'  Bull.  798,  U.  S.  Dept.  Agr.) 

Among  the  more  common  representatives  of  this  family,  besides 
the  sheep-tick,  found  in  this  country  are  the  following. 

Oljersia  americdna.- — This  is  a  yellowish  winged  species  rather 
common  on  owls  and  other  raptorial  birds,  and  on  the  partridge  or 
ruffed  grouse. 

Lipoptena  depressa.- — ^This  species  is  found  on  deer.  The  young 
adults  are  vv^inged  and  probably  fly  about  in  search  of  their  host ;  but 
later  after  becoming  established  on  a  deer  they  shed  their  wings. 

Family  STREBLID^ 

The  Bat-Ticks  in  part 

This  family  and  the  following  one  include  small  flies  that  are 
parasitic  upon  bats.  In  this  family  the  head  is  of  moderate  size, 
with  a  freely  movable  neck,  but  is  not  bent  back  upon  the  dorsum 
of  the  thorax,  as  in  the  following  family.  The  eyes  are  vestigial  or 
wanting;  the  ocelli  are  wanting;  the  palpi  are  broad  and  project  leaf- 
like in  front  of  the  head ;  the  wings  are  sometimes  wanting  or  vestigial. 

In  this  family,  as  in  the  Hippoboscidag,  the  larva  becomes  fully 
grown  within  the  body  of  the  parent  female. 

For  figures  and  descriptions  of  some  of  our  species  of  this  family 
see  Ferris  ('16). 

The  genus  A  scoMpteron,  species  of  which  are  found  in  the  Australian  region  and 
in  other  parts  of  the  Eastern  Hemisphere,  is  of  great  interest,  because  the  females 
become  endoparasites.  The  adults  of  both  sexes  are  winged  at  first.  Later  the 
female,  probably  after  copulation,  cuts  a  hole  through  the  skin  of  a  bat  and  after 
shedding  her  wings  and  legs  nearly  completely  imbeds  herself  in  her  host.  The 
insect  then  increases  greatly  in  size  and  becomes  a  flask-shaped  creature,  both 
head  and  thorax  becoming  invaginated  so  that  they  are  not  visible.  The  caudal 
end  of  the  body  projects  from  the  cavity  in  which  the  insect  lies.  The  larvse, 
which  become  full-grown  one  at  a  time,  are  ejected  from  the  uterus  and  fall  to 
the  ground,  where  they  pupate.     For  a  more  detailed  account  see  Muir  ('12). 

Family  NYCTERIBIID^ 

The  Bat-Ticks  in  part 

This  family  includes  small,  spider-like,  wingless  flies,  which  are 
parasitic  upon  bats.  The  head  is  narrow,  and  when  at  rest  is  folded 
back  in  a  groove  on  the  dorsum  of  the  thorax.  The  eyes  and  ocelli 
are  vestigial;  the  antennas  are  short  and  only  two-jointed;  the  legs 
are  long,  and  the  tarsal  claws  of  ordinary  form;  although  these  insects 
are  wingless,  the  halteres  are  present,  but  sometimes  vestigial. 


876 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  reproduction  of  these  flies  is  of  the  pupiparous  type.  When 
the  mature  larva  is  born  it  is  fastened  in  some  cases  to  the  host, 
(Muir,  '12)  and  in  others  the  female  leaves  the  host  for  a  short  time 
and  fastens  the  larva  to  the  perch  to  which  the  bats  cling  (Scott, 
'17).  In  each  case  the  larva  is  pressed  against  the  supporting  object 
to  which  it  adheres  firmly. 

Only  a  few  species  have  been  found  in  this  country,  for  figures 
and  descriptions  of  these  see  Ferris  ('16  and  '24). 

Family  BRAULID^ 

The  Bee-Lice 


This  family  includes  only  a  single  genus,  Braula,  of  which  there 
is  only  one  well-known  species,  Braula  cceca.    This  is  a  minute  insect, 

1.5  mm.  in  length, 
which  is  parasitic  up- 
on the  honey-bee  (Fig. 
1 1 20).  It  is  found 
clinging  to  the  thorax 
of  queens  and  drones. 
It  is  wingless  and  also 
lacks  halteres ;  the 
head  is  large ;  the  ocelli 
are  wanting;  the 
eyes  are  vestigial;  the 
legs  are  comparatively 
short;  and  the  last 
segment  of  the  tarsi 
is  furnished  with  a 
pair  of  comb-like  ap- 
pendages. 

The  bee-louse  was  described  by  Reaumur  nearly  two  hundred 
years  ago  and  remained  the  only  known  species  of  this  family  till  1914, 
when  another  species,  Braula  kohlt,  was  described  from  the  Belgian 
Kongo;  this  species  is  parasitic  on  an  African  honey-bee.  Apis  mellifica 
var.  adamsoni. 

The  affinities  of  this  family  are  in  doubt.  Until  recently  Braula 
has  been  supposed  to  be  similar  in  its  mode  of  development  to  the 
sheep  tick,  and  for  this  reason  the  family  classed  with  the  Pupipara. 
But  it  is  now  known  that  Braula  lays  eggs;  and  the  developmental 
stages  have  been  found  in  tunnels  under  the  capping  of  sealed  honey 
(See  "Monthly  Letter"  of  the  U.  S.  Bureau  of  Entomology,  Nimiber 
113,  September  1923). 

It  is  maintained  by  both  Borner  and  Bezzi  that  Braula  should  be 
classed  near  the  Phoridas.  But  Muggenburg  ('92)  has  shown  that 
there  is  a  ptilinimi  in  this  genus.  It,  therefore,  does  not  belong  to 
the  series  Aschiza. 


(From  Starp  after  Mein- 


CHAPTER  XXIX 
ORDER  SIPHONAPETRA* 

The  Fleas 

The  members  of  this  order  are  small,  wingless  insects,  in  which  the 
body  is  laterally  compressed,  so  that  the  transverse  diameter  is  small, 
the  vertical  one  great.  The  mouth-parts  are  formed  for  piercing  and  suck- 
ing.    The  metamorphosis  is  complete. 

The  name  of  this  order  refers  to  the  form  of  the  mouth-parts  and 
to  the  wingless  condition  of  these  insects. 

These  tiny  tormentors  are  best  known  to  us  in  the  adult  state; 
for  it  is  only  "the  adults  that  annoy  us  and  our  household  pets.  The 
larvae  and  pupae  are  rarely  observed  except  by  students  who  search 
for  them. 

The  body  of  the  adult  is  oval  and  greatly  compressed,  which  allows 
the  insect  to  glide  through  the  narrow  spaces  between  the  hairs  of  its 
host.  The  integument  is  smooth,  quite 
hard,  and  armed  with  bristles,  which 
are  arranged  with  great  regularity  (Fig. 
1121)  and  thus  afford  good  characters  for 
distinguishing  the  different  species.  The 
smoothness  and  firmness  of  the  bodv 
make  it  easy  for  the  insect  to  escape  when 
caught  between  the  fingers  of  man  or  the 
teeth  of  lower  animals.  When  once  out 
of  the  clutch  of  an  enemy  it  quickly 
leaps  away.  Fig.  ii2i.^The  dog-flea  and 

The  head  is  broadly  joined  to  the  thor- 
ax.    There  are  no  compound  eyes;  but 

on  each  side  of  the  head  there  is  usually  an  unfaceted  eye;  these, 
however,  are  sometimes  wanting.  Each  antenna  lies  in  a  groove 
somewhat  behind  and  above  the  eye  (Fig.  1122).  The  antennae  are 
three-jointed;  the  third  joint,  the  flagellum,  often  called  the  club, 
may  be  unsegmented,  segmented  on  the  posterior  border  only,  or 
completely  segmented  into  several,  usually  nine,  more  or  less  separate 
pseudo-segments  (Fig.  1123^!).  There  is  usually  an  internal  thicken- 
ing of  the  body-wall  extending  over  the  vertex  from  one  antennal 
groove  to  the  other  (Fig.  1122,  /),  this  is  known  as  ihe  falx  or  sickle- 
shaped  process.  That  part  of  the  dorsal  wall  of  the  head  in  front 
of  the  antennal  groove  and  this  thickening  is  termed,  by  writers  on 
the  Siphonaptera,  thefrons;  the  part  behind  them,  the  occiput;  and 
the  lateral  aspects  of  the  head,  below  and  behind  the  eyes,  the  genoe 
or  cheeks. 

A  remarkable  feature  of  the  head  of  the  Siphonaptera  is  the  fact 
that  in  the  more  generalized  forms  it  is  divided   into  two  distinct 

*Siphonaptera :  siphon    {ffl<pu)v)    a    tube;    apteros     {dirrepos)    without    wings. 
(877) 


878 


AN  INTRODUCTION  TO  ENTOMOLOGY 


parts  with  a  somewhat  flexible  articulation  between  them.      (Fig. 

1 1 24);  the  anterior  part  bears  the  mouth-parts  and  the  eyes,  while 

the  antennse  are  joined  to  the 
posterior  part.  The  falx  (Fig. 
1 122,  /),  which  is  present  in 
many  of  the  more  specialized 
fleas  is  evidently  a  vestige  of 
the  articulation  between  the 
two  parts  of  the  head;  even 
this  vestige  is  wanting  in  many 
fleas. 

The  mouth-parts  are  form- 
ed for  piercing  and  sucking. 
When  seen  without  dissection 
these  parts  are  apparent:  the 
maxillae,  which  are  triangular 
plates  (Fig.  11 22,  mx);  the 
maxillary  palpi,  which  are  long 
and  four-jointed  (Fig.  1122, 
mx.  ^);  and  the  proboscis,  (Fig. 
1 1 22,  p). 

The  proboscis  consists  of  an 
elongated  labrum-epipharynx, 
two  long  and  slender  mandi- 
bular   blades,    and    a   sheath 

formed  by  the  labium  and  the  labial  palpi.    The  space  between  the 

labrum-epipharynx,    in    the  lower  side  of  which  there  is  a  groove, 


Fig.  1 122. — Head  of  a  flea,  Cetatophyllus 
multis  pinosus:  f,  falax;  mx,  maxilla; 
mx.p,  maxillary  palpi;  p,  proboscis. 
(After  Baker.) 


Fig.  1 1 24. — Head  and  prothorax  of 
Ischnopsvllus:    F,  frons;   O,  occi- 
Fig.    1 123.-  Antenna    of   fleas:         put;  N,  pronotum;  P,  propleurum; 

A,      Ctenocephalus  felis;  B,  Cer-         o,  antenna;  c,  ctemdia;  m,  maxilla; 

atophyllusfasciatus.    (After  Pat-         «^P,  maxillary  palpus. 

ton  and  Cragg.). 
and  the  mandibular  blades,  which  are  closely  applied  to  the  lab- 
rum-epipharynx, serves  as  a  food-canal,  through  which  the  blood 
taken  from  the  host  is  sucked  into  the  alimentary  canal.  There  is 
also  a  second  canal  formed  by  the  apposition  of  two  grooves,  one  on 
the  inner  side  of  each  of  the  mandibles;  through  this  canal  the 
salivary  secretion  is  forced  into  the  wound.  The  piercing  organ  is 
the  mandibles;  the  distal  part  of  each  mandible  is  beset  with  re- 
curved teeth ;  and  the  proximal  end  of  the  blade  is  connected  with  a 
chitinous  lever,  which  in  turn  articulates  with  the  head-capsule;  by 


SIPIIONAPTERA  879 

the  action  of  muscles  attached  to  this  lever,  the  blade  of  the  mandible 
can  be  forced  in  and  out.  The  number  of  segments  of  the  labial  palpi 
varies  from  two  to  seventeen. 

The  three  segments  of  the  thorax  are  quite  distinct  from  one 
another  although  closely  joined.  The  ventral  part  of  the  prothorax 
extends  forward  under  the  head,  so  that  the  first  pair  of  legs  appear 
to  depend  from  the  head.  There  is  usually  one,  but  there  may  be 
two  or  three,  transverse  rows  of  bristles  on  each  thoracic  segment. 
There  are  no  vestiges  of  wings.  The  legs  are  long  and  strong  and 
fitted  for  leaping;  the  hinder  pair  are  largest  and  the  middle  pair 
next  in  size. 

The  abdomen  is  composed  of  ten  segments ;  the  first  seven  of  these 
are  comparatively  simple  in  structure;  the  last  three  are  specially 
modified  for  sexual  purposes.  The  variations  in  form  of  the  sclerites 
of  these  segments  and  of  the  genital  appendages  afford  characters 
much  used  in  the  classification  of  these  insects.  The  ninth  tergite 
bears  what  is  evidently  a  sensory  plate;  on  the  surface  of  this  there 
is  a  mmiber  of  clear  areas  from  each  of  which  there  projects  a  long 
slender  and  extremeh'-  fine  hair.  The  function  of  this  organ  is  unknown. 

A  conspicuous  feature  of  many  fleas  is  the  presence  of  a  series  of 
short,  stout  spines  on  various  parts  of  the  body;  these  are  known  as 
combs  or  ctenidia.  The  presence  or  absence  of  ctenidia  and  their 
location  when  present  are  important  distinctive  characters.  In  the 
dog-flea  (Fig.  1 1 2 1 )  there  are  ctenidia  on  the  genas  and  on  the  posterior 
border  of  the  prothorax. 

Large  bristles  placed  at  the  dorsal  angle  of  the  seventh  abdominal 
segment  are  termed  the  antipygidial  bristles. 

The  eggs  of  fleas  are  scattered  about  the  floors  of  dwellings  and 
in  the  sleeping-places  of  infested  animals.  The  larvae  are  slender, 
worm-like  creatures,  with  a  distinct  head  and  without  legs.  (Fig. 
1 121).  They  have  biting  mouth-parts,  and  feed  upon  the  decaying 
particles  of  animal  and  vegetable  matter  always  to  be  found  in  the 
dirt  in  which  they  live.  When  full-grown  the  larva  spins  a  cocoon 
within  which  the  pupa  state  is  passed. 

Fleas  are  parasitic  only  in  the  adult  state.  Some  species  infest 
birds,  but  by  far  the  larger  number  prey  upon  mammals,  and  most 
mammals  are  subject  to  the  attacks  of  these  parasites.  Although  the 
different  species  of  fleas  infest  different  hosts  they  are  not  so  restricted 
in  their  host  relations  as  are  many  parasites,  and  may  pass  from 
their  normal  host  to  another  species;  for  example,  both  the  dog-flea 
and  the  cat-flea  frequently  attack  man. 

Formerly  fleas  were  regarded  as  merely  annoying  pests  of  man  and 
his  pets;  but  it  has  been  found  that  fleas  are  the  carriers  of  bubonic 
plague;  this  fact  has  greatly  increased  the  interest  in  these  insects. 
A  result  of  this  increased  interest  is  that  extended  studies  of  the 
Siphonaptera  have  been  made  recently  and  are  being  made  now.* 

*It  is  now  known  that  the  bubonic  plague,  which  has  caused  the  death  of  many 
millions  of  people,  is  a  specific  infectious  disease  caused  by  one  of  the  bacteria, 
Bacillus  pestis;  and  that  it  is  primarily  a  disease  of  rodents,  especially  of  rats. 
It  has  been  shown  by  experiments  that  this  disease  is  transmitted  from  one  ro- 


880  AN  INTRODUCTION  TO  ENTOMOLOGY 

To  rid  a  dog  or  cat  of  fleas  Persian  insect  powder  should  be  carefully 
rubbed  into  its  hair,  or  powdered  naphthalene  or  moth  balls  used  in 
the  same  way.  The  animal  should  be  treated  on  paper  spread  on  the 
floor,  and  the  stupified  fleas  that  come  to  the  surface  of  the  hair  or 
drop  out  collected  and  burned.  The  bedding  in  kennels  should  be  of 
some  substance  that  can  be  replaced  frequently,  as  shavings  or  straw, 
and  when  replaced  the  old  bedding  should  be  burned,  and  the  floors 
wet  with  kerosene  emulsion  or  some  other  insecticide  that  will  de- 
stroy the  eggs  and  larvEe.  The  animals  should  be  kept  from  beneath 
dwellings  where  fleas  may  breed  rapidly,  and  where  it  is  difficult  to 
reach  the  breeding  places. 

In  regions  where  fleas  abound  much  relief  can  be  obtained  by  the 
use  of  rugs  on  the  floors  of  dwellings  instead  of  carpets.  The  frequent 
shaking  of  the  rugs  and  cleaning  of  the  floors  will  prevent  the  breeding 
of  these  pests  within  the  house.  As  a  single  flea  will  inflict  many  bites, 
it  often  happens  that  a  house  will  seem  to  be  overrun  by  them  when 
only  a  few  are  present.  In  such  cases  a  careful  search  for  and  the 
capture  of  the  offenders  will  soon  remedy  the  evil. 

People  that  suffer  from  the  attacks  of  these  pests  can  also  gain 
much  relief  by  dusting  the  upper  part  of  their  stockings  each  morning 
with  Persian  insect  powder,  and  by  sprinkling  a  small  quantity  of  this 
powder  between  the  sheets  of  their  beds  at  night. 

The  destruction  of  rats  and  the  fleas  that  they  harbor  in  a  region 
where  bubonic  plague  exists  is  the  most  important  means  of  preventing 
the  spread  of  this  disease.  This  has  been  done  very  efflciently  by  the 
United  States  Marine  Hospital  Ser^dce  in  those  cases  where  the  plague 
has  been  introduced  into  this  country. 

Except  where  bubonic  plague  is  present  the  bites  of  fleas  are  not 
likely  to  cause  serious  results,  although  they  may  be  very  annoying. 
The  irritation  caused  by  them  can  be  relieved  by  the  use  of  some 
cooling  application  as  menthol,  camphor,  or  carbolated  vaseline. 
Scratching  the  bites  should  be  avoided  as  that  aggravates  the  in- 
flammation. 

This  order  includes  about  500  described  species,  and  additions  to 
the  list  are  constanth'  being  made.  A  revision  of  the  American  species 
was  published  by  Baker  ('04  and  '05).  Later  Oudemans  ('10)  pub- 
lished a  new  classification  of  the  order  in  which  he  gave  a  table  of  the 
families  and  genera  of  the  world.  The  more  striking  features  of  the 
classification  by  Oudemans  are  the  division  of  the  order  into  two 
suborders  and  the  proposed  establishment  of  several  new  families, 
some  of  which  have  not  been  adopted  by  other  authors.  In  the 
following  account  reference  is  made  only  to  North  American  forms. 

The  division  of  the  order  into  two  suborders  is  based  on  the 
structure  of  the  head.  In  the  first  suborder,  the  Fractictpita,  are  in- 
cluded those  fleas  in  which  the  head  is  jointed;  the  second  suborder, 
the  Integriclpita,  includes  those  fleas  in  which  the  head  is  not  jointed. 

dent  to  another  by  fleas;  and  from  rodents  to  monkeys  in  the  same  manner. 
It  is  concluded,  therefore,  that  the  disease  is  carried  to  man  also  by  fleas.  See 
textbooks  of  medical  entomology. 


SIPHONAPTERA  881 

Suborder  FRACTICIPITA 
The  Broken-headed  Fleas 

In  the  members  of  this  suborder  the  head  is  divided  into  two 
distinct  parts  with  a  somewhat  flexible  articulation  between  them. 
On  the  dorsal  wall  of  the  head  the  anterior  part,  the  frons,  overlaps 
the  posterior  part,  the  occiput  (Fig.  1124). 

Representatives  of  two  subfamilies  of  this  suborder  occur  in  our 
fauna;  these  families  can  be  separated  as  follows. 

A.  Ctenidia  of  the  head  consisting  only  of  two  broad  teeth  on  each  side  in  front  of 
the  maxillary  palpi,  none  between  the  palpi  and  the  antennal  groove;  apex  of 
maxillte  truncate,  p.  881 Ischnopsyllid^ 

AA.  Genal  ctenidia,  when  present,  placed  between  the  maxillary  palpi  and  the 
antennal  grooves  or  extending  from  the  antennal  groove  to  the  anterior  margin 
of  the  head;  apex  of  maxillae  pointed,  p.   881 LEPXOPSYLLiDiE 

Family  LSCHNOPSYLLID^ 

This  family  includes  those  Fracticipita  in  which  the  ctenidia  of 
the  head  consist  only  of  two  broad  teeth  on  each  side  close  to  the 
lower  anterior  angle  of  the  head,  in  front  of  the  maxillary  palpi, 
(Fig.  1 124),  and  in  which  the  apex  of  the  maxillee  is  truncate.  It  is 
represented  in  our  fauna  by  only  a  few  described  species ;  these  infest 
bats  and  are  occasionally  found  on  mice  of  the  genus  Peromyscus. 

Family  LEPTOPSYLLID^ 

To  this  family  belong  most  of  our  members  of  the  suborder  Fracti- 
cipita. In  these  the  genal  ctenidia,  when  present,  are  placed  between 
the  maxillary  palpi  and  the  antennal  grooves  or  extend  from  the 
antennal  groove  to  the  anterior  margin  of  the  head ;  the  apex  of  the 
maxillae  is  pointed. 

Many  Amerian  species  have  been  described;  the  greater  number 
of  these  infest  rodents,  a  few  species  are  found  on  birds,  and  some  of 
those  infesting  rats  will  attack  man. 

Suborder  INTEGRICIPITA 

The  Unbroken-headed  Fleas 

In  the  members  of  this  suborder  the  head  is  not  divided  into 
two  distinct  parts  by  an  articulation,  although  a  vestige  of  the  seg- 
mentation, the  falx,  may  be  present  (Fig.  1122,/).  The  frons  does  not 
overlap  the  occiput  on  the  dorsal  wall  of  the  head. 

Representatives  of  three  families  of  this  suborder  occur  in  our 
fauna,  these  families  can  be  separated  as  follows. 

A.  Abdomen  with  small,  sharply  pointed  spines  on  apices  of  tergites;  inner 
surface  of  anterior  portion  of  hind  coxae  without  small  spines,  although  a 
patch  of  bristles  is  sometimes  present,  p.  882 Ceratophillid^ 


882  AN  INTRODUCTION  TO  ENTOMOLOGY 

AA.     Abdomen  without  apical  spines  on  the  tergites;  inner  surface  of  anterior 
portion  of  hind  coxae  with  one  row  of  small  spines,  rarely  with  more  than  one 
row. 
B.     Thorax  longer  than  the  head,  not  shorter  than  the  first  abdominal  tergite, 

p.  882 PULICID^ 

BB.     Thorax  shorter  than  the  head,  also  shorter  than  the  first  abdominal 
tergite.  p.  882 Echidnoph.\gid^ 

Family  CERATOPHILLID^ 

This  family  includes  those  Integricipita  in  which  there  are  small, 
sharply  pointed  spines  on  the  apices  of  some  of  the  abdominal  tergites. 
It  is  represented  in  this  country  by  many  species ;  these  infest  various 
rodents,  mink,  birds,  and  man. 

Family  PULICID^ 

This  family  includes  those  Integricipita  without  apical  spines  on 
the  abdominal  tergites  in  which  the  thorax  is  longer  than  either  the 
head  or  the  first  abdominal  tergite.  It  includes  some  of  our  most 
common  and  best-known  species;  among  these  are  the  following. 

The  cat-flea,  Ctenocephalus  felis. — This  is  the  species  that  is  most 
often  found  in  our  dwellings  in  the  East  and  in  the  South,  and  the 
one  that  most  often  attacks  man  in  these  regions.  Both  the  genae 
of  the  head  and  the  pronotum  are  armed  with  ctenidia;  the  genal 
ctenidia  extend  from  the  antennal  groove  to  the  anterior  margin  of 
the  head.  The  first  spine  of  the  genal  ctenidia  is  about  as  long  as 
the  second.    This  species  infests  dogs  as  well  as  cats. 

The  dog-flea,  Ctenocephalus  canis. — This  species  is  closely  allied 
to  the  cat -flea,  but  in  this  species  the  first  spine  of  the  genal  ctenidia 
is  only  about  one-half  as  long  as  the  second  spine.  This  flea  infests 
dog,  cat,  and  man. 

The  htiman  flea,  Pulex  irntans. — On  the  Pacific  Coast  this  is  the 
species  that  is  most  often  found  in  houses  attacking  man.  It  is 
easily  distinguished  from  the  two  preceding  species  by  the  fact  that 
its  head  and  thorax  lack  ctenidia.  Man  is  its  natural  host;  but  it 
will  infest  various  other  animals  temporarily. 

The  Indian  rat-flea,  Xenopsylla  cheopis. — Among  the  various  spe- 
cies that  are  supposed  to  transmit  the  bubonic  plague,  this  cosmo- 
politan species  is  regarded  as  one  of  the  more  important.  It  resembles 
the  htmian  flea  in  lacking  ctenidia,  but  can  be  distinguished  from 
that  species  by  the  fact  that  the  mesostemite  is  broad,  with  a  rod-like 
internal  thickening  extending  from  the  insertion  of  the  coxa  upward. 

Hoplopsyllus  anomalus. — This  is  the  plague  carrier,  of  the  Cali- 
fornia ground  squirrels,  and  it  also  infests  rats.  In  this  species  there 
is  a  ctenidium  on  the  pronotum,  but  none  on  the  head. 

Family  ECHIDNOPHAGIDyE 

In  this  family  the  thoracic  segments  are  short,  the  three  segments 
together  being  shorter  than  the  first  abdominal  segment  in  the  dorsal 


SIPIIONAPTERA  883 

line;  the  <^enal  marj^in  of  the  head  is  ])roduced  into  a  triangular 
process  at  the  ventral  oral  angle ;  and  ctenidia  are  lacking.  The  two 
following  species  are  the  best-known  members  of  this  family. 

The  sticktight  flea,  Echidnophaga  gallindcea. — This  is  a  very 
serious  pest  of  poultry  especially  in  the  southern  and  southwestern 
portions  of  the  United  States.  It  is  a  small,  dark  brown  species,  which 
is  often  found  in  dense  masses  attached  to  its  host ;  heads  of  chickens 
are  often  covered  with  dark  patches  of  these  fleas.  This  species  is 
known  as  the  sticktight  flea  because  it  seldom  hops  about,  biting  here 
and  there,  as  do  most  fleas,  but  settles  down  on  its  host,  deeply  insert- 
ing its  mouth-parts,  and  remains  for  days  or  weeks.  While  this 
species  is  chiefly  a  pest  of  poultry,  it  is  often  found  in  dense  masses 
on  the  ears  of  dogs  and  cats. 

The  chigoe  (chig'o)  or  jigger,  Tiinga  penetrans: — This  is  a  small 
flea  found  in  the  West  Indies,  Mexico,  Central  and  South  America, 
and  in  tropical  Africa.  It  has  been  reported  from  Florida  but  it  is 
not  known  to  be  established  in  the  United  States.  The  males  and  the 
tmimpregnated  females  live  in  dry,  sandv  soil;  they  are  only  about  one 
millimeter  in  length,  and  behave  in  the  ordinary  manner  of  fleas, 
feeding  on  the  blood  of  man  and  many  other  animals,  domestic  and 
wild,  and  even  birds.  When  impregnated,  the  female  burrows  into 
the  skin  of  her  host.  Soon  after  this  the  abdomen  becomes  distended 
with  eggs  and  acquires  the  size  of  a  small  pea.  This  species  often 
causes  serious  injury  to  man  by  burrowing  beneath  the  skin  of  the 
foot,  causing  the  formation  of  a  sore,  which  may  become  infected 
with  bacteria,  and  cause  the  loss  of  a  toe  or  a  leg. 

In  the  southern  United  States  the  names  chigoe  and  jigger  are 
improperly  applied  to  the  harvest-mites,  which  are  the  immature  six- 
legged  forms  of  various  mites  that  attach  themselves  like  ticks  to  the 
skin  and  become  gorged  with  blood. 


CHAPTER  XXX 
ORDER  HYMENOPTERA* 

Bees,  Wasps,  Ants,  and  others 

The  winged  members  of  this  order  have  four  wings;  these  are  mem- 
branous and  have  the  wing-venation  more  or  less  reduced.  The  hind 
wings  are  smaller  than  the  fore  wings.  The  mouth-parts  are  formed  for 
chewing  or  for  both  chewing  and  sucking.  The  abdomen  in  the  females 
is  usually  furnished  with  a  sting,  piercer,  or  saw.  The  metamorphosis 
is  complete. 

The  Hymenoptera  is  a  very  large  order,  including  a  vast  number 
of  species.    The  bees,  wasps,  and  ants  are  among  the  better-known 


Fig.  1 125. —Wings  of  Apis  showing  hamuli. 

members  of  it ;  but  in  addition  to  these  it  includes  a  large  number  of 
less  familiar  forms.  Many  of  these  are  minute  parasites  of  other  in- 
sects; others  cause  the  growth  of  galls  on  plants;  and  still  others,  in 
their  larval  state,  feed  on  the  foliage  of  plants  or  are  borers  in  the 
stems  of  bush}'  or  herbaceous  plants  or  in  the  limbs  and  trunks  of 
trees. 

The  members  of  this  order  are  chiefly  of  small  or  moderate  size, 
and  many  of  them  abound  wherever  flowers  bloom.  From  very  early 
times  some  of  them  have  been  favorites  with  students  of  the  habits 
of  animals,  for  among  them  we  find  wonderful  developments  of  in- 
stinctive powers.  Many  voltimes  have  been  written  regarding  their 
ways,  and  much  remains  to  be  discovered ,  even  concerning  our  most 
common  species. 

*Hymen6ptera :  Hymen  (vfj-vv),  membrane;  pteron  (irTepSv),  wing. 
(884) 


HYMENOPTERA 


885 


The  membranous  nature  of  the  wings,  which  suggested  the  name 
of  the  order,  is  not  a  distinctive  characteristic,  for  it  is  possessed  by 
the  wings  of  many  other  insects. 

The  two  pairs  of  wings  are  similar  in  texture.  The  wings  of  each 
side  are  held,  together  by  a  row  of  hooks,  the  hamuli,  on  the  front  mar- 


Fig.  1 1 26. — The  veins  of  a  typical  hymenopterous  wing. 

gin  of  the  hind  wing  (Fig.  1125);  these  hooks  fasten  to  a  fold  in 
the  hind  margin  of  the  front  wing,  so  that  the  two  wings  present  a 
continuous  surface.  The  hind  wings  are  smaller  than  the  fore  wings 
and  have  a  more  reduced  venation.    Some  forms  are  apterous. 

This  is  one  of  the  orders  in  which  in  the  specialization  of  the 
wings  the  wing-venation  is  reduced .  In  the  more  generalized  members 
of  the  order  this  reduction  of  the  wing-venation  is  slight,  but  in  the 
more  specialized  forms  it  is  extreme.  Even  in  the  more  generalized 
forms,  where  nearly  all  of  the  veins  are  preserved,  the  courses  of  the 
branches  of  the  forked  veins  have  been  greatly  modified.  This  has 
been  brought  about  by  the  coalescence  of  veins  from  the  margin  of 


Fig.  1 127. — The  cells  of  a  typical  hymenopterous  wing. 

the  wing  inward.  To  understand  this  one  should  study  a  series  of 
wings  of  Diptera  in  which  all  stages  of  the  modification  of  the  venation 
in  this  way  are  illustrated,  for  in  the  H>Tnenoptera  only  the  later 
stages  are  shown.  The  series  of  figures  illustrating  the  coalescence 
of  veins  Cuo  and  2d  A  in  the  Diptera  will  aid  in  understanding  what 
has  happened  in  the  Hymenoptera. 

Figures  11 26  and  1127  represent  what  may  be  regarded  as  a 


886 


AN  INTRODUCTION  TO  ENTOMOLOGY 


typical  hymenopterous  wing;  in  the  former  the  veins  are  lettered,  in 
the  latter,  the  cells.  These  are  figures  of  a  fore  wing  of  Pamphilius 
(Fig.  1 13 5)  except  that  vein  R2,  which  is  lacking  in  this  genus,  is 
added.  This  vein  is  well  preserved  in  Macroxyela  (Fig.  1134);  but 
in  Macroxyela  vein  Cu2  is  lost ;  the  position  of  the  last  forking  of  the 
cubitus  is  indicated,  however,  by  a  bend  in  this  vein.  In  these  figures 
of  the  typical  hymenopterous  wing  the  lines  indicating  the  course  of 
the  free  part  of  media,  after  it  separates  from  radius,  are  crossed  by 
short  lines. 

The  cells  marked  m,  m,  m,  in  Figure  1127  are  termed  the  marginal 
cells;  and  those  marked  sm,  sm,  sm,  sm,  the  submarginal  cells;  the 
three  cells,  M4,  ist  Mo,  and  M3  are  termed  the  discal  cells. 

The  working  out  of  the  various  ways  in  which  the  wing-venation 
has  been  reduced  in  the  more  specialized  families  is  an  exceedingly 
difficult  problem,  one  that  is  beyond  the  scope  of  this  book.  A  general 
discussion  of  it  has  been  published  by  the  writer  (Comstock  '18); 
a  special  paper  on  the  venation  of  the  Chalastogastra  has  been  pub- 
lished by  Professor  A.  D.  MacGillivray  ('06);  and  a  very  detailed 
account  of  the  modifications  of  the  wing-venation  in  the  Clistogastra 
has  been  prepared  by  Professor  J.  C.  Bradley  and  will  probably  soon 
be  published. 

The  mouth-parts  are  formed  for  chewing  in  all 
Hymenoptera,  and  in  the  more  specialized  members 
of  the  order  they  are  fitted  for  both  chewing  and  for 
sucking  or  lapping  liquid  food.  In  the  saw-flies,  for 
example,  the  mouth-parts  resemble  quite  closely  the 
orthopterous  type,  while  in  the  bees  they  differ 
markedly  from  this  type;  and  intermediate  forms 
exhibit  intermediate  degrees  of  modification  of  the 
mouth-parts. 

In  the  long-tongued  bees  the  labrum  and  man- 
dibles retain  the  form  characteristic  of  chewing  in- 
sects and  the  mandibles  function  as  organs  for  crush- 
ing or  cutting ;  but  the  labium  and  maxillae  are  elon- 
gated; the  maxillae  form  a  sheath  to  the  labium;  the 
three  organs  thus  constituting  a  suctorial  apparatus 
(Fig.  1 128).  In  this  figure  the  maxilla?  are  repre- 
sented separated  from  the  labiimi. 

The  legs  of  the  Hymenoptera  present  characters 
that  are  much  used  in  the  classification  of  these  in- 
sects. Among  the  more  striking  of  these  are  the  fol- 
lowing; the  trochanter  may  consist  of  two  segments 
(Fig.  67,6)  or  of  only  one;  the  metatarsus  of  the  hind 
legs  is  greatly  enlarged  in  bees  (Fig.  67,  C);  and  in  several  families 
the  fore  legs  are  fitted  with  an  organ  which  is  used  in  cleaning  the 
antenna?,  the  antenna  cleaner  or  strtgilis.    This  consists  of  a  curved, 


Fig.  1 128.— Head 
of  a  honey-bee: 
a,  antenna;  c, 
clypeus;  u,  lab- 
rum  ;  m ,  man- 
dible; mx,  max- 
illa; p,  labial 
palpus ;  /,  la- 
bium. 


HYMENOPTER. 


887 


Fig.  1 1 29. — Leg  of  an  ant,  and  strigilis 
enlarged.  (From  A.  B.  Comstock,  Hand- 
book of  Nature  Study.) 


comb-like,  movable  spur  on  the  distal  end  of  the  fore   tibia  (Fig. 

1 1 29)  and  opposite  this,  on 
the  base  of  the  metatarsus,  a 
concavity  fringed  with  hairs. 
In  cleaning  an  antenna  it  is 
drawn  through  the  space  be- 
tween these  two  parts  of  the 
strigilis. 

In  addition  to  the  terms 
defined  above  the  following 
are  used  in  descriptions  of  Hy- 
menoptera. 

The  malar  space. — The  area 
on  each  side  of  the  head  includ- 
ed between  the  proximal  end  of 
the  mandible  and  the  ventral 
end  of  the  compound  eye. 

The  propddeum.- — The  first 
abdominal    segment    when    it 

forms  a  part  of  the  alitrunk  or  wing-bearing  region  of  the  body.    See 

characterization  of  the  suborder  Clistogastra.      This  is  often  called 

the  epinotmn  by  writers  on  ants. 

The  pardpsides  or  scdpulcs.- — In  many  Hymenoptera  the  prescutum 

of  the  mesothorax  is  prolonged  backward  to  a  greater  or  less  extent; 

in  some  it  extends  a  considerable 

distance    toward    the    scutellum 

but  does  not  reach  it  (Fig.  1130, 

B) ;  in  others  it  reaches  the  scu- 
tellum dividing  the  scutiun  into 

two  parts  (Fig.   1130,  A);  these 

separated  halves  of  the  scutum 

are  commonly  called  the  parap- 

sides  or  scapulcB.  (Fig.  1130,  par) 
The  parapsidal  furrows  or  no- 

tauli. — The  sutures  separating  the 

prescuttim.  from  the  parapsides. 

(Fig.  1 130,  p.f). 

The  posterior  lobes  of  the  pro- 

notum.- — A   distinctly    differenti- 
ated rounded  lobe,  on  each  side 

covering  the  spiracle,  which  forms  the  lateral  extension  of  the  pro- 

notum  of  Sphecoidea. 

The  prepectus. — An  area  along  the  cephalic  margin  of  the  epi- 

stemum  of  the  mesothorax  which  in  some  Hymenoptera  is  separated 

by  a  suture-like  furrow. 

The  epicnemium . — This  is  the  same  part  as  the  prepectus. 

The  cenchri.- — A  pair  of  membranous  lobes  or  areas  on  the  meta- 

notum  of  all  Chalastogastra. 


Fig.  1 130. — A.  Mesonotum  of  Eury- 
loma.  B.  Mesonotum  of  Cimbex. 
(After  Snodgrass.)  psc,  prescutum, 
set,  scutellum,  par,  parapsides;  p.f, 
parapsidal  furrows. 


888  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  gaster. — The  swollen  portion  of  the  abdomen  behind  the  pedi- 
cel in  the  suborder  Clistogastra. 

The  pygidial  area. — In  many  of  the  aculeate  or  stinging  H}Tnen- 
opetra  there  is  an  area  on  the  pygidium  which  is  bounded  on  each 
side  by  a  carina,  the  two  carinae  meeting  posteriorly  on  the  middle 
line  of  the  segment;  this  area  is  known  as  the  pygidial  area. 

The  anal  lobe. — The  posterior  lobe  of  the  wings,  which  is  defined 
on  page  6i  (Fig.  71,  Z)  is  also  called  the  anal  lobe.  In  the  suborder 
Clistogastra  the  presence  or  absence  of  an  anal  lobe  in  the  hind  wings 
is  an  important  taxonomic  character. 

The  preaxillary  excision.—ln  the  hind  wings  of  some  H\Tnenoptera 
there  is  in  addition  to  the  axillary  excision,  defined  on  page  61,  an- 
other notch,  the  preaxillary  excision.  In  the  hind  wings  of  the 
H^Tnenoptera  the  axillary  excision,  when  present,  is  at  the  apex  of 


ae  pae 

Fig.  1 131. — ^Wings  of  Elis:  ae,  axillary  excision;  pae,  preaxillary  excision. 

thefsecond  anal  furrow,  which  lies  between  the  second  and  the  third 
anal  veins  (Fig.  1131,  ae);  the  notch  may  be  present  in  forms  in 
which  both  the  furrow  and  the  veins  are  lacking.  The  preaxillary 
excision  is  situated  at  the  apex  of  the  first  anal  fold,  which  is  just 
cephalad  of  the  first  anal  vein  (Fig.  1131,  pae). 

The  preanal  lobe.- — That  portion  of  the  anal  area  of  the  hind  wings 
that  lies  between  the  axillary  excision  and  the  preaxillary  excision 
constitutes  the  preanal  lobe. 

In  the  Hymenoptera  the  metamorphosis  is  complete.  The  larvae 
of  the  Chalastogastra  are  caterpillar-like  in  form  and  are  furnished 
with  thoracic  legs  and  usually  with  abdominal  prolegs;  but  in  some, 
mostly  borers  or  internal  feeders,  the  prolegs  are  wanting.     In  all 


HYMENOPTERA  889 

Clistogastra  the  larvae  are  maggot-like  in  form  and  have  no  legs.  The 
pupas  are  of  the  exarate  type,  that  is,  the  legs  and  wings  are  free,  as 
in  the  Coleoptera.  With  many  species  the  larva,  before  changing  to 
a  pupa,  spins  a  cocoon  about  its  body.  With  some  this  cocoon  is 
composed  of  comparatively  loose  silk,  and  resembles  somewhat  the 
cocoon  of  a  moth.  In  others  the  cocoon  is  of  a  dense  parchment-like 
texture,  and  in  still  others  it  resembles  a  very  delicate  foil. 

Parthenogenesis. — The  production  of  young  by  females  that  have  not  mated  is 
known  to  occur  in  members  of  several  families  of  this  order.  In  some  species  the 
young  thus  produced  are  all  males;  in  others  they  are  all  females;  and  in  still 
others  both  males  and  females  are  developed  from  unfertilized  eggs.  Among  the 
well-known  examples  of  parthenogenetic  reproduction  are  the  following.  Some- 
times a  queen  honey-bee  produces  eggs  before  she  has  mated;  from  such  eggs 
only  males  are  developed.  The  eggs  produced  by  fertile  worker  bees  and  fertile 
worker  ants,  neither  of  which  mate,  develop  only  into  males.  In  certain  gall- 
flies there  is  an  alternation  of  a  generation  consisting  of  males  and  females  and  a 
generation  consisting  only  of  females,  which  reproduce  parthenogenetically; 
the  young  of  the  latter  are  males  and  females.  In  some  species  of  the  Tenthred- 
inidae  the  reproduction  is  believed  to  be  entirely  parthenogenetic,  males  of  these 
species  being  unknown. 

Polyembryony. — ^In  several  genera  of  minute  parasitic  Hymenoptera  the 
number  of  young  produced  is  not  dependent  upon  the  number  of  eggs  laid,  for 
with  these  insects  many  embryos  are  developed  from  a  single  egg.  This  type  of 
development  is  termed  polyembryony;  and  has  been  investigated  by  several 
workers.  A  recent  paper  on  this  subject  is  that  of -Dr.  R.  W.  Leiby  ('22),  in 
which  there  is  a  list  of  the  earlier  papers.  Dr.  Leiby  traced  the  development  of 
Copidosoma  gelechice,  a  parasite  of  the  solidago  gall-moth,  the  insect  that  makes 
the  spindle-shaped  gall  on  golden-rod  (Fig.  769).  The  parasite  oviposits  in  the 
eggs  of  the  moth  which  it  finds  on  leaves  or  stems  of  goldenrod  in  early  fall. 
By  the  arrival  of  cold  weather  the  developing  egg  or  parasite  body  is  found  as  a 
polynuclear  mass  within  the  completely  formed  host  embryo,  which  has  developed 
sychronously.  WTien  the  host  larva  hatches  in  the  spring  the  parasite  body  is 
found  lodged  in  the  fat-body  of  the  host.  As  the  host  larva  grows  the  polygermal 
mass  becomes  a  mass  of  embryos,  which  are  later  set  free  into  the  body-cavity  of 
the  host  larva  as  parasitic  larvas.  These  larvae  feed  upon  the  body  content  of  the 
host  devouring  the  blood,  muscles,  fatty  tissue,  and  in  fact  everything  except  the 
chitinous  parts.  An  average  of  163  adult-parasites  is  developed  from  a  single  egg. 
The  details  of  this  development  are  described  at  length  by  Dr.  Leiby  and  are  illus- 
trated by  many  figures. 

In  a  later  paper  Dr.  Leiby  and  C.  C.  Hill  ('23)  described  the  development  of 
Platygaster  heimales,  a  parasite  of  the  Hessian  fly.  From  some  of  the  eggs  of  this 
parasite  a  single  larva  is  developed;  but  from  others  two  larvas  are  produced. 
This  species  is  of  great  interest  as  illustrating  the  beginning  of  polyembryony. 

Aquatic  Hymenoptera. — It  has  long  been  known  that  the  adults  of  certain 
parasitic  Hymenoptera  descend  beneath  the  surface  of  water  in  order  to  ovi- 
posit. One  of  these  is  a  parasite  of  caddice-worms,  the  others  whose  hosts  are 
known  lay  their  eggs  in  the  eggs  of  various  aquatic  insects.  JVIost  of  the  observa- 
tions on  these  insects  have  been  made  in  Europe  but  recently  Professors  Mathe- 
son  and  Crosby  ('12)  have  described  the  habits  of  three  minute  species  which 
have  been  reared  at  Ithaca,  N.  Y.;  they  also  give  a  list  of  the  known  aquatic 
Hymenoptera. 

The  classification  of  the  Hymenoptera.- — The  classification  of  the 
Hymenoptera,  i.  e.,  the  sequence  of  the  families  and  the  groupings  of 
these  families  into  superfamilies,  adopted  in  this  chapter  is  that 
recently  worked  out  by  Messrs.  J.  C.  Bradley,  S.  A.  Rohwer,  and 
J.  Bequaert. 

Authorities  are  not  in  agreement  as  to  the  proper  application  of  certain  generic 
family  and  other  grdup  names  in  the!  order  Hymenoptera.     The  matter  is  a 


890  AN  INTRODUCTION  TO  ENTOMOLOGY 

technical  one,  and  is  before  the  International  Commission  on  Zoological  Nomen- 
clattire  for  a  definite  decision.  Until  such  a  decision  is  rendered,  we  prefer  to  re- 
tain the  long  established  usage  of  these  names,  as  indicated  below,  where  is  also 
shown  the  equivalent  name  used  by  some  recent  authors. 

Argidae  instead  of  Cryptidae  for  a  family  of  sawflies. 

Cimbicidae  instead  of  Crabronidse  for  a  family  of  sawflies. 

Proctotrupidae  instead  of  Serphida;  for  a  family  of  parasitic  wasps. 

Proctotrupoidea  instead  of  Serphoidea  for  a  superfamily  of  parasitic  wasps. 

Ceraphronidae  instead  of  Calliceratidae  for  a  family  of  parasitic  wasps. 

Toryminae  instead  of  Callimoninae  for  a  subfamily  of  chalcid-flies. 

Lasius  instead  of  Acanthomyops  or  Donisthorpea  for  a  genus  of  ants. 

PompilidcB  instead  of  Psammocharidae  for  the  family  of  spider-wasps. 

Bethylidae  instead  of  Psilidje  for  a  family  of  parasitic  wasps. 

Prosopidae  instead  of  Hylasidae  for  a  family  of  bees. 

Prosopis  instead  of  Hylaeus  for  a  genus  of  bees. 

Bombidae  instead  of  Bremid^  for  the  family  of  bumblebees. 

Bombus  instead  of  Bremus  for  a  genus  of  bees. 

Anthophora  instead  of  Lasius  or  Podalirius  for  a  genus  of  bees. 

Ammophila  instead  of  Sphex  for  a  genus  of  thread-waisted  wasp. 

SYNOPSIS  OF  THE  HYMENOPTERA 

Suborder  CHALASTOGASTRA.     The  sawflies  and  horn-tails,  p.  891. 

The  Xyelid    sawflies.    p.    894 Family  Xyelid^ 

The  Web-spinning  and  the  leaf-rolling  Sawflies.  p.  895. Family  Pamphiliid^ 

The  Horn-tails,     p.     896 Family  Siricid^ 

The  Xiphydriid   sawflies.    p.    897 Family  Xiphydriid^ 

The  Stem     Sawflies.     p.     898 Family  Cephid^ 

The  Cimbicid    Sawflies.    p.    900 Family  Cimbicid^ 

The  Typical  Sawflies.  u.  900 Family  Tenthredinid^ 

The  Argid    Sawflies.    p.    902 Family  Argid^ 

Suborder  Idiogastra. 

The  Oryssids.     p.     903 Family  Oryssid^ 

Suborder  Clistogastra  or  Apocrita. 
Superfamily  Ichneumonidea 

The  Braconids.    p.    916 Family  Br.\conid^ 

The  Ichneumon-flies,  p.  917 Family  Ichneumonid^ 

The  Trigonalids.   p.   918 Family   Trigonalid^ 

The  Aulacids.     p.     918 Family  Aulacid^ 

The  Stephanids.    p.    918 Family  Stephanid.e 

The  Gasteruptionids.     p.  919 Family  Gasteruptionid^ 

Superfamily  Proctotrupoidea. 

The    Roproniids.    p.    921 Family  Roproniid^ 

The  Helorids.    p.    921 Family  Helorid^ 

The  Vanhorniids.  p.  921 Family  Vanhorniid^ 

The  Belytids.     p.     921 Family  Belytid^ 

The  Proctotrupids.  p.  921 Family  Proctotrupid^ 

The  Ceraphronids.  p.  921 Family  Ceraphronid^ 

The  Scelionids.    p.    921 Family  Scelionid^ 

The  Platygasterids.  p.  921 Family  Platygasterid^e 

The  Pelecinids.   p.    921 Family  Pelecinid^ 

Superfamily  Cynipoidea.     The  Cynipids. 

The  Gali-flies  or  Gall-wasps  and  their  Allies,  p.  922 .  .  .  Family  Cynipids 
Superfamily  Chalcidoidea. 

The  Chalcid-flies.    p.     927 Family  Chalcidid^ 

Superfamily  Evanioidea. 

The  Ensign-flies,     p.     932 Family  Evaniid^e 

Superfamily  Vespoidea.    The  Vespoid- wasps. 

The  Spider-wasps,     p.     933 Family  Pompilid^ 

The  Embolemids.    p.    934 Family  Embolemid^ 

The  Cleptids.     p.     934 Family  Cleptid^ 


HYMENOPTERA  891 

The  Cuckoo-wasps,    p.    934 Family    Chrysidid/e 

The  Anthoboscids.    p.    935 Family   Anthoboscid^ 

The  Sapygids.    p.     935 , Family  Sapygid^ 

The  Thynnids.    p.    935 Family    Thynnid.'E 

The  Tiphiids.    p.     936 Family     TiphiidvE 

The  Velvet-ants.    p.    936 Family    Mutillid.'E 

The  Scoliids.     p.     937 Family     vScoliid/E 

The  Ants.    p.    937 Family    Formicid^ 

The  Bethylids.     p.    948 Family    Bethylid^ 

The  Rhopalosomids.   p.   948 Family  Rhopalosomid^ 

The  Typical  Wasps  or  Diploptera.  p.  948 Family  Vespid^ 

Superfamily  Sphecoidea.     The  Sphecoid-wasp  anrl  the  Bees. 

I.  The  vSphecoid-Wasps. 

The  AmpuHcids.     p.    961 Family   Ampulicid^ 

The  Dryinids.    p.    961 Family    Dryinid^ 

The  Typical    vSphecoid-wasps.    p.    962 Family    Sphecid^ 

II.  The  Bees.    p.  972 

The  Bifid-tongued    Bees.    p.    976 Family    Prosopid^ 

The  Andrenids.  p.  978 Family    Andrenid^ 

The  Leaf-cutter  Bees  and  their  Allies,  p.   982 Family   Megachilid.-e 

The  Bumblebees,     p.     984 Family     Bombid/E 

The  Honey-bees.    p.    988 Family    Apid.e 

KEY  TO  THE  SUBORDERS  OF  THE  HYMENOPTERA 

A.    Base  of  the  abdomen  not  slender  but  broadly  joined  to  the  thorax. 

B.  Antennae  inserted  between  the  eyes  above  the  base  of  the  clypeus  with  the 
bases  of  the  antennas  exposed;  front  wings  with  the  transverse  part  of  vein 
M2  present  or  if  wanting  (Hylotoma)  then  vein  R^  is  present  in  the  hind 
wings,  which  therefore  have  a  closed  submarginal  cell;  ovipositor  either 
sawlike  or  a  sturdy  borer,  never  threadlike  or  capable  of  being  coiled  within 

the  body.  p.   891 Chalastogastra 

BB.  Antennas  inserted  below  the  eyes  immediately  above  the  mandibles  under 
a  transverse  ridge,  their  bases  concealed;  front  wings  with  the  transverse 
part  of  vein  M.  wanting;  vein  R4  in  the  hind  wings  wanting,  therefore  no 
closed  submarginal  cells;  ovipositor  threadlike  and  coiled  within  the  meso- 
thorax.      p.     993 Idiogastra 

AA.    Base  of  the  abdomen  constricted  into  a  narrow  pedicel,  p.  905.  Clistogastra 

Suborder  CHALASTOGASTRA  or  SYMPHYTA* 

The  Sawflies  and  Horn-tails 

This  suborder  includes  the  more  generahzed  members  of  the 
Hymenoptera,  those  in  which  the  form  of  the  body  is  less  modified 
and  the  venation  of  the  wings  less  reduced  than  is  the  case  with  other 
members  of  the  order. 

The  basal  segments  of  the  abdomen  are  similar  in  fonn  and  the 
abdomen  is  broadly  joined  to  the  thorax  as  in  the  more  generalized 
orders  of  insects.  The  first  abdominal  segment  is  not  closely  anchy- 
losed  to  the  thorax,  forming  a  propodeirm,  as  is  the  case  in  the  Clisto- 
gastra, and  its  tergimi  is  usually  longitudinally  divided  on  its  middle 
line. 


*The  name  Chalastogastra  is  the  one  most  commonly  applied  to  this  sub- 
order and  for  that  reason  is  used  in  this  work;  but  some  authors  use  Symphyta, 
which  is  really  the  older  name.     The  etymology  of  these  names  is  as  follows: — 

Chalastogastra;  chalastos    (K;aXa(rT6s),    loose;    gastros     (faarpSs),     the     belly. 

Symphyta:  sym  {<tvv)  with;  phyton  {(pvrdv)^  j)lant. 


892  •  AN  INTRODUCTION  TO  ENTOMOLOGY 

A  similar  form  of  the  abdomen  is  also  characteristic  of  the  second 
suborder,  the  Idiogastra,  except  that  the  tergimi  of  the  first  abdominal 
segment  is  not  longitudinally  divided.  But  this  suborder  can  be  dis- 
tinguished from  the  Idiogastra  by  the  characters  given  in  the  table 
above. 

There  are  no  wingless  forms  of  the  Chalastogastra.  In  the  more 
generalized  members  of  the  suborder  nearly  all  of  the  wing-veins  are 
preserved,  although  the  courses  of  the  branches  of  the  forked  veins 
have  been  greatly  modified,  as  indicated  on  an  earlier  page,  and  as  is 
shown  in  the  figures  of  wings  given  later. 

The  ovipositor  of  the  females  is  well  developed  and  complicated 
in  structure.  It  is  fitted  for  making  incisions  in  the  leaves  or  stems 
of  plants  and  is  more  or  less  saw-like  in  form.  It  is  this  fact  that 
suggested  the  common  name  sawflies  which  is  applied  to  members  of 
this  order. 

The  ovipositor  and  its  sheath  consists  of  three  pairs  of  appendages 
or  gonopophyses ;  one  pair  arising  from  the  sternum  of  the  eighth 
abdominal  segment  and  two  pairs  from  the  sternimi  of  the  ninth 
abdominal  segment.  The  outer  pair  of  the  ninth  abdominal  segment 
constitute  the  sheath  of  the  ovipositor,  so  called  because  when  the 
ovipositor  is  not  in  use  it  is  enclosed  between  the  two  members  of 
this  pair  of  gonopophyses.  The  ovipositor  is  a  double  organ,  con- 
sisting of  two  similar  blades  situated  side  by  side.  Each  blade  con- 
sists of  two  gonopophyses,  an  upper  or  posterior  one,  known  as  the 
support  or  lance,  and  a  lower  or  anterior  one,  the  so-called  saw  or 
lancet.  The  supports  are  the  inner  gonopophyses  of  the  ninth  ab- 
dominal segment,  and  the  saws  are  the  gonopophyses  of  the  eighth 

abdominal  segment. 

Although  each  of  the  saws 
is  closely  joined  to  its  support 
it  can  be  moved  backward  and 
forward  along  it.  Figure  113 2 
represents  one  of  the  blades  of 
the  ovispositor  of  Cimhex  amer- 
icana. 

The  ovipositor  of  this  saw- 
Fig.  1 132. — Blade  of  ovipositor  of  Cimhex      fly  is  fitted  for  cutting  slits  in 
americana;  a,  support ;  b,  lancet.  leaves  in  which  the  eggs  are  de- 

posited. In  those  members  of 
this  suborder  that  deposit  their 
eggs  m  the  stems  of  plants  or  the  trunks  of  trees,  as  the  Siricidce,  the 
ovipositor  is  slender  and  long.  After  a  slit  has  been  cut  or  a  hole 
drilled  in  the  trunk  of  a  tree,  as  the  case  may  be,  an  egg  is  forced  down 
between  the  blades  of  the  ovipositor  to  the  nidus  prepared  for  it 
The  larvae  of  the  Chalastogastra  are  all  plant-feeders.  With  the 
exception  of  those  that  are  leaf-miners  they  are  caterpillar-like  in  form. 
Prolegs  are  present  in  the  Xyelidae,  Cimbicidae,  Tenthredinida  and 


HYMENOPTERA  893 

Argidce;  but  these  are  not  provided  with  hooks  as  are  the  prolegs  of 
caterpillars. 

A  striking  feature  of  the  larvae  of  this  suborder  is  the  possession 
of  a  pair  of  ocelli,  one  on  each  side,  which  in  their  position  and  in 
their  structure  agree  with  the  ocelli  of  adult  insects,  that  is,  they  are 
primary  ocelli.  This  characteristic  distinguishes  these  larvae  from 
the  larvee  of  Lepidoptera,  which  have  only  adaptive  ocelli,  usually 
several  on  each  side  (wSee  page  136). 

A  classification  of  thelarvas  of  this  suborder  was  published  by 
Yuasa  ('22). 

TABLE  FOR  DETERMINING  THE  FAMILIES  OF  THE 
CHALASTOGASTRA 

A.  Front  wings  with  three  marginal  cells,  both  vein  r  and  R2  being  present;  the 
basal  segments  of  the  fiagellum  are  consolidated,  thus  forming  what  appears  to 
be  a  very  long  third  segment,  and  the  remaining  segments  are  smaU.  p.  894. 
Xyelid^e 

AA.     Front  wings  with  the  free  part  of  vein  R2  always  wanting;  antennae  with 
three  or  more  segments,  third  segment  never  as  long  as  all  the  following  seg- 
ments together;  if  the  third  segment  be  long,   antenna,   consisting  of  only 
three  segments. 
B.     Front  wings  with  subcosta  present  as  a  distinct  longitudinal  vein.  p.  895. 

FAMPHILIIDiE 

BB.  Front  wings  with  subcosta  absent;  rarely  it  is  present  as  a  pale,  very  in- 
distinct line,  closely  appressed  to  vein  R  +  M,  or  vein  Sci  may  be  present  as  a 
transverse  vein. 

C.    Radial  cross- vein  (r)  of  the  front  wings  received  by  the  2nd  submarginal 

cell  (Rs)  or  if  it  is  absent  or  the  2nd  and  3rd  submarginal  cells  united 

(R4  united  with  R5),  then  the  anterior  tibiae  have  a  single  apical  spur. 

D.     Front  wings  with  the  cross-vein  m-cii  subequal  in  length  to  the  first 

section  of  the  free  part  of  media. 

E.  Vein  Sci  absent  in  the  front  wings;  the  last  abdominal  segment 
bears  a  more  or  less  horn-like  prolongation;  maxillary  palpi  one- 
segmented;  labial  palpi  two-  or  three-segmented,  the  last  segment 
enlarged  and  bearing  a  large   sensory   cup,   the  first   segment  not 

elongate,    p.    896 Siricid^ 

EE.  Vein  Sci  present;  last  abdominal  segment  without  horn-like  pro- 
longation; maxillary  palpi  four-segmented;  labial  palpi  three-seg- 
mented, the  last  without  a  sense-cup,  the  first  elongate,  p.  897..  . 

XlPHYDRUD^ 

DD.    Front  wings  with  the  cross-vein  m-cii  joined  to  vein  M  at  or  near  its 

separation  from  vein  R.  p.  898 Cephid^ 

CC.  Radial  cross- vein  (r)  of  the  front  wings  received  by  the  3rd  or  4th 
submarginal  cell  (cell  R4  or  R3)  or  wanting;  anterior  tibiae  always  with 
two  apical  spurs. 

D.     Abdomen  with  distinct  pleural  sclerites;  bearing  the  spiracles,  an- 
tennae   clavate.    p.    900 Cimbicid^e 

DD.    Abdomen  without  separate  pleural  sclerites;  antennas  not  clavate  in 
North  American  forms. 
E.     Scutellum  with  a  distinct  apical  plate,  the  post-tergite;  posterior 

coxffi  contiguous  or  nearly  so.  p.  900 Tenthredinid/E 

EE.  Scutellum  without  a  post-tergite;  posterior  coxae  often  wide  y 
separated,     p.     902 ArgiDae 


894 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Family  XYELID^ 

The  Xyelid  Sawflies 

The  members  of  this  family  can  be  recognized  by  the  form  of  the 

antennas  and  the  venation  of  the  wings.    The  basal  segments  of  the 

flagellum  are  consolidated,  thus  forming  what  appears 

to  be  a  very  long  third  segment  of  the  antenna  and  the 

remaining  segments  of  the  flagellum  are  small   (Fig. 

1 133).     Except  in  Neoxyela  alberta,  a  species  recently 

described  from  Banff,   Alberta,   the  members  of  this 

family  differ  from  all  other  Hymenoptera  in  that  the 

free  part  of  vein  Ro  of  the  fore  wings  is  present  (Fig. 

1134)- 

The  posterior  margin  of  the  pronotum  is  straight  or 
nearly  so.  The  mesonotum  is  short  and  never  extends 
much  beyond  the  anterior  margins  of  the  tegulas.  The 
anterior  tibise  are  armed  with  two  apical  spurs.  In 
some  species  the  ovipositor  is  very  long,  in  others  it  is 
of  moderate  length. 

The  described  larvse  feed  on  the  foliage  of  hickory, 
butternut,  pecan,  elm,  and  the  staminate  flowers  of 
pine.  In  the  larvae  each  of  the  ten  abdominal  segments 
bears  a  pair  of  prolegs,  although  in  some  species  those 
of  the  first  and  ninth  segments  are  smaller  than  the 
others. 


Fig.    1 134- — Wings   of    Macroxyela. 
cells  are  lettered. 


The 


HYMENOPTERA  895 

Family  PAAIPHILIID.-E 

The  Web-spinning  and  the  Leaf-rolling  Sawflies 

The  common  names  given  above  were  suggested  by  the  fact  that 
the  larva;  of  some  species  build  nests  by  tying  the  leaves  of  their 
food  plants  together  with  a  web  of  silk,  and  others  build  nests  by 
rolling  the  edge  of  a  leaf  and  live  inside  the  tube  so  formed.  The  larvae 
of  some  species  are  gregarious.  The  larvae  of  members  of  this  family 
have  long,  seven-jointed  antennae,  well-developed  thoracic  legs,  but 
lack  abdominal  prolegs. 

In  the  fore  wings  of  the  adult  (Fig.  1135)  vein  Sc  is  preserved  as 
a  distinct  vein ;  the  free  part  of  vein  Ro  is  wanting ;  and  vein  Cu2  is 
usually  preserved,  at  least  as  a  short  spur.  In  the  hind  wings  vein  Sc 
is  more  or  less  distinctly  preserved. 

The  body  of  the  adult  is  robust.  The  posterior  margin  of  the 
pronotum  is  straight  or  nearly  so.  The  mesonotimi  is  short  and 
never  extends  much  beyond  the  anterior  margins  of  the  tegulae.  The 
anterior  tibiae  are  armed  with  two  apical  spurs.  The  ovipositor  of 
the  female  is  short. 

More  than  fifty  species  have  been  described  from  America  north  of 
Mexico ;  but  the  larvs  of  only  a  few  of  these  are  known ;  among  these 
are  the  following. 

The  pliim  web-spinning  sa\vfiy,  Neurotmna  inconspicua. — The  lar- 
vae of  this  species  feed  on  the  foliage  of  plum  and  cherry;  they  are 
gregarious  and  form  unsightly  nests  by  spinning  webs  over  the 
leaves ;  frequently  these  webs  cover  an  entire  tree.  The  injury  is  done 
in  early  summer.  When  full-grown  the  larvae  find  their  way  to  the 
ground,  where  they  pass  the  remainder  of  the  summer  and  winter  in 
earthen  cells,  they  transform  to  pupae  in  the  spring,  and  the  adults 
emerge  in  May  or  June.  This  pest  is  controlled  by  spraying  or  dusting 
the  infested  trees,  with  lead  arsenate. 

The  peach  sawfly,  Pamphtlius  persicus. — This  pest  of  the  peach 
is  one  of  the  leaf -rolling  species.  The  adults  emerge  from  the  ground 
late  in  May  or  early  in  June  and  lay  their  eggs  on  the  leaves;  the 
eggs  soon  hatch ;  each  larva  cuts  a  slit  in  a  leaf  and  then  rolls  over  a 
portion  of  the  leaf,  making  a  case  within  which  it  stays  during  the 
daytime,  feeding  chiefly  at  night.  There  is  a  single  generation  a  year. 
The  larva  passes  the  winter  in  the  ground.  The  same  method  of 
control  is  used  as  with  the  preceding  species. 


896 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  1 135. — Wings  oi  Pamphilus.    The  veins  are  lettered. 


Family  SIRICID^ 


The  Horn-tails 


The  common  name  horn-tails  is  appHed  to  members  of  this 
family  because  the  last  abdominal  segment  bears  a  more  or  less 
horn-like  prolongation.  This  is  short  and  triangular  in  the  males,  and 

is  a  prolongation  of  the  last  ven- 
tral segment;  in  the  females  it  is 
long  and  often  spear-shaped,  and  is 
a  prolongation  of  the  last  dorsal 
segment. 

The  body  is  cylindrical  (Fig. 
1 13 6);  the  head  large  and  widened 
behind  the  eyes;  the  pronotum  is 
right-angled,  so  that  it  presents  both 
a  strictly  dorsal  and  a  cephalic  as- 
pect, the  latter  concave;  vein  Sci  of 
the  front  wings  is  absent  (Fig.  1 137) ; 
the  propodeum  is  divided  longitu- 
dinally ;  the  anterior  tibiae  each  with 
only  one  apical  spur;  the  sheath  of 
the  ovipositor  is  very  long  and  exserted  beyond  the  end  of  the  ab- 
domen ;  the  ovipositor  is  fitted  for  boring. 


Fig.  1 136. — Tremex  columba. 


IIYMENOPTERA 


897 


The  Siricidae  is  a  small  family;  only  about  fifty  species  represent- 
ing five  genera  are  known.  The  North  American  species,  of  which 
there  are  twenty,  have  been  monographed  by  Bradley  ('13). 

The  larva?  bore  in  the  trunks  of  trees;  our  best-known  sjjecies  is 
the  following  one. 

The  pigeon  horn-tail,  Trcmex  columha. — The  larva  of  this  species 
infests  maple,  elm,  apple,  pear,  beech,  oak,  and  sycamore.  The  female 
(Fig.  1 136)  in  order  to  oviposit  pierces  the  wood  of  a  tree  to  the  depth 
of  10  to  12  mm;  the  eggs  are  laid  singly;  sometimes  her  ovipositor 
gets  wedged  in  the  wood  and  holds  her  a  prisoner  until  she  dies. 
The  larva  is  cylindrical  and  attains  a  length  of  40  mm.  It  transforms 
within  its  burrow,  in  a  cocoon  made  of  silk  and  fine  chips. 


C -\-  8c^        Sc 


5+  M, 


+  Cu,,2  +  1st  +  «d  +  3d  A 


Wings  of  Sirex  juvencus.     (From  Bradley.) 


The  adults  of  this  species  vary  in  color  and  marking;  based  on 
these  variations,  three  fairly  distinct  races  have  been  recognized, 
which  to  a  considerable  extent  are  geographical,  although  their 
ranges  overlap.  In  the  typical  form,  race  columha,  the  abdomen  is 
black,  with  ochre-yellow  bands  and  spots  along  the  sides;  this  is  the 
common  form  in  Quebec,  Ontario,  and  the  northeastern  United  States. 
In  the  race  aureus  the  ground  color  of  the  abdomen  is  yellow  and  the 
markings  black;  this  is  the  common  form  in  the  Rocky  Mountains 
and  is  found  on  the  Pacific  Coast.  In»the  race  sericetis  the  entire 
body  is  fulvous,  the  legs  beyond  the  femora  yellow,  and  the  wings 
dark  reddish  brown;  this  race  is  found  in  the  southeastern  United 
States  and  as  far  north  as  Pennsylvania  and  West  to  Utah. 

Family  XIPHYDRIID^ 

The  Xiphydriid  Saw/lies 


This  family  is  composed  of  a  small  number  of  species  which  are 
closelv  allied  to  the  Siricidce  but  which  differ  from  them  in  several 


898 


AN  INTRODUCTION  TO  ENTOMOLOGY 


important  particulars.  As  with  the  horn-tails  the  body  is  cylindrical 
but  the  last  abominal  segment  is  not  terminated  by  a  triangular  or 
lanceolate  process.  The  back  of  the  head  is  separated  from  the  pro- 
notum  by  an  elongate  neck;  the  pronotum  is  very  short  medially 
and  not  angulate  laterally;  vein  Sci  is  present  in  the  front  wings  as 
a  transverse  vein  (Fig.  1 138)  and  the  sheath  of  the  ovipositor  is  seldom 
longer  than  the  last  tergite. 


-yn.^.-^' 


Wings  of  Xiphydria  maculata.     (From  MacGillivray.) 


The  members  of  this  family  are  of  moderate  size.  Less  than  a  dozen 
species  have  been  described  from  North  America. 

The  known  larvae  bore  in  dead  and  decaying  wood  of  deciduous 
trees. 

Family  CEPHID^ 


The  Stem  Sawflies 

The  stem  sawflies  are  so-called  because  the  larvce  bore  into  the 
stems  of  plants  or  in  the  tender  shoots  of  trees  and  shrubs.  The  adults 
are  slender,  elongate  insects  of  moderate  size.  The  pronotum  is 
more  or  less  quadrate  and  longer  than  is  usual  in  theHymenoptera. 
The  front  wings  are  without  a  distinct  cell  between  the  costa  and 
vein  Sc+R+M,  and  with  cross- vein  m-cu  joined  to  vein  M  at  or 
near  its  separation  from  vein  R  (Fig.  1139).  The  anterior  tibia?  are 
armed  with  one  terminal  spur. 

This  family  is  of  moderate  size ;  less  than  a  score  of  species  have 
been  found  in  our  fauna;  but  these  represent  nine  genera.  Some  of 
the  species  are  of  economic  importance.  Several  species  bore  in  the 
stems  of  grains  and  grasses,  the  following  species  illustrate  the  habits 
of  these. 


HYMENOPTERA 


899 


The  wheat-sawfly-borer,  Cephus  pygmceus. — The  larva?  of  this 
species  bore  in  the  stems  of  wheat,  a  single  larva  in  a  stem,  dwarfing 
and  stunting  the  growth  of  the  plant.  As  the  grain  becomes  ripe  the 
larva  works  its  way  toward  the  ground;  and  at  the  time  of  harvest 
the  greater  number  of  them  have  penetrated  the  root.  Here,  in  the 
lowest  part  of  the  cavity  of  the  straw,  they  make  preparations  for 
passing  the  winter,  and  even  for  their  escape  from  the  straw,  as  adults, 
the  following  year.  This  is  done  by  cutting  the  straw  circularly  on 
the  inside,  nearly  severing  it  a  short  distance  from  the  ground,  so 
that  a  strong  wind  will  cause  it  to  break  off  at  this  point.  After  the 
circular  cut  has  been  made,  the  larva  fills  the  cavity  of  the  straw  just 
below  it  for  a  short  distance  with  a  plug  of  borings.    Between  this 


IstMz 


Fig.   1 139. — Wings  of  Cephus  pygmceus.     The  cells  are  lettered.     (From  Mac- 
Gillivray.) 

plug  and  the  lower  end  of  the  cavity,  the  wall  of  the  cavity  is  lined 
with  silk  forming  a  cocoon  within  which  the  larva  passes  the  winter 
and  changes  to  a  pupa  in  March  or  April.  The  adult  insects  emerge 
early  in  May. 

The  currant-stem  girdler,  Janus  Integer. — The  larva  of  this  species 
bores  in  the  upper  portion  of  the  canes  of  currant.  Its  presence  is 
indicated  by  the  wilting  and  drooping,  in  late  spring,  of  the  new 
growth  at  the  tip  of  the  infested  cane.  This  is  due  to  the  fact  that 
the  parent  sawfiy  after  depositing  her  egg  in  the  cane  moves  up  a 
short  distance  above  where  the  egg  is  deposited  and  with  her  ovipositor 
girdles  the  cane,  sometimes  nearly  severing  it.  This  killing  of  the 
tip,  and  thus  checking  the  growth  of  the  cane,  seems  to  be  necessary 
for  the  development  of  the  egg  and  larva.  The  larva  bores  in  the 
pith  of  the  cane.  In  the  fall  it  eats  a  hole  through  the  woody  wall 
of  the  cane  to  the  outer  bark,  thus  making  provision  for  the  escape 
of  the  adult,  and  then  spins  a  cocoon  in  which  it  hibernates.     The 


900 


AN  INTRODUCTION  TO  ENTOMOLOGY 


change  to  the  pupa  state  takes  place  in  April  and  the  adult  emerges 
in  May.  The  obvious  method  of  control  of  this  pest  is  to  remove 
and  burn  the  infested  portion  of  the  canes  while  the  larvae  are  in  them. 


Fig.  1 140. — Cimbex  americana.  Abdomen 
except  first  segment:  7,  8,  g,  pleurites; 
T,  T,  T,  tergites;  S,  S,  S,  sternites;..  cr, 
cercus;  sp,  spiracle.    (After  Snodgrass.) 


Family  CIMBICID^ 

The  Cimhicid  Sawfiies 

This  is  a  small  family,  which  is  represented  in  our  fauna  by  a 
few  genera  and  a  limited  ntmiber  of  species.    In  this  family  the  body 

is  stout  and  often  very  large ; 
there  are  distinct  pleural  scler- 
ites  in  the  abdomen  (Fig.  1 140) 
and  the  antennae  are  clavate. 
The  anterior  tibi«  and  meta- 
tarsi bear  ribbon-shaped  or 
spatulate  hairs ;  the  pulvilli  are 
large,  broadly  sessile  on  the 
last  tarsal  segment,  and  are 
not  retractile.  The  sheath  of 
the  ovipositor  extends  but  lit- 
tle if  at  all  beyond  the  end  of 
the  abdomen. 

The  bod}^  of  the  larvcC  is  cylindrical,  stout,  and  covered  with  a 
waxy  bloom  when  living;  the  thoracic  legs  are  well-developed  and 
five-jointed;  and  the  abdomen  bears  eight  pairs  of  prolegs.  The  lar- 
vae live  free  upon  foliage  upon  which  they  feed. 

The  American  sawfiv^  Chnhex  americana. — This  is  the  largest  of 
our  common  sawfiies.  The  female  is  about  1 8  mm.  in  length  and  has  a 
black  head  and  thorax,  a  steel-blue  or  purplish  abdomen,  with  four  yel- 
lowish spots  on  each  side,  smoky  brown  wings,  and  black  legs,  while  her 
feet  and  short,  knobbed  antennae  are  pale  yellow.  The  male  is  longer 
and  slenderer  and  differs  somewhat  in  color.  Several  varieties  of  this 
species,  differing  in  color,  have  been  described.  The  eggs  are  laid  in 
June  in  crescent-shaped  slits  made  in  leaves.  The  food  plants  are  elm, 
birch,  linden,  and  willow.  The  larva  is  greenish  yellow,  with  black 
spiracles  and  a  black  stripe  down  its  back.  When  disturbed  it  spurts 
forth  a  fluid  from  glands  just  above  the  spiracles.  It  clings  to  the 
upper  surface  of  a  leaf  and  feeds  on  the  edge  of  the  leaf.  When  not 
feeding  it  rests  on  one  side  with  the  body  curled  up  in  a  spiral  fonn. 
There  is  but  one  generation  each  3'ear.  When  the  larva  is  full-grown 
it  burrows  in  the  ground,  makes  an  oval,  brownish  cocoon,  and  there 
spends  the  winter,  not  changing  to  a  pupa  until  spring.  The  adults 
appear  in  May  or  June. 


Family  TENTHREDINID^ 

The  Typical  Sawfiies 

This  is  a  very  large  family,  including  more  than  seven-eighths  of 
all  of  the  members  of  the  suborder  Chalastogastra.     To  this  family 


HYMENOPTERA 


901 


belon^^  all  of  the  Chalastogastra  in  which  the  radial  cross-vein  of  the 
fore  wings  is  opposite  cell  R4,  or  cell  R;,,  or  is  wanting,  except  the 
small  family  Cimbicida^.  The  typical  sawfhes  differ  from  the  Cimbi- 
cid^e  in  lacking  pleural  sclerites  in  the  abdomen  and  in  that  the 
antennae  are  not  clavate.  The  anterior  tibicc  and  tarsi  do  not  bear 
ribbon-shaped  or  spatulate  hairs,  as  in  the  Cimbicidaj;  and  the  pulvilli 
are  inserted  on  the  end  of  the  last  tarsal  segment  and  are  retractile, 
like  the  finger  of  a  glove.  The  sheath  of  the  ovipositor  extends  but 
little  if  at  all  beyond  the  end  of  the  abdomen. 

The  larvffi  are  caterpillar-like;  the  thoracic  legs  are  always  present 
and  are  usually  well  developed,  but  are  vestigial  in  some  species. 
Prolegs  are  usually  present ;  these  are  borne  on  abdominal  segments 
2-7  and  10  or  2-8  and  10,  rarely  the  prolegs  are  vestigial.  Thelarva3 
of  the  different  species  differ 
greatly  in  size,  varying  from 
10-40  mm.  in  length. 

The  larvae  of  the  majori- 
ty of  the  species  live  free  on 
the  foliage  of  plants,  upon 
which  they  feed  (Fie.  1 1 4 1 ) . 
The  plants  infested  by  the 
different  species  include 
trees,  both  deciduous  and 
conifers,  shrubs,  herbs, 
grasses,  and  ferns.  The  lar- 
vas  of  some  species  are  leaf- 
miners;  others  fold  the 
edges  of  leaves ;  some  make 
galls  on  leaves,  especially  of 
willow  and  poplar;  others 
make  galls  in  the  stems  of 
these  plants;  and  one  spe- 
cies, Caulocampa  acericau- 
Its,  bores  in  the  petioles  of 
maple  leaves.  Among  the 
species  that  have  attracted 
attention  on  account  of  their 
economic  importance  are  the 
following. 

The  imported  currant- 
worm,  Pteronidea  ribesi. — 
This  is  the  commonest  and 
best-known  of  the  garden  pests.  The  adult  sawflies  appear  early  in 
the  spring  and  the  females  lay  their  eggs  in  rows  along  the  principal 
veins  on  the  underside  of  the  leaves  of  currants  and  gooseberries. 
The  eggs  are  glued  to  the  leaf-veins  and  not  inserted  in  slits,  as  is 
usually  the  case  with  sawflies,  and  they  increase  considerably  in  size 
before  hatching.  They  hatch  in  a  week  or  ten  days;  and  the  larvas 
begin  at  once  to  feed  upon  the  leaves.     Often  by  the  time  the  larvas 


Fig.  1 141. — The  locust  saw-fly,  Pteronidea 
trilineata:  a,  egg;  b,  young  larva;  c,  full- 
grown  larva;  d,  anal  segment  of  full-grown 
larva;  e,  cocoon;/,  adult. 


902  AN  INTRODUCTION  TO  ENTOMOLOGY 

become  full-grown  the  infested  bush  is  completely  stripped  of  its 
foliage.  The  larvae  are  at  first  whitish,  as  they  increase  in  size  the 
color  changes  to  green ;  after  the  first  molt  the  body  becomes  covered 
with  many  black  spots  and  the  head  is  black ;  at  the  last  molt  they 
lose  their  black  spots  and  assume  a  uniform  green  color  tinged  with 
yellow  at  the  ends.  When  full-grown  the  larvae  descend  to  the 
ground  and  spin  their  cocoons,  either  just  below  the  surface  of  the 
ground  or  beneath  rubbish;  sometimes  the  cocoons  are  attached  to 
the  stems  or  leaves  some  distance  from  the  ground.  A  second  genera- 
tion of  the  sawflies  appears  late  in  June  or  early  in  July ;  and  some- 
times a  third  generation  is  developed ;  this  makes  it  necessary  to  fight 
this  pest  throughout  the  spring  and  summer.  The  larvae  can  be  easily 
destroyed  in  the  spring  b}^  spraying  the  bushes  with  Paris  green  or 
with  arsenate  of  lead;  later  when  the  fruit  is  near  maturity  fresh 
hellebore  should  be  used  at  the  rate  of  four  ounces  in  two  or  three 
gallons  of  water,  or  as  a  dry  application,  one  pound  in  five  pounds  of 
flour  or  air-slacked  lime. 

The  pear-slug,  Caliroa  cerasi. — This  is  a  well-known  pest  of  pear, 
cherry,  and  plum.  It  causes  the  leaves  of  the  infested  tree  to  turn 
brown.  When  such  leaves  are  examined  it  is  found  that  the  injury 
is  due  to  small,  slim}^  slug-like  larvee,  which  have  eaten  off  the  upper 
surface  of  the  leaves,  leaving  the  skeleton  of  veins  and  the  lower 
epidermis  to  turn  brown,  wither  and  fall ;  sometimes  trees  are  entirely 
defoliated  in  this  way  by  midsummer.  When  full-grown  the  larvae 
descend  and  burrow  into  the  ground  a  short  distance,  where  each 
constructs  an  earthen  cell  in  which  it  transforms.  A  second  genera- 
tion of  the  sawflies  appear  and  lay  their  eggs  about  three  weeks  later. 
The  larvae  can  be  destroyed  by  the  use  of  arsenate  of  lead  spray  or 
by  dusting  the  leaves  with  freshly  slaked  lime. 

The  rose-slug,  Cladius  isomerns.- — Often  in  the  sirmmer  our  rose- 
gardens  look  as  if  fire  had  swept  over  them,  so  scorched  and  brown 
are  the  leaves.  The  cause  of  this  apparent  conflagration  is  a  trans- 
parent jelly-like  slug,  greenish  above  and  yellowish  below,  which  eats 
the  upper  surface  of  the  leaves,  leaving  patches  of  the  lower  siirface 
and  the  veins.  These  slugs  usually  feed  by  night  and  remain  hidden 
on  the  lower  surface  of  the  leaves  by  day.  When  ready  to  pupate  they 
crawl  down  or  drop  to  the  ground  and  burrow  beneath  the  surface; 
here  each  makes  a  little  cell  and  then  transforms.  The  adult  fly  is 
shining  black  with  smoky  wings  and  with  the  fore  and  middle  legs 
grayish  or  dirty-white.  The  female  is  5  to  6  mm.  in  length.  There 
are  two  broods  a  year,  one  in  June  and  one  in  August.  The  last 
brood  passes  the  winter  in  the  ground.  This  pest  can  be  destroyed 
with  a  solution  of  whale-oil  soap,  or  with  kerosene  emulsion. 

Family  ARGID^ 

The  Argid  Saw-flies 
This  family  has  been  recently  separated  from  the  Tenthredinidae, 
from  which  it  is  distinguished  by  the  absence  of  a  post-tergite.    This 
is  a  distinct  apical  plate  borne  by  the  scutellum,  which  is  present  in 
all  of  the  Tenthredinidae  and  absent  in  this  family. 


HYMENOPTERA 


903 


The  family  Argidas  consists  chiefly  of  tropical  insects,  but  a  few- 
representatives  of  the  family  are  found  in  this  country.  Among  these 
are  two  species  of  Sterictlphora,  the  larvae  of  which  occasionally  infest 
sweet  potatoes  to  an  injurious  extent. 

Suborder  IDIOGASTRA* 


This  suborder,  the  establishment  of  w^hich  was  recently  proposed 
by  Rohwer  and  Cushman  ('17)  includes  a  single  small  family  of  rare 
insects,  the  Oryssidse,  which  formerly  was  included  in  the  suborder 
Chalastogastra. 

The  suborder  Idiogastra  stands  intermediate  between  the  other 
two  suborders  of  the  H^Tnenoptera.  In  this  suborder  the  adults  re- 
semble the  Chalastogastra  in  the  shape  of  the  abdomen;  but  the  form 
and  habits  of  the  larvae  are  those  characteristic  of  the  Clistogastra. 
The  distinctive  characteristics  of  the  Idiogastra  are  those  of  the  single 
familv  included  in  it. 


Family  ORYSSID^ 


The  Oryssids 


In  the  shape  of  the  body  (Fig. 
1 142,  A)  the  members  of  this 
family  strongly  resemble  the  Siri- 
cidfe.  They  are  easily  distin- 
guished, however,  from  all  of  the 
Chalastogastra  by  the  anomalous 
position  of  the  antennee,  which  are 
inserted  far  below  the  eyes,  im- 
mediately above  the  mandibles, 
under  a  transverse  ridge  (Fig. 
1142,  B);  by  the  more  reduced 
venation  of  the  wings;  and  by 
the  remarkable  foiTn  of  the  ovi- 
positor. 

In  the  fore  wings  (Fig.  1143) 
the  transverse  part  of  vein  M2  is 
wanting;  and  in  the  hind  wings 
R4  is  wanting;  therefore,  there 
are  no  closed  submarginal  cells 
in  the  hind  wings.  This  combina- 
tion of  characters  distinguishes 
the  Oryssidaj  from  all  of  the  Chal- 
astogastra.    In  the  Oryssida3  the 

first  anal  cell  of  the  fore  wings  is  preserved,  in  which  respect  the 
members  of  this  family  differ  from  all  of  the  Clistogastra. 

*Idiogastra:  idio  (iStos),  distinct;  gaslros  (yaffTp6s),  the  belly. 


Fig.  1 1 42. — Oryssus  sayi;  A,  female;  B, 
head  seen  from  in  front.  (From 
Sharp.) 


904  AN  INTRODUCTION  TO  ENTOMOLOGY 

In  the  form  of  the  ovipositor  and  in  its  position  when  at  rest  the 


4+5 


K. 


43. — Wings  of  Oryssus  abietinus.     (From  MacGillivray.) 

Oryssidae  differ  from  all  other  Hymenoptera.    The  following  account 
of  this  organ  is  that  of  Rohwer  and  Cushman  ('17). 

Lying  below  and  on  each  sfde  of  the  eighth  tergite  in  the  female  is  a  large 
heavily  chitinized  plate,  the  two  together  forming  ventrally  a  channel  for  the  re- 
ception of  the  ovi- 
positor, and  each 
bearing  at  its  tip  a 
small  triangular  ap- 
pendage. These 
plates  apparently 
represent  the  fused 
ninth  and  tenth  ter- 
gites  which  are  lon- 
gitudinally divided 
dorsally  (Fig.  1144, 
9T  and  loT),  and 
the  appendages  are 
apparently  the  cer- 
ci  (Fig.  1 144,  c);  the 
eighth  sternite  is  in- 
t  ernal  and  lies 
above  and  some- 
what behind  the 
ninth,  and  is  rep- 
resented by  two 
triangular  plates, 
from  the  upper 
angle  of  which  or- 
iginate the  lancets 
(fi  r  s  t  gonopophy- 
ses)  (Fig.  1 145,  //); 


Fig.  1 1 44. — Lateral  aspect  of  abdomen  of 
the  female  of  Oryssus.  (After  Rohwer 
and  Cushman.) 


Fig.  1 145. — Details  of  the  ovipositor  of  Oryssus:  9  T,  10  T, 
ninth  and  tenth  tergites;  8  S,  eighth  sternite;  9  S,  ninth 
sternite;  //,  lancet;  /,  lance;  sh,  sheath;  0,  ovipositor;  c, 
cerci.     (After  Rohwer  and  Cushman.) 


the  ninth  sternite  is  also  internal,  lying  below  and  in  front  of  the  eighth 
and  represented  by  two  more  or  less  triangular  plates  which  extend  postero- 
ventral;  the  lance  (second  gonopophyses)  originates  from  the  inner  ends  of  these 
plates  and  becomes  fused  a  short  distance  cephalad  of  its   origin  (Fig.  1145,  /); 


IIYMENOPTERA 


905 


the  two  parts  of  the  sheath  (third  gonopophyses)  arise  from  the  apices  (Fig. 
1 145,  vSh).  Shortly  cephalad  of  the  origin  of  the  lance  and  lancets  the  latter  en- 
ter the  groove  of  the  former,  the  complete  ovipositor  as  thus  formed  extending 
cephalad  in  an  inverted  position  enclosed  within  a  membraneous  sac,  probably  in- 
vaginated  intersegmental  skin,  into  the  mesothorax,  where  it  is  coiled,  and  re- 
turning upon  itself  continues  caudad  in  its  normal  position  and  enters  the  base  of 
the  sheath  (Fig.  1145). 

The  OryssidcC  is  a  widely  distributed  family,  members  of  it  having 
been  found  in  all  of  the  major  geographical  regions  of  the  world.    But 
it  is  a  small  family,  including  only  a  few  genera  and 
species.    A  single  genus,  Oryssus,  is  found  in  North 
America,  of  which  about  a  dozen  species  have  been 
described  from  this  region. 

The  adults  are  very  active  and  are  found  running 
over  the  trunks  of  trees  and  on  timber.  The  larvae 
were' formerly  supposed  to  be  borers  in  the  trunks  of 
trees;  but  it  has  been  shown  by  Burke  ('17)  that 
they  are  parasitic  on  the  larvae  of  Buprestis  and  prob- 
ably on  other  wood-boring  larvae. 

The  larva  of  only  a  single  species,  Oryssus  occi- 
dentalis,  is  known.  This  is  white,  subcylindrical, 
about  one-third  as  thick  as  long,  and  legless;  but  the 
positions  of  the  legs  are  indicated  by  chitinized  disks. 
The  mouth -parts  are  very  simple,  the  labrum,  labium, 
and  maxillffi  being  merely  fleshy  lobes,  but  the 
mandibles  are  heavily  chitinized;  the  antennas  are 
tubercle-like  and  set  at  the  summits  of  rounded 
elevations. 


Fig.  1146.— 
Pupa  of  Ory- 
ssus, female. 
(After  Roh- 
wer  and  Cush- 
man.) 


In  the  pupa  of  the  female  (Fig.  1 146)  the  terminal 
portion  of  the  ovipositor  is  external  and  extends  over 
the  back  the  entire  length  of  the  body.     Referring  to  this,  Rohwer 
and  Cushman  ('17)  state  as  follows: 

The  reason  for  the  formation  in  the  pupa  of  the  long  external  ovipositor  is  in- 
explicable, and  its  reduction  to  the  form  existing  in  the  adult  is  equally  inex- 
plicable. This  is  rendered  all  the  more  difficult  to  understand  by  the  fact  that  in 
the  prepupa  the  ovipositor  is  coiled  as  it  is  in  the  adult,  while  in  the  pupa  it  forms  a 
simple  loop  in  the  thorax. 


Suborder  CLISTOGASTRA  or  APOCRITA* 

This  most  striking  characteristic  of  this  suborder  is  the  fact  that 
what  appears  to  be  the  first  abdominal  segment,  but  which  is  really 
the  second,  is  greatly  constricted  forming  a  slender  petiole  or  waist 
between  the  larger  portion  of  the  abdomen  and  the  alitrunk  or  wing- 
bearing  region  of  the  body  (Fig.  1147). 

*The  name  Clistogastra  is  the  one  most  commonly  appHed  to  this  suborder 
and  for  that  reason  is  used  in  this  work;  but  some  authors  use  Apocrita,  which  is 
really  the  older  name.  The  etymology  of  these  names  is  as  follows  Clistogastra: 
clisto  (x^e'ffrrfs),  closed;  gastros  [ya'STpos),  the  belly.  Apocrita:  apocritos 
(dTTO/cpn-oj),  separated;  apo  (aird),  from,  crino  (Kplvi,}),  to  separate. 


906  AN  INTRODUCTION  TO  ENTOMOLOGY 

In  this  suborder  the  intermediate  region  of  the  body  is  not  merely 
the  thorax  but  includes  also  the  first  abdominal  segment,  only  the 
tergum  of  which  is  preserved  in  the  adult.    This 
is  known  as  the  median  segment,  or  the  propodeum 
and  can  be  identified  by  its  spiracles,  the  third 
pair  of  this  region  of  the  body.     It  should  be  re- 
Fig  114-  membered  that  the  thorax  bears  only  two  pairs 
of  spiracles  (See  page  115).     From  the  above  it 
follows  that  what  appears  to  be  the  first  abdominal  segment  in  the 
CHstogastra,  and  which  is  usually  so-called,  is  really  the  second. 
In  the  CHstogastra  the  ovipositor  and  its  sheath  are  composed  of 
the  same  morphological  elements  as  are  those  of  the  sawflies  described 
on  an  earlier  page;  but  these  parts  differ  greatly  in  form  in  different 
members  of  this  suborder.    In  some  the  ovipositor  is  a  boring  instru- 
ment by  means  of  which  deep  holes  are  made  into  trees  and  eggs 
placed  in  these  holes;  in  others  it  is  used  for  thrusting  the  eggs  into 
the  bodies  of  other  insects ;  and  in  still  others  it  is  modified  so  as  to 
form  a  sting  with  which  poison  glands  are  connected. 

TABLE  OF  FAMILIES  OF  THE  CLISTOGASTRA* 

A.     With  well-developed  wings. 

B.     Hind  wings  without  an  anal  lobe.t 

C.    No  erect  scale  or  node  between  the  gaster  and  the  propodeum. 

D.  The  costal  cell  of  the  fore  wings  eliminated  by  the  coalescence  of  the 
costal  and  subcostal  veins,  except  in  the  case  of  two  or  three  rare  genera. 
The  venter  is  membranous  and  has  in  dried  specimens  a  longitudinal 
fold. 

E.     The  transverse  part  of  vein  M2  of  the  fore  wings  wanting,  causing 
the  union  of  cells  Mi  and  ist  M^  (Fig.  1148). 

F.      The  abdomen   not   very  long  and  slender   and   strongly   com- 
pressed,   p.    916 Braconid^ 

FF.      The  abdomen  very  long,   slender,   and  strongly   compressed. 

(The    genus    Pharsalia)    p.  917 Ichneumonid^ 

EE.    Cells  Mi  and  ist  M2  separated  by  the  transverse  part  of  vein  M2 

(Fig.     I  152).    p.    917 ICHNEUMONID^ 

DD.     The  costal  cell  of  the  fore  wings  present.     The  venter  chitinized. 
E.    Abdomen  borne  on  the  dorsal  surface  of  the  propodeum  far  above 
the  middle  coxae. 
F.     The  transverse  part  of  vein  M2  present  in  the  front  wings,  which 

have  at  least  two  closed  submarginal  cells,  p.  918 Aulacid^ 

FF.     The  transverse  part  of  vein  M2  wanting  in  the  front  wings, 

which  do  not  have  two  closed  submarginal  cells,  p.  919 

Gasteruptionid^ 

EE.    Abdomen  borne  between  the  hind  coxa?,  or  on  the  end  of  the  pro- 
podeum sliehtly  above  them. 

F.     The  transverse  part  of  vein  M  present  and  situated  close  to  the 
stigma. 

*This  table  of  families  of  the  North  American  Clistogastra  is  compiled  from  a 
table  of  the  families  of  the  Clistogastra  of  the  world  prepared  by  Professor  J. 
Chester  Bradley  and  kindly  placed  at  my  disposal. 

tin  the  hind  wings  of  the  insects  belongmg  under  this  category  neither  the 
second  anal  furrow  nor  the  axillary  excision  is  present,  but  there  is  sometimes 
present  a  weak  preaxillary  excision,  more  rarely  (some  genera  of  Braconidae) 
a  pronounced  notch,  but  never  forming  a  deep  slit.   See  also  footnote  on  page.  909. 


HYMENOPTERA  907 

G.     Antennae  in  both  sexes  of  more  than  fifteen  segments;  tro- 
chanters clearly  two-segmented. 
H.    Two  or  three  closed  submarginal  cellsin  theforewings.  p.  918. 

Trigonalid^ 

HH.    Only  one  closed  submarginal  cell  in  the  forewings.p.  918. 

vStephanid^ 

GG.    Antennae  of  thirteen  segments  in  the  male  and  twelve  in  the 
female;  trochanters  one-segmented. 

H.  Pronotum  without  posterior  lobes  (see  page  — )  its  lateral 
extensions  reaching  the  tegulas. 

I.  Cell  M4  of  the  forewings  shorter  than  cell  Cu  +  Cui  or 
absent     (Mutillinge).     p.     936 Mutillid^ 

II.  Cell  M4  of  the  forewings  present  and  longer  than  cell  Cu  + 
Cui  (Fig.   1 182).     (Vespinae)  p.  948 Vespid^ 

HH.  Pronotum  with  posterior  lobes  terminating  at  a  distance 
from  the  tegulee  (Fig.  1195).  (This  distance  is  short  in  the 
Ampulicinas). 

I.  Abdomen  of  male  with  only  six  exposed  segments,  the 
fourth  and  following  scarcely  exposed;  that  of  the  female 
with  compressed  apex.  Prothorax  elongate,  usually  with  a 
median  longitudinal  groove.  Nude  insects,  often  brilliantly 
metalHc.       (Ampulicinae) .    p.    961 Ampulicid^ 

II.  Abdomen  of  male  with  seven  exposed  segments;  that  of 
the  female  not  compressed  at  apex.  Prothorax  short  with- 
out median  longitudinal  groove.  Usually  hairy  insects, 
some  of  the  hairs  plumose.  (A  few  genera  in  the  various 
families  of  bees.    Pass  to  EE  on  page  912). 

FF.  The  transverse  part  of  vein  M  situated  about  two-thirds  of  the 
way  from  the  wing  base  to  the  end  of  the  costal  cell  (C  -f  Sci) 
or  wanting. 

G.     Wings  not  longitudinally  plaited  in  repose.     Ovipositor  not 
carried  along  the  mid-dorsal  line. 

H.  The  pronotum  laterally  reaching  the  tegulas.  No  prepectus 
present. 

I.  Hind  metatarsi  one-fourth  the  length  of  the  following 
segment.  Large  insects;  the  abdomen  of  the  female  filiform 
and  several  times  the  length  of  the  head  and  thorax  together; 
that   of   the   male   long   and   clavate.   p.   921 .  Pelecinid^ 

II.  Hind  metatarsi  at  least  as  long  as  the  following  segment. 
J.    Mandibles  in  a  reversed  position,  their  apices  directed  out- 
wardly,  away  from  the  mouth-opening,    p.    921 

Vanhorniid^ 

JJ.     Mandibles  in  a  normal  position. 

K.     Cells  Cu  +  Cui  and  M3  of  the  forewings  fully  en- 
closed and  separated  from  each  other  by  perfect  veins. 
L.     Cell  M4  of  the  forewings  triangular;  antenna  com- 
posed of  sixteen  segments,  p.  921    Helorid/e 

LL.      Cell   M4   of  the  forewings   irregularly   six-sided; 
antennas    composed    of    fourteen  segments,    p.  921. 

ROPRONIID^ 

KK.     Cells  Cu  +  Cui  and  M3  partly  enclosed  by  brown 
lines,    or    altogether    wanting.      Claws    not    pectinate. 
L.     Abdomen  sharply  margined  by  a  carina  along  the 
sides;  antennee  arising  near  the  clypeus. 
M.      Antennas   of   never   more   than   ten   segments, 
rarely  with  only  eight  or  nine.     Front  wings  with- 
out vein  C  or  "stigmal"  vein   (Sc2   +  Ri),  often 
without    any    venation,    p.    921 .  Platygasterid.e 
MM.     Antennas  usually  of  twelve  segments,   more 
rarely  of  eleven  segments,  or  if  of  seven  or  eight 
segments    the    club    is    unsegmented.    p.  921.... 

SCELIONID^ 


908  AN  INTRODUCTION  TO  ENTOMOLOGY 

LL.     Abdomen   immargined  laterally   (acute  in   Tele- 
nominae  but  without  a  carina). 
M.    Forewings  with  a  distinct  stigma. 

N.  A  closed,  usually  very  short,  marginal  cell 
(2d  Ri  +  R2)  present.  Antennae  of  thirteen 
segments.  Abdomen  with  a  short  clyindrical 
petiole,  the  second  segment  much  longer  and 
larger  than  the  others,  p.  921 .  PROCTOTRUPiDyE 
NN.  No  closed  marginal  cell  (2d  Ri  +  R.)  but  the 
basal  part  of  the  marginal  vein  (vein  r)  often 
present  in  the  forewings. 
O.      Antennae    of    eleven    segments.       (Megas- 

pilinas).  p.  921 Ceraphronid^ 

00.     Antennae  of  twelve  or  more  segments   (a 
-    few  genera  of   Diapriinae).   p.  921 .  Belytid^ 
MM    Forewings  without  a  distinct  stigma. 

N.     Costal  cell  (C  +  Sci)  either  closed  along  the 
margin,   or  if  open  very  narrow;  the  marginal 
cell  (2d  Ri  +  R2)  if  present  narrowly  triangular, 
its  proximal   margin  a  straight  line:  Abdomen 
not    compressed    nor    dorsally    keeled.      Hypo- 
pygium  of  the  female  not   divided,  but  closely 
applied  to  the  pygidium,  the  ovipositor  issuine 
from  between  them  at  the  tip  of  the  abdomen. 
O.     Hind  wines  with  a  closed  median  cell  (M). 
Forewings    almost    invariably    with    a    closed 
marginal  cell  (2d  Rj  +  R^).    Antennae  of  four- 
teen or  fifteen  segments.      (Belytinae).   p.  921. 

BELYTIDyE 

00.      Hind    wings    without    any    closed    cells; 

forewings    without    a    closed    marginal    cell 

(2d  R,  '+  R.). 

P.  Abdomen  margined  laterally,  the  margin 
acute  but  not  sharply  carinate.  Antennee 
arising  from  near  the  clypeus  and  composed 
of  ten  to  twelve  segments.  Scutellum 
not  divided  into  three  lobes.   (Talenominae). 

p.  92  I SCELIONID/E 

pp.  Abdomen  not  at  all  margined  laterally. 
vScutellum  divided  by  two  oblique  curved 
impressed    lines   into    three   lobes.      (Calli- 

ceratinae).  p.  921 Ceraphronid^ 

NN.  Costal  cell  (C  +  Sc,)  open  along  the  costal 
margin  and  abnormally  wide.  The  marginal 
cell  (2d  Ri  +  R2)  present;  often  closed;  often 
open  along  the  costal  margin,  sometimes  at  tip, 
it  is  always  four-sided,  acute  at  apex  and  at  its 
base.  Abdomen  more  or  less  strongly  com- 
pressed and  with  a  mid-dorsal  keel,  if  rarely  but 
little  compressed  and  without  a  keel,  it  is  more  or 
less  swollen  dorsally.  Hypopygium  of  the  female 
divided,  the  ovipositor  issuing  from  the  cleft 
thus  formed,  anterior  to  the  apex  of  the  ab- 
domen,    p.    922 Cynipid^ 

HH.  The  pronotum  not  reaching  the  tegulae,  separated  there- 
from by  a  chitinized  sclerite,  the  prepectus.  Antennae  el- 
bowed, never  more  than  thirteen-segmented.  Fore  wings  with 
a  short  narrow  costal  cell  open  along  its  anterior  margin 
(Fig.  1 166);  its  apex  remote  from  the  stigmal  vein  (Fig.  1166, 
d);  a  more  or  less  elongate  marginal  vein  (Fig.  1166,  b); 
postmarginal  and  a  stigmal  spur  (Fig.  1166,  d).    An  occasional 


HYMENOPTERA  909 

trace  of  the  transverse  part  o^  vein  M  is  the  onlv  additional 
vein  present,   there  being  never  any  closed   cells,  p.  927.  .  . 

Chalcidid^ 

GG.  'Wins;s  longitudinally  plaited  in  repose,  ovipositor  carried 
along  the  mid-dorsal  line.  Pronotum  reaching  the  tegulae,  the 
prepectus   not    being   distinctly   set   off.      (Leucospis).  p.  927. 

Chalcidid^ 

CC.     An  erect  scale  or  one  or  two  nodes  between  the  propodeum  and  the 

gaster.     p.     937 Formicid>e 

BB.     Hind  wings  with  an  anal  lobe.*  If  there  are  any  closed  cells  in  the  hind 
wings  the  antennae  are  thirteen-segmented   in  the  male,  twelve-  in  the  fe- 
male, except  in  a  few  instances  where  the  number  is  reduced  by  fusion,  but 
then  the  apical  segments  always  form  a  club,  or  are  abruptly  recurved  or 
otherwise  strikingly  modified,  (except  that  in  some  species  of  Crabro  both 
sexes  have  twelve-segmented,  otherwise  normal  antennae). 
C.    Hind  wings  without  closed  cells.    Number  of  antennal  segments  variable, 
but  never  thirteen  in  the  male  and  twelve  in  the  female,  nor  are  the  apical 
segments  in  the  male  either  formed  into  a  distinct  club,  or  strongly  re- 
flexed    or    otherwise    peculiarly    modified.      Vein    dissolution    extensive. 
D.     Abdomen  attached  to  the  dorsal  surface  of  thepropodeum.    p.  932. 

EVANIID^ 

DD.     Abdomen  attached    normally,    at    the    apex    of    the   propodeum 
between  or  slightly  above  the  hind  coxs. 

E.  Antennae  composed  of  ten  segments,  or  if  of  thirteen  in  the  female 
{Ampulicomorpha)  then  the  pronotum  is  elongate  and  has  a  median 
longitudinal  sulcus. 

F.    Antennae  inserted  on  a  frontal  prominence  distinct  from  the  cly- 

peus;  mouth    ventral.      Fore   tarsi   simple,    p.    934.  Embolemid^ 

FF.    Antennas  inserted  close  to  the  clypeus.    Fore  tarsi  of  the  female 

usually    chelate,    p.     961 Dryinid^ 

EE.  Antenna  usually  composed  of  thirteen  segments,  more  rarely  of 
twelve  or  eleven  segments,  or  multiarticulate. 

F.     Abdomen  with  six  exposed  segments  or  less.     Forewings  always 
with  cells  M  and  Cu  +  Cui  closed.    Ovipositor  an  extensile  jointed 
tube. 
G.     Venter  convex;  abdomen  with  .six  exposed  segments,  p.  934. 

Cleptid^ 

GG.  Venter  strongly  concave;  abdomen  with  at  most  five  usually 
three   or   four   exposed   segments.      Brilliantly  metallic,   p.  934. 

Chrysidid^ 

FF.     Abdomen  with  eight  exposed  segments,  the  petiolar  segment 
very  short  and  scarcely  perceptible.  Ovipositor  a  true  sting,  p.  948. 

Bethylid^ 

CC.  Hind  wings  with  at  least  a  closed  median  cell  (cell  M).  Males  with 
thirteen,  females  with  twelve  antennal  segments,  except  in  rare  instances, 
where  they  have  been  reduced  slightly  below  that  number  in  the  males,  in 
which  case  they  usually  either  end  in  a  jointed  club  or  the  last  segments  are 
recurved  or  hooked  or  otherwise  modified.  Venation  usually  well  pre- 
served. 

*If  there  is  a  very  deep  or  slit-like  incision  on  the  margin  of  the  hind  wing,  the 
insect  is  certain  to  come  under  this  heading.  There  are  some  genera  of  Sphecidae 
(of  the  tribes  Larrini,  Astatini  and  the  subfamily  Sphecinae)  in  which  the  axillary 
excision  or  both  axillary  and  preaxillary  excisions  are  reduced  to  small  and  incon- 
spicuous notches,  close  to  one  another,  and  in  some  cases  the  axillary  excision  is 
altogether  lacking.  But  in  all  such  cases  the  second  anal  furrow  is  distinct,  its 
apex  close  to  that  of  the  first  anal  furrow,  and  it  delimits  a  large  anal  area  behind 
it,  which  therefore  lacks  only  the  notch  itself  in  order  to  become  a  distinct  anal 
lobe.  In  all  insects  falling  under  grouping  B  this  furrow  is  wanting,  due  to  the  re- 
duction or  entire  absence  of  the  area  which  in  a  more  primitive  condition  exists 
behind  it  and  forms  the  anal  or  posterior  lobe  of  the  wing. 


910  AN  INTRODUCTION  TO  ENTOMOLOGY 

D.  The  pronotum  extending  laterally  directly  to  the  tegulae,  where  its 
lateral  prolongations  do  not  terminate  in  the  form  of  a  rounded  "pos- 
terior lobe"  covering  the  spiracles. 

E.     Cell  M4  of  the  forewings  longer  than  cell  Cu  +  Cui.     Lateral  pro- 
longations of  pronotum  forming  a  posterior  angle  which  lies  above  the 
tegulffi.      Wings   usually   longitudinally   plaited,   p.   948 .  .  .  Vespid^ 
EE.     Cell  M4  of  the  forewings  shorter  than  cell  Cu  +  Cui  or  absent. 
Lateral  prolongations  of  pronotum  bluntly  rounded,  not  lying  dorsad 
of  the  tegulae.    Wings  never  longitudinally  plaited. 
F.     Mesopleura  divided  by  a  transverse  suture  into  an  upper  and 
lower   plate.      First    and    second    abdominal    sternites   imbricate. 
Coxae  very  large  and  long;  the  legs  long   and   tisualty   distinctly 

spinose.     p.     933 Pompilid^ 

FF.    Mesopleura  not  divided  by  a  transverse  suture.    Coxae  and  legs 
not  unusually  long. 

G.  First  abdominal  segment  united  by  a  ball  and  socket  joint  to  the 
second,  and  itself  forming  an  almost  completely  separated 
"scale"  or  "node."  Hypopygium  of  male  unciform.  Females 
winged;  a  worker  caste  present.    (Some  more  primitive  genera  of 

ants.)     p.     937 FoRMiciD^ 

GG.  First  abdominal  sternite  attached  to  the  second  by  a  suturi- 
form  articulation  or  more  or  less  imbricate,  the  first  segment  not 
forming  a  "scale"  or  "node"  between  the  propodeum  and  the 
gaster.* 

H.  Mesosternum  not  forming  with  the  metasternum  a  con- 
tinuous plate  overlying  the  bases  of  the  hind  and  middle 
coxas.  Axillary  excision  of  the  hind  wings  in  normal  position, 
apex  of  male  abdomen  without  three  retractile  spurs  between 
the  last  tergite  and  its  sternite. 

I.  Vein  M4  +  Cui  of  the  forewings  opposite  vein  m-cu  or 
nearly  so.  Second  and  third  tarsal  segments  of  the  female 
not  dilated. 

J.    Mesosternum  with  two  laminae  which  overlie  the  bases  of 
the  middle  coxae. 

K.  Little  or  no  constriction  between  the  first  and  second 
abdominal  sternites,  which  are  almost  or  somewhat 
imbricate.  A  trace  of  a  vein  (base  of  Rs)  often  divides 
the  first  submarginal  cell  (R  +  ist  Ri)).  Hypopygium 
of  male  not  unciform.  Apex  of  the  marginal  cell  (2d  Ri 
+  R2)  distant  from  the  wing  apex  by  not  more  than  the 
length    of    the    cell.      Both    sexes    winged,    p.  935... 

Anthoboscid^ 

KK.    First  and  second  abdominal  sternites  separated  by  a 
strong  and  distinct  suturiform  articulation  and  either 
the  hypopygium  of  the  male  is  unciform,  or  the  females 
are  wingless  and  carried  about  by  the  males  in  mating. 
L.     Hypopygium  of  the  male  not  unciform;  but  some- 
times it  is  tridentate  at  apex  with  the  middle  tooth 
long  and  spiniform.     Females  apterous  and  carried 
about  by  the  males  in  mating.     First  submarginal 
cell  usually  divided   by  a   weak  vein    (base  of  the 

radial   sector),    p.    935" Thynnid^ 

LL.  Hypopygium  of  male  unciform,  known  American 
females  winged.  First  submarginal  cell  not  divided 
(base  of  Rs  wanting). 

M.      Diurnal   insects   with   normal   eyes   and   ocelli. 
Females   winged.     (Tiphiinas).     p.     936.Tiphiid^ 


*Some  genera  of  Mutillidae  in  which  the  first  or  first  and  second  abdominal 
segments  are  more  or  less  nodose  may  be  recognized  as  falling  in  this  category  by 
the  unciform  hypopygium  of  the  males,  the  apterous  females,  and  the  absence  of  a 
neuter  caste. 


H  YME  NOP  TERA  911 

MM.  Nocturnal  insects  with  enlarged  eyes  and  ocelli. 
The  marginal  cell  (2d  R,  +  R2)  removed  from  the 
apex  of  the  wing  by  several  times  its  length.  Fe- 
males unknown  but  presumably  apteroas.   (Brachy- 

cistinse).    p.    936 Mutillid^ 

J  J.     Mesosternum  simple  or  with  two  minute  erect  teeth 
between  the  bases  of  the  coxae. 

K.  Marginal  cell  (2d  Ri  +  R2)  removed  by  less  than  its 
length  from  the  wing  apex;  the  fourth  submarginal  cell 
(R3)  not  traversed  by  an  adventitious  vein.  Abdomen 
never  petiolate. 

L.  No  constrictions  between  the  abdominal  segments 
(except  between  the  first  and  the  second),  all  tergites 
and  all  but  the  first  and  second  sternites  loosely  im- 
bricated plates.  The  last  tergite  of  the  male  a  small 
simple  lamina.  Edges  of  the  hypopygium  of  the  fe- 
male turned  upwards  and  meeting  on  the  mid  dorsal 
line,  often  fused,  enclosing  the  sting  in  a  cone.  Both 
sexes  winged.  Vein  ni  and  M,  of  the  hind  wings 
wanting.     Mesosternum  unarmed,  upper  .surface  of 

hind    coxae    simple,    p.    935 Sapygid^ 

LL.  Strong  constrictions  between  each  of  the  ab- 
dominal segments,  the  tergites  and  sternites  all 
heavily  chitinized  and  not  loosely  imbricate;  the 
last  tergite  modified  and  hood-like.  Female  apterous. 
Upper  surface  of  the  hind  coxae,  at  least  in  the  male, 
with  a  lamella.    (MethocinaeandMyrmosinae).  p.  936. 

TlPHIID^ 

KK.  Marginal  cell  (2d  Ri  -f  R2)  removed  by  two  or  more 
times  its  length  from  the  apex  of  the  wing;  cell  R3  when 
present  usually  traversed  by  a  longitudinal  adventitious 
vein.  Often  nocturnal  insects  with  largeeyes  and  ocelli. 
Females     apterous.       (Several     subfamilies),     p.    936. 

N  MUTILLID^ 

II.  Vein  M4  -f  Cui  of  the  forewings  more  than  two-thirds  its 
length  apicad  of  vein  m-cu.  Second  and  third  tarsal  seg- 
ments of  the  female  dilated,  deeply  excised,  and  filled  with 
membrane  between  the  lobes.  Nocturnal  insects  with  very 
large  eyes  and  ocelli.    Petiole  long  and  slender.  Hypopygium 

unarmed,    p.    948 Rhopalosomid^ 

HH.     Mesosternum  and  metasternum  together  forming  a  con- 
tinuous plate   overlying  the  bases  of  the  hind  and  middle 
coxae,    separated   from   each    other   by   a   transverse   suture. 
Axillary  excision  of  the  hind  wings  almost  opposite  the  apex  of 
cell  M3  -f  Cui  -f  Cu.     Abdomen  of  male  with  three  spines, 
retractile    between    the    last    sternite    and    tergite.      Tongue 
elongate.     Wings  with  membrane  striolate.  p.  937.  vScoliid^ 
DD.     Pronotum  terminating  behind  laterally  in  the  form  of  two  clearly 
differentiated  rounded  "posterior  lobes,"  covering  the  spiracles.     These 
lobes  reach  the  tegulae  in  North  American  forms  only  in  the  extremely 
rare  genus  Dolichurtis. 

E.  Posterior  metatarsus  not  dilated.  No  plumose  hairs.  Females 
without  pollen-collecting  apparatus,  but  often  with  a  comb  on  the  an- 
terior tarsi.  Maxillae  rarely  elongate;  if  so,  either  the  ocelli  are 
distorted,  or  the  abdomen  has  a  petiole  composed  only  of  the  first 
sternite. 

F.     Abdomen  of  the  male  with  only  three  or  four  exposed  tergites. 
Last  sternite  of  the  female,  enclosing  the  sting,  its  edges  fused  in  the 

mid-dorsal   Hne.      (Dolichurinae).    p.    961 Ampulicid^ 

FF.    Abdomen  of  the  male  with  seven  exposed  tersites.    Sting  not  en- 
closed  by   the   hypopygium.   p.   962 Sphecid^ 


912  AN  INTROD UCTION  TO  ENTOMOLOG Y 

EE.  Posterior  metatarsi  elongate  and  dilated.  Some  of  the  hairs, 
especially  of  the  thorax,  plumose.  A  pollen-collecting  brush  or  a 
corbicula  present  in  the  majority  of  females.  Maxillae  usually  with 
either  the  stipes  or  the  lacinia  elongate;  the  latter  often  very  long 
and  covering  the  tongue;  the  ocelli  never  distorted;  the  abdomen 
rarely  petiolate,  and  never  with  a  petiole  composed  only  of  the  first 
sternite. 

F.    Hind  tibiae  with  apical  spurs.     If  the  marginal  cell  (2d  Ri  +  Rj) 

is  long  and  slender,  reaching  nearly  to  the  wing  apex,  the  anal  lobe  is 

short  and  fully  separated.    Cell  M4  usually  as  large  as  cell  1st  M2. 

G.     Females  without  a  corbicula.     First  submarginal  cell   (R   + 

1st  Ri)  rarely  divided  (by  the  base  of  Rs)  in  which  case  there  is  a 

large  anal  lobe  present.    In  case  the  marginal  cell  (2d  Ri  +  R2)  is 

longer  than   the  three   submarginals,   taken   together,   there  is 

usually  a  well-marked  anal  lobe  in  the  hind  wings. 

H.    Wings  with  two  submarginal  cells  (very  rarely  less). 

I.  Tongue  short  and  the  basal  segments  of  the  labial  palpi  not 
sheath-like;  or  the  labrum  is  large  and  free  and  uncovered. 
Females  without  a  ventral  pollen-collecting  brush;  often 
with  a  pygidial  area. 

J.  Tongue  short,  its  apex  bifid;  labial  palpi  normal.  Fe- 
male only  rarely  with  a  pygidial  area.  Mesepisternal 
suture  present.  Labrum  hidden  (Prosopinas).  p.  976. 
Prosopid^ 

JJ.  Tongue  long  or  short,  but  its  apex  acute;  the  iabial 
palpi  normal  or  their  basal  segments  sheath-like.  Mes- 
episternal suture  wanting.  (Many),  p.  978.  . .  Andrenid^ 

II.  Tongue  elongate,  the  basal  segments  of  the  labial  palpi 
sheath-like.  Labrum  not  large  and  free,  usually  entirely 
covered  by  the  clypeus,  or  if  somewhat  visible,  then  strongly 
inflexed.  Females  without  a  pygidial  area;  those  of  the 
non-parasitic  species  with  a  ventral  pollen-collecting  brush, 
p.  982 Megachilid^ 

HH.     Wings  with  three  submarginal  cells.     Females  without  a 
ventral   pollen-collecting  brush;  often   with  a  pygidial  area. 

I.  Tongue  short,  its  apex  bifid.  Labial  palpi  normal.  Fe- 
males rarely  with  a  pygidial  area.  Mesepisternal  furrow 
present.     Labrum  hidden.    (Colletinae).   p.  976.  Prosopid^ 

II.  Tongue  long  or  short,  but  its  apex  acute.  The  labial 
palpi  normal,  or  the  basal  segments  sheath-like.  Mes- 
episternal suture  rarely  present.  (Most),  p. 978.  Andrenid^ 

GG.  Females  and  workers  with  corbicula  (except  Psithynis). 
First  submarginal  cell  divided  by  a  transverse,  hair-like  chitinized 
streak  (base  of  Rs),  rarely  indistinct.  Marginal  cell  (2d  Ri  -f 
R2)  rather  long  and  pointed  or  appendiculate,  usually  as  long  as 
the  three  submarginal  cells  taken  together,  and  extending  far 
beyond  the  apex  of  the  third  (R4).  Malar  space  large  and  distinct. 
Hind  wings  stalked,  the  anal  lobe  absent.  Tongue  very  long, 
the  two  basal  segments  of  the  labial  palpi  and  the  laciniae  elon- 
gate,  and  forming   a  sheath.      Social  insects  with  normally  a 

worker  caste   (except   in  Psithyrus).  p.  984 Bombid^e 

FF.  Hind  tibiae  without  apical  spurs.  Social  insects  with  a  worker 
caste.  Workers  with  corbiculae;  females  without  functionally  de- 
veloped ones.  Alarginal  cell  (2d  Ri  +  R^)  long  and  slender 
reaching  nearly  to  the  wing  apex.  Anal  lobe  of  the  hind  wing  long 
and  scarcely  separated.     Cell   ist  M2  much  larger  than  cell  M^. 

Eyes  hairy,  p.  988 Apid^e 

AA.     Apterous  or  subapterous  (the  wings  so  reduced  as  to  interfere  with  the 
normal  venation). 

B.     The  ventral  segments  membranous,  more  or  less  concave  with  a  longi- 
tudinal fold  in  dried  specimens. 


HYMENOPTERA  913 

C.     Second  and  third  abdominal  tergites  connate.* 

D.    Abdomen  sessile,  or  if  petiolate,  the  petiole  not  curved,  or  expanded  at 

apex.     (A  few  genera),  p.  916 Braconid^e 

DD.    Abdomen  with  an  elongate  petiole,  which  is  strongly  decurved  and 
expanded  at  apex.   {Thaumatotypidea  in  Stilpnini).  p.  917  ICHNEUMONiDiE 
CC.    Second  and  third  abdominal  tergites  not  connate. 

D.    Abdomen  petiolate,  the  first  segment  elbowed  and  enlarged  posteriorly 

(Cryptin^   in   part),    p.    917 Ichneumonid^ 

DD.     Abdomen  sessile  (Aphidiinas  in  part),  p.  916 Braconid^ 

BB.    The  ventral  segments  chitinized,  convex  and  without  a  longitudinal  fold. 
C.     Pronotum  separated  from  the  tegute  laterally  by  the  interposition  of  a 
chitinized  sclerite,  the  prepectus.    Antennas  elbowed.    Hypopygium  of  the 
female  divided,  the  ovipositor  issuing  from  anterior  to  the  tip  of  the  ab- 
domen.    (A  few  genera),  p.  927 Chalcidid^ 

CC.     Pronotum  reaching  the  tegulse  laterally  or  the  latter  altogether  ab- 
sent; no  prepectus  present. 

D.  First  abdominal  segment  not  forming  a  "scale"  or  "node"  between  the 
propodeum  and  the  gaster.  Thorax  sometimes  with  sutures  largely 
obliterated. 

E.    Fore  tarsi  chelate.     (Females  of  Anteoninee).  p.  961 ...  .  Dryinid^ 
EE.    Fore  tarsi  normal. 

F.  Hypopygium  of  the  female  divided,  the  ovipositor  issuing  from 
before  the  tip  of  the  abdomen,  which  is  more  or  less  strongly  com- 
pressed and  with  a  mid-dorsal  keel.  Second  abdominal  tergite  the 
longest.  Petiole  very  short,  cylindrical,  scarcely  visible.  Wingless 
or    subapterous    forms    are    usually    agamic    females.        (Mostly 

Cynipinte).     p.     922 Cynipid^e 

FF.  Hypopygium  of  the  female  not  divided,  but  closely  applied  to 
the  pygidium,  the  ovipositor  or  sting  issuing  from  between  the  two, 
at  the  tip  of  the  abdomen.  Abdomen  rarely  or  never  strongly  com- 
pressed, without  a  mid-dorsal  ridge. 

G.     Mesopleuras  not  divided  by  a  transverse  suture.     Coxag  and 
legs  not  unusually  long. 

H.    Abdomen  margined  laterally,  the  sides  sometimes  only  acute, 
but  usually  with  a  blade-like  carina. 

I.  Antennee  composed  of  ten  segments,  rarely  less,  but  in  that 
case  without  an  unsegmented  club.  p.  921 .  Platygasterid^ 

II.  Antenna  composed  of  eleven  or  twelve  segments,  or  if  of 
seven   or   eight    they   have   an  unsegmented  club.    p.    921. 

SCELIONIDvE 

HH.    Abdomen  neither  acute  nor  margined  laterally. 

I.  Males. 

J.      Antennae  of  ten  segments   {Myrmecomorphus) .   p.   934. 

Embolemid^ 

JJ.  Antennae  of  thirteen  segments,  p.  936.Mutillid^ 
JJJ.     Antenna  of  fifteen    segments.      (Belytinag).  p.  921. 

Belytid^ 

II.  Females. 

J.     Antennae  of  ten  or  eleven  segments. 

K.     Antennas  of  eleven  segments.      (Six  genera),  p.  921. 

Ceraphronid^ 

KK.    Antennas  of  ten  segments. 

L.     Antennas  inserted  close  to  the  mouth.      (Several 

genera),  p.  921 Ceraphronid^e 

LL.    Antennas  inserted  on  a  frontal  prominence  in  the 
middle    of    the    face    {Myrmecomorphus).     p.    934. 

Embolemid^ 

JJ.    Antennae  of  twelve  segments.     (See  also  JJJ). 

*If  the  suture  is  entirely  obliterated,  the  presence  of  two  pairs  of  spiracles 
will  indicate  that  the  apparent  second  segment  consists  really  of  the  second  and 
third. 


914  AN  INTRODUCTION  TO  ENTOMOLOGY 

K.  Prothorax,  mesothorax,  and  propodeum  more  or  less 
intimately  fused  into  a  chitinous  box;  usually  with 
little  or  no  trace  of  sutures,  more  rarely  with  the  sutures 
visible  but  connate;  still  more  rarely  the  prothorax 
is  fully  separated. 

L.  First  tergite  not  reaching  the  base  of  the  petiole, 
but  forming  an  apical  gibbous  cap  thereto.  Pro- 
thorax separated.     (Apterogyninae  and  Chyphotinae). 

p.  936 MUTILLID^ 

LL.     First  tergite  reaching  the  base  of  the  petiolar 

segment. 

M.  Upper  surface  of  posterior  coxae  with  an  erect 
inner  lamella  at  base.  Pronotum  separated  from 
mesothorax  by  a  movable  suture.     (Myrmosinae). 

p.  936 TiPHIID.E 

MM.  Posterior  coxse  simple.  Pronotum  and  pro- 
podeum fused  to  the  thorax,  the  sutures  lacking. 

Ocelli   wanting,    p.    936 Mutillid^, 

KK.  Prothorax,  mesothorax,  and  propodeum  fully 
separated. 

L.  Hind  edge  of  mesosternum  with  two  horizontal 
lamellae    between    the     middle     coxae,     which     they 

partly    overlap,    p.    935 Thynxid^e 

LL.     Mesosternum  without  such  lamellae  overlapping 
the  bases  of  the  coxae. 

M.  Mesosternum  with  two  minute,  erect  teeth 
between  the  middle  coxae.  Mesothorax  elongate. 
Moderately  large  ant-like  insects.      (Methocinae). 

p.  936 TlPHIID^ 

MM.  Mesosternum  unarmed.  Mesothorax  rarely 
elongate. 

N.  Head  oblong,  porrect;  antennae  inserted  close 
to  the  mouth,  never  geniculate.  Femora,  es- 
pecially of  the  fore-legs,  usually  strongly  thick- 
ened in   the   middle.      Scutellum  without  pits. 

p.  921 Bethylid^ 

NN.     Head  usually  globular  or  transverse.     An- 
tennas inserted  in  the  middle  of  the  face.    Femo- 
ra not  mediallj'  strongly  thickened.      Scutellum 
usually  foveolate. 
O.    Antennae  geniculate.     Scutellum  with  deep  an- 
terior foveas;  or  if  these  are  absent  it  is  not 
distinctly    separated    from    the    mesonotum. 

(Sixteen   genera),    p.  921 Belytid,^ 

00.     Antennae  not  geniculate.     Scutelkxm  dis- 
tinct,  without   foveae.     (New  genus  in  Myr- 

mosinas).     p.  936. Tiphiid.e 

JJJ.    Antennae  of  from  thirteen  to  fifteen  segments. 

K.  Antennas  inserted  close  to  the  mouth.  Head  oblong, 
porrect.     Anterior     femora     spindle-shaped,     p.     948. 

Bethylid^ 

KK.  Antennae  inserted  on  the  middle  of  the  face.  Head 
globuler  or  transverse. 

L.  Abdomen  produced  behind  into  a  pointed  tube.  Spur 
of  the  anterior  tibiae  without  a  ventral  blade-like 
lamella.  (Three  genera),  p.  921 .  .Proctotrupid^ 
LL.  Abdomen  not  produced  behind  into  a  tube.  Spur 
of  the  anterior  tibias  with  two  prongs  and  no  ventral 
lamina.     Anterior  femora  clavate.  p.  921  .Bely'TID^ 


HYMENOPTERA  915 

GG.    Mesopleura  divided  by  a  transverse  suture  into  an  upper  and 
lower  plate.    Coxa;  very  large  and  long ;  the  legs  long  and  usually 

distinctly    spinose.    p.    933 Pompilid^ 

DD.  First  abdominal  segment  forming  a  "scale"  or  "node"  between  the 
propodeum  and  the  gaster.  Thorax  with  its  sutures  distinct,  but  the 
mesothorax  usually  much  reduced  in  size.  p.  937 Formicid^ 

SuPERFAMiLY  ICHNEUMONOIDEA 

The  Ichneumon- flies  and  their  Allies 

When  the  discouraged  fanner  sees  his  crops  harvested  before  due 
time  by  hordes  of  hungry  insects,  he  is  apt  to  long  for  a  miracle  to 
remove  the  plague  from  his  fields.  Oftener  than  he  dreams  the  miracle 
takes  place,  and  millions  of  insect  pests  never  live  to  lay  their  eggs 
for  another  brood.  Such  miracles  are  most  frequently  wrought  by 
members  of  a  large  group  of  insects,  which  is  commonly  known  as 
the  parasitic  Hymenoptera,  and  by  the  tachina-fiies  discussed  in  the 
chapter  treating  of  the  Diptera. 

Although  some  of  these  insects  are  external  parasites,  most  of 
them  live  within  the  bodies  of  their  hosts,  within  which  they  pass 
their  entire  larval  existence.  Their  presence  in  this  strange  situation 
is  due  to  the  fact  that  the  parent  lays  her  eggs  within  or  upon  the 
body  of  the  victim.  When  the  egg  is  laid  upon  the  body  of  the 
victim  the  larva  as  soon  as  it  hatches  bores  its  way  into  the  body. 
So  in  either  case  the  3^oung  parasite  is  in  the  midst  of  suitable  food. 
It  is  probable  that  the  parasite  feeds  at  first  only  on  the  blood  of 
its  host;  hence  the  parasitized  insect  is  not  destroyed  at  once,  but 
lives  on  with  the  parasite  within  it,  which  gradually  attains  its  growth. 
Finally,  the  parasitized  insect  perishes;  and  from  the  larva  that  has 
been  nourished  in  its  body  there  is  developed  a  winged  creature, 
which  in  turn  lays  its  eggs  in  other  victims.  Frequently  a  parasitic 
insect  lays  several  eggs  within  a  single  victim,  so  that  a  number  of 
parasites  may  be  developed  within  the  body  of  a  single  insect.  Each 
species  of  these  parasites  infests  only  certain  insects,  each  insect  hav- 
ing, to  a  great  extent,  its  peculiar  parasites. 

It  has  been  proposed  recently  to  term  these  insects  that  eventually 
kill  their  victims  parasitoid  instead  of  parasitic,  on  the  ground  that 
they  are  not  true  parasites  but  "extremely  economic  predators." 
(See  Wheeler  ('23),  page  46).  In  the  preparation  of  this  work,  it  has 
seemed  best  to  continue  the  use  of  the  term  parasite  in  the  broad 
sense  in  which  it  is  generally  used  by  entomologists. 

The  parasitic  Hymenoptera  does  not  constitute  a  natural  division 
of  the  order  but  includes  representatives  of  several  superfamilies,  of 
which  the  Ichneumonoidea  is  one. 

The  Ichnetmionoidea  is  the  largest  of  the  superfamilies  of  the 
Hymenoptera,  except  the  Chalcidoidea,  including  hundreds  of  genera 
and  many  thousand  species.  All  of  the  species  are  parasitic;  eggs, 
larvae,  pupae,  and  even  adult  insects  are  infested  by  them;  and  mem- 
bers of  nearly  all  of  the  orders  of  insects  are  subject  to  their  attacks. 
They  are  therefore,  of  extremely  great  economic  importance. 


916 


AN  INTRODUCTION  TO  ENTOMOLOGY 


A  classification  of  this  superfamily  was  published  bv  Ashmead 
Coo). 

Six  of  the  families  constituting  the  superfamily  Ichneumonoidea 
are  represented  in  America  north  of  Mexico.  These  families  can  be 
distinguished  by  the  characters  given  in  the  table  above,  p.  609. 

Family  BRACONID^ 
The  Braconids 
The  family  Braconidae  includes  a  large  nimiber  of  species,  which 

are  small  or  of  mod- 
erate size.  In  this 
and  in  the  following 
family  the  costal 
cell  of  the  fore  wings 
has  been  eliminated 
by  the  coalescence 
of  veins  (Fig.  11 48) 
and  the  venter  is 
membranous  and 
has  in  dried  speci- 
mens a  longitudinal 
fold.  In  the  Bra- 
conidse  the  vein  be- 
tween cell  Ml  and 


Wings  of  a  braconid. 


Fig.     1 149. — Caterpillar    with 
coons  of  a  braconid. 


cell  I  St  M2  of  the  fore  wing  is  wanting. 

It  is  not  an  uncommon  thing, 
especially  in  vineyards  to  find  a 
feeble  caterpillar  with  its  back  cov- 
ered with  little,  white,  oblong 
bodies,  which  the  ignorant  usually 
think  are  eggs  (Fig.  1149).  These 
are  the  cocoons  of  braconid  para- 
sites .  The  larvae  obtain  their  growth 
within  the  body  of  the  caterpillar,  and  just  before  it  perishes  they 
leave  it,  and  spin  their  silken  cocoons  upon  its  back. 
When  these  cocoons  are  examined  with  a  lens  they 
are  found  to  be  beautiful  objects,  resembling  in 
miniature  those  of  the  silkworm.  The  adult  para- 
site in  emerging  from  its  cocoon  cuts  a  neat  little 
lid  at  its  upper  end.  These  parasites  belong  to  the 
genus  Microgaster.  Bunches  of  white  or  yellow  co- 
coons of  Microgaster  are  often  found  attached  to 
grass  or  other  plants  instead  of  to  the  back  of  the 
caterpillar  which  the  larvae  have  destroyed  (Fig. 
1150). 

Perhaps  the  most  interesting  of  the  common 
forms  belonging  to  this  family  are  those  belonging 
to  the  genus  ApMdius.  The  members  of  this  genus 
are  minute  creatures  which  infest  plant-lice.  If 
colonies  of  aphids  be  examined,  the  dried  bodies  of 
Fig.  1 1 50.  dead  ones  may  be  found  in  which  the  abdomen  is 


HYMENOPTERA 


917 


more  or  less  spherical,  being  greatly  distended.  These  bod- 
ies remain  clinging  to  the  leaves  in  the  position  in  which 
the  insects  were  when  they  died.  From  each  one  there 
emerges  in  due  time  an  Aphidius.  The  parasite  in  emerging 
cuts  a  very  regular  circular  lid  in  the  dorsal  wall  of 
the  abdomen  of  its  host  (Fig.  1151).  We  have 
watched  with  much  interest  these  little  braconids 
ovipositing  in  the  bodies  of  plant-lice.  When  one 
has  selected  a  plant-louse  in  which  to  oviposit  she 
stands  with  her  head  toward  it,  and  bending  her 
abdomen  under  her  thorax  between  her  legs  she 
darts  her  ovipositor  forward  into  the  body  of  the 
aphid.  The  species  of  this  genus  do  not  construct  cocoons,  but  under- 
go their  metamorphosis  within  the  dried  skins  of  plant-lice. 


Fig.  1 152. — Wings  of  an  Ichneumon  fly. 

In  this  family,  as  in  the  preceding  one, 
wings  has  been  eliminated  by 
the  coalescence  of  veins  and  the 
venter  is  usually  membranous 
and  has  in  dried  specimens  a 
longitudinal  fold.  The  ichneu- 
mon flies  differ  from  the  bra- 
conids in  that  Cell  Mi  and  cell 
ist  M2  of  the  fore  wings  are 
separate  (Fig.  1152),  except  in 
a  single  genus,  Pharsalia.  For 
distinguishing  characters  of 
this  genus  see  the  table  of 
famiHes. 

Students  collecting  H}Tnen- 
optera  will  find  many  species  of 
ichneumon-flies ;  and  those  at- 
tempting to  rear  caterpillars 
will  be  disappointed  often  by 
the  breeding  of  ichneumon-flies 
instead  of  moths  or  butterflies. 


Family 
ICHNEUMONID^ 

The  Ichneumon- flies 

This  is  a  large  fam- 
ily including  a  great 
number  of  genera  and 
species.  Although  it 
includes  some  minute 
forms  the  species  are 
mostly  of  considerable 
size,  and  here  belong 
the  larger  of  the  para- 
sitic Hymenoptera. 
the  costal  cell  of  the  fore 


Megarhyssa  lunator. 


918  AN  INTRODUCTION  TO  ENTOMOLOGY 

Megarhyssa  lundtor,  which  was  formerly  known  as  Thalessa  lund- 
tor,  is  one  of  the  larger  of  ichneiimon -flies  (Fig.  1153).  It  is  a  parasite 
of  the  wood-boring  larva  of  the  pigeon  horn-tail  Tremex  columba. 
When  a  female  finds  a  tree  infested  by  this  borer  she  selects  a  place 
which  she  judges  is  opposite  a  Tremex-burrow,  and  elevating  her 
long  ovipositor  in  a  loop  over  her  back,  with  its  tip  on  the  bark  of  the 
tree  (Fig.  1153),  she  makes  a  derrick  out  of  her  body  and  proceeds 
with  great  skill  and  precision  to  drill  a  hole  into  the  tree.  When  the 
Tremex-burrow  is  reached  she  deposits  an  egg  in  it.  The  larva  that 
hatches  from  this  egg  creeps  along  this  burrow  until  it  reaches  its 
victim,  and  then  fastens  itself  to  the  horn-tail  larva,  which  it  destroys 
by  sucking  its  blood.  The  larva  of  Megarhyssa  when  full  grown 
changes  to  a  pupa  within  the  burrow  of  its  host,  and  the  adult  gnaws 
a  hole  out  through  the  bark  if  it  does  not  find  a  hole  already  made 
by  the  Tremex.  Sometimes  the  adult  Megar- 
hyssa, like  the  adult  Tremex,  gets  her  ovi- 
positor wedged  in  the  wood  so  tightly  that 
it  holds  her  a  prisoner  until  she  dies. 

Among  the  more  common  of  our  larger 

Ichneumon-flies    are    those    of    the    genus 

Ophion  (Fig.  1 1 54) ;  these  have  yellow  bodies. 

/  Y  ^ I  )^  One  species  infests  the  caterpillars  of  the 

Fig  \\^±— ophion  Polyphemus-moth  and  only  a  single  egg  is 

laid  within  each  victim.    The  caterpillar  lives 

until  it  spins  a  cocoon,  but  does  not  change 

to  a  pupa.     The  Ichneumon  larva  when  full  grown  spins  a  dense 

brownish  cocoon  within  the  cocoon  of  the  caterpillar.    Another  smaller 

Ichneumon-fly,  Agrothereutes  extrematis,  infests  the  same  caterpillar, 

but  more  than  one  egg  is  laid  in  a  caterpillar  by  the  female.    We  have 

bred  thirty-five  of  these  Ichneumon-flies  from  one  caterpillar.     The 

larvae  of  this  species  also  spin  their  cocoons  within  the  cocoon  of  their 

host. 

Family  TRIGONALID^E 
The  Trigonalids 
In  this  family  and  in  the  three  following  families  there  is  a  distinct 
cell  between  the  costa  and  the  radius  of  the  fore  wings ;  these  insects 
differing  markedly  in  this  respect  from  the  braconids  and  the  ichneu- 
mon-flies. In  the  trigonalids  and  stephanids  the  insertion  of  the  ab- 
domen is  normal,  differing  in  this  respect  from  the  Aulacidse  and  the 
Gasteruptionid^.  In  the  trigonalids  there  are  two  or  three  closed  sub- 
marginal  cells  in  the  fore  wings,  which  distinguishes  them  from  the 
Stephanidae. 

This  family  is  represented  in  our  fauna  by  only  a  small  number  of 
species.  Some  species  infest  nests  of  social  wasps,  some  have  been 
bred  from  Dupse  of  Lepidoptera,  and  one  was  bred  from  the  cocoon  of 
an  Ophion  m  a  cocoon  of  Telea  polyphemus. 

Family  AULACID^ 
The  Aulacids 
In  this  family  the  abdomen  is  borne  on  the  dorsal  surface  of  the 
propodeum  far  above  the  middle  coxas;  in  this  respect  these  insects 


HYMENOPTERA  919 

resemble  the  Gasteruptionidas,  but  they  can  be  distinguished  from 
them  by  the  presence  of  at  least  two  closed  submarginal  cells  in 
the  fore  wings  (Fig.  1155). 

This  is  a  comparatively  small  family;  some  of  the  species  are 


Fig.  1 1 55. — Wings  of  Aulacus. 

parasitic  on  saw-fly  larvae  of  the  genus  Xiphydria;  but  so  far  as  is 
known  most  of  the  species  infest  the  larvse  of  Coleoptera. 

A  monograph  of  the  family  is  included  by  Kieffer  ('12)  in  his 
Evaniidas. 

Family  STEPHANID^ 

The  Stephanids 

In  this  family,  as  in  the  Trigonalidae,  the  abdomen  is  borne  be- 
tween the  hind  coxse,  or  on  the  end  of  the  propodetmi  slightly  above 
them ;  but  in  this  family  there  is  only  one  closed  submarginal  cell  in 
the  fore  wings. 

This  is  a  small  family,  which  is  represented  in  our  fauna  by  but 
few  species;  these  are  parasitic  on  wood-boring  larvae. 

Family  GASTERUPTIONID^ 

The  Caster iiptionids 

In  this  family,  as  in  the  Aulacida?,  the  abdomen  is  borne  on  the 
dorsal  surface  of  the  propodeimi  far  above  the  middle  coxee;  but  in 
this  family  there  are  not  two  closed  sub- 
marginal  cells  in  the  fore  wings.  A  striking 
feature  of  this  family  is  the  fact  that  the 
wings  when  at  rest  are  folded  longitudinally, 
Fig.  1 1 56.  ^^  ^^  ^^^  Vespidffi,  and  in  the  genus  Leucospis 

of  the  Chalcididae.  Figure  11 57  represents 
the  venation  of  Gasterupiion  tncertus. 

The  family  Gasteruptionidae  is  represented  in  our  fauna  by  the 
genus  Gasterupiion  of  which  twenty-two    North  American    species 


920 


AN  INTRODUCTION  TO  ENTOMOLOGY 


have  been  described.  A  species  of  this  genus  is  represented  by  Figure 
1 1 56.  A  monograph  of  the  family  is  included  by  Kieffer  ('12)  in  his 
Evaniidce. 


Fig.  1 157. — Wings  of  Gasteruption  incertus. 

The  members  of  this  family  are  parasitic  on  solitary  wasps  and 
solitary  bees. 


SuPREFAMiLY  PROCTOTRUPOIDEA 


The  Proctotrupids 


In  the  Proctotrupoidea  the  hind  wings  are  without  an  anal  lobe; 
the  pronotum  extends  back  on  each  side  reaching  the  tegulas ;  and  the 
hypopygiimi  of  the  female  is  not  divided,  but  closely  applied  to  the 
pygidium,  the  ovipositor  issuing  from  between  the  two  at  the  tip  of 
the  abdomen. 

Themembersof  this  superfamily  are  slender  insects  and  mostly  of 
minute  size.  Their  color  is  almost  invariably  black  or  brown  without 
metallic  luster.  The  venation  of  the  wings  is  greatly  reduced  and  in 
many  forms  the  wings  are  veinless ;  there  are  also  many  wingless  species. 
Figure  1158  represents  a  proctotrupid  great- 
ly enlarged. 

The  proctotrupids  are  nearly  all  para- 
sitic; and  very  many  of  them  infest  the  eggs 
of  other  insects.  The  female  proctotrupid 
bores  a  hole  with  her  ovipositor  through  the 
shell  of  an  egg  of  one  of  the  larger  insects, 
and  deposits  one  of  her  eggs  inside  of  it. 
Here  the  young  parasite  when  it  hatches 
finds  itself  in  the  midst  of  food  which  is 
sufficient  for  it  till  it  is  fully  grown.     The 

transformations  are  passed  within  the  infested  egg,  from  which  the 
parasite  comes  forth  an  adult.  Other  species  are  internal  parasites 
of  larvae,  and  some  are  secondary  parasites,  that  is,  parasites  upon 


Fig.  1 158. 


HYMENOPTERA  921 

other  parasites.  A  few  species  are  inquilines,  but  none  has  been 
found  to  be  injurious  to  vegetation. 

The  North  American  Proctotrupoidea  were  monographed  by 
Ashmead  ('93).  Note  that  the  first  three  subfamihes  of  Ashmead's 
classification,  those  in  which  there  is  an  anal  lobe  in  the  hind  wings, 
are  not  now  included  in  the  Proctotrupoidea. 

The  Proctotrupoidea  is  represented  in  our  fauna  by  nine  families ; 
these  can  be  separated  by  the  table  of  families  on  pages  906  to  915. 
A  list  of  these  families  follows. 

The  family  ROPRONIID^  is  represented  by  a  single  genus, 
Roprdnia,  which  includes  a  small  number  of  rare  species,  the  habits  of 
which  are  unknown. 

The  family  HELORID^  includes  the  genus  Heldrus,  the  larvas 
of  which  are  parasitic  in  the  cocoons  of  Chrysopa. 

The  family  VANHORNIID^  includes  a  single  rare  species, 
Vanhornia  eucnemiddrum,  which  is  parasitic  on  larvse  of  beetles  of 
the  family  Eucnemidse  and  has  been  found  in  New  York,  Maryland 
and  Virginia.    See  Crawford  ('09). 

The  family  BELYTID^.- — Some  species,  at  least,  are  parasitic 
in  the  larvee  of  Diptera.  For  a  monograph  of  the  family  see  Kieffer 
('16). 

The  family  PROCTOTRUPID^.— Parasitic  on  dipterous  and 
coleopterous  larvae.    For  a  monograph  of  th?  family  see  Kieffer  ('14). 

The  family  CERAPHRONIDyE.— Some  of  the  species,  at  least, 
are  parasitic  on  aphids  and  cecidomviids. 

The  family  SCELIONIDyE.— This  is  a  very  extensive  family  and 
one  of  great  economic  importance.  The  species  are  egg-parasites, 
infesting  the  eggs  of  practically  all  orders  of  insects  and  the  eggs  of 
spiders. 

The  family  PLATYGASTERID^.— Parasitic  in  the  larva?  of 
Cecidomyiidce  and  Tipulidge. 

The  family  PELECINID^.— This  family  is  represented  in  our 
fauna  by  a  single  species  Peleclnus  polyturdtor,  which  is  a  very  remark- 
able insect.  The  fe- 
males are  common 
where  they  occur 
and  are  easily  rec- 
ognized by  the 
slender  and  long  ab- 
domen (Fig.  1 1 59). 
The  abdomen  of  the 
male  is  club-shaped 
and  only  about 
twice  as  long  as  the 
head    and    thorax.  Fig-  ii59- 

This    sex    is    very 

rare  in  this  country  but  is  common  in  some  parts  of  South  America ; 
it  can  be  recognized  by  the  venation  of  the  wings,  which  is  similar  to 
that  of  the  female.  This  species  is  parasitic  on  the  larvas  of  May- 
beetles. 


922  AN  INTRODUCTION  TO  ENTOMOLOGY 

Although  the  family  Pelecinidae  is  believed  to  be  allied  to  the  pre- 
ceding families  of  the  Proctotrupoidea  it  forms  a  quite  distinct  di- 
vision of  this  superfamih'. 

SUPERFAMILY  CYNIPOIDEA 

The  Cynipids 

Most  members  of  this  superfamily  are  small  insects  and  many  of 
them  are  minute;  for  this  reason  they  are  not  commonly  observed; 
but  the  galls  produced  by  some  species,  especially  those  that  are 
found  on  oaks  and  roses,  are  very  familiar  objects.  Not  all  cynipids, 
however,  produce  galls;  some  are  parasites  and  others  are  inquilines, 
living  in  galls  produced  by  other  species. 

The  antennae  of  the  cynipids  are  not  elbowed  and  only  rarely 
composed  of  more  than  sixteen  segments ;  the  pronotum  is  produced 

on  each  side  so  as  to  reach  the  tegula 
or  is  separated  from  it  only  by  a 
membranous  area ;  the  wings  lack  a 
stigma  and  have  at  most  five  closed 
cells;  the  wings  are  rarely  wanting; 
the  abdomen  is  stronglv  compressed. 
In  most  genera  the  tergites  of  the 
basal  abdominal  segments  differ 
greatly  in  length ;  in  some  the  sec- 
ond is  half  as  long  as  the  entire  ab- 
domen (Fig.  1 1 60). 

For  papers  on  the  classification 
of  the  C>^nipoidea  see  Ashmead  ('03) 
160.— Amphibollps.  and  Dalla  Torre  and  Kieffer   ('02 

and  '10).  Dalla  Torre  and  Kieffer 
recognize  only  a  single  family  of  cynipids,  the  Cynipidaj;  this  they 
divide  into  ten  subfamilies,  seven  of  which  are  "represented  in  our 
fauna. 

These  are  the  Ibaliinas,  Anacharitins,  Aspicerinas,  Figitinse,  Euco- 
ilina?,  Charipina?,  and  Cynipins.  The  first  six  of  these  subfamilies 
include  comparatively  few  species.  These  are  parasitic,  infesting 
chiefly  dipterous  larvas  and  aphids.  The  last  subfamilv,  the  ,Cvni- 
pinae  merits  a  more  detailed  discussion. 

Subfamily  CYNIPIN^ 

This  subfamily  is  composed  of  the  gall-flies  or  gall-wasps  as  thev 
are  termed  by  some  writers.  Most  of  the  species  cause  the  growth  of 
galls  on  plants,  but  some  species,  the  guest  gall-flies,  are  inquilines 
living  in  galls  produced  by  other  species. 

Although  these  insects  are  known  as  the  gall-flies  it  should  be 
remembered  that  galls  are  produced  by  many  insects  that  do  not 
belong  to  this  subfamily.    Galls  made  by  plant-lice,  flies,  and  moths 


HYMENOPTERA  923 

have  been  described  in  the  preceding  pages,  and  galls  are  also  produced 
by  beetles  and  certain  other  insects;  but  the  great  majority  of  these 
strange  growths  are  made  either  by  gall-midges,  mites,  plant-lice,  or 
true  gall-flies  (Cynipinao). 

The  galls  made  by  mites  and  plant-lice  have  open  mouths,  from 
which  the  young  of  the  original  dweller  escape.  But  in  the  case  of 
the  gall-flies  the  gall  is  closed,  and  a  hole  must  be  made  by  the  insect 
in  order  to  emerge.  Moreover,  there  is  no  reproduction  of  insects 
within  the  galls  of  gall-flies,  as  there  is  within  the  galls  of  mites  and 
plant-lice. 

It  is  a  remarkable  fact  that  each  species  of  gall-insects  infests  a 
special  part  of  one  or  more  particular  species  of  plants,  and  the  gall 
produced  by  each  species  of  insect  is  of  a  definite  form.  Hence  when 
an  entomologist  who  has  studied  these  insects  sees  a  familiar  gall,  he 
knows  at  once  what  species  of  insect  produced  it. 

Naturalists  have  speculated  much  as  to  the  way  galls  are  made  to 
grow.  It  has  been  supposed  that  at  the  time  the  egg  is  laid  there  is 
deposited  in  the  tissue  of  the  plant  with  it  a  drop  of  poison,  which 
causes  the  abnormal  growth.  By  this  theory  the  differences  between 
the  galls  of  different  insects  was  explained  by  supposing  that  the 
fluid  produced  by  each  species  of  insect  had  peculiar  properties. 
There  are  certain  kinds  of  galls  which  may  be  produced  in  this  wa3\ 
Thus  it  is  said  that  the  wound  made  by  a  certain  saw-fly  in  the  leaves 
of  willow  causes  an  abundant  formation  of  plant-cells,  and  the  gall 
thus  formed  attains  its  full  growth  at  the  end  of  a  few  days,  and 
before  the  larva  has  escaped  from  the  egg.  But  with  the  gall-flies 
the  gall  does  not  begin  to  grow  until  the  larva  is  hatched;  but  as 
soon  as  the  larva  begins  to  feed,  the  abnormal  growth  of  the  plant 
commences.  In  this  case,  therefore,  if  the  gall  is  produced  by  a 
poison,  this  poison  must  be  excreted  by  the  larva. 

Galls  produced  by  the  different  species  of  cynipids  differ  greatly 
in  form  and  are  found  on  all  parts  of  plants.  A  most  useful  manual 
for  the  identification  of  galls  is  the  "Key  to  American  Insect  Galls" 
by  Dr.  Felt  ('i8)  in  which,  are  figures  of  the  galls  of  many  of  our 
gall-making  insects,  including  those  of  all  orders. 

There  are  two  terms  that  are  frequently  used  in  the  descriptions 
of  galls ;  these  are  monothalamous ,  indicating  that  the  gall  contains  a 
single  larval  cell,  and  polythalamous  indicating  that  the  gall  is  com- 
pound, containing  more  than  one  larval  cell. 

Certain  insect-galls  have  been  found  valuable  for  various  purposes ; 
they  have  been  used  in  medicine,  in  the  manufacture  of  ink,  for  tan- 
ning, and  for  dyeing.  A  sumanary  of  the  literature  dealing  with  the 
uses  of  insect-galls  was  published  by  Fagen  ('i8). 

There  exists  in  many  species  of  gall-flies  an  alternation  of 
generations;  that  is,  the  individuals  of  one  generation  do  not  re- 
semble their  parents,  but  are  like  their  grandparents.  In  many  cases 
the  two  succeeding  generations  of  a  species  differ  so  greatly  that 
they  have  been  considered  as  distinct  species  until  by  careful  studies 
of  the  life-cycle  one  has  been  found  to  be  the  offspring  of  the  other. 


924 


AN  INTRODUCTION  TO  ENTOMOLOGY 


In  those  species  where  an  alternation  of  generations  exists,  one 
generation  consists  only  of  agamic  females  while  the  other  consists 
of  both  males  and  females,  which  reproduce  sexually.  In  some  cases 
the  galls  produced  by  the  two  generations  are  quite  similar;  but  in 
others  they  are  very  different  and  are  found  on  different  parts  of  the 
host  plant.  For  an  example  of  this  see  the  account  of  the  hedgehog 
gall-fly,  Andricus  erindcei,  given  below. 

The  guest  gall-flies  or  inquilines. — Some  species  of  this  subfamily 
do  not  form  galls  but  lay  their  eggs  in  the  galls  made  by  other  species. 
The  larvae  of  these  inquilines  feed  upon  the  galls  produced  by  their 
hosts  and  in  some  cases  do  not  discommode  the  owners  of  the  galls 
in  the  least.  But  some  guest  gall-flies  are  parasites  as  well  as  guests. 
For  example,  Triggerson  in  his  study  of  the  hedgehog  gall-fly  ('14) 
found  that  the  larva  of  Synergus  erindcei,  a  guest  in  the  hedgehog 
gall,  mines  from  cavity  to  cavity  of  the  gall  and  feeds  on  the  occupant 
of  each  in  turn. 

Among  the  more  conspicuous  of  our  cynipid  galls  are  the  following. 
The  oak  hedgehog  gall,  Andricus  erindcei. — A  common  gall  on  the 
leaves  of  white  oak  is  one  known  as  the  oak  hedgehog  gall.  This  gall 
is  rounded  or  oblong,  with  the  surface  finely 
netted  with  fissures,  and  more  or  less  densely 
covered  with  spines  (Fig.  1161,  a).  It  varies 
in  length  from  10  mm.  to  15  mm.,  and  occurs 
on  both  sides  of  the  leaves.  The  point  of  at- 
tachment is  generally  on  the  midrib,  though  it 
is  often  found  on  the  lateral  veins.  When  young 
the  gall  is  yellowish  green,  but  in  autimin  it 
becomes  yellowish  brown.  This  gall  is  poly- 
thalamous,  containing  from  two  to  eight  larval 
cells  (Fig.  1 1 61,  6). 

Within  the  hedgehog  galls  is  developed  one 
generation,  the  agamic  one,  oi  Andricus  erinacei. 
The  alternating  generation,  the  sexual  one,  is 
developed  in  very  different  galls  made  on  the 
terminal  growing  points  of  buds  and  bud-scales. 
These  are  small,  thin-walled,  elongate,  egg- 
shaped  galls,  from  2  to  3  mm.  in  length,  and  are  monothalamous. 
The  life-cycle  of  this  species  was  very  carefully  worked  out  by 
Triggerson  ('14),  from  whose  account  the  data  given  here  are  com- 
piled. The  two  generations  are  distinguished  by  the  use  of  trinominal 
names,  as  follows. 

Andricus  erinacei  erinacei. — This  is  the  agamic  form,  which  is  de- 
veloped in  the  oak  hedgehog  galls.  In  this  form  the  wings  are  vestigial 
not  twice  the  length  of  the  scutellum.  The  adults  emerge  in  November 
and  deposit  their  eggs  in  the  leaf-  and  flower-buds. 

Andricus  erinacei  bicolens .—This  is  the  sexual  form,  which  is  de- 
veloped in  the  galls  formed  in  the  buds.  The  larvae  hatch  in  May, 
from  eggs  laid  by  the  agamic  form  the  previous  autimm  and  produce 
the  galls  known  as  the  soft  oak-bud  galls.  The  adults,  male  and 
female,  emerge  early  in  June,  and  the  females  lay  their  eggs  in  the 


Fig.  1 161. —The  oak 
hedgehog  gall:  a, 
gall  on  leaf;  b,  sec- 
tion of  gall. 


HYMENOPTERA 


925 


leaf-veins;  from  these  e<;gs  hatch  the  larvae  that  cause  the  growth  of 
the  oak  hedgehog  galls.  In  the  sexual  form  the  wings  are  well- 
developed  .  The  name  bicolens  was  proposed  for  this  form  by  Kinsey 
('20). 

The  oak-apples.- — There  are  various  kinds  of  galls  found  on  the 
leaves  and  stems  of  oaks  that  are  commonly  known  as  oak-apples,  a 
name  suggested  by 
the  spherical  form 
and  large  size  of 
some  of  them.  Sev- 
eral of  these  are 
quite  similar  in  ex- 
ternal appearance 
but  are  markedly 
different  in  internal 
structure.  In  all 
there  is  a  firm  outer 
wall  and  a  small, 
central  larval  cell 
(Fig.  1 162).  The 
part  of  the  gall  be- 
tween the  larval 
cell  and  the  outer 
wall  differs  in  struc- 
ture in  the  galls  of 
different  species  of 
gall-flies;  in  some 
it  is  filled  with  a 
spongy  mass  of  tis- 
sue, in  others  the  larval  cell  is  held  in  place  by  a  small  niimber  of 
filaments  that  radiate  from  it  to  the  outer  wall. 

The  large  oak-apple,  Amphtbolips  confltlens .■ — This  is  the  largest 
of  our  common  oak-apples,  measuring  from  18  to  50  mm.  in  diameter. 
It  occurs  on  several  species  of  oak  and  is  usually  attached  to  a  vein 
or  the  petiole  of  a  leaf.  The  space  between  the  larval  cell  and  the 
outer  wall  of  the  gall  is  filled  with  a  spongy  mass  of  tissue,  in  which 
in  some  of  the  galls  there  are  many  radiating  fibers,  as  shown  in  the 
figure  above,  but  in  other  galls  these  fibers  are  indistinct,  the  space 
being  filled  with  an  amorphous  mass  of  tissue. 

In  spite  of  the  fact  that  these  galls  are  common  and  conspicuous 
the  life-cycle  of  the  species  that  produces  them  has  not  been  fully 
worked  out.  What  is  known  of  it  is  based  chiefly  on  the  observations 
of  Walsh  (1864),  little  has  been  added  during  the  long  interval  since 
this  publication. 

The  oviposition  has  not  been  observed.  The  galls  appear  on  the 
leaves  early  in  the  spring;  from  some  of  them  there  emerges  in  June 
a  generation  of  gall-flies  consisting  of  both  males  and  females;  and 
from  other  galls  there  emerges  in  the  autumn  a  generation  of  gall-flies 
which  consists  only  of  females. 


Fig.  1 1 62. — An  oak-apple. 


926 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Fig.  1 1 63. — The  large  empty 
oak-apple. 


The  large  empty  oak-apple,  Amphtbolips  indnis. — There  are  two 
oak-apples  which  are  ven^  similar  in  structure,  and  which  may  be 
termed  the  empty  oak-apples.  In  these 
the  space  between  the  central  larval  cell 
and  the  outer  shell  contains  only  a  few, 
very  slender,  silky  filaments,  which  hold 
the  larval  cell  in  place  (Fig.  1163).  The 
larger  of  these  two  galls,  measures  from 
25  to  35  mm.  in  diameter,  and  is  found 
on  the  leaves  of  the  scarlet  oak  and  red 
oak.  Externally  this  gall  resembles  that 
of  the  preceding  species  but  is  easily  dis- 
tinguished by  its  internal  structure.  The 
adult  gall-flies  emerge  in  June  and  early 
in  July;  they  are  male  and  female;  an 
agamic  form  of  this  species  is  not  known. 
The  smaller  empty  oak-apple,  Diplo- 
lepis  centrtcola. — This  gall  is  found  on  the 
lower  side  of  leaves  of  the  post-oak  and  measures  from  15  to  20  mm. 
in  diameter.  It  is  sometimes  tinged  with  pink  and  covered  with  a 
white  bloom.  The  adult  gall-flies  emerge  in  October  and  are  all 
females.     A  sexual  generation  of  this  species  is  not  known. 

The  oak-bullet- 
gall,  Disholcdspis 
globulus.- — One  of 
the  most  common 
galls  on  white  oak, 
chestnut  oak,  and 
scrub  chestnut  oak 
is  a  bullet-shaped 
gall  which  is  at- 
tached to  the  small 
twigs  of  these  trees. 
This  gall  measures 
from  8  to  16  mm. 
in  diameter  and  oc- 
curs singly  or  in 
clusters  of  two, 
three,  or  more.  In- 
ternally it  is  of  a 
compact,  rather 
hard,  corky  texture, 
and  contains  a  free, 

oval,  larv^al  cell,  re-  -p-        ^       n., 

sembling     an     egg.  Fig.  ii64.-The  mossy  rose-gall. 

The  adult  gall-flies  emerge  during  October  and  November;  these  are 
all  females;  a  sexual  generation  of  this  species  has  not  been  identified. 

The  giant  oak-gall,  Andricus  californicus. — This  is  the  most  com- 
mon oak-gall  of  the  Pacific  Coast.    It  is  very  abundant  on  the  twigs 


HYMENOPTERA 


927 


and  branches  of  the  Cah'fornia  white  oaks,  and  durinj?  the  winter, 
when  the  trees  are  bare,  it  is  a  very  conspicuous  object,  on  account 
of  its  abundance  and  large  size.  It  varies  in  shape  from  globose  to 
reniform  and  also  varies  greatly  in  size,  some  of  the  larger  ones 
measure  more  than  loo  mm.  in  their  greatest  diameter.  The  outer 
surface  of  the  gall  is  white  and  usually  smooth ;  the  interior  is  more 
or  less  filled  with  a  compact  soft  material,  and  contains  from  one  to 
a  dozen  larval  cells.  Several  varieties  of  the  gall-fly  that  produces 
this  gall  are  described  by  Kinsey  ('22). 

The  mossv  rose-gall,  Rkodltes  roses. — This  is  a  very  common  poly- 
thalamous  gall,  which  is  formed  on  the  stems  of  rose  bushes,  especially 
of  the  sweetbrier.  The  gall  consists  of  a  large  mass  of  moss-like 
filaments  surrounding  a  cluster  of  hard  kernels  (Fig.  11 64).  In  each 
of  these  kernels  a  gall-fly  is  developed.  The  galls  appear  early  in  the 
summer  but  the  adults  do  not  emerge  till  the  following  spring.  These 
are  male  and  female;  there  is  no  alternation  of  generations  in 
this  species. 

SupERFAMiLY  CHALCIDOIDEA 


The  Chalcid-flies 

This  superfamily  is  the  larg- 
est in  number  of  species  of  the 
superfamilies  of  the  HATnenop- 
tera,  including  many  thousand 
species.  Most  of  the  species  are 
very  small  insects  and  some  are 
minute  measuring  not  more  than 
a  quarter  of  a  millimeter  in  length ; 
some  species  are  much  larger  but 
these  do  not  exceed  the  honey-bee 
in  size.  Most  of  the  species  are 
black,  with  strong  metallic  re- 
flections, although  some  are  yel- 
low and  some  of  the  larger  species 
have  red  markings.  The  head  is  usually  large  (Fig.  1165) ;  the  pro- 
thorax  does  not  extend  back  on 
each  side  to  the  tegula;  the  ve- 
nation of  the  wings  is  greatly  re- 
duced ;  and  the  ovipositor  is  usu- 
ally hidden;  issuing  before  the 
apex  of  the  abdomen,  but  in  some 
genera  it  is  very  long. 

In  most  of  the  Chalcidoidea 
the  venation  of  the  wings  is  re- 
duced to  the  type  shown  in  Fig- 
gure  1 1 66;  in  a  few,  however,  there  are  vestiges  of  other  veins;  but 
in  none  are  there  any  closed  cells. 


A.  chalcid-fly,  Aphycus 


Fig.  1 1 66. — Fore  wing  of  a  chalcid-fly. 


928 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  vein  that  persists  in  the  wings  of  chalcid-flies  consists  probably 
of  the  coalesced  subcosta,  radius,  media,  the  stigma,  the  radial 
cross-vein,  and  the  base  of  vein  R3 ;  but  writers  on  the  Chalcidoidea 
make  use  of  a  special  set  of  terms  in  describing  the  different  parts  of 
this  compound  vein.  These  are  the  suhniarginal  vein  or  subcostal  vein 
(Fig.  1 166,  a),  the  marginal  vein  (Fig.  1166,  h),  the  postmarginal  vein 
(Fig.  1 1 66,  c),  and  the  stigmal  vein  (Fig.  1166,  d). 

The  chalcid-fiies  constitute  an  exceedingly  important  group  of  in- 
sects from  an  economic  standpoint ;  and  nearly  all  of  them  are  bene- 
ficial, beine  parasites  that  do  much  to  keep  in  check  noxious  insects. 
A  few  species,  however,  are  ph>i;ophagous ;  among  these  are  those  of 
the  genus  Isosoma  that  infest  the  stalks  of  growing  grain,  and  species 
of  several  genera  that  infest  the  seeds  of  various  plants.  While  these 
are  noxious,  the  fig-insects,  forming  the  subfamily  Agaoninee,  although 
phytophagous  are  very  beneficial  to  man. 

Insects  in  all  stages  of  their  development  suffer  from  the  attacks 
of  chalcid-flies,  eggs,  larvee,  pupse,  and  even  adults  in  a  few  cases 
being  attacked  by  them.  The  larvae  of  chalcid-flies  usually  feed 
within  the  body  of  their  host,  but  some  species  are  external  parasites 
of  other  larva. 

While  the  development  of  most  species  of  chalcid-flies  is  a  normal  one,  in 
certain  species  remarkable  modifications  of  the  usual  course  exists.  The  phe- 
nomenon of  polyembryony  which  has  been  observed  in  several  species  is  dis- 
cussed on  an  earlier  page.  Another  modification  of  the  usual  course  of  develop- 
ment is  the  existence  of  a  hypermetamorphosis  that  occurs  in  some  genera. 


Fig.    1 1 67. — Planidium   of   Perilampus.      From   left   to 
right,  dorsal,  lateral,  and  ventral  views.    (After  Ford.) 


Fig.  \\6d,.— Peril- 
ampus hyalinus. 
Mature  larva, 
greatly  enlarged. 
(From   Smith.) 


In  these  cases  the  larvae  when  they  leave  the  egg  differ  greatly  in  form  from 
ordinary  chalcid-larvas  (Fig.  1167).  and  are  active,  moving  about  in  search  of 
their  prey.     This  active  instar  was  termed  by  Professor  Wheeler,  who  first  de- 


HYMENOPTERA  929 

scribed  it,  the  planidium,  from  the  Greek  meaning  diminutive  wanderer.  The 
planidea  of  the  species  of  three  genera  have  been  described.  Two  of  these, 
Orasema  viridis,  described  by  Wheeler  ('07a)  and  Psilogaster  fasciiventris  de- 
scribed by  Brues  ('19)  are  parasites  of  ants,  and  Perildmpiis  hyallnus  described  by 
H.  S.  Smith  ('12)  is  a  secondary  parasite  of  the  tachinid  and  ichneumonid  para- 
sites of  the  fall  web  worm.  The  planidium  figured  above  was  found  by  Miss 
Norma  Ford  within  the  bodies  of  dissected  specimens  of  one  of  the  meadow- 
grasshoppers,  Conocephalus  fasciattts;  it  is  probably  a  secondary  parasite  of  some 
parasite  of  the  grasshopper  (Ford  '22). 

The  development  of  Perilampus  hyalinus  will  serve  as  an  illustration  of  the 
life-cycle  of  these  remarkable  parasites.  The  egg  has  not  been  observed,  but  it 
seems  probable  that  it  is  deposited  upon  the  food  plant  of  the  fall  webworm  in  the 
vicinity  of  a  colony  of  this  insect.  The  planidia,  which  measure  less  than  0.3  mm. 
in  length  and  are  therefore  almost  invisible  to  the  unaided  eye,  were  found  first  on 
the  exterior  of  the  caterpillars;  later  within  their  bodies,  having  bored  through  the 
cuticula  of  the  caterpillar  by  means  of  their  well-developed  mandibles,  still  later 
the  planidia  were  endoparasitic  within  the  larvae  of  parasites  of  the  caterpillars. 
After  feeding  for  a  time  the  planidium  molts;  the  second  instar  is  ovate  in  shape, 
with  the  head  bent  underneath.  After  another  short  period  of  feeding  the  larva 
molts  a  second  time  and  becomes  greatly  changed  in  form  (Fig.  1168).  Finally 
after  the  primary  parasite  has  left  the  caterpillar  and  pupated  the  larva  of  Peril- 
ampus becomes  an  ectoparasite.     It  then  soon  completes  its  growth  and  pupates. 

Family  CHALCIDID^ 

The  chalcid-fiies  are  now  regarded  by  most  authorities  on  the 
Hymenoptera  as  constituting  a  single  family,  the  Chalcididse,  the 
distinctive  characteristics  of  which  are  those  of  the  superfamily 
Chalcidoidea  given  above. 

This  family  has  been  divided  into  a  score,  more  or  less,  of  sub- 
families, which  are  regarded  as  families  by  some  authors.  For  a  dis- 
cussion of  the  characteristics  of  these  subfamilies  the  student  is  re- 
ferred to  the  special  works  on  chalcid-flies;  among  these  are  Ashmead 
('04),  Schmiedknecht  ('09),  and  Viereck  ('16).  Space  can  be  taken 
here  to  mention  only  a  few  of  the  subfamilies. 

Subfamily  LEUCOSPIN^ 

The  members  of  this  subfamily  agree  with  the  Vespidas  and  differ 
from  all  other  H\Tnenoptera,  except  the  Gasteruptionid^e  and  the  genus 
Galesus  of  the  family  Belytida?,  in  having  the  fore  wings  folded  longi- 
tudinally when  at  rest.  They  are  also  peculiar  in  having  the  ovipositor 
of  the  female  curved  up  over  the  dorsimi  of  the  abdomen,  often  reach- 
ing the  scutellum.  These  insects  are  parasitic  in  the  nests  of  bees. 
Our  most  common  species  is  Leucospis  affmis,v^h\ch  measures  from 
6  to  12  mm.  in  length.  It  has  been  bred  from  nests  of  a  leaf -cutter 
bee,  Megachile. 

Subfamily  CHALCIDIN^ 

This  family  includes  chalcid-flies  in  which  the  hind  femora  are 
greatly  swollen  and  usually  dentate  or  serrate.  In  this  respect  they 
resemble  the  Leucospinae,  but  they  differ  from  the  Leucospinse  in  not 


930 


AN  INTRODUCTION  TO  ENTOMOLOGY 


having  the  fore  wings  folded  when  at  rest  and  in  never  having  the 
ovipositor  curved  forward  over  the  dorsum.  In  these  two  subfamiHes 
are  found  the  largest  of  our  chalcid-flies.  Most  of  the  species  of  the 
Chalcidinas  are  parasitic  on  lepidopterous  larvae  or  pupaj;  a  few  are 
parasitic  on  other  insects. 

vSuBFAMILY  APHELININ^ 

This  subfamily  is  composed  of  small  species  that  are  parasitic 
upon  coccids,  aphids  and  aleyrodids;  it  includes  the  most  important 
parasites  of  the  Diaspina?.  For  a  table  of  genera  and  figures,  and 
descriptions  of  many  species  see  Howard  ('95  and  '07). 

vSUBFAMILY  MYMARIN^ 


Fig.  1 169. — Cosmocoma  elegans. 


To  this  subfamily  belong  some  of  the  smallest  of  insects.  All  of 
the  species  so  far  as  is  known  are  parasites  in  the  eggs  of  other  insects. 

In  this  family  the  hind 
wings  are  linear  and  pe- 
dunculate at  the  base 
(Fig.  1169). 

Subfamily 
EURYTOMIN^ 

This  subfamily  is  re- 
markable on  account  of 
the  diversity  of  habits 
among  the  various  groups 
of  genera  composing  it. 
Some,  like  most  other 
chalcid-flies,  are  parasit- 
ic ;  among  these  are  those 
that  infest  the  nests  of  bees  and  wasps ;  other  that  are  parasitic  upon 
gall-making  Hymenoptera  and  Diptera ;  some  that  are  parasitic  upon 
Coleoptera  and  other  insects;  and  a  few  that  destroy  the  eggs  of 
orthopterous  insects.  In  addition  to  this  diversity  of  parasitic  habits 
is  the  anomalous  fact  that  certain  genera  are  phytophagous;  among 
the  more  important  of  these  are  the  following. 

The  grass  and  grain  joint -worm  flies,  HarmolUa  {=Isosdma): — The 
members  of  this  genus  infest  the  stalks  of  growing  grasses  and  grains, 
often  causing  the  formation  of  gall-like  swellings  at  or  just  above  the 
first  joint,  hence  the  common  name  joint-worm  flies.  The  two  follow- 
ing species  are  of  considerable  economic  importance. 

The  wheat  joint-worm,  Harmollta  trttici. — This  is  a  well-known 
pest  which  infests  the  stalks  of  growing  wheat  and  certain  grasses. 
It  causes  a  woody  growth  which  fills  up  the  cavity  of  the  stalk,  and 
sometimes  also  causes  a  joint  to  swell  and  the  stalk  to  bend  and  lop 
down.     The  presence  of  this  insect  is  often  indicated  by  pieces  of 


HYMENOPTERA  ,  931 

hardened  straw  coming  from  the  threshing  machine  with  the  grain. 
There  is  but  a  single  generation  of  this  species  in  a  year.  The  insect 
remains  in  the  straw  and  stubble  during  the  winter,  the  adults  emerg- 
ing in  the  spring.  The  methods  of  control  of  this  pest  are  rotation  of 
crops,  burning  or  deep  ploughing  under  of  stubble  when  practicable, 
or  harvesting  of  stubble  in  spring  with  a  horse-rake  and  burning  it 
before  the  adults  emerge. 

The  wheat  straw-worm,  Harmolita  grdndis. — This  species  is  often 
a  serious  pest  of  wheat  west  of  the  Mississippi  River;  it  also  occurs 
in  the  East,  but  is  rarely  so  injurious  in  this  section  as  is  the  wheat 
joint-worm.  The  adults  differ  from  our  other  species  of  Harmolita 
in  that  the  mesonotimi  is  smooth,  polished,  and  shining.  This  species 
also  differs  in  that  it  exhibits  a  seasonal  dimorphism.  There  is  a 
summer  generation,  which  consists  only  of  winged  females,  and  a 
winter  and  spring  generation  which  consists  of  both  males  and  females. 
These  are  smaller  than  the  summer  form  and  are  frequently  wingless. 
The  adults  of  the  winter  and  spring  generations  emerge  in  April  and 
the  females  deposit  their  eggs  in  the  young  wheat  plants;  the  larvae 
eat  out  and  totally  destroy  the  forming  heads  of  wheat.  The  adults 
of  the  second  generation  deposit  their  eggs,  about  the  time  the  wheat 
is  heading,  just  above  the  youngest  and  most  succulent  joints  which 
are  not  so  covered  by  the  enfolding  leaf-sheaths  as  to  be  inaccessible 
to  them.  The  larvee  pupate  by  October  and  the  winter  is  passed  in 
the  straw  or  stubble. 

Seed-infesting  Eurytomids. — ^ Among  the  phytophagous  members  of 
this  subfamily  are  several  species  that  infest  seeds.  The  grape-seed 
chalcid,  Evoxysoma  vitis,  is  common  in  the  seeds  of  wild  grapes  and 
occasionally  infests  cultivated  varieties,  which  are  injured  by  punc- 
tures made  by  the  females  in  ovipositing.  The  injured  berries  color 
prematurely  and  sometimes  shrivel  and  drop. 

Another  species  that  is  of  economic  importance  is  the  clover-seed 
chalcid,  Bruchophagus  funebris,  which  infests  the  seeds  of  red  and 
crimson  clovers  and  alfalfa.  This  insect  usually  winters  over  in  the 
seed  as  a  well-developed  larva;  the  pupal  stadium  is  rather  short 
and  the  adult  lays  her  eggs  in  May  and  June.  For  an  account  of  seed- 
infesting  chalcid-flies  see  Crosby  ('09). 

Subfamily  TORYMIN^ 

This  subfamily  like  the  preceding  one  includes  both  parasitic  and 
phytophagous  species.  Many  of  the  parasitic  species  prey  upon  gall- 
making  Lepidoptera  and  Diptera.  Among  the  phytophagous  species 
are  the  apple-seed  chalcid,  Syntomdspis  dntpdrum,  and  various  species 
of  Megastigmus,  which  infest  the  seeds  of  various  plants.  See  Cros- 
by ('09). 

Subfamily  AGAONIN^ 
The  Fig-insects 

This  subfamily  is  composed  of  those  remarkable  insects  that  live 
within  figs  and  fertilize  them.    It  is  represented  in  the  United  States 


932  AN  INTRODUCTION  TO  ENTOMOLOGY 

by  a  single  species,  Blastophaga  psenes,  which  was  introduced  into 
California  in  order  to  make  possible  the  production  of  the  Smyrna 
fig  in  that  state. 

The  fruit  of  the  fig-tree  consists  of  a  hollow  receptacle  on  the 
lining  of  which  the  flowers  are  borne.  At  the  apex  of  the  fig  there  is 
a  more  or  less  distinct  opening  leading  into  the  interior;  it  is  through 
this  opening  that  the  female  fig-insect  leaves  the  fig  in  which  she  was 
developed  and  enters  a  young  fig  in  order  to  oviposit. 

The  eggs  are  laid  at  the  base  of  a  modified  form  of  pistillate  flowers, 
known  as  gall-flowers,  that  are  found  in  wild  figs;  and  the  larvae 
produce  little  galls  in  which  they  develop.  The  female  fig-insect  when 
leaving  the  fig  in  which  she  was  developed  becomes  covered  with 
pollen  which  is  thus  carried  into  the  young  fig  which  she  enters  to 
oviposit,  and  thus  the  flowers  in  this  fig  are  fertilized. 

The  male  fig-insect  is  wingless.  It  crawls  about  over  the  galls  in 
the  fig  in  which  it  was  developed  and  when  it  finds  a  gall  containing 
a  female  it  gnaws  a  hole  in  it  and  then  thrusting  the  tip  of  its  abdomen 
through  the  puncture  fertilizes  the  female. 

It  is  only  in  the  wild  figs  that  the  gall-flowers  are  developed;  for 
this  reason  only  the  wild  figs  are  suitable  for  the  development  of  the 
fig-insects;  but  the  female  fig-insects  will  enter  the  cultivated  figs 
seeking  a  place  to  oviposit  and  will  thus  fertilize  them. 

Although  the  nimierous  varieties  of  common,  cultivated  figs  do 
not  require  the  stimulus  of  pollination  and  the  resulting  fertilization 
of  the  ovary  to  make  the  fruit  set,  in  the  case  of  the  Smyrna  fig, 
which  is  the  most  desirable  variety  grown,  without  this  stimulation 
the  young  figs  soon  turn  yellow  and  drop.  It  is  the  oily  kernel  of  the 
fertile  seed  that  gives  the  Smyrna  figs  their  superior  quality. 

The  fertilization  of  the  edible  figs  is  termed  caprification ;  and  it 
is  brought  about  by  placing  in  the  fig-trees  fruit  of  the  wild  figs  con- 
taining the  fig-insects.  In  order,  therefore,  to  produce  the  Smyrna 
figs  it  is  necessary  to  grow  also  the  wild  figs,  or  caprifigs  as  they  are 
termed. 

There  are  many  species  of  fig-insects  living  in  the  wild  figs  of 
tropical  and  semi-tropical  countries. 

SUPERFAMILY  EVANIOIDEA 
Family  EVANIID^ 

The  Ensign-flies 

The  family  Evaniidse  is  so  distinctly  separated  from  all  other 
families  of  the  H}anenoptera  that  it  is  regarded  as  constituting  a 
separate  superfamily.  We  have  in  this  case  a  superfamily  represented 
by  a  single  family. 

The  family  Evaniidee  differs  from  all  of  the  preceding  families  in 
the  presence  of  a  well-marked  anal  lobe  in  the  hind  wings  (Fig.  1170) 
and  it  differs  from  all  of  the  following  families  in  that  the  petiole  of 


HYMENOPTERA 


933 


Fig.  1171.— 
Evania  ap- 
pendigaster 


the  abdomen  is  attached  to  the  dorsal  surface  of  the  propoieum  (Fig. 

I  I  7  I )  in- 
stead of  at 
the  hind 
end  of  it,  as 
it  is  in  the 
following 
families. 
The ab- 
domen   is 

short  and  carried  aloft ^ — 
like  a  flag;  this  fact  sug- 
gested the  common  name 
ensign-flies  for  these  in- 
sects. 
The  venation  of  the  wings  is  greatly  reduced,  and  in  the  hind 

wings  there  are  no  closed  cells;  the  trochanters  are  two-segmented; 

and  the  ovipositor  is  not  at  all  or  but  little  exserted. 

All  of  the  species  are  parasitic  in  the  eggs  of  cockroaches. 

This  family  was  monographed  by  Bradley  ('08)  and  Kieffer  ('12) 

It  is  represented  in  our  fauna  by  two  genera,  Evania  and  Hyptia. 

SUPERFAMILY  VESPOIDEA 


Fig.  1 1 70. — Wings  of  Evania  appendigaster;l,  anal 
lobe. 


The  Vespoid-Wasps 

This  superfamily  is  one  of  three  superfamilies,  the  Evanioidea, 
the  Vespoidea,  and  the  Sphecoidea,  in  which  the  hind  wings  are 
typically  furnished  with  an  anal  lobe;  but  in  some  of  the  more 
specialized  members  of  the  Vespoidea  and  of  the  Sphecoidea  the  anal 
lobe  has  been  lost.  This  is  the  case  in  certain  genera  of  the  Formi- 
cidffi,  Mutillidae,  and  Vespidse;  these  exceptional  forms  can  be  placed 
by  the  table  of  families  on  pages  go6  to  915. 

The  members  of  Vespoidea  differ  from  the  Evanioidea  in  that  the 
petiole  of  the  abdomen  is  attached  to  the  hind  end  of  the  propodeum ; 
and  they  differ  from  the  Sphecoidea  in  that  the  lateral  extensions  of 
the  pronotttm,  which  reach  the  tegulas  (except  in  the  Cleptidae  and 
Chrysididae) ,  are  not  in  the  form  of  v/ell-differentiated  rounded  lobes, 
as  is  the  case  in  the, Sphecoidea.    See  Figure  1195  on  a  later  page. 

The  Vespoidea  is  represented  in  our  fauna  by  fourteen  families; 
these  can  be  separated  by  the  table  of  families  referred  to  above. 


Family  POMPILID^ 

The  Spider-Wasps 

The  members  of  this  family  are  commonly  called  spider-wasps, 
because  they  provision  their  nests  with  spiders;  this  habit,  however,  is 
not  distinctive  as  certain  other  wasps  use  spiders  for  this  purpose. 


934  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  members  of  this  family  are  slender  in  form,  with  long  spiny 
legs,  (Fig.  1 172).  The  pronotum  extends  back  on  each  side  to  the 
tegula;  and  the  abdomen  is  sessile.  Many  of  the 
species  are  of  medium  size,  but  some  are  very  large; 
in  fact,  the  largest  of  our  Hymenoptera  belong  to 
this  family. 

Most  of  the  Pompilida;  make  their  nests  in  the 
ground.  The  wasp  first  finds  a  spider  and  stings  it 
until  it  is  paralyzed,  and  then  digs  a  burrow,  which 
rig.  1 1 72.—  A  ^g  enlarged  at  the  lower  end,  forming  a  cell  for  the 
spi  er--nasp.  j-gception  of  the  spider;  the  spider  is  then  dragged 
down  into  the  cell  and  an  egg  attached  to  it;  then 
the  passage  leading  to  the  cell  is  filled  with  earth.  Detailed  accounts 
of  the  actions  of  these  spider-wasps  when  making  and  provisioning 
their  nests  are  given  bv  Peckham  and  Peckham  ('98)  and  by  Rau 
andRau  ('18).  " 

Among  the  giant?  of  this  family  are  the  well-known  tarantula- 
hawks  of  the  genus  Pepsis  of  the  Southwest,  which  store  their  bur- 
rows with  tarantulas.  Many  a  hard -fought  battle  do  these  spider- 
wasps  have  with  these  enormous  spiders,  and  sometimes  the_v  are 
conquered  and  ignominiously  eaten. 

Not  all  members  of  this  family  are  digger-wasps,  for  some  are 
mason-wasps.  The  species  of  the  genus  Pseudagenia  make  thimble- 
shaped  cells,  of  mud,  attached  to  the  lower  surface  of  stones,  in 
chinks  of  walls,  under  bark  and  in  various  other  situations;  and  at 
least  one  species  oiCeropales  is  said  to  be  parasitic  in  the  nests  of 
Pesudagenia. 

More  than  one  hundred  species  belonging  to  this  family  have  been 
described  from  our  fauna.  A  classification  of  the  family  was  pub- 
lished by  Banks  ('11). 

The  family  EMBOLEMID^  includes  only  a  few  rare  species  the 
habits  of  which  are  unknown. 

Family  CLEPTID^ 

Cleptes 

This  family  includes  only  the  genus  Cleptes,  which  was  formerly 
included  in  the  following  family.  But  the  genus  Cleptes  differs  from 
the  Chr^^sididce  in  that  there  are  six  exposed  segments  in  the  abdomen 
and  the  venter  is  convex.  It  is  believed  that  these  wasps  are  parasitic 
in  the  cocoons  of  saw-flies;  as  one  of  them  infests  the  currant -worm 
in  Europe.    Several  native  species  are  found  in  the  Far  West. 

Family  CHRYSIDID^ 

The  Cuckoo-Wasps 

The  cuckoo-wasps  are  wonderfully  beautiful  creatures,  being  usu- 
ally a  brilliant  metallic  green  in  color.    The  species  are  of  moderate 


HYMENOPTERA  935 

size,  the  largest  beine:  only  about  12  mm.  in  length.    They  can  be 
distinguished  from  other  H^Tnenoptera  by  the  form  of  the  abdomen, 
in  which  there  are  at  most  five  and  usually 
only  three  or  four  exposed  segments  (Fig. 
1 1 73),  and  which  is  strongly  concave  below, 

so  that  it  can  be  readily  turned  under  the      ^"'^"I^^^BBfej^^^"-'^ 
thorax  and  closely  applied  to  it.     In  this          *'       yf^^-    --Ju--..- 
way  a  cuckoo-wasp  rolls  itself  into  a  ball 
when  attacked  leaving  only  its  wings  ex- 
posed. ^ ^ 

In  this  family  and  in  the  preceding  one         p-^  ,      . 

the  antennae  are  13 -segmented  in  both  sexes;  nitidnia.        "^^''^ 

the  pronotum  does  not  reach  the  tegulse; 

there  are  no  closed  cells  in  the  hind  wings;  and  the  ovipositor  is  an 
extensile  jointed  tube. 

The  cuckoo-wasps  are  so-called  because  they  are  parasitic  in  the 
nests  of  solitary  wasps  and  solitary  bees.  A  cuckoo-wasp  seeks  until 
it  finds  a  wasp  or  bee,  building  its  nest,  and  when  the  owner  of  the 
nest  is  off  collecting  provisions  steals  in  and  lays  its  egg,  which  the 
unconscious  owner  walls  in  with  her  own  egg.  Sometimes  the  cuckoo- 
wasp  larva  eats  the  rightful  occupant  of  the  nest,  and  sometimes, 
starves  it  by  eating  up  the  food  provided  for  it.  The  bees  and 
wasps  know  "this  foe  very  well,  and  tender  it  so  warm  a  reception  that. 
the  brilliant-coated  little  rascal  has  reason  enough  to  double  itself  up 
so  the  righteous  sting  of  its  assailant  can  find  no  hole  in  its  armor. 
There  is  one  instance  on  record  where  an  outraged  wasp,  unable  to 
sting  one  of  the  cuckoo-flies  to  death,  gnawed  off  her  wings  and 
pitched  her  out  on  the  ground.  But  the  undaunted  invader  waited 
until  the  wasp  departed  for  provisions,  and  then  crawled  up  the  post 
and  laid  her  egg  in  the  nest  before  she  died. 

A  monograph  of  the  North  American  species  was  published  by 
Aaron  ('85),  one  of  the  species  of  the  world  by  Mocsary  ('89),  and 
another  by  Bischoff  ('12). 

The  family  ANTHOBOSCID^  is  represented  in  North  America 
by  a  single  species,  Sierolomorpha  amblgua.  This  is  shining  black, 
with  an  oval  abdomen,  the  first  segment  of  which  is  constricted  off 
from  the  rest.    It  measures  4.5  to  6  mm.  in  length. 

Family  SAPYGID^ 

The  Sapygids 

This  is  a  small  family  including  only  three  North  American 
genera,  and  but  little  more  than  twenty  species.  These  insects  are  of 
moderate  size,  with  short  legs,  and  are  usually  black,  spotted  or  banded 
with  yellow,  rarely  entirely  black.  So  far  as  their  habits  are  known, 
they  are  inquilines  in  the  nests  of  solitary  wasps  and  solitary  bees. 

The  family  THYNNID^E  is  represented  in  our  fauna  by  a  single 
rare  species  of  the  genus  Glyptometopa,  found  in  California. 


936  AN  INTRODUCTION  TO  ENTOMOLOGY 

Family  TIPHIID^ 

The  Tiphiids 

The  tiphiids  are  quite  closely  related  to  the  following  family,  the 
velvet -ants.  In  fact,  some  of  the  genera  now  included  in  the  Tiphiidae 
have  been  classed  in  the  Mutillidas.  The  characters  separating  these 
two  families  are  indicated  in  the  table  of  families  of  the  Hymenoptera 
given  above.    The  family  Tiphiidae  includes  three  subfamilies. 

The  subfamily  TIPHIIN^  is  represented  in  our  fauna  by  five 
genera;  these  are  Pterombus,  Epomidiopteron,  Elis  {Myzine),  Tiphia, 
and  Paratipha.    One  of  the  most  common  species 
is  Tiphia  inorndta  (Fig.  1174).    This  is  a  shining 
black  species ;  the  male  measures  from  7  to  1 1  mm. 
in  length  and  has  an  upward  projecting  spine  near 
the  tip  of  the  abdomen.     The  female  measures 
Fig    1174— Tiphia      ^^°"^  12  to  14  mm.  in  length.    The  accompanying 
inornaia.  figure  represents  a  female;  in  this  sex  the  anten- 

na are  curled  much  more  than  is  indicated  in  the 
figure.    This  species  is  parasitic  upon  white-grubs, 
the  larvae  of  the  May-beetles.    For  descriptions  of  species  of  Tiphia 
see  Malloch  ('18). 

The  subfamily  METHOCIN^  includes  forms  in  which  the  two 
sexes  are  very  dissimilar;  the  males  are  winged,  the  females  are  wing- 
less and  resemble  ants.  Our  most  common  species  is  Methdca  stygia. 
The  subfamily  MYRMOSIN^  includes  two  genera,  Mynnosa  and 
Myrmosula.  The  males  are  winged  and  the  females  are  wingless. 
Our  most  common  species  is  Myrmosa  umcolor.  The  subfamily  has 
been  monographed  by  Bradley  ('17). 

Family  MUTILLID^ 

The  Velvet-ants 

These  handsome  insects  resemble  ants  in  the  general  form  of  the 
body,  but  lack  the  scale-like  knot  of  the  pedicel  of  the  abdomen 
characteristic  of  the  true  ants,   although  there  is 
sometimes  a  constriction  between  the  first  and  second         t^%  ■> 
abdominal  segments  (Fig.  1175).    The  body  is  often      ^^^^'^p^^ 
densely  clothed  with  hair,  which  gives  the  insects  the      ^         vT^ 
appearance  of  being  clothed  in  velvet;  and  as  the  Fig.  1175. 

body  is  usually  ringed  or  spotted  with  two  or  more 
strongly  contrasting  colors,  they  are  very  conspicuous.  But  in  many 
species  the  body  is  naked.  The  colors  most  commonly  worn  by  the 
velvet-ants  are  black  and  scarlet.  The  males  are  winged  and  frequent 
flowers.  The  females  are  wingless,  but  they  run  very  rapidly  and 
they  sting  severely.  In  the  western  states  there  are  many  straw  yellow 
species,  which  are  nocturnal. 

^    These  insects  are  abundant  in  the  warmer  portions  of  our  country, 
and  several  species  occur  in  the  North.    A  large  species,  Dasymutilla 


HYMENOPTERA  937 

occidentalis,  which  measures  from  1 6  to  30  mm.  or  more  in  length,  is 
known  in  the  South  as  the  "cow-killer  ant"  because  of  the  popular 
superstition  that  its  sting  is  very  dangerous  to  live  stock. 

Andre  ('03)  states  that  the  mutillids  of  which  the  habits  have 
been  observed  are  parasites  of  nest-buildine  H}Tnenoptera  in  the  cells 
of  which  they  deposit  their  eggs.  The  larvse  attack  those  of  the 
owners  of  the  nest  without  touching  the  provisions  which  the  cell 
may  contain. 

In  this  country  a  species  has  been  reared  from  the  cells  of  the 
solitary  bee,  Nomia  pattern,  and  one  from  the  nests  of  the  mud- 
dauber,  Chalybion  ccsruleum.  In  Europe  several  species  are  parasitic 
in  the  nests  of  bumblebees;  and  in  Africa  several  species  have  been 
found  to  be  parasitic  on  the  tsetse  fly. 

The  Mutillida?  of  North  America  have  been  monographed  by  Fox 
('99)   and  those  of  the  Eastern  United  States  by  Bradley   ('16). 

Family  SCOLIID^ 
The  Scoliids 

The  scoliids  are  quite  closely  related  to  the  preceding  family  but 
differ  in  their  general  appearance,  resembling  wasps  rather  than  ants. 
They  are  parasitic  on  white  grubs,  the  larvae  of  Scarabaeidae.  In 
their  habits  they  do  not  exhibit  as  much  intelligence  as  do  most  digger 
wasps;  for  they  do  not  build  nests  and  transport  prey  to  them  for 
their  carnivorous  larvae.  Instead  of  this  they  dig  in  the  ground 
where  the  white  grubs  are,  and  finding  one  they  sting  it  in  order  to 
paralyze  it,  work  out  a  crude  cell  about  it,  and  attach  an  egg  to  a 
ventral  abdominal  segment  of  the  grub.  The  larva  of  the  scoliid  con- 
sumes the  grub  and  then  spins  a  cocoon  and  completes  its  development 
in  this  place. 

The  members  of  this  family  are  very  striking  in  appearance,  being 
of  large  size  and  with  the  abdomen  marked  with  conspicuous  spots. 
Two  genera  are  represented  in  our  fauna,  Scolia  and  Cam-psonieris 
(Elis) .  In  Scolia  the  transverse  part  of  vein  M2  of  the  fore  wings  is 
wanting,  in  Camposomeris  it  is  present. 

Family  FORMICID^ 

The  Ants 

The  great  number  of  ants  and  their  wide  distribution  render  them 
the  most  familiar  of  all  insects  except  perhaps  the  house-fly.  As  has 
been  said  by  Professor  Wheeler,  an  indefatigable  investigator  of  these 
insects,  "Ants  are  to  be  found  every^where,  from  the  arctic  regions  to 
the  tropics,  from  timberline  on  the  loftiest  mountains  to  the  shifting 
sands  of  dunes  and  seashores,  and  from  the  dampest  forests  to  the 
driest  deserts.  Not  only  do  they  outnimiber  in  individuals  all  other 
terrestrial  animals,  but  their  colonies  even  in  very  circumscribed 


938  AN  INTRODUCTION  TO  ENTOMOLOGY 

localities  often  defy  enumeration."  The  present  time  has  been  termed 
the  "age  of  insects"  and  of  all  insects  the  Formicidaj  is  the  dominant 
family. 

The  habits  of  ants  have  attracted  the  attention  of  students  of 
animal  behavior  from  very  early  times  and  many  volumes  have  been 
written  on  this  subject.  Among  those  most  often  quoted  and  to  be 
found  in  most  public  libraries  are  those  of  Gould  (1747),  P.  Huber 
(18 10),  and  Lubbock  (1894).  The  most  comprehensive  contributions 
have  been  made  by  Forel  and  Emory,  each  of  whom  has  published 
more  than  one  hundred  papers  in  various  European  journals,  and  by 
Wheeler  in  this  countr^^  Among  the  other  American  writers  who 
have  made  important  contributions  to  our  knowledge  of  the  ways  of 
ants  are  Buckley,  Miss  Fielde,  Leiby,  Lincecum,  AlcCook,  Pricer, 
Mrs.  Treat,  and  Turner.  But  the  most  important  work  on  this  sub- 
ject is  Professor  Wheeler's  "Ants,  their  Structure,  Development  and 
Behavior"  Cio).  In  the  following  pages  there  is  space  for  only  the 
more  important  generalizations  that  can  be  made  regarding  this  family. 
Ants  are  easily  recognized  by  the  well-known  form  of  the  body. 
The  most  distinctive  feature  is  the  form  of  the  pedicel 
of  the  abdomen;  this  consists  of  either  one  or  two 
segments,  and  these  segments  are  either  nodiform 
or  bear  an  erect  or  inchned  scale  (Fig.  11 76). 
Fig-  1 1 76.  When  the  pedicel  of  the  abdomen  consists  of  a 

single  segment  it  is  known  as  the  petiole;  when  it 
consists  of  two  segments  the  first  segment  is  termed  the  petiole  and 
the  second  segment  the  postpetiole.  The  swollen  portion  of  the  ab- 
domen behind  the  pedicel  is  known  as  the  gaster. 

Another  striking  characteristic  of  ants  is  that  in  the  antenna  of 
females  and  workers  and  of  the  males  of  some  species  the  basal 
joint,  the  scape,  is  long  and  the  antennae  are  abruptly  elbowed  at 
the  extremity  of  this  joint. 

The  ants  are  all  social  insects,  there  being  no  solitary  species. 
Each  colony  consists  of  three  castes,  the  males,  the  female  or  queen, 
and  the  workers.  As  with  the  social  bees  and  the  social  wasps,  and 
unlike  the  termites,  the  workers  are  all  modified  females.  With  most 
ants  the  males  and  the  queens  are  winged  and  the  workers  wingless; 
the  wings  of  queens,  however,  are  deciduous.  In  certain  genera  that 
live  as  parasites  in  the  nests  of  other  ants  the  worker  caste  is  wanting, 
and  in  some  species  the  females  are  wingless. 

With  many  ants  the  pohonorphism  is  not  restricted  to  the 
presence  of  three  uniform  castes  for  one  or  more  of  the  castes  may  be 
represented  by  more  than  one  form.  Of  the  males  there  may  be  either 
an  unusually  large  form,  or  dwarfs,  or  ergatoid  males,  that  is,  males 
that  resemble  workers  in  having  no  wings  and  in  the  structure  of  the 
antennas.  The  queens  exhibit  a  similar  series  of  forms;  those  of 
unusually  large  stature ;  dwarfs  which  are  sometimes  smaller  than  the 
largest  workers;  and  ergatoid  queens,  which  are  a  worker-like  form, 
with  ocelli,  large  eyes,  and  a  thorax  more  or  less  like  that  of  the 
normal  queens,  but  without  wings.     The  workers  are  even  more 


HYMENOPTERA  939 

pol\Tnorphic  than  the  sexual  forms.  In  many  species  the  workers 
are  of  two  distinct  sizes,  the  worker  majors  and  the  worker  minors. 
In  colonies  that  are  founded  by  an  isolated  female  the  first  brood  of 
workers  is  of  the  worker  minor  form.  With  many  species  a  worker 
form  exists  in  which  the  head  and  the  mandibles  are  very  large,  the 
soldier  caste.  And  with  the  honey-ants  in  some  of  the  workers,  the 
repletes,  the  gaster  is  a  larger  spherical  sac,  being  distended  by  the 
crop  which  is  used  as  a  reservoir  for  storing  honey-dew  to  be  used 
later  by  the  colony. 

Although  all  ants  are  social,  great  differences  exist  among  them 
as  to  the  size  of  their  colonies.  In  the  more  primitive  species  the 
fully  developed  colony  consists  of  only  a  few  dozen  individuals  with 
comparatively  feeble  caste  development;  while  in  the  m.ore  highly 
specialized  forms  a  colony  mav  consist  of  hundreds  of  thousands  of 
individuals  and  exhibit  an  elaborate  polymorphism. 

The  different  species  of  ants  differ  also  in  their  nesting  habits. 
By  far  the  greater  number  of  species  excavate  their  nests  in  the 
ground.  Certain  species  are  often  seen  burrowing  in  paths  or  other 
open  places ;  but  many  more  are  to  be  found  under  small  flat  stones 
or  other  objects  lying  on  the  ground.  Some  species,  especially  those 
in  which  the  colonies  become  large,  build  large  mounds  of  the  exca- 
vated material.  These  mounds  are  ver}""  familiar  objects  in  many 
parts  of  our  country. 

A  striking  difference  between  the  nests  of  ants  and  those  of  wasps 
and  bees  is  that  the  ants  do  not  construct  premanent  cells  for  their 
brood.  The  eggs,  larvs  and  pupae  are  stored  in  chambers  of  the  nest 
and  are  moved  from  one  to  another  in  order  to  take  advantage  of 
the  changes  in  temperature  and  moisture.  Thus  the  brood  may  be 
brought  near  the  surface  of  the  nest  during  the  warmer  portion  of  the 
day  and  removed  to  deeper  chambers  at  nightfall. 

While  most  species  of  ants  nest  in  the  soil,  there  are  many  that 
build  their  nests  in  wood,  in  timbers,  in  the  trunks  of  decaying  trees, 
in  or  under  bark,  or  in  hollow  stems.  Others,  especially  certain 
tropical  species,  build  in  cavities  of  living  plants;  and  still  others,  as 
Cremasto gaster,  build  carton  nests. 

Large  swarms  of  winged  ants  are  often  seen.  These  are  composed 
of  recently  matured  males  and  females  that  have  emerged  at  the  same 
time  from  many  different  nests,  probably  from  all  of  the  nests  of  the 
particular  species  involved  that  exist  in  the  immediate  region,  and  in 
which  young  queens  and  males  have  been  developed.  The  object  of 
these  flights  is  mating,  and  they  render  probable  the  pairing  of  males 
and  females  from  different  nests,  thus  preventing  too  close  inter- 
breeding. The  factors  that  determine  the  occurrence  of  the  nuptial 
flights  from  all  the  nests  of  a  species  in  one  locality  at  the  same  time 
are  not  understood.  In  the  case  of  those  species  in  which  the  female 
is  wingless  the  mating  must  take  place  either  in  the  nest  or  on  the 
ground  outside.  Hy 


940  AN  INTRODUCTION  TO  ENTOMOLOGY 

After  the  pairing  of  the  sexes  the  males  soon  die  and  each  female 
proceeds  to  found  a  new  colony  if  she  is  not  captured  by  workers 
and  taken  into  a  colony  already  established  or  finds  her  own  way 
into  one.  Except  among  the  parasitic  ants  the  method  of  founding 
a  colony  is  as  follows:  The  female  breaks  off  her  wings;  then  seeks 
out  a  small  cavity  under  a  stone  or  under  bark  or  makes  one  in  the 
ground.  She  closes  the  entrance  to  this  cavity  and  remains  isolated 
without  food  for  weeks  or  months  while  the  eggs  in  her  ovaries  are 
developing.  During  this  period  there  is  a  histolysis  of  the  large 
wing-muscles  the  products  of  which  are  used  as  food .  When  the  eggs 
are  mature  they  are  laid  and  the  larvae  that  hatch  from  them  are  fed 
by  the  female,  or  queen  as  she  is  termed,  with  her  saliva  till  they 
are  readv  to  pupate.  As  the  young  queen  takes  no  food  during  this 
period,  that  fed  the  larvae  must  be  derived  from  the  fat  stored  in  her 
body  and  the  dissolved  wing-muscles.  The  adults  that  are  developed 
from  this  first  brood  or  larvae  are  workers,  but  owing  to  the  limited 
amount  of  food  that  they  have  received  they  are  abnormally  small; 
that  is,  of  the  form  known  as  worker  minors.  These  open  the  chamber 
in  which  they  were  developed  and  go  forth  to  collect  food  for  them- 
selves and  for  the  queen,  and  they  take  charge  of  the  second  brood 
of  larvas,  which  being  supplied  with  abundant  food  develop  into 
larger  workers.  The  nest  is  now  enlarged  by  the  addition  of  new 
chambers  and  the  growth  of  the  colony  continues.  A  few  years  later 
ntimerous  males  and  females  are  developed,  which  at  the  proper  time 
leave  the  nest  for  their  nuptial  flight. 

The  method  of  founding  colonies  described  above  is  the  usual  one. 
But  in  some  species  the  females  have  lost  the  power  of  establishing 
a  colony  unaided  and  must  be  adopted  by  workers  of  her  own  species 
or  by  workers  of  an  alien  species.  The  adoption  of  a  queen  by  workers 
of  an  alien  species  explains  the  existence  of  some  of  the  mixed  colonies 
which  are  sometimes  observed.  The  practice  of  slave-making  de- 
scribed later,  is  the  explanation  of  others.  In  certain  highly  parasitic 
species  the  worker  class  is  wanting  and  the  queens  must  become 
established  in  the  nest  of  an  alien  species. 

The  worker  ants  are  so-called  because  upon  this  caste  devolve  all 
the  labors  of  the  colony  after  they  appear  on  the  scene  in  the  founda- 
tion chamber.  As  a  rule  workers  are  sterile;  but  sometimes,  as  with 
bees,  and  wasps,  fertile  workers  occur.  It  is  believed  that  only  males 
are  developed  from  eggs  laid  by  workers. 

The  feeding  habits  of  ants  differ  greatly  in  different  members  of 
the  family.  wSome  of  the  more  primitive  forms  are  strictly  carnivo- 
rous, feeding  on  insects  and  other  small  animals  that  they  can  destroy ; 
while  others  add  vegetable  substances  to  their  diet.  Many  feed  on 
sweet  fluids,  as  sap  exuding  from  wounded  stems,  the  nectar  excreted 
by  extrafloral  nectar  glands,  and  honey-dew  produced  by  aphids, 
membracids,  the  larvae  of  certain  butterflies,  and  other  insects,  and 
the  leaf-cutting  ants  cultivate  fungi  upon  which  they  feed. 

Ants  also  lick  their  larvae  in  order  to  feed  on  the  exudates  excreted 
by  them.     This  exchange  of  nourishment  between  the  workers  and 


HYMENOPTERA  941 

their  wards,  which  is  known  as  trophallaxis,  is  discussed  in  the  chapter 
on  Isoptera  (pp.  279-280). 

The  study  of  the  habits  of  ants  in  the  field  is  often  supplemented 
by  observations  on  colonies  kept  in  artificial  nests.  Several  types  of 
such  nests  are  in  use;  for  descriptions  of  them  see  Wheeler  ('10). 

The  family  Formicida?  includes  seven  subfamilies,  all  of  which  are 
represented  in  the  United  States;  but  two  of  these  subfamilies,  the 
Cerapachyince  and  the  Pseudomyrminae,  are  confined  to  tropical  and 
subtropical  regions  and  their  range  extends  only  into  the  southern 
part  of  our  territory,  where  they  are  represented  by  only  a  very  small 
number  of  species.  The  workers  of  the  other  subfamilies  can  be 
separated  by  the  following  table,  which  is  based  on  one  published  by 
Professor  Wheeler  in  "The  Hymenoptera  or  Wasp-like  Insects  of 
Connecticut"  (Vierick  '16).  This  work  includes  also  tables  of  the 
genera  and  subgenera  of  ants  found  in  America  north  of  Mexico. 
For  keys  to  the  subfamilies,  genera,  and  subgenera  of  the  world  see 
Wheeler  ('22). 

KEY  TO  THE  SUBFAMILIES  OF  ANTS 

(Includes  only  the  workers) 

A.  Anal  oriface  round,  terminal,  surrounded  by  a  fringe  of  hairs;  abdominal 
pedicel  consisting  of  a  single  segment;  no  constriction  between  the  first  and 
second  segments  of  the  gaster;  pupae  rarely  naked  most  frequently  in  a  co- 
coon p.  946 FORMICIN^ 

AA.  Anal  orifice  ventral;  in  the  shape  of  a  slit;  pedicel  of  the  abdomen  con- 
sisting of  one  or  two  segments. 

B.  Pedicil  of  the  abdomen  consisting  of  a  single  segment;  no  constriction 
between  the  first  and  second  segments  of  the  gaster;  sting  vestigial;  pupae 

naked,    p.   945 Dolichoderin^ 

BB.  Pedicil  of  the  abdomen  consisting  of  one  or  two  segments,  when  only  of 
one,  a  distinct  constriction  between  the  first  and  second  segments  of  the 
gaster,  sting  developed,  sometimes  very  small  but  capable,  nevertheless,  of 
being  exerted  from  the  abdomen. 

C.  Pedicil  of  the  abdomen  consisting  of  a  single  segment,  gaster  with  a 
distinct  constriction  between  its  first  and  second  segments;  frontal  carinas 
separated  or  close  together,  when  close  together,  dilated  to  form  oblique  or 
horizontal  laminae  partly  covering  the  insertions  of  the  antennae;  pupae 

always  enclosed  in  cocoons,  p.  942 Cerapachyin^  and  Ponerin^ 

CC.    Abdominal  pedicil  consisting  of  two  segments;  pupae  naked. 

D.  Frontal  carinas  very  close  together,  almost  vertical,  not  at  all  covering 
insertions  of  antennas;  eyes  always  very  small  or  absent;  tropical  and 

subtropical,    p.  941 -. Dorylin^ 

DD.  Frontal  carinae  of  a  different  conformation  and  covering  the  antennal 
insertions;  eyes  rarely  vestigial  or  absent;  cosmopolitan,  p.  942,  943. 
" Pseudomyrmin^  and  Myrmicin/E 

Subfamily  DORYLIN^ 

The  Legionary  or  Visiting  Ants 

The  members  of  this  subfamily  are  largely  confined  to  Equatorial 
Africa  and  tropical  America.  The  colonies  are  nomadic,  wandering 
from  place  to  place  in  search  of  prey,  and  forming  only  temporary 
nests.    Some  of  the  species  travel  in  vast  armies  and  often  overrun 


942  AN  INTRODUCTION  TO  ENTOMOLOGY 

houses  in  the  tropics,  clear  out  the  vermin  with  which  they  may  be 
infested,  and  compel  the  human  inhabitants  to  leave  for  a  time. 

The  subfamily  is  represented  in  our  fauna  by  a  single  genus, 
Eciton,  species  of  which  occur  from  North  Carolina  and  Colorado 
southward.  Our  species,  however,  do  not  form  large  armies,  though 
they  hunt  in  files  like  the  tropical  species,  and  the  colonies  of  some 
of  the  species  may  consist  of  thousands  of  individuals.  Some  of  the 
species  are  fond  of  kidnapping  the  brood  of  other  ants.  The  females 
are  wingless  and  much  larger  than  the  workers.  The  workers  are 
polymorphic. 

The  subfamily  CERAPACHYIN^  is  represented  in  our  fauna 
by  two  genera,  Cerapachys  and  Acanthostichus ,  species  of  which  occur 
in  Texas.  These  genera  were  formerly  included  in  the  subfamily 
Ponerinae. 


Subfamily  PONERIN^ 

The  Ponerine  Ants 

In  the  ants  of  this  subfamily  the  pedicel  of  the  abdomen  consists 
of  a  sinele  segment  and  there  is  a  distinct  constriction  between  the 
first  and  second  segments  of  the  gaster  (Fig. 
1 1 77).  The  constriction  between  the  first  and 
second  segments  of  the  gaster  distinguishes 
these  ants  from  those  other  ants  in  which  the 
Fig' 1 177.— A  ponerid.  pedicel  of  the  abdomen  consists  of  a  single  seg- 
ment. 

Our  representatives  of  this  subfamily  are  rare  or  of  local  occurrence 
in  the  North,  where  they  form  small  colonies,  often  of  a  few  dozen 
individuals.  They  make  their  nests  in  the  soil  or  in  old  logs.  As  a 
rule  the  queens  are  but  little  larger  and  the  males  but  little  smaller 
than  the  workers,  and  there  is  only  a  single  form  of  worker  in  a 
species.  The  pupa  stage  is  passed  within  a  cocoon.  These  ants  are 
carnivorous,  feeding  on  other  insects  and  do  not  collect  honey-dew. 
In  the  South  Odontomachus  is  common,  forming  large  colonies  of 
active  ants  of  large  size,  under  old  logs. 

The  subfamily  PSEUDOMYRMIN.zE  includes  four  genera  only 
one  of  which,  Pseudomyrma,  is  represented  in  North  America.  This 
is  a  neotropical  genus,  species  of  which  are  found  from  Florida  to 
Texas,  and  in  southern  California.  They  are  verv^  slender  ants  and 
make  their  nests  in  hollow  twigs  or  other  cavities  of  plants.  The 
larvae  are  of  a  remarkable  form;  the  body  is  long,  the  head  large 
and  ventrally  placed,  and  the  thoracic  and  first  abdominal  segments 
are  furnished  with  peculiar  exudatory  papillae,  which  form  a  cluster 
about  the  mouth.  These  ants  were  formerly  included  in  the  sub- 
family Myrmicinae. 


HYMENOPTERA  943 

Subfamily  MYRMICIN^ 
The  Myrmicine  Ants 

In  this  subfamily  the  pedicel  of  the  abdomen  consists  of  two 
segments  (Fig.  1178)  and  the  frontal  carina?  cover  the  antennal  in- 
sertions. This  is  a  large 
subfamily ;  more  than 
half  of  the  species  of  ants 
found  in  America  north 
of  Mexico  belong  to  it. 
The  following  species  will 
serve  to  illustrate  the  re- 
markable differences   in 

habits    of    its    different  Fig.  11 78. — A  myrmicid. 

members. 

The  little  yellow  house-ant,  Monomorium  pharaonis.- — -This  is  the 
species  commonly  known  as  the  "little  red  ant"  although  it  is  light 
vellow  in  color.  It  is  the  most  troublesome  of  all  ants  that  invade 
our  dwellings.  When  these  ants  build  their  nests  within  the  walls 
or  beneath  the  foundations  of  a  house  it  is  almost  impossible  to  dis- 
lodge them.  By  trapping  and  destroying  the  workers  their  nimibers 
can  be  lessened  somewhat;  but  so  long  as  the  queens  are  undisturbed 
in  their  nests  the  supply  of  workers  will  continue.  Sometimes  the 
nests  can  be  reached  by  pouring  carbon  bisulphid  into  the  crevices 
from  which  the  workers  come. 

The  thief  ant,  Solenopsis  molestus. — This  is  a  species  with  minute 
yellow  workers  and  much  larger  browm  females  and  blackish  males, 
which  is  common  in  open  grassy  places,  where  it  may  have  independent 
nests  under  stones.  But  they  often  make  burrows  in  the  walls  of 
nests  of  other  and  much  larger  ants,  from  which  they  emerge  to  prey 
upon  the  larvae  and  pupae  of  the  larger  ants,  which  are  unable  to 
follow  them  into  their  tenuous  burrows. 

The  harvesting  ants. — Several  genera  of  myrmicine  ants  feed  on 
seeds,  and  as  they  collect  these  seeds  and  store  them  in  their  nests 
they  are  known  as  harvesting  ants.  It  was  to  these  ants  that  Solomon 
referred.  They  have  also  been  known  as  agricultural  ants;  for  it  was 
formerly  believed  that  they  sow  around  their  nests  seeds  of  the  plants 
from  which  they  collect  the  grain  that  they  use.  But  this  has  been 
disproved.  Most  of  our  harvesting  ants  are  confined  to  the  warm 
and  arid  regions  of  the  Southwest,  where  insect  prey  is  scarce  and 
the  ants  are  compelled  to  feed  on  seeds.  A  single  species,  Pheidole 
piltfera,  which  is  a  southern  species,  occurs  along  the  coastal  plain  as 
far  north  as  Massachusetts. 

The  shed-builder  ant,  Crematogaster  lineoldta: — In  the  tropics  ants 
belonging  to  several  genera  build  carton  nests  attached  to  branches 
of  trees.  One  of  these  genera  is  Crematogaster  of  which  we  have  a 
common  species,  C.  lineoldta,  in  the  Northern  States  and  Canada. 
This  is  a  small  ant,  the  workers  measuring  from  3  to  4.5  mm.  in  length. 


944  AN  INTRODUCTION  TO  ENTOMOLOGY 

It  is  usually  yellowish  brown,  with  a  black  abdomen;  but  it  varies 
greatly  in  color.  Its  favorite  nesting-place  is  under  stones  or  under- 
neath and  within  the  decayed  matter  of  old  logs  and  stumps.  Out 
of  this  material  the  ants  sometimes  make  a  paper-like  pulp  with 
which  they  build  a  nest  attached  to  the  side  of  a  log,  or  even  to  the 
branches  of  a  shrub  at  some  distance  from  the  ground.  While  such 
nests  are  uncommon  these  ants  often  build  small  sheds  at  some  dis- 
tance from  the  nest,  over  the  herds  of  aphids  or  coccids  from  which 
they  obtain  honey-dew  (Fig.  1179).     In  these  cases  the  aphids  or 


Fig.  1 179.— A  "cow-shed"  built  by  ants.     (From  A.  B.  Comstock,  Handbook  of 
Nature  Study.) 

coccids  are  huddled  together  on  a  branch,  from  which  they  are  de- 
riving their  nourishment,  and  are  completely  covered  by  the  "cow- 
shed" built  by  the  ants. 

An  inquiline  or  guest  ant,  Leptothorax  emersoni. — This  ant,  the 
habits  of  which  are  described  in  detail  by  Wheeler,  lives  only  associ- 
ated with  another  species,  Myrmtca  brevinodes.  The  Myrmica  "builds 
its  nest  in  the  soil  of  bogs,  in  clumps  of  moss  (Polytrichum)  or  under 
logs  and  stones,  and  the  Leptothorax  excavates  small  cavities  near 
the  surface  and  communicating  by  means  of  short,  tenuous  galleries 
with  those  of  its  host.  The  broods  of  both  species  are  brought  up 
separately.  The  Leptothorax,  though  consorting  freely  with  the 
Myrmica  workers  in  their  galleries,  resents  any  intrusion  of  these  ants 
into  its  own  chambers.  The  inquilines  do  not  leave  the  nest  to  forage 
but  obtain  all  their  food  in  a  very  interesting  manner,  from  their 
hosts.  Both  in  the  natural  and  artificial  nests  the  Leptothorax  are 
seen  to  mount  the  backs  of  the  Myrmicas  and  to  lick  or  shampoo 


HYMENOPTERA  945 

their  surfaces  in  a  kind  of  feverish  excitement.  This  shampooing  has 
a  two-fold  object :  to  obtain  the  oleaginous  salivary  secretion  with 
which  the  Myrmicas  cover  their  bodies  when  they  clean  one  another, 
and  to  induce  these  ants  to  regurgitate  the  liquid  food  stored  in 
their  crops." 

The  fungus-growing  ants.- — Among  the  many  remarkable  examples 
of  insect  behavior  none  is  more  marvellous  than  the  habits  of  the 
fungus-growing  ants,  although  analogous  habits  are  exhibited  by 
certain  termites  and  by  the  ambrosia  beetles,  discussed  in  earlier 
chapters  of  this  book. 

The  fungus-growing  ants  constitute  one  of  the  tribes,  the  Attii, 
of  the  Myrmicinae,  of  which  about  loo  species,  subspecies,  and 
varieties  have  been  described.  They  are  confined  almost  exclusively 
to  tropical  and  subtropical  America;  but  one  species  is  found  as 
far  north  as  New  Jersey.  Many  accounts  have  been  published  re- 
garding these  insects,  which  have  been  commonly  known  as  the  leaf- 
cutting  ants  or  the  parasol  ants.  These  names  were  suggested  by 
the  fact  that  these  ants  cut  pieces  from  the  leaves  of  trees  and  carry 
them,  like  parasols,  into  their  nests. 

The  use  that  the  ants  make  of  the  leaves  that  they  carry  into  their 
nests  was  long  a  mystery.  But  it  is  now  known  that  the  leaves  are 
used  as  a  culture  medium  upon  which  they  cultivate  a  fungus,  which 
they  eat  and  feed  to  their  larvae,  and  which  is  their  only  food. 

Professor  Wheeler  ('07  b)  has  published  a  monograph  of  the 
fungus-growing  ants  of  North  America  in  which  is  given  a  resume  of 
the  writings  of  previous  students  of  the  Attii;  and  a  chapter  is  de- 
voted to  these  insects  in  his  volimie  on  "Ants"  ('10). 

Subfamily  DOLICHODERIN^ 

In  this  subfamily,  as  in  the  following  one,  the  pedicel  of  the  ab- 
domen consists  of  a  single  segment  and  there  is  no  constriction  between 
the  first  and  second  segments  of  the  gaster;  but  these  ants  can  be  dis- 
tinguished from  the  Formicinae  by  the  fact  that  the  anal  orifice  is  in 
the  form  of  a  slit.  These  ants,  also,  often  possess  in  addition  to  the 
poison  glands,  anal  glands  which  excrete  a  foul  smelling,  sticky  fluid, 
which  is  used  as  a  means  of  defense  in  their  combats  with  other  ants. 

Only  about  a  dozen  species  have  been  described  from  our  fauna 
and  most  of  these  are  southern.  Certain  tropical  species  build  carton 
nests  attached  to  trees  and  some  of  our  species  make  carton  nests 
under  stones.  The  members  of  this  subfamily  are  especially  fond  of 
honey-dew  and  attend  aphids  and  coccids  to  secure  it.  Some  of  the 
species,  "establish  their  nests  on  or  near  the  nests  of  larger  ants  and 
either  feed  on  the  refuse  food  or  waylay  the  workers  when  they  return 
home  and  compel  them  to  give  up  their  booty"  (Wheeler).  The 
most  important  species  of  the  subfamily  in  our  fauna  is  the  following. 

The  Argentine  ant,  Iridomyrmex  humilis. — This  is  an  introduced 
species,  which  has  become  an  exceedingly  serious  pest  in  the  Gulf 
States  and  in  Southern  California.     Its  injuries  are  of  two  kinds: 


946  AN  INTRODUCTION  TO  ENTOMOLOGY 

first,  as  a  household  pest,  entering  and  overrunning  dwellings;  and 
second,  as  an  orchard  pest.  Its  injuries  in  orchards  are  due  to  the 
fact  that  it  protects  aphids  and  coccids  in  order  to  secure  the  honey- 
dew  that  they  excrete.  The  ants  drive  away  the  insect  enemies  of 
the  aphids  and  coccids,  which  as  a  result  multiply  to  an  abnormal 
extent.  It  has  been  found  that  this  ant  can  be  exterminated  in 
houses  and  orchards  by  the  use  of  an  arsenical  poisoned  syrup. 
Detailed  directions  for  the  preparation  and  use  of  this  syrup  are  given 
in  bulletins  published  by  the  U.S.  Department  of  Agriculture. 

Subfamily  FORMICIN^ 

The  Typical  Ants 

This  subfamily  is  characterized  by  the  form  of  the  anal  orifice, 
which  is  round,  terminal,  and  surrounded  by  a  fringe  of  hairs.    The 

pedicel  of  the  abdomen  consists 

of  a  single  segment  and  there  is 

no  constriction  between  the  first 

and  second  segments  of  the  gaster 

(Fig.   1 1  So).     The  following  are 

some  of  our  more  common  species. 

The   carpenter   ant,    Campo- 

notus  herculeanus  pennsyhdnicus . 

Fig.  1 1 80.— A  formicid  ant.  —This  is  one  of  the  largest  of  our 

common   ants.      It   is  the  large 

black  species  that  builds  its  nests  in  the  timbers  of  buildings,  in  logs 

and  in  the  trunks  of  trees.    Frequently  it  builds  in  the  dead  interior 

of  a  living  tree,  excavating  a  complicated  series  of  chambers. 

The  mound-building  ant,  Formica  exsectoides. — This  species  is  the 
builder  of  our  largest  ant-hills;  these  are  often  one  meter  in  height 
and  two  meters  across,  and  sometimes  they  are  much  larger  than  this. 
New  colonies  are  often  formed  by  fission,  a  portion  of  the  colony 
emigrating  and  founding  a  new  colony  with  one  or  more  queens.  In 
this  way  many  colonies  are  often  established  in  a  limited  area.  The 
head  and  thorax  of  this  ant  are  rust-red,  while  the  legs  and  abdomen 
are  blackish  brown. 

The  blood-red  slave-maker,  Formica  sangmnea. — More  than  a 
century  ago  Pierre  Huber  called  attention  to  the  fact  that  this  species 
which  is  common  in  both  Europe  and  America,  keeps  in  its  nests 
the  workers  of  other  species  of  Formica,  which  aid  in  performing  the 
labors  of  the  colony.  The  relations  of  the  two  species  thus  associated 
have  been  commonly  regarded  as  that  of  slaveholders  and  slaves. 
The  slaveholders  obtain  their  slaves  by  making  periodical  forays  on 
the  colonies  of  the  common  black  Formica  fusca,  and  of  other  species 
of  Formica,  and  bringing  to  their  own  nest  the  worker  larvse  and 
pupae.  Some  of  these  are  eaten,  but  others  are  reared,  and  these 
knowing  no  other  home  take  their  place  as  active  members  of  the 
colony. 


HYMENOPTERA  947 

In  the  blood-red  slave-maker  the  gaster  is  black  or  brown  and 
there  is  a  notch  in  the  margin  of  the  clypeus.  The  nests  of  this 
species  are  low  obscure  mounds  of  earth  or  are  excavated  under  stones 
or  logs  or  around  stumps.  Many  subspecies  and  varieties  of  this 
species  are  recognized,  some  of  which  do  not  keep  slaves. 

The  shining  amazon,  Polycrgus  Incidus: — ^The  species  of  the  genus 
Polyergus  were  named  amazons  by  Pierre  Htiber  on  account  of  their 
warring  habits.  Species  of  this  genus  occur  in  this  country  as  well 
as  in  Europe.  The  shining  amazon  is  a  beautiful,  brilliant  red  species 
widely  distributed  in  the  Eastern  and  Middle  states.  The  species 
of  this  genus  are  slave-makers  that  have  become  absolutely  dependent 
on  their  slaves.  They  cannot  build  their  own  nests  or  feed  themselves 
or  care  for  their  young,  but  have  only  retained  the  power  of  fighting 
to  get  more  slaves.  Their  mandibles  are  sickle-shaped  and  fitted 
only  as  weapons  of  offence.  Like  Formica  sanguinea,  these  ants  make 
periodical  forays  on  the  colonies  of  other  species  of  Formica  and  carry 
home  the  worker  larvae  and  pupae.  The  workers  developed  from 
these  perform  all  of  the  labors  of  the  colony  except  that  of  the  making 
of  forays  on  the  colonies  of  other  ants,  in  which  they  take  no  part. 
The  young  queens  of  Polyergus,  being  unable  to  work,  establish  new 
colonies  of  their  species  by  securing  adoption  in  some  small  weak 
colony  of  another  species  of  Formica  after  killing  its  queen  by  piercing 
her  head. 

The  corn-field  ant,  Ldsius  niger  americdnus. — To  the  genus  Lasius 
belong  several  common  species  of  small  brown  ants  that  make  small 
mounds  in  various  situations.  These  ants  are  fond  of  honey-dew 
and  not  only  care  for  the  aphids  from  which  they  obtain  it  but  collect 
the  eggs  of  the  aphids  and  store  them  in  their  nests  through  the  winter, 
and  in  the  spring  place  the  recently  hatched  plant-lice  on  the  stems 
and  roots  of  the  plants  on  which  they  feed.  A  well-known  species 
of  this  genus  is  the  corn-field  ant,  the  habits  of  which  are  discussed  in 
the  account  of  the  corn-root  aphis,  p.  419. 

The  honey -ants,  Myrmecocystus.  — The  ants  of  this  genus  are  found 
in  the  arid  regions  of  the  Southwest,  from  the  city  of  Mexico  to 
Southern  California  and  to  Denver,  Colorado.  They  have  received 
the  name  of  honey-ants  from  the  remarkable  fact  that  with  them 
some  of  the  workers  function  as  honey-pots  or  reservoirs  for  storing 
the  honey-dew  collected  by  other  workers,  from  nectar  excreting 
galls  on  trees  and  from  aphids  and  coccids.  The  individuals  in  which 
the  honey-dew  is  stored  are  known  as  repletes. 
The  workers  that  collect  the  honey-dew  swallow 
it  and  carry  it  in  their  crop  to  the  nest.  There 
they  regurgitate  it  and  feed  it  to  a  replete,  which 
in  turn  swallows  it  and  retains  it  in  its  crop.  The  -  "^^^ 
crop  of  the  replete  becomes  so  greatly  distended 
that  the  gaster  becomes  a  translucent  sphere,  as 
large  as  a  pea,  on  the  surface  of  which  the  sclerites 
appear  as  isolated  patches  separated  by  the  tense,  pelucid,  yellowish, 
intersegmental  membrane  (Fig.  ii8i)..  .The  repletes  are  unable  to  go 


948  AN  INTRODUCTION  TO  ENTOMOLOGY 

about  but  remain  quiet  clinging  to  the  roof  of  a  chamber  of  the  nest. 
When  the  season  for  obtaining  honey-dew  is  passed,  these  living  cells 
disgorge  their  supply  through  their  mouths,  for  the  use  of  the  colony. 
There  are  several  species  and  subspecies  of  Myrmecocystus  in  some 
of  which  the  replete  form  has  not  been  found. 

Family  BETHYLID^ 
The  Bethylids 

This  is  a  large  family  of  parasitic  wasps,  including  many  genera 
and  species.  The  family  is  widely  distributed,  representatives  of  it 
being  found  in  all  parts  of  the  world.  Our  species  are  of  small  or 
moderate  size.  Those  whose  habits  are  known  prey  upon  either 
coleopterous  or  lepidopterous  larv'as,  and  before  pupating  most  of 
them  spin  cocoons. 

In  this  family  there  are  eight  exposed  segments  in  the  abdomen, 
the  petiolar  segment  is  very  short  and  scarcely  perceptible,  and  the 
ovipositor  is  a  true  sting.  The  majority  of  genera  comprise  species 
that  are  winged  in  both  sexes;  but  in  a  few  genera  the  males  alone 
are  winged.   Some  of  the  wingless  females  are  ant-like  in  appearance. 

Among  those  species  that  prey  upon  important  insect  pests  are 
Neoscleroderma  tarsdlis,  which  is  parasitic  on  the  beetle,  Silvdnus 
surinamensis ,  and  an  undescribed  species  of  Goniozus,  which  is 
parasitic  on  the  codlin-moth  in  Kansas.  A  detailed  account  of  the 
life-history  of  LcbUus  trogodermatis,  which  is  an  external  parasite  of 
dermestid  larvce,  is  given  by  Howard  ('oi).  This  family  was  mono- 
graphed by  Kieffer  ('14). 

The  family  RHOPALOSOMID^  although  widely  distributed  is 
a  very  small  family.  It  is  represented  in  our  fauna  by  Rhopalosdma 
poeyi,  the  larva  of  which  was  found  by  Hood  ('13)  to  be  an  external 
parasite  of  a  bush-cricket,  Orocharis  saltdtor,  in  Maryland.  The 
adult  is  nocturnal ;  it  has  very  large  eyes  and  ocelli,  and  the  petiole 
of  the  abdomen  is  long  and  slender. 


Family  VESPID^ 

The  Typical  Wasps  or  Diploptera 

The  family  Vespidee  includes  our  most  familiar  wasps,  the  hornets, 
and  the  yellow-jackets,  and  their  near  allies.  All  members  of  this 
family  are  winged  and  nearly  all  of  them  when  at  rest  fold  their  wings 
lengthwise  like  a  fan ;  for  this  reason  they  are  often  termed  the  Diplop- 
tera or  the  diplopterous  wasps.  In  the  habit  of  folding  their  wings 
when  at  rest,  the  typical  wasps  differ  from  all  other  H^nnenoptera 
except  the  Gasteruptionidae,  the  chalcid  genus  Leucospis  and  the 
genus  Galesus  of  the  family  Belytidae.  In  this  family  the  lateral  ex- 
tensions of  the  pronotimi  are  angular  extensions  behind  and  above  the 


HYMENOPTERA 


949 


tegulas;   cell    M4  of  the  fore  wings    is    longer  than   cell   Cu+Cui 
(Fig.  1 182);  and  there  are  closed  cells  in  the  hind  wings. 

The  typical  wasps  found  in  America  north  of  Mexico  represent 
seven  subfamilies  of  the  family  Vespida\     These  can  be  separated 


Fig.  1 182. — Wings  of  Vespa  diabolica:  pr.  I,   preanal  lobe;  pr.  exc,  preaxillary 
excision.     (From  Bradley.) 

by  the  following  table,  for  which  I  am  indebted  to  Professor  J.  C. 
Bradley. 

A.    Fore  wings  with  two  submarginal  cells;  antennae  clavate.  p.  950.Masarin^ 
AA.     Fore  wings  with  three  submarginal  cells. 

B.    Vein  M4  +  Cui  of  the  fore  wings  elongate  (Fig.  1183);  cell  M,  four-sided ; 

wings     not     plaited,     p.      950 Euparaghn^ 

BB.  Vein  M4  +  Cui  of  the  fore  wings  exceedingly  short  (Fig.  1 189) ;  cell  M.,  a 
scalene  triangle  (Fig.  1189);  wings  longitudinally  plaited  when  at  rest. 
C.    Hind  wings  with  an  anal  lobe  (Fig.  1 189). 

D.    Tarsal  claws  bifid;  middle  tibise  with  one  apical  spur;  solitary  wasps 
without  a  worker  caste. 

E.  JVIandibles  short,  obliquely  truncate  and  toothed  at  the  apex, 
folding  above  each  other  beneath  the  clypeus  or  very  slightly  crossing ; 
head  quadrate;  abdomen  petiolate,  the  apex  of  the  petiole  globose 
and  strongly  constricted  before  the  second  segment,  p.  951  .Zethin^ 
EE.  Mandibles  elongate,  crossing  each  other  or  placed  parallel  on  a 
long  sharp  beak;  if  the  abdomen  is  petiolate  the  head  is  transverse. 

p.  952 EUMENIN^ 

DD.     Tarsal  claws  simple;  middle  tibiae  with  two  apical  spurs;  social 

wasps  building  open  or  closed  paper  nests. 

E.  Extensory  muscle  of  the  abdomen  fixed  on  the  thorax  in  an  oval 
slit  between  the  apical  scales  of  the  propodeum;  the  slit  always 
broadly  rounded  at  its  upper  angles,  p.  956 Epiponin^ 

EE.  Extensory  muscle  of  the  abdomen  fixed  on  the  thorax  in  a  narrow 
and  much  compressed  slit  between  the  apical  scales  of  the  propodeum. 

p.  957 POLISTIN^ 

CC.  Hind  wings  without  an  anal  lobe,  somewhat  stalked  (Fig.  1182);  ab- 
domen conical;  social  wasps  with  a  worker  caste,  building  closed  paper 
nests;  tarsal  claws  simple;  middle  tibiae  with  two  apical  spurs,  p.  958. 
Vespin^ 

If  we  take  into  account  only  the  habits  of  these  insects  the  sub- 
families of  the  typical  wasps  can  be  separated  into  two  groups,  the 
solitary  Diploptera,  those  in  which  a  single  female  makes  a  nest  for 
her  young,  and  the  social  Diploptera  or  social  wasps,  in  which  many 
individuals  work  together  to  make  a  nest.     This  grouping  of  the 


950 


AN  INTRODUCTION  TO  ENTOMOLOGY 


subfamilies,  however,  is  not  regarded  as  a  natural  division  of  the 
family  Vespidae,  as  each  of  the  two  groups  is  believed  to  be  poly- 
phyletic,  and  too,  F.  X.  Williams  ('19)  has  shown  that  in  the  genus 
Stenogaster,  found  in  the  Oriental  and  Australian  regions,  some  species 
are  solitary  and  others  are  social;  but  this  grouping  is  useful  in  a 
discussion  of  the  habits  of  these  insects. 

THE  SOLITARY  DIPLOPTERA 


Fig.  1 1 83. — Wings  of  Euparagia  scutellaris. 
Bradley.) 


(After 


The  subfamily  EUPARAGIIN^  includes  the  genus  Eupdrgia, 
two  species  of  which  are  found  in  the  Southwest.    These  wasps  differ 

from  other  Vespidae 
in  that  cell  M3  of  the 
fore  wings  is  four-sid- 
ed (Fig.  1 1 83).  Very 
little  is  known  regard- 
ing the  habits  of  these 
insects.  For  figures 
and  descriptions  of 
the  species  see  Brad- 
ley ('22). 

The  subfamily 
MASARIN.^isaver>' 
widely  distributed 
group  but  it  is  repre- 
sented in  our  fauna 
only  by  the  genus 
Pseudomdsaris ,  of 
which  thirteen  species  have  been  described;  these  are  found  in  the 
Far  West  and  Southwest.  In  these  wasps  there  are  only  two  sub- 
marginal  cells  in  the  fore  wings  and  the  antennas  are  clavate.  The 
North  American  species  were  monographed  by  Bradley  ('22). 

There  are  but  few  accounts  of  the  nest-building  habits  of  masarid 
wasps.  Giraud  ('71)  describes  the  habits  of  Ceramius  lusitdnicus,  a 
species  found  in  France.  This  is  a  mining  wasp,  which  digs  a  burrow 
in  the  ground,  leading  to  a  cell,  in  which  the  larva  lives.  The  larva 
is  fed  by  the  mother,  who  brings  to  it  from  time  to  time  a  supply  of 
a  paste,  described  as  being  somew^hat  like  dried  honey.  When  the 
larva  is  full-grown  it  lines  its  cell  with  a  layer  of  silk,  otherwise  the 
pupa  is  naked. 

Ferton  ('10)  describes  the  habits  of  CelonUes  ahhrevidtus,  another 
species  found  in  France.  This  is  a  mason  wasp,  which  makes  earthen 
cells  attached  to  the  sides  of  rocks  or  to  stems  of  plants.  A  figure  of 
one  of  these  nests  is  given  by  Sharp  ('99)  page  89.  In  this  figure 
the  cells  are  represented  as  opening  downward.  This  species  also 
provisions  its  nest  with  a  paste  made  of  pollen  and  honey ;  and  the 
full-grown  larva  lines  its  cell  with  silk. 

The  most  remarkable  feature  in  the  habits  of  these  two  species 
is  that  they  provision  their  nests  with  a  paste  made  of  pollen  and 


HYMENOPTERA  951 

honey.  In  this  respect  they  differ  from  other  sohtary  wasps  in  the 
same  way  that  the  sohtary  bees  differ  from  other  sphecoid  wasps. 
But  this  difference  in  habits  is  not  true  of  all  masarid  wasps  as  is 
shown  by  the  habits  of  the  following  species,  which  provisions  its 
nests  with  larvae. 

The  only  published  account  of  the  nest-building  habits  of  an 
American  masarid  is  that  by  Dr.  Anstruther  Davidson  ('13)  who 
described  the  nest  of  Pseudomdsaris  vespoides.  This  is  our  largest 
and  most  handsome  species;  it  measures  from  15  to  22  mm.  in  length, 
is  black  marked  with  yellow,  and  is  widely  distributed  in  the  Far 
West;  but  is  not  common.  Dr.  Davidson's  account  of  the  nest 
follows. 

Their  nests,  a  combination  of  cells  as  shown  in  the  accompanying  illustration, 
are  built  after  the  manner  of  the  common  mud  dauber  wasp  and  when  completed 
are  plastered  over  with  a  further  layer  of  clay.  They  are  usually  attached  to  a 
twig  in  a  low  bush,  the  one  in  the  illustration  being  found  on  a  Audibertia  shrub. 
When  the  cell  is  completed  the  opening  is  closed  by  a  stopper  of  clay  which  is, 
however,  always  depressed  below  the  rim  of  the  cell  so  that  the  top  shows  as  a 
series  of  miniature  cups.  The  clay  used  is  that  common  to  the  neighborhood, 
but  in  the  process  of  building  it  is  mixed  with  some  secretion  that  makes  the  whole 
of  such  stony  hardness,  that  it  seems  impossible  any  insect  could  possibly  cut  its 
way  through  it.  Perhaps  the  cup  shaped  depression  on  top  may  be  a  device  to 
conserve  the  rain  necessary  to  soften  the  stopper  and  render  the  exit  of  the  wasp 
possible.  That  rain  or  excessive  moisture  is  necessary  before  the  insect  can 
successfully  emerge  is  suggested  by  the  results  attained  in  indoor  hatching. 
In  those  nests  kept  indoors  in  dry  receptacles  while  the  wasp  usually  attains  the 
mature  state,  it  only  exceptionally  cuts  its  way  out.  Kept  under  these  conditions 
the  larvae  do  not  always  mature  in  the  following  spring  as  the  following  record 
makes  evident.  Of  a  cluster  of  cells  gathered  in  June,  1902;  in  April,  .1903,  I 
opened  two  of  them  to  find  one  had  pupated  while  the  other  was  still  in  the  larval 
state.  It  remained  in  this  state  till  March,  1905,  when  it  died.  The  other  cells 
were  then  opened,  one  contained  a  live  larva,  the  other  four  or  five  contained 
perfect  insects  all  dead,  apparently  unable  to  emerge.  The  capability  of  insects  to 
siu-vive  for  more  than  one  season  in  the  larval  stage  is  probably  an  evolutionary 
acquirement,  and  a  necessity  to  those  insects  living  on  a  food  supply  that  is 
wholly  dependent  on  climatic  conditions.  As  the  writer  has  shown  elsewhere  in  re- 
cording a  similar  experience  with  Anthidium  consimile,  this  is  a  very  necessary 
acquirement  in  a  country  where,  as  sometimes  happens,  no  rain  at  all  may  fall, 
and  no  food  supply  would  in  those  seasons  be  available.  The  cells  are  stored  with 
small  larvae  of  what  species  I  am  unable  to  determine. 

As  in  the  nests  of  the  European  species,  the  cells  are  lined  with  a 
layer  of  silk.  Figure  1 184,  a  represents  a  nest  given  me  by  Professor 
Doane  of  Stanford  University;  this  is  an  incomplete  nest  in  which 
the  cells  have  not  been  plastered  over  with  an  additional  layer  of 
clay;  Fig.  1184,  6  is  a  diagram  of  a  longitudinal  section  of  a  single 
cell  showing  the  cup  at  the  upper  end;  Figure  1184,  c  represents 
a  completed  nest;  this  was  given  me  by  Dr.  Davidson. 

The  subfamily  ZETHIN^  is  represented  in  our  fauna  by  a  single 
genus  Zethus.  of  which  there  are  two  species,  Zethns  sphiipes  and 
Zethus  slossoncB,  common  in  the  southeastern  part  of  the  United 
States. 

Ashmead  ('94)  states  that  our  Zethus  splnipes  builds  globular  cells 
of  clay  or  sand  and  mud  mixed,  which  are  attached  by  a  small  pedicel 


952 


AN  INTRODUCTION  TO  ENTOMOLOGY 


to  some  shrub  or  tree.  I  find  no  other  account  of  the  habits  of  this 
species,  and  the  other  species  of  Zethus  the  habits  of  which  have  been 
described  build  nests  of  a  very  different  type.  Saussure  ('75)  states 
that  Zethus  romandmus,  found  in  Cayenne,  "constructs  with  woody 
fibres  and  gummy  materials  several  rounded  cells,  with  thick  walls 
toward  the  bottom  and  irregularly  united,  recalling  a  little  those  of 
Bombus."  Ducke  ('14)  describes  and  figures  the  nest  of  a  Brazilian 
species,  Zethus  lobuldtus.  This  nest  consists  of  a  long  mass  of  cells, 
suspended  from  a  twig  and  is  composed  of  fragments  of  leaves  cement- 


/ 


Fig.  1 1 84. — Nests  of  Pesudomasaris  vespoides:  a,  incomplete  nest;  b,  diagram  of  a 
cell  showing  the  cup  at  the  upper  end;  c,  completed  nest. 

ed  together  by  a  resinous  substance.  Williams  ('19)  describes  the 
nest  of  Zethus  cyanopterus,  which  he  observed  in  the  Philippines;  this 
nest  is  made  of  bits  of  leaves  which  "are  chewed  along  one  or  more 
of  their  edges  which  makes  them  adhere  the  more  firmly  to  the  nest." 
This  author  says  nothmg  about  the  use  of  a  gummy  material  for 
cementing  together  the  fragments  of  leaves. 

Subfamily  EUMENIN^ 
The  Eunienids 


This  subfamily  includes  by  far  the  greater  nimiber  of  our  species 
of  the  solitary  Diploptera ;  and  is  represented  in  our  fauna  by  about 
eight  genera.  The  distinguishing  features  of  these  wasps  are  indicated 
in  the  table  of  subfamilies  given  above. 


HYMENOPTERA  953 

The  different  species  of  eumenids  differ  jjjreatly  in  habits;  many 
are  miners  digging  burrows  in  the  earth  leading  to  cells  in  which  pro- 
visions are  placed  for  their  young;  some  make  burrowsin  wood,  which 
they  divide  into  cells  by  partitions  of  mud;  some  build  their  nests 
in  the  stems  of  pithy  plants  or  make  use  of  any  suitable  cavity  that 
they  find;  and  others  are  mason  or  potter-wasps,  making  cells  of 
earth,  which  are  built  in  holes,  or  on  the  surface  of  the  ground,  or 
attached  to  twigs. 

Although  the  adult  eumenids  do  not  confine  themselves  to  a 
carnivorous  diet  but  often  visit  flowers  to  obtain  nectar,  they  all 
provision  their  nests  with  insects,  which  they  have  paralyzed  with 
their  sting ;  usually  only  a  single  species  of  caterpillar  is  used  for  this 
purpose  by  each  wasp. 

A  remarkable  feature  that  has  been  observed  in  the  nesting  habit 
of  many  etmienids  and  perhaps  is  true  of  all,  is  that  after  the  cell  is 
prepared  the  egg  is  suspended  by  a  slender  thread  from  the  ceiling 
or  side  of  the  cell.  In  some  cases,  at  least,  this  is  done  before  the  pro- 
visioning of  the  nest  is  begun.  An  African  species,  Odynerus  tropicdlis, 
the  habits  of  which  are  described  by  Roubaud  ('i6)  does  not  provision 
its  cell  with  prey  amassed  in  advance,  but  feeds  its  larva  from  day  to 
day  with  small,  entire,  paralyzed  caterpillars,  and  does  not  close  the 
cell  until  the  larva  has  completed  its  growth. 

The  following  examples  will  serve  as  illustrations  of  the  habits  of 
members  of  the  subfamily.  Among  the  more  detailed  accounts  of  the 
activities  of  some  of  our  species  are  those  of  Peckham  and  Peckham 
('05),  Hartman  (05),  Isley  ('13)  and  Rau  and  Rau  ('18).  For  a 
general  account  of  the  habits  of  these  insects  see  Roubaud  ('16). 

Odynerus. — The  greater  number  of  our  species  of  eumenids  belong 
to  the  genus  Odynerus.  In  this  genus  the  abdomen  is  sessile.  The 
shape  of  the  body  and  frequently  the  coloration  resemble  those  of 
the  social  wasps  known  as  yellow-jackets,  although  usually  the  body 
is  more  slender  and  smaller.  The  common  species  are  quite  neighbor- 
ly; and,  owing  to  this  resemblance  to  the  yellow-jackets  they  inspire 
us  with  a  fear  that  is  out  of  all  proportion 
to  their  will  or  ability  to  inflict  pain. 

Many  species  of  Odynerus  are  miners. 
Their  burrows  are  to  be  found  both  in  level 
ground  and  in  the  sides  of  cliffs.  Branch- 
ing from  these  burrows  are  short  passages, 
each  leading  to  a  cell,  from  the  ceiling  of 
which  an  egg  is  suspended  by  a  slender 
thread;  and  in  which  food  is  stored  for  the  Fig.  1185. — Turret  over  the 
larva.  In  the  species  that  have  been  stud-  burrow  of  Odynerus  gem- 
ied,  this  food  consists  of  small,  paralyzed  ^""^-  ^^^^er  Rau  and  Rau.) 
caterpillars.    Some  of  the  mining  species 

while  digging  the  burrow  build  a  turret  over  the  entrance  of  it,  made  of 
pellets  of  mud  removed  from  the  burrow;  one  of  these  turrets  is 
figured  by  the  Raus  (Fig.  11 85).  The  material  of  which  the  turret  is 
composed  is  used  to  fill  up  the  burrow  after  the  cells  are  finished. 


954  AN  INTRODUCTION  TO  ENTOMOLOGY 

In  digging  the  burrow  and  in  tearing  down  the  turret  the  earth  is 
softened  with  water,  which  the  wasp  brings  in  her  mouth  from  some 
pool  or  stream. 

Not  all  species  of  Odynerus  mine  in  the  ground;  many  burrow  in 
the  stems  of  pithy  plants,  making  a  series  of  cells  separated  by  parti- 
tions of  mud ;  other  species  will  avail  themselves  of  any  convenient 
cavity  in  which  to  make  their  nest,  frequently  utilizing  the  deserted 
nests  of  the  sphecoid-wasps  known  as  mud-daubers.     In  this  case  a 


Fig.  1 1 86. — Eumenes  fraternus  and  its  nests. 


single  cell  of  a  mud-dauber  is  divided  by  a  transverse  partition,  mak- 
ing two  cells  for  the  smaller  Odynerus.  One  year  these  wasps  plastered 
up  many  of  the  keyholes  in  our  house,  including  those  in  bureaus. 

Some  species-  of  Odynerus  are  masons  constructing  nests  entirely 
of  mud.  One  of  our  species,  Odynerus  birenimaculdtus,  makes  a  nest 
about  the  size  of  a  hen's  egg.  This  is  composed  of  hard  clay,  fastened 
to  a  twig  of  a  bush,  and  contains  many  cells. 

The  jug-builders,  Eumenes.- — The 
.>^_^  wasps  of  the  typical  genus  of  this  sub- 

'  /^,f'^^^^    family  are  potter-wasps  which  build  nests 
2^^^^^    that   appear   like  miniature   water-jugs. 
'^  i    -^^i-^^^  '^^^  nests  of  our  common  species,  Eumenes 

\^Sr\  fraternus,   are   often   found   attached  to 

/    J^m    \  twigs  (Fig.  ii86).     In  this  genus  the  ab- 

"*       W^       »  domen  of  the  adult  is  petiolate.     These 

^  wasps  provision  their  nests  with  cater- 

pillars and  frequently  with  cankerworms. 
Fig.    ii87.-Monobta   quad-  p^^       ^j^^    studied  the  habits  of  a 

rtaens.  t^  '  .  .    „  ,  . 

i/Uropean  species  of  Eumenes  observed 

what  goes  on  within  the  nest  by  making  a  window  in  the  side  of  it. 
The  egg  is  suspended  from  the  ceiling  of  the  nest  by  a  slender  thread ; 


HYMENOPTERA 


955 


when  the  larva  hatches  it  at  first  makes  use  of  the  egg-shell  as  its 

habitation  and  stretches  down  to  feed  on  the 

caterpillar  below  it;  if  disturbed  it  retreats  up 

its  support.     Later  when  the  lar\'a  has  increased 

in  size  and  strength  it  descends  to  the  mass  of 

food. 

Monohia  qnadridens. — This  species  (Fig.  1 187)       ,  ,        ^-  -^  1  , 
is  common  in  most  of  the  states  east  of  the  Missis-       ' ,  \^  ^11} 

sippi.  It  is  larger  than  the  jug-builders,  and  the 
abdomen  of  the  adult  is  sessile.  Figure  1 188  repre- 
sents a  nest  of  this  species,  now  in  the  Cornell 
University  collection,  which  was  made  in  a  board 
in  the  side  of  a  bam.  The  partitions  are  made  of 
mud.  Each  cell  contained  a  pupa  when  the  nest 
was  opened,  hence  it  was  not  evident  what  the 
food  of  the  larvae  had  been ;  but  several  observers 
state  that  this  species  stores  its  nests  with  large 
cutworms ;  and  it  is  doubted  that  this  species  is  a 
carpenter-wasp.  It  seems  probable  that  the  nest 
figured  here  was  made  in  a  deserted  burrow  of  the 
large  carpenter-bee.  A' j/oco^a  wrgzw/ca.  It  differs  1  ,,ij 
from  a  nest  of  this  bee  only  in  that  the  partitions 
are  made  of  mud. 


THE  SOCIAL  WASPS 


rm 


Since  the  social  Diploptera  are  the  only  wasps 
that  are  social  they  are  commonly  referred  to  as 
the  social  wasps  instead  of  the  more  technical 
name. 

As  with  the  ants  the  colonies  of  social  wasps 
consist  of  three  castes,  the  female  or  queen,  the 
workers,  and  during  the  later  part  of  the  season, 
the  males.  The  workers  are  females  in  which  the 
reproductive  organs  are  imperfectly  developed.  i'| 
In  the  genus  Belonogaster  a  worker  caste  is  be- 
lieved to  be  lacking.  In  Polisles  it  is  very  difficult 
to  make  a  distinction  between  females  and  work-  ill  iJiH 
ers,  for  they  can  apparently  all  become  fertile. 

In  the  temperate  regions  the  colonies  exist 
for  only  one  season;  the  males  and  the  workers 
die  in  the  autumn ;  the  females  hibernate  and  each 
starts  a  new  colony  in  the  spring.  At  first  the  fe- 
male performs  the  functions  of  both  worker  and 
queen,  starting  the  building  of  the  nest  and  laving  Fig-  1 188. — Nest  oi 
the  eggs.  In  the  early  part  of  the  season  only  ff^l°^'''  ^""''^'"'' 
workers  are  developed;  after  they  appear  they 
carry  on  the  labors  of  the  colony,  expanding  the 
nest  and  procuring  the  food  for  the  larvag;  the  only  function  of^the 


ilii^IAlLiil 


956 


AN  INTRODUCTION  TO  ENTOMOLOGY 


queen  then  is  to  produce  the  eggs.  In  the  later  part  of  the  season 
males  and  females  are  developed. 

The  social  wasps  are  predacious,  and  they  feed  their  larvag  upon 
insects  which  they  have  malaxated.  The  wasps  are  also  fond  of  the 
sweets  of  flowers,  the  juices  of  fruits,  and  of  honey-dew.  They  also 
feed  upon  a  liquid  which  the  wasp  larva  emits  from  its  mouth.  This 
exchange  of  nourishment  between  the  larvae  and  the  adults,  termed 
trophallaxis,  is  discussed  in  the  Chapter  on  Isoptera,  page  279. 

In  the  temperate  regions  the  multiplication  of  colonies  is  brought 
about  by  the  production  of  many  males  and  females  in  the  nest  in  the 
later  part  of  the  season;  these  pair,  the  females  hibernate,  and  each 
female  founds  a  new  colony  in  the  spring.  But  in  the  Tropics  many 
of  the  Epiponinee  form  large  perennial  colonies,  which  from,  time  to 
time  give  off  swarms,  in  a  way  quite  similar  to  the  well-known 
swarming  of  the  honey-bee. 

Representatives  of  three  of  the  subfamilies  of  social  wasps  are 
found  in  America  north  of  Mexico.  The  distinguishing  characters 
of  these  are  indicated  in  the  table  of  subfamilies  of  the  Vespidas  given 
above. 

Subfamily  EPIPONIN^ 

This  is  a  large  group  of  wasps  including  a  great  variety  of  forms, 
which  exhibit  great  differences  in  the  architecture  of  their  nests. 


'■^'«+2d4 


Fig.  1 189. — Wings  of  Mischocytlarus  labiatus:  pi,  posterior  or  anal  lobe;  ax.  exc, 
axillary  excision.     (From  Bradley.) 


The  species  are  mostly  confined  to  tropical  America;  but  three 
are  found  in  the  southern  portions  of  the  United  States.  Figure  1 189 
represents  the  venation  of  the  wings  of  Mischocytlarus  labiatus. 

Brachygastra  lechegudna.- — This  species  is  found  within  the  limits 
of  our  territory  only  along  the  Mexican  border.  Its  nest  resembles 
inform  externally  those  of  hornets  {Vespa)  but  the  combs  are  attached 


HYMENOPTERA  957 

to  the  envelope.  This  wasp  is  especially  interesting  from  the  fact 
that  it  frequently  stores  honey  in  the  combs  of  its  nest;  but  the 
honey  is  probably  not  an  exclusive  or  essential  constituent  of  the  larval 
food. 

Mischocyttarus .■ — This  tropical  genus  is  represented  in  our  fauna 
by  two  species,  one,  Mischocyttarus  cubensis,  found  in  Florida  and  in 
Southern  Georgia,  one,  Mischocyttarus  flavitdrsis,  found  in  the  South- 
west, Colorado,  and  California. 

These  wasps  make  small,  few-celled  paper  nests,  without  an  en- 
velope like  those  of  Polistes;  but  the  wasps  are  easily  distinguished 
from  Polistes  by  the  form  of  the  first  segment  of  the  abdomen  which 
is  slender  and  elongate,  forming  a  pedicel.  The  nests  of  M.  cubensis 
are  found  on  palmetto  leaves. 

Subfamily  POLISTIN^ 

Polistes 

The  wasps  of  the  genus  Polistes  and  their  nests  are  very  familiar 
objects.  The  nests  consist  each  of  a  single  comb  suspended  by  a 
peduncle,  and  the  comb  is  not  enclosed  in  an  envelope  (Fig.  1190). 
These  nests  are  often  built  under  the  eaves  of  buildings,  in  garrets,  and 
in  sheds  and  barns ;  they  are  also  often  made  under  flat  stones  in  fields, 
and  sometimes  attached  to  bushes.  The  combs  of  our  species  of 
Polistes  are  horizontal;  but  the  nests  of  Polistes  linedtus,  which  I 


Fig.  1 190. — Nest  oi  Polistes.  Fig.  1191. — Polistes. 

found  hanging  from  the  ceiling  of  a  cave  in  Cuba,  are  long,  narrow, 
vertical  combs,  from  one  to  two  inches  in  width  and  from  twelve  to 
eighteen  inches  in  length. 

The  nests  are  made  of  a  grayish  paper-like  material,  composed  of 
fibers  of  weather-worn  wood,  which  the  wasps  collect  from  the  sides 
of  unpainted  buildings,  fences,  and  other  places,  and  convert  into  a 
paste  by  the  action  of  the  jaws  and  the  addition  of  some  fluid,  prob- 
ably an  oral  secretion.  The  nests  of  Polistes  are  usually  comparatively 
small ;  but  some  have  been  found  in  Texas  that  measured  more  than 
a  foot  in  diameter. 

In  this  genus  the  abdomen  is  long  and  spindle-shaped  (Fig.  1 191). 


958 


^A^  INTRODUCTION  TO  ENTOMOLOGY 


Several  of  the  species  are  known  to  store  small  quantities  of  honey 
in  their  combs. 

These  wasps  are  often  infested  by  stylopids. 

Subfamily  VESPIN^ 
The  Hornets  and  the  Yellow- Jackets 

This  subfamily  includes  those  wasps  that  are  commonly  known 
as  hornets  and  the  yellow-jackets.     With  these  insects  the  body  is 


Fig.  1 192. — 
Vespa. 

comparatively 
short  and  rather 
stout  (Fig.  1 192); 
the  abdomen  is  at- 
tached to  the  thor- 
ax by  a  very  short 
pedicel;  and  the 
color  is  black,  spot- 
ted  and  banded 
with  yellow  or  yel- 
lowish white.  The 
members  of  this  sub- 
family differ  from 
other  vespoid  wasps 
in  that  the  hind 
wings  are  without 
an  anal  lobe  (Fig. 
1182). 

These  wasps 
make  their  nests  of 
paper,  which  in 
some  cases  is  com- 
posed  of  fibers   of 

weather-worn  wood,  like  that  of  Polistes  described  above,  in  other 
cases  of  fragments  of  more  or  less  decayed  wood.  These  nests  consist 
of  a  series  of  horizontal  combs  suspended  one  below  another  and  all 
enclosed  in  a  paper  envelope  (Fig.  1193). 

When  the  wasps  wish  to  enlarge  their  nest  they  remove  the  inner 
layers  of  the  envelope,  and  add  to  the  sides  of  the  combs,  build  addi- 
tional combs  below,  and  put  on  new  layers  on  the  outside  of  the 


Fig.  1 1 93. — Nest  of  Vespa,  with  side  removed.     (From 
A.  B.  Comstock,  Handbook  of  Nature  Study.) 


HYMENOPTERA 


959 


Early  stage  of  nest  of  Vespa. 


envelope.    B}^  these  additions  the  nest  may  become  of  large  size  by 
the  end  of  the  season. 

Ven^  small  empty  nests  consisting  of  a  single  comb  with  but  few 
cells  and  enclosed  in  an  envelope  of  only  one  or  two  layers  of  paper 
are  often  found  (Fig.  1194). 
Such  a  nest  is  evidence  of  a  trag- 
edy. A  queen  wasp,  in  the 
spring,  had  started  to  found  a 
colony.  It  was  necessary  for  her 
to  go  back  and  forth  in  the  fields 
collecting  material  for  her  nest 
and  food  for  her  larv^;  and  be- 
fore a  brood  of  workers  were  de- 
veloped to  relieve  her  of  this 
dangerous  occupation  she  became 
the  prey  of  some  bird  and  the  de- 
velopment of  the  colony  was 
wrecked. 

Two  quite  different  types  of 
nests  are  made  by  different  spe- 
cies of  these  wasps,  and  these  are 
made  in  quite  different  situations. 
One  kind  is  built  above  ground; 
these  are  attached  to  bushes  or 
trees,  or  beneath  the  eaves  of 
buildings;  they  are  made   of  a 

grayish  paper  composed  of  fibers  of  weather-worn  but  not  decayed 
wood.  This  paper  is  comparatively  strong,  so  that  the  envelope  of 
the  nest  is  composed  of  sheets  of  paper  of  considerable  size,  a  single 
sheet  often  completely  enveloping  the  nest. 

The  other  kind  of  nest  is  built  in  a  hole  in  the  ground,  which  is 
enlarged  by  the  wasps  as  they  need  more  room  for  the  expansion  of 
the  nest.  The  paper  of  which  these  nests  are  made  is  brownish  in 
color  and  is  made  out  of  partially  decayed  wood;  it  is  very  fragile 
and  would  not  be  suitable,  therefore,  for  use  in  nests  built  in  exposed 
places.  Even  though  the  nest  is  built  in  a  protected  place,  the  use 
of  this  fragile  material  necessitates  a  different  style  of  architecture. 
The  enveloping  layers  of  the  nest,  instead  of  being  composed  of  sheets 
of  considerable  size,  are  made  up  of  small,  overlapping,  shell-like 
portions,  each  firmly  joined  by  its  edges  to  the  underlying  parts. 

If  a  completed  hornet's  or  ^^ellow-jacket's  nest  be  examined  it 
will  be  found  that  some  of  the  later-built  combs  consist  wholly  or  in 
part  of  cells  that  are  larger  than  those  in  the  first -made  combs;  the 
smaller  cells  are  those  in  which  workers  were  developed;  the  larger 
ones  those  in  which  the  sexual  forms  were  reared. 

It  has  been  found  that  at  least  two  species  of  this  subfamily  are 
social  parasites.  In  these  species  the  worker  caste  has  been  lost, 
there  being. only  males  and  females.  The  female  enters  the  nest  of 
another  species  of  Vespa  and  lays  her  eggs,  and  her  larvae  are  reared 


960  AN  INTRODUCTION  TO  ENTOMOLOGY 

by  the  rightful  owners  of  the  nest.  The  species  that  are  known  to 
be  parasites  are  Vespa  drctica,  which  infests  the  nests  of  Vespa 
diabolica,  and  Vespa  austraca,  which  infests  the  nests  of  Vespa  rufa 
in  Europe.  Vespa  austraca  has  been  found  in  this  country  but  Vespa 
rufa  is  not  known  to  occur  here.  The  American  host  of  Vespa 
austraca  has  not  been  definitely  ascertained,  but  is  thought  to  be 
Vespa  consobrina.    See  Wheeler  and  Taylor  ('21). 

The  members  of  the  subfamily  Vespinse  found  within  the  limits 
of  our  territory  are  commonly  included  in  a  single  genus,  Vespa;  but 
some  writers  place  all  of  our  species  except  Vespa  crabro  in  a  separate 
genus  Vespula;  Only  a  few  of  our  species  can  be  mentioned  here. 

The  giant  hornet,  Vespa  crabro.— This  is  our  largest  species, 
measuring  from  18  to  22  mm.  in  length.  It  is  brown  and  yellow  in 
color  and  .is  found  around  New  York  City,  on  Long  Island,  and  in 
Connecticut.  It  builds  its  nests  in  hollow  trees  and  within  buildings 
suspended  from  the  roof. 

The  white-faced  hornet,  Vespa  maculdta. — This  is  the  common, 
large  black  and  white  hornet.  It  is  widely  distributed  in  the  United 
States  and  Canada.  The  nest,  which  is  sometimes  very  large  is 
usually  attached  to  the  limb  of  a  tree. 

The  yellow-jackets. — This  common  name  is  applied  to  several 
small,  black  and  yellow  species  of  Vespa,  which  are  so  closely  related 
that  it  is  difficult  to  distinguish  them.  Most  of  the  species  build 
their  nests  in  the  ground ;  these  are  the  brownish  paper  nests  described 
above.  Sometimes  the  nest  is  built  in  a  stimip  or  under  some  object 
lying  on  the  ground.  On  one  occasion  I  found  a  fine  large  nest  under 
the  base-board  of  one  of  my  bee-hives,  and  into  which  I  inadvertantly 
thrust  my  toes,  with  sad  results,  while  examining  the  hive.  The  nest 
is  now  in  the  Cornell  collection. 

SUPERFAMILY  SPHECOIDEA 

The  Sphecoid-wasps  and  the  Bees 

The  superfamily  Sphecoidea  resembles  the  two  preceding  super- 
families  in  the  presence  of  an  anal  lobe  in  the  hind  wings,  except  in 


Fig.  1 195. — A,  Head  and  thorax  of  a  vespoid-wasp,  p,  pronotum;  t,  tegula.  B, 
Head  and  thorax  of  a  sphecoid-wasp,  p,  pronotum,  p.  I.,  posterior  lobe  of  the 
pronotum;  t,  tegula. 

some  specialized  genera  of  the  Ampulicidae  and  some  bees;  it  differs 


HYMENOPTERA  961 

from  the  Evanioidea  in  that  the  petiole  of  the  abdomen  is  attached 
to  the  hind  end  of  the  propodeinn;  and  it  differs  from  the  Vespoidea 
in  that  there  is  on  each  side  a  lateral  extension  of  the  pronotum  in 
the  form  of  a  distinctly  differentiated  rounded  lobe,  which  covers 
the  spiracle  (Fig.  1195,  B);  these  lobes  are  known  as  the  posterior 
lobes  of  the  pronotum ;  they  do  not  reach  the  tegulas  except  in  some 
Dryinida?  and  Ampulicidas.  These  exceptional  forms  can  be  placed 
in  their  families  by  the  table  on  pages  906  to  914. 

The  families  constituting  the  superfamily  Sphecoidea,  which  can 
be  separated  by  the  table  referred  to  above,  represent  two  quite  dis- 
tinct groups  of  families,  known  respectively  as  the  sphecoid-wasps 
and  the  bees.  These  two  groups  of  families  are  distinguished  as 
follows. 

A.    First  segment  of  the  posterior  tarsi  cylindrical  and  naked;  or  with  but  little 

hair;  hairs  clothing  the  thorax  simple;  nests  provisioned  with  animal  food. 

p.  961 The  Sphecoid-Wasps 

AA.    First  segment  of  the  posterior  tarsi  elongate  and  dilated;  some  of  the  hairs, 

especially  of  the  thorax,  plumose;  nests  provisioned  with  honey  and  pollen. 

p. 972  The  Bees 

THE  SPHECOID-WASPS 

The  group  known  as  the  Sphecoid-wasps  includes  three  families, 
the  Ampulicidas,  the  Dryinidse,  and  the  Sphecidae.  These  three  fam- 
ilies and  certain  families  of  the  Vespoidea  were  formerly  classed  to- 
gether as  the  Fossores  or  digger-wasps ;  which  names  were  suggested 
by  the  fact  that  most  of  the  species  belonging  to  these  families  make 
nests  for  their  young  by  digging  burrows  in  the  ground  or  in  wood. 
But  this  group  is  no  longer  regarded  as  a  natural  one  notwithstanding 
the  striking  similarity  in  habits  exhibited  by  its  members. 

The  family  AMPULICID^  is  represented  in  our  fauna  by  only 
two  geneva,  Rhinopsts  and  Dolichums,  the  species  of  which  are  very 
rare.  So  far  as  is  known  the  members  of  this  family  prey  on  cock- 
roaches, with  which  they  store  their  nests. 

Family  DRYINID^ 
The  Dryinids 

This  family  is  composed  of  small  parasitic  wasps;  it  is  widely 
distributed  over  the  world  and  is  represented  in  our  fauna  by  many 
genera. 

The  fore  wings  have  a  lanceolate  or  ovate  stigma ;  the  hind  wings 
are  without  closed  cells;  the  antennae  consist  of  ten  segments,  the 
anterior  tarsi  of  the  female  are  usually  chelate ;  and  either  the  pro- 
notum has  a  longitudinal  sulcus  or  the  antennae  are  borne  close  to 
the  clypeus.  The  females  of  the  genus  Gonatopus  are  wingless,  ant- 
like, and  are  without  a  scutellum. 

These  parasites  confine  their  attacks  to  the  homopterous  insects 
belonging  principally  to  the  families  Fulgoridae,  Membracidas,  and 
Cicadellidae. 


962  AN  INTRODUCTION  TO  ENTOMOLOGY 

The  female  dnanid  seizes  her  victim  with  her  raptorial  fore  legs; 
one  pair  of  pincers  usually  grips  the  neck  of  the  prey,  the  other  pair 
grips  the  abdomen  towards  the  apex  or  the  hind  legs.  The  wasp 
then  inserts  her  egg  into  the  body  of  the  bug.  A  few  days  later  the 
immature  larva  of  the  parasite  appears  outside  the  body  of  its  host 
enclosed  in  a  sac  composed  of  molted  skins.  Here  it  remains,  with  its 
head  in  the  opening  in  the  body- wall  of  its  host,  until  it  has  com- 
pleted its  growth.  It  then  leaves  its  host  and  spins  a  silken  cocoon, 
which  in  some  cases  is  furnished  with  an  outer  covering  formed  of 
the  larv^al  sac  or  of  round  patches  of  epidermis  stripped  oif  from  the 
leaf  surface. 

A  detailed  account  of  the  habits  of  these  remarkable  insects  is 
given  by  Perkins  (05)  and  the  family  Dryinidag  was  monographed 
by  Kieffer  (07),  and  Kieffer  ('14)  in  a  paper  on  the  Bethylidas. 

Family  SPHECID.E 
The  Typical  Sphecoid  Wasps 

In  this  famil}^  the  hind  wings  have  an  anal  lobe  and  some  closed 
cells ;  the  abdomen  of  the  male  has  seven  exposed  tergites ;  the  sting 
of  the  female  is  not  enclosed  by  the  hypopygium ;  the  posterior  meta- 
tarsi are  not  dilated  as  in  the  bees  and  there  are  no  plumose  hairs. 
All  members  of  the  Sphecidae  are  winged. 

To  this  family  belong  all  of  our  common  nest-building  sphecoid 
wasps.  These  differ  from  the  bees  in  that  they  provision  their  nests 
with  animal  food,  insects  or  spiders,  which  they  have  paralyzed  by 
stinging  them.  Different  members  of  the  family  differ  greatly  in 
their  nesting  habits;  some  are  mason-wasps,  building  cells  of  earth; 
many  burrow  in  the  ground ;  and  others  burrow  in  the  stalks  of  pithy 
plants  or  make  use  of  cavities  that  they  find. 

Most  members  of  the  Sphecidae,  after  preparing  their  nest,  rapidly 
accimiulate  an  amount  of  prey  sufficient  to  enable  the  young  to 
develop  to  maturity,  lay  an  egg  with  it,  and  then  close  the  cell  before 
the  egg  has  hatched.  This  method  is  termed  mass  provisioning. 
But  certain  members  of  the  family,  Eenihex  and  some  others,  feed 
their  young  from  day  to  day  as  long  as  they  remain  in  the  larval  state. 
This  method  is  termed  progressive  provisioning.  As  each  larva  re- 
quires constant  attention  for  a  considerable  time  only  a  few  young 
can  be  reared  by  a  single  female  in  this  way. 

Many  of  these  wasps  after  stinging  their  prey  and  before  placing 
it  in  their  nest  malaxate  {i.  e.  chew)  its  neck  or  some  other  part  of 
the  body  and  lap  up  the  exuding  juices. 

The  family  Sphecidse  is  divided  into  six  subfamilies,  some  of 
which  include  two  or  more  quite  distinct  groups  of  genera  or  tribes. 
As  many  of  these  tribes  are  given  subfamily  rank  by  some  writers 
each  of  those  represented  in  our  fauna  is  defined  below.  These 
tribes  can  be  separated  by  the  following  key,  which  has  been  kindly 
prepared  for  me  by  Professor  J.  Chester  Bradley. 


HYMENOPTERA  963 

A  KEY  TO  THE  TRIBES  OF  SPHECID^  OCCURRING 
IN  THE  UNITED  STATES 

A.    Postscutellum  with  squamae  which  project  backward,  and  base  of  propodeum 

with  a  median  spine,  p.  972 OxYBELlNl 

AA.    Postscutellum  and  propodeum  simple. 

B,     Only  I  submarginal  cell.     Inner  margins  of  eyes  emarginate  or  strongly 
converging  toward  the  clypeus  (except  in  Anacrabro,  which  may  be  recog- 
nized by  its  flat  venter) . 

C.    Inner  margins  of  eyes  entire,  p.  971 Crabronini 

CC.     Inner  margins  of  eyes  deeply  emarginate.  p.  965 Trvpoxylonini 

BB.  Usually  3  submarginal  cells,  sometimes  two,  rarely  only  one,  in  which  case 
the  inner  margins  of  the  eyes  are  neither  emarginate  nor  strongly  convergent 
toward  the  clypeus. 

C.     Anal  lobe  large,  reaching  to  opposite  or  beyond  the  apex  of  the  cell 
M3  +  Cu,  +  Cu. 
D.     The  marginal  cell  not  appendiculate.     Abdomen  with  a  cylindrical 

petiole.     Middle  tibiae  with  two  apical  spurs,  p.  966 Sphecini 

DD.    The  marginal  cell  appendiculate.    Abdomen  not  petiolate. 

E.     Ocelli  normal.     Middle  tibiae  with  two  apical  spurs,  p.  964.... 

ASTATINI 

EE.      Ocelli   distorted.      Middle  tibiae   with   one  apical  spur,   p.964. 

Larrini 

CC.     Anal  lobe  small,  not  reaching  to  opposite  the  apex  of  the  cell  Mj  + 
Cui  +  Cu. 
D.     Ocelli  normal,  circular  and  convex. 

E.    Antennae  inserted  low  on  the  face,  near  the  base  of  the  eyes. 
F.     No  epicnemium. 

G.     First  abdominal  segment  sessile  or  with  a  cylindrical  petiole 
which  is  composed  only  of  the  sternite.     Middle  tibiae  with  a 
single  apical  spur. 
H.     An  appendiculate  cell  present,  or  the  mandibles  with  an 

external  notch,  usually  both.  p.  965 Dinetini 

HH.     No  appendiculate  cell.     Mandibles  without  an  external 

notch,  p.  968 Pemphredonini 

GG.  First  abdominal  segment,  petioliform,  the  petiole  consisting 
however  of  both  sternite  and  tergite,  nodose  at  apex.     Middle 

tibiae  with  two  apical  spurs,  p.  969 Mellimis  in  Nyssonini 

FF.     An  epicnemium  present.     Middle  tibiae  with  two  apical  spurs. 

p.  969 Nyssonini 

EE.    Antennae  inserted  near  the  middle  of  the  face  above  the  bases  of 
the  eyes. 

F.    Abdomen  without  a  cylindrical  petiole  which  is  composed  only  of 
the  sternite. 

G.  Transverse  part  of  vein  M  distant  from  the  stigma  by  less, 
usually  much  less,  than  twice  the  -distance  between  the  apex 
of  the  cell  2d  Ri  +  R2  and  the  apex  of  the  wing.  Labrilm  rarely 
exserted. 

H.      Hind   femora    without   a   transversely   expanded   reniform 
apical  plate. 

I.  Upper  margin  of  clypeus  extending  across  in  a  straight  line 
or  arch,  without  a  median  lobe.  Cell  R5  usually  small  and 
triangular,  or  if  not,  the  middle  tibiae  have  two  apical  spurs, 
P-  969 Nyssonini 

II.  Upper  margin  of  clypeus  with  a  median  lobe  extending  up- 
ward toward  the  antennae.  Cell  R5  four-sided.  Middle 
tibiae  with  one  apical  spur.   p.   969 Philanthini 

HH.    Hind  femora  broadened  at  ajaex,  there  forming  a  transverse 
reniform  plate,  p.  969 Cercerini 


964 


AN  INTRODUCTION  TO  ENTOMOLOGY 


GG    Transverse  part  of  vein  M  distant  from  the  stigma  by  two  or 

more  times  the  distance  between  the  apex  of  cell  2d  Ri   +  R2 

and  the  apex  of  the  wing.     Labrum  exserted.  p.  970.  .Stizini 

FF.     Abdomen  with  a  cylindrical  petiole  which  is  composed  only  of 

the    sternite.    p.    967 Psenini 

DD.      Ocelli   distorted,    p.    971 Bembicini 

Subfamily  LARRIN^ 

Tribe  ASTATINI 

The  members  of  this  tribe  are  rather  small,  seldom  more  than 
12  mm.  in  length.  They  are  usually  black  or  black  and  red.  As  in 
the  following  tribe  the  anal  lobe  of  the  hind  wings  is  large,  the  marginal 
cell  of  the  fore  wings  is  appendiculate,  and  the  abdomen  is  not  petio- 
late;  but  these  wasps  differ  from  the  Larrini  in  that  the  ocelli  are 
normal  and  the  middle  tibiae  are  armed  with  two  apical  spurs. 

The  habits  of  Astdtus  unicolor  and  of  Astdtus  blcolor  are  described 
by  the  Peckhams  ('98) ;  these  species  burrow  in  the  ground  and  pro- 
vision their  nests  with  bugs. 


Tribe  LARRINI 

Most  members  of  the  Larrini  are  of  moderate  size,  but  our  species 
range  from  3  mm.  to  about  23  mm.  in  length.  They  are 
usually  rather  stoutly  built  insects  (Fig.  11 96).  The 
anal  lobe  of  the  hind  wings  is  long  and  scarcely  sepa- 
rated from  the  preanal  lobe  (Fig.  1197);  the  marginal 
cell  of  the  fore  wings  is  appendiculate;  the  ocelli  are 
Tachysphex  distorted;  and  the  middle  tibiae  are  armed  with  one 
terminatuT.       apical  spur. 

Nearly  all  of  the  species  burrow  in  sandy  places 
and  provision  their  nests  with  orthopterous  insects  or  with  bugs;  but 


^3  +  0,:+ Or 

Fig.  1 197. — -Wings  of  Tachysphex  terminatus. 

Williams  ('13)  states  that  a  few  of  the  smaller  species  make  their 
nests  in  brambles. 


HYMENOPTERA 


965 


Some  members  of  the  Larrini  (Tdchysphex)  dig  short  burrows  in 
the  ground  at  the  bottom  of  which  the  prey  is  placed  with  an  egg, 
and  then  the  burrow  is  closed  with  loose  sand,  there  being  no  well- 
formed  cell ;  several  of  these  burrows  are  often  made  and  stored  in  a 
single  day.  Other  members  of  the  Larrini  make  deeper  burrows 
which  contain  from  a  few  to  many  cells. 

For  a  monograph  of  this  tribe  see  Fox  ('93). 

Tribe  DINETINI 

In  this  tribe  the  anal  lobe  of  the  hind  wings  is  small,  not  reaching 
to  opposite  the  apex  of  cell  Ma+Cui+Cu;  the  ocelli 
are  normal,  circular  and  convex. 

The  tribe  is  composed  chiefly  of  small  and  little 
known  insects  except  the  genus  Lyroda.  A  common 
species  of  this  genus,  Lyroda  subita,  practises  progressive 
provisioning,  feeding  its  young  from  day  to  day  with 
crickets  of  the  genus  Nemobius;  its  nest  is  made  in  the 
ground.  The  small  wasps  of  the  genus  Mtsopiis  prey  on 
spiders. 

For  a  monograph  of  this  tribe  see  Fox  ('93). 

Subfamily  TRYPOXYLONIN^ 

This  subfamily  includes  a  single  tribe,  the  Trypoxy- 
lonini.  In  these  wasps  the  inner  margin  of  the  eyes  is 
deeply  incised,  the  ocelli  are  normal,  the  marginal  cell 
of  the  fore  wings  is  not  appendiculate,  and  there  is  only 
one  submarginal  cell.  The  body  is  black,  slender,  and 
of  medium  size. 

I  have  found,  in  New  York,  the  nests  of  Trypoxylon 
frigidum  very  common  in  branches  of  sumac  (Fig. 
1 198),  more  common  than  those  of  any  other  insect 
except  the  little  carpenter-bee,  Ceratina.  The  cells  of 
the  nests  of  Trypoxylon  are  separated  by  partitions  of 
mud  and  are  stored  with  spiders.  The  larva  of  Try- 
poxylon frigidum  when  full-grown  makes  a  very  slender 
cocoon,  with  the  upper  end  rounded  and  sometimes 
slightly  swollen,  and  the  lower  end  blunt  and  of  denser 
texture  than  the  remainder  of  the  cocoon. 

An  extended  account  of  the  habits  of  two  other 
species  of  Trypoxylon,  T.  albopilosum  and  T.  rubro- 
cinctwm,  is  given  by  the  Peckhams  ('89),  who  studied 
these  species  in  Wisconsin.  Of  special  interest  are  the 
observations  made  by  these  writers  on  the  cooperation 
of  the  males  and  females  during  the  nest-building 
period.    They  state  as  follows. 

"With  both  species  when  the  preliminary  work  of 
clearing  the  nest  and  erecting  the  inner  partition  has 
been  performed  by  the  female,  the  male  takes  up  his  station  inside 


Fig.  ii9<s.— 
Nest  of  Try- 
poxylon frig- 
idum. 


966  AN  INTRODUCTION  TO  ENTOMOLOGY 

the  cell,  facing  outward,  his  little  head  just  filling  the  opening. 
Here  he  stands  on  guard  for  the  greater  part  of  the  time  until  the 
nest  is  provisioned  and  sealed  up,  occasionally  varying  the  monotony 
of  his  task  by  a  short  flight."  "We  have  frequently  seen  him  drive 
away  the  brilliant  green  Chrysis  fly  which  is  always  waiting  about 
for  a  chance  to  enter  an  unguarded  nest."  "In  one  instance,  with 
ruhrocinctum  where  the  work  of  storing  the  nest  had  been  delayed  by 
rainy  weather,  we  saw  the  male  assisting  by  taking  the  spiders  from 
the  female  as  she  brought  them  and  packing  them  into  the  nest, 
leaving  her  free  to  hunt  for  more." 

Some  species  of  Trypoxylon  are  mud-daubers.  Trypoxylon  alhi- 
tarsis,  a  shiny  black  species  with  white  tarsi,  builds  large  nests  of  mud, 
which  consist  of  several  parallel  tubes,  often  three  inches  or  more  in 
length,  placed  side  by  side.  These  nests  are  known  as  pipe-organ 
nests.  Each  tube  is  divided  by  transverse  partitions  into  several 
cells,  which  are  provisioned  with  spiders.  The  tubes  when  completed 
are  not  covered  with  an  extra  layer  of  mud  as  is  commonly  the  case  in 
the  nests  of  other  mud-daubers.  When  an  adult  is  ready  to  emerge 
from  the  cell  in  which  it  was  developed,  it  mkes  a  hole  through  the 
exposed  side  of  the  tube. 

For  a  monograph  of  Trypoxylon  see  Fox  ('93). 

Subfamily  SPHECIN^ 
The  Thread-waisted  Wasps 
These  insects  are  termed  the  thread-waisted  wasps  on  account  of 
the  great  length  of  the  petiole  of  the  abdomen  (Fig.  1199).     With 
these  wasps  the  marginal  cell  of  the  fore  wings 
(2d   Ri-fR2)    is  not   appendiculate;  the   anal 
lobe  of  the  hind  wings  is  large,  extending  to  the 
/f        "^  ^P^^"^  ^f  cell  Ms-f  Cui-|-Cu2  or  beyond   (Fig. 

1200);  and  the  middle  tibiae  bear  two  apical 
Fig.  iigg.—Sceliphron      spurs. 

emen  anum.  These  are  the  most  commonly  observed  of 

all  of  our  sphecoid  wasps,  as  certain  species 

build  their  mud  nests  in  the  attics  of  our  houses;  and,  too,  the 


Fig.  1200. — Wings  of  Sceliphron  cementarium. 


HYMENOPTERA 


967 


lower 
These 


peculiar  shape  of  the  body  makes  them  ver^-  conspicuous.  Most  of 
the  species  burrow  in  the  ground  and  store  their  nests  either  with 
caterpillars  or  with  Orthoptera.  But  those  best  known  to  us  are  the 
mvid-daubers. 

The  mud-daubers  make  nests  of  mud  attached  to  the 
surface  of  flat  stones  or  to  the  ceilings  or  walls  of  buildings, 
nests  usually  consist  of 
several  tubes  about 
twenty-five  millimeters 
in  length  placed  side  by 
side  (Fig.  1201)  and  are 
provisioned  with  spiders. 
The  mud-daubers  may 
be  seen  in  damp  places 
collecting  mud  for  their 
nests,  or  exploring  build- 
ings in  search  of  a  place 
to  build.  They  have  a 
curious  habit  of  jerking 
their  wings  frequently  in 
a  nervous  manner.  There 
are  in  this  country  two 
widely  distributed  and 
common  species  of  mud- 
daubers;  these  are  the 
blue  mud-dauber,  Chaly- 

bion  ccBruliuni,  which  is  steel  blue  with  blue  wings,  and  the  yellow 
mud-dauber,  Sceliphron  cementdrium,  which  is  black  or  brown  with 
yellow  spots  and  legs.  The  latter  of  these  species  has  been  commonly 
described  under  the  generic  name  PelopcEus. 

The  tool-using  wasps,  Ammophila. — Among  the  members  of  the 
Sphecina?,  that  burrow  in  the  ground  and  store  their  nest  with  cater- 
pillars are  certain  species  of  the  genus  Ammophila.  These  are  of 
especial  interest  on  account  of  the  habit,  first  observed  by  the 
Peckhams,  of  pounding  down  the  earth  with  which  they  close  their 
burrow  by  taking  a  stone  or  some  other  object  in  their  mandibles  and 
using  it  as  a  hammer. 

The  genus  Chlorion,  formerly  known  as  Sphex,  includes  species 
which  are  among  the  most  common  of  flower  visitors  in  the  warmer 
parts  of  our  country,  and  are  among  the  largest  and  most  handsome, 
and  therefore  most  often  observed  of  our  wasps.  In  the  West  the 
common,  very  large,  all  metallic  green  Chlorion  cydneum  is  a  very 
striking  insect;  and  in  the  East  Chlorion  ichneumdneum,  which  is 
brownish  red  with  the  end  of  the  abdomen  black  is  the  most  noticeable. 


Fig.  1201. — Nest  of  a  mud-dauber  removed  from 
a  wall  exposing  the  cells:  a,  larva  full-grown;  h, 
cocoon,  c,  young  larva  feeding  on  its  spider- 
meat;  d,  an  empty  cell.  (From  A.  B.  Comstock, 
Handbook  of  Nature  Study.) 


Subfamily  PSENIN^ 

This  subfamily  includes  two  tribes,  the  Psenini  and  the  Pemphre- 
donini;  each  of  these  has  been  regarded  as  a  separate  subfamily  or 
family. 


968 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Tribe  PSENINI 

The  Psenini  are  small  sphecoid-wasps  in  which  the  base  of  the 
abdomen  is  slender,  forming  a  petiole  much  like  that  of  the  Sphecina?, 
but  differing  in  being  flattened  and  usually  furrowed 
above  (Fig.  1202),  and  these  wasps  are  much  smaller 
than  the  true  thread-waisted  wasps.  The  antennas 
are  inserted  at  the  level  of  the  middle  of  the  eyes; 
and  there  are  three  complete  submarginal  cells  in 
the  fore  wings.  These  wasps  make  their  burrows 
either  in  sand  or  in  the  pith  of  brambles,  and  pro- 
vision them  with  aphids  or  other  small  Homoptera. 


Tribe  PEMPHREDONINI 


In  this  tribe  the  antennas  are  inserted  low  on  the 
face,  near  the  level  of  the  base  of  the  eyes ;  and  there  are  at  most  two 
submarginal  cells  present,  sometimes  a  trace  of  vein  r-\-m  and  Rs 


Fig.  1203. — Wings  of  Stigmus  podagric  us.     (From  Bradley). 


incompletely  indicates  a  third  (Fig.  1203).  The  ab- 
domen is  sometimes  sessile. 

The  pemphredonids  usually  burrow  in  the  pith  of 
dry  branches  and  provision  their  burrows  with  plant- 
lice.  A  very  common  species  in  the  East  is  Stigmus 
fraternus.  This  insect  measures  5  mm.  in  length,  and 
makes  tortuous  burrows  in  the  pith  of  sumac  (Fig. 
1204).  Other  common  members  of  the  tribe  are  larger. 
Some  species  of  Xylocelia  {Diodontus)  have  been  found 
to  burrow  in  the  ground. 

This  tribe  was  monographed  by  Fox  ('92). 


Fig.  1204.— 
Nest  of  Stig- 
musfraternus. 


HYMENOPTERA 
Subfamily  BEMBICIN^ 


969 


Tribe  PHILANTHINI 


In  this  tribe  the  upper  margin  of  the  clypeus  is  suddenly  expanded 
into  a  broad  median  lobe,  usually  rhomboidal,  extending  upward 
toward    the    antennae 
(Fig.  1205). 

These  wasps  bur- 
row in  the  ground; 
some  species  provision 
their  nests  with  ants, 
others  with  bees. 


Fig.    1205. — Face    of    £ 
philanthid;  c,  clypeus 


Fig.     1206. — Hind     leg 
Cerceris  clypeata. 


Tribe    CERCERINI 


In    the    Cercerini 

the  hind   femora   are 

broadened  at  the  apex, 

there  forming  a  trans- 
verse reniform  plate  (Fig.  1206);  in  both  male  and  female  there  is  a 
distinct  pygidial  area;  the  transverse  part  of  vein  M  is  distant  from 
the  stigma  by  less  than  twice  the  distance  between  the  apex  of  the 
cell  2dRi-hR,3  and  the  apex  of  the  wing  (Fig.  1207);  and  the  anal 
lobe  of  the  hind  wings  is  large. 


Fig.  1207. — Wings  of  Cerceris. 


The  species  of  Cerceris  usualh'  burrow  in  the  ground  and  provision 
their  nests  with  beetles;  but  some  provision  their  nests  with  bees 
(Halictus) . 

Tribe  NYSSONINI 

In  the'  Nyssonini  the  ocelli  are  never  distorted  and  the  upper 
margin  of  the  clypeus  extends  directly  across  in  a  straight  line  or  an 


970 


AN  INTRODUCTION  TO  ENTOMOLOGY 


arch  without  a  median  lobe.    In  most  genera  the  middle  tibiae  have 
a  single  apical  spur  and  the  second  submarginal  cell  (R5)  is  small 

and  triangular;  but  in 
some  the  middle  tibiae 
have  two  apical  spurs 
and  cell  R5  is  four-sided. 
These  wasps  burrow 
in  the  ground ;  some  spe- 
cies store  their  nests  with 
Homoptera,  others  with 
Orthoptera. 

Our  best-known  rep- 
resentative of  this  tribe 
is   the  Cicada-Killer, 

_.  „  ,     .  .  Sphecius  speciosus.    This 

rig.  1208. — bphectus  speciosns.  ■  r         -j   i_i       •  x 

^  i-  /-  IS    a   formidable    msect, 

measuring  about  30  mm.  in  length  (Fig.  1208).    It  is  black,  sometimes 

of  a  rusty  color,  and  has  the  abdomen  banded  with  yellow.     It  digs 

deep  burrows  in  the  earth  and  provisions  each  with  a  Cicada.     Figure 

1209  represents  its  wings. 


Fig.  1209. — Wings  of  Sphecius  speciosus. 


Tribe  STIZINI 

In  the  Stizini  the  transverse  part  of  vein  M  is  distant  from  the 
stigma  by  two  or  more  times  the  distance  between  the  apex  of 
cell  2dRi+R2  and  the  apex  of  the  wing;  the  labnmi  is  usually 
transverse,  rarely  long  and  pointed;  the  ocelli  are  normal;  and  the 
middle  tibiae  are  armed  with  two  apical  spurs. 

The  species  of  the  genus  Stizus  are  gregarious,  many  individuals 
building  their  burrows  near  together.  The  common  and  conspicuous 
western  Stizus  unicinctus  is  believed  to  lay  eggs  in  nests  of  Chlorion 
(Priononyx)  atratrum. 


ky^fxj 


HYMENOPTERA  971 

Tribe  BEMBICINI 

With  these  wasps  the  ocelH  are  distorted,  the  middle  tibiae  are 
armed  with  only  one  evident  apical  spur;  and  the  labrum  is  elongate, 
pointed,  rostriform  (Fig.  1210). 

Our  best -known  representatives  of  this  tribe  belong  to  the  genus 
Bemhix;  these  are  stout -bodied  wasps,  usually  black  with  greenish 
or  greenish-yellow  bands.  They  burrow  in  the 
sand  and  provision  their  nests  with  flies.  Some 
species  at  least  practise  progressive  provisioning. 
After  excavating  its  burrow  and  making  a  cell, 
the  wasp  captures  a  fly  and  stings  it  to  death, 
then  places  it  on  the  floor  of  the  cell  and  attaches  „ 

an  egg  to  it.     After  the  larva  has  hatched,  the  1 

mother  collects  flies  from  day  to  day,  feeding  the  * 

larva  till  it  is  ready  to  change  to  a  pupa,  closing      Fig-  1210.— Faceof 
the  nest  behind  her  each  time  she  leaves  it.  Bembex:   I,    lab- 

A  common  and  well-known  member   of  this 
tribe  in  the  South  is  Sticta  Carolina,  which  is  called 
the  "horse  guard."    This  is  a  large  species  which  hunts  about  horses 
in  order  to  capture  flies. 

Microhemhex  monodonta  is  one  of  the  most  abundant  of  wasps 
along  the  seashore  everywhere  on  the  Atlantic,  Gulf,  and  Pacific 
coasts.  This  species  is  black  with  greenish-white  markings;  the 
pleurse  and  mesoscutum  are  black  and  the  wings  are  slightly  dusky. 

The  North  American  Bembicini  were  monographed  by  Parker 
('17). 

Subfamily  CRABJIONIN^ 

This  subfamily  differs  from  all  other  Sphecidas  except  the  Try- 
poxylonini  in  having  only  one  submarginal  cell  (Fig.   12 11),  and  it 


Fig.  121 1. — Wings  of  Crabro  singularis;  ap,  appendiculate  cell. 

differs  from  the  Trypoxylonini  in  that  the  inner  margin  of  the  eyes  is 
not  emarginate.  It  includes  two  tribes,  each  of  which  is  classed  as 
a  subfamily  by  some  writers. 


972  AN  INTRODUCTION  TO  ENTOMOLOGY 

Tribe  CRABRONINI 

In  the  Crabronini  the  postscutellmn  and  the  base  of  the  propodeum 
are  unarmed;  the  eyes  are  usually  much  widened  below,  their  inner 
margins  strongly  converging  towards  the  clypeus;  and 
the  longitudinal  free  part  of  vein  M  of  the  fore  wings  is 
complete.  The  head  is  generally  large  and  square  when 
viewed  from  above,  and  sometimes  broader  than  the 
thorax  (Fig.  12 12). 

The  different  members  of  this  tribe  vary  greatly  in 
their  nesting  habits.  Some  mine  in  the  pith  of  such  plants 
as  sumac  and  elder;  some  bore  in  more  solid  wood;  some 
dig  burrows  in  the  ground;  and  others  make  use  of  any 
suitable  hole  they  can  find,  often  the  deserted  burrow  of 
some  other  insect.  These  insects  usually  provision  their  nests  with 
flies. 

The  North  American  Crabronini  was  monographed  by  Fox  ('95). 

Tribe  OXYBELINI 

The  oxybelini  are  easily  distinguished  from  all  other  sphecoid 
wasps  by  the  two  squamae  projecting  back  from  the  metanotirm  and 
by  a  median  spine  borne  by  the  base  of 
the  propodeum  (Fig.  12 13).  The  inner 
margin  of  the  eyes  is  convex,  not  converg- 
ing toward  the  clypeus;  and  the  longi- 
tudinal free  part  of  vein  M  is  lost  or 
present  as  a  trace. 

These  wasps  nest  in  sand  and  provision 
their  nests  with  flies. 

Fig.   i2i3.-Metanotum  and  rj.^^   g^^g 

propodeum     01     Oxyoelus: 


sq.,  squama;  sp.,  spme. 


Super  family  Apoidea  of  Authors 


The  bees  constitute  a  very  large  group  of  insects,  including  besides 
the  well-known  honey-bee  and  the  bumblebees  thousands  of  other 
species,  many  of  which  can  be  observed  visiting  flowers  on  any  pleasant 
stmimer  day.  Friese  ('23)  statesthat  12,000  species  of  bees  have  been 
described,  of  which  2,500  are  from  North  America  and  estimates  that 
there  are  20,000  living  species  in  the  world. 

The  bees  differ  from  all  other  H\Tnenoptera,  except  some  members 
of  a  small  subfamily  of  vespoid  wasps,  the  Masarinas,  in  that  they 
provision  their  nest  with  pollen  and  honey  instead  of  with  animal 
food,  as  do  other  nest-building  Hymenoptera.  The  honey  is  obtained 
from  flowers  in  the  form  of  nectar,  which  is  swallowed  and  trans- 
ported to  the  nest  in  the  crop.  While  in  the  crop  the  nectar  undergoes 
a  chemical  change,  which  is  probably  due  to  a  mixture  with  it  of  a 
ferment  derived  from  the  salivary  glands,  and  becomes  what  is 
known  as  honev. 


HYMENOPTERA 


973 


The  distinctive  characteristics  of  bees  that  have  been  recognized 
are  chiefly  those  that  are  correlated  with  the  habit  of  collecting  pollen 
and  nectar  for  provisioning  their  nests.  These  consist  in  specializa- 
tions of  the  form  and  arrangement  of  some  of  the  hairs,  fitting  them 
for  collecting  and  carrying  pollen;  in  the  dilation  of  the  metatarsus 
of  the  hind  legs,  which  forms  a  part  of  the  pollen-collecting  apparatus; 
and  in  varying  degrees  of  specialization  of  the  maxilla  and  labium  to 
form  a  proboscis  fitted  for  extracting  nectar  from  flowers. 

These  characteristics  are  easily  recognized  in  the  higher  bees,  but 
in  the  most  generalized  bees  (Prosopis)  they  are  feebly  developed, 
and  too  as  male  bees  do  not  collect  and  carry  pollen  to  nests  they  do 
not  possess  organs  for  this  purpose;  this  is  also  true  of  both  sexes 
of  the  parasitic  bees,  the  females  of  which  have  acquired  the  habit 


Fig.  1214. — Hairs  of  various  bees:  a-f,  of  bumblebees;  g-j,  of  Melissodes  sp.;  ^-«, 
of  Megachile  sp.  (After  John  B.  Smith.) 


of  laying  their  eggs  in  the  nests  of  other  bees,  and  consequently,  have 
become  degenerate  so  far  as  their  pollen-collecting  apparatus  is  con- 
cerned. 

A  characteristic  of  bees  found  in  only  a  few  other  Hymenoptera 
is  the  presence,  especially  on  the  thorax,  of  plumose  hairs.  Many 
forms  of  these  hairs  exist ;  some  of  them  are  represented  in  Figure  1 2 14. 
In  this  figure  there  is  also  represented  (Fig.  12 14,  n)  another  type  of 
hair  which  is  spirally  grooved;  this  type  is  found  in  the  pollen  brush 
of  leaf-cutter  bees,  Megachilida.  It  has  been  suggested  that  the 
pltmiose  hairs  serve  to  hold  the  grains  of  pollen  that  become  en- 
tangled among  them  when  a  bee  visits  a  flower;  but  they  occur  in 
males  and  in  parasitic  bees  neither  of  which  gathers  pollen;  they 
are  lacking,  however,  in  some  parasitic  bees. 


974 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Female  bees,  excepting  those  of  the  genus  Prosopis  and  of  the 
parasitic  bees,  are  furnished  with  pollen-brushes  or  scopce,  for  collect- 
ing and  transporting  pollen.  In  most  bees  these  consist  of  brushes  of 
hairs  borne  by  the  hind  legs,  but  in  the  Megachilidae  the  brush  is  on 
the  ventral  side  of  the  abdomen. 

In  some  bees  the  pollen  brushes  are  restricted  to  the  tibia  and  the 
metatarsus  of  the  hind  legs,  in  others  they  are  borne  on  these  two 
segments  and  on  the  femur,  trochanter  and  coxa  as  well  (Fig.  12 15). 
With  the  queens  and  workers  of  the  nest-building  bumblebees  and 
with  the  workers  of  the  honey-bee  the  pollen  carr^'ing  apparatus  is 


Fig.  12 15. — Hind  leg  of 
female  of  Colletes.  (From 
Brane.) 


Fig.  12 16. — A.  Inner  surface  of  the  left  hind  leg 
of  a  worker  honey-bee;  B.  Outer  surface  of 
the  same.     (After  D.  B.  Casteel.) 


very  highly  specialized  (Fig.  1 2 16).  On  the  outer  surface  of  the  tibia 
of  the  hind  legs  there  is  a  smooth  area  which  is  margined  on  each  side 
by  a  fringe  of  long  curved  hairs;  this  structure  is  known  as  the  pollen 
basket  or  corMcula;  and  on  the  inner  surface  of  the  metatarsus, 
termed  planta  by  some  writers,  there  is  a  brush  of  stiff  hairs  by  means 
of  which  the  bee  gathers  the  pollen  from  its  body.  In  the  honey-bee 
the  hairs  composing  this  brush  are  arranged  in  transverse  rows  and 
are  termed  the  pollen  combs. 

The  mouth-parts  differ  greatly  in  form  in  the  different  groups  of 
bees ;  this  is  especially  true  of  the  maxillag  and  labitmi,  which  together 
constitute  the  proboscis,  used  for  extracting  nectar  from  flowers. 
The  mandibles  are  fitted  for  chewing  and  do  not  vary  so  much  in 
form. 


HYMENOPTERA 


975 


In  the  most  generalized  bees,  the  Prosopidae,  the  proboscis  is  com- 
paratively short  and  the  labiimi  is  either  notched  at  the  tip  (Prosopis, 
Fig.  12 1 7)  or  is  quite  deeply  bifid  (Colletes,  Fig.  12 18).  In  all  other 
bees  the  labium  is  pointed  at  the  tip.  Among  the  bees  with  a  pointed 
labium  the  proboscis  varies  greatly  in  length;  in  some  (Sphecodes, 
Fig.  1 2 19)  it  is  comparatively  short,  while  in  the  more  specialized 
forms,  as  in  Apis  (Fig.  1220)  it  is  greatly  elongate. 


Fig.  1217. — Pro- 
boscis of  Pro- 
sopis. (After 
Saunders.) 


Fig.  12 1 8. — Probos- 
cis of  Colletes. 
(After  Saunders.) 


Fig.  1220. — La- 
bium of  the 
honey-bee.  (Af- 
ter Saunders.) 


The  two  sexes  of  bees  differ  in  the  number  of  abdominal  tergites 
exposed  to  view;  in  the  male  there  are  seven,  in  the  female,  only  six. 

The  different  species  of  bees  exhibit  great  differences  in  habits; 
some  are  solitary;  each  female  providing  a  nest  for  her  young; 
some  are  parasitic,  the  females  laying  their  eggs  in  the  nests  of  other 
bees  and  the  larvae  feeding  on  the  provisions  stored  by  their  hosts; 
and  some  are  social,  living  in  colonies  consisting  of  many  individuals. 

The  social  bees  are  the  honey-bees,  the  bumblebees,  and  the 
stingless  honey-bees  of  the  Tropics.    In  all  of  these,  as  with  the  social 


976  AN  INTRODUCTION  TO  ENTOMOLOGY 

wasps  and  the  ants,  there  is  in  addition  to  the  males  and  the  egg- 
laying  females  a  worker  caste ;  with  all  other  bees  there  are  only  two 
forms,  the  males  and  the  females. 

The  parasitic  bees  do  not  constitute  a  natural  division  of  the 
group  of  bees,  as  was  formerly  supposed,  instead  of  that  it  is  evident 
that  members  of  several  of  the  families  of  bees  have  acquired  the 
parasitic  habit.  The  bees  of  the  genus  Psithyrus,  which  are  parasitic 
in  the  nests  of  bumblebees,  are  closely  allied  to  the  bumblebees  and 
should  be  placed  with  them  in  the  family  Bombidae;  the  parasitic 
genera  Stelis  and  Coelioxys  are  evidently  members  of  the  leaf -cutter- 
bee  family,  the  Megachilidse ;  and  there  are  many  parasitic  genera 
belonging  to  the  family  Andrenidse. 

The  nests  of  solitary  bees,  like  those  of  the  digger-wasps,  are  of 
many  forms.  The  mining-bees  dig  tunnels  in  the  ground ;  the  mason- 
bees  build  nests  of  mortar-like  material;  the  carpenter-bees  make 
tunnels  in  the  stems  of  pithy  plants  or  bore  in  solid  wood ;  and  some 
bees  make  nests  of  comminuted  vegetable  matter.  The  distinctive 
characteristic  of  the  nests  of  bees  is  the  fact  that  they  are  always 
provisioned  with  honey  and  pollen.  In  many  cases  closely  allied  spe- 
cies of  bees  differ  in  their  nesting  habits;  for  example,  different  spe- 
cies of  the  genus  Osmia  build  very  different  kinds  of  nests. 

Although  many  entomologists  have  studied  the  bees  intensively, 
no  classification  of  them  has  been  proposed  that  is  generally  ac- 
cepted. Some  writers  regard  them  as  constituting  a  single  family, 
the  Apidse;  other  writers  recognize  several  families  and  restrict  the 
term  Apidae  to  the  honey-bee  family ;  but  these  writers  differ  among 
themselves  as  to  the  number  of  families  that  should  be  recognized. 

When  several  families  of  bees  are  recognized  they  are  commonly 
grouped  together  as  the  superf amily  Apoidea ;  but  the  writers  whose 
classifications  I  have  adopted  believe  that  the  bees  are  a  group  of 
sphecoid  wasps  that  have  acquired  the  habit  of  provisioning  their 
nests  with  honey  and  pollen,  and  should  not,  merely  for  this  reason, 
be  placed  in  a  separate  superf  amily.  An  analogous  case  is  that  of 
the  subfamily  Masariuce  some  members  of  which  differ  from  other 
Vespidas  in  nest-provisioning  habits  in  the  same  way  that  bees  differ 
from  other  sphecoid  wasps. 

Family  PROSOPID^ 
The  Bifid-tongued  Bees 

The  members  of  this  family  differ  from  all  other  bees  in  having 
the  tip  of  the  labium  either  shallowly  emarginate  at  the  apex  or  deeply 
bifid.  In  all  of  them  the  labiimi  is  comparatively  short.  This  family 
has  been  commonly  known  as  the  wasp-like  bees.  It  includes  two 
quite  distinct  subfamilies. 

Subfamily  PROSOPIN^ 
This  subfamily  is  represented  in  our  fauna  by  a  single  genus, 
Prosopis.     The  members  of  this  genus,  of  which  there  are  many 


HYMENOPTERA  977 

Species,  are  small  black  bees,  with  pale,  usually  yellow,  marks.  They 
are  the  least  specialized  of  the  bees.  The  body  is  almost  bare,  but  an 
examination  with  a  microscope  will  reveal  the  presence  on  the  thorax 
of  a  few  of  the  plumose  hairs  characteristic  of  bees;  the  labium  is 
short  and  broad  and  shallowly  emarginate  at  the  apex  (Fig.  12 17) 
and  the  hind  legs  of  the  females  are  not  furnished  with  pollen  brushes. 

The  numerous  species  of  this  genus  build  nests  in  the  stems  of 
pithy  plants,  or  in  burrows  in  the  ground,  or  in  crevices  in  walls. 
I  have  found  them  in  dead  branches  of  sumac.  In  some  cases,  at 
least,  the  burrow  used  was  an  old  burrow  made  by  some  other  pith- 
mining  bee  or  wasp.  After  the  burrow  is  made  or  selected,  the  walls 
of  it  are  coated  with  a  glistening  substance,  probably  silk,  which  is 
sometimes  dense  enough  to  form  a  distinct  membrane.  Then  a  cell 
is  formed  at  the  bottom  of  the  burrow  of  the  same  material;  and  at 
the  bottom  of  the  cell  a  denser  circular  disk  is  spun,  which  makes  a 
quite  firm  partition,  the  edges  of  which  extend  slightly  up  the  sides 
of  the  cell. 

The  cell  is  provisioned  with  a  semi-liquid  paste  consisting  largely 
of  honey  but  containing  also  some  pollen.  It  is  said  that  when  collect- 
ing provisions  for  its  nest  the  bee  swallows  both  pollen  and  nectar, 
brushing  the  pollen  to  the  mouth  by  aid  of  the  front  legs. 

Usually  several  cells  are  made,  one  above  another,  in  the  burrow; 
although  the  walls  of  the  cells  are  quite  delicate,  the  cells  are  firmly 
separated  by  the  dense  silken  partition  at  the  bottom  of  each. 

Subfamily  COLLETIN^ 

In  this  subfamily  the  labium  is  short,  and  deeply  emarginate  at 
the  apex;  (Fig.  12 18).  The  body,  especially  the  head  and  thorax,  is 
more  or  less  densely  clothed  with  hair;  and  in  the  female  the  hind 
legs  are  furnished  with  pollen -brushes.  Our  most  common  repre- 
sentatives belong  to  the  genus  Colletes. 

Colletes. — In  most  species  of  this  genus  the  abdomen  is  marked 
with  pubsecent  white  bands.  All  of  the  species,  the  habits  of  which 
have  been  described,  burrow  in  soil,  either  that  which  is  level  or  in 
banks,  or  sometimes  in  the  interstices  of  walls.  In  favorable  situ- 
ations, some  of  the  species  are  gregarious,  many  individuals  digging 
their  tunnels  in  a  limited  area.  Sharp  ('99)  in  writing  of  Colletes 
states :  "They  have  a  manner  of  nesting  peculiar  to  themselves;  they 
dig  cylindrical  burrows  in  the  earth,  line  them  with  a  sort  of  slime, 
that  dries  to  a  substance  like  gold-beater's  skin,  and  then  by  partitions 
arrange  the  burrow  as  six  to  ten  separate  cells,  each  of  which  is  filled 
with  food  that  is  more  liquid  than  usual  in  bees." 

Professor  J.  B.  Smith  ('01)  in  his  account  of  Colletes  compdcta 
states  that  this  species  digs  a  burrow  which  extends  from  18  to  28 
inches  down;  from  this,  lateral  branches  from  two  to  six  inches  in 
length  are  made,  at  the  end  of  each  of  which  a  cell  is  formed.  The 
bee  begins  making  cells  from  the  bottom  of  the  burrow  and  works  up, 
never  making  more  than  four  and  rarely  more  than  two  cell-bearing 


978  AN  INTRODUCTION  TO  ENTOMOLOGY 

laterals  from  one  upright.     How  many  such  burrows  an  individual 
female  may  make  was  not  determined. 

Family  ANDRENID^ 
The  Andrenids 

The  family  includes  those  solitary  nest-building  bees  and  their 
parasitic  allies  in  which  the  tongue  is  either  short  or  long  but  is 
pointed  at  the  apex,  and  in  which  the  pollen-brushes  of  the  nest- 
building  females  are  borne  by  the  hind  legs.  To  this  family  belong  a 
large  portion  of  the  species  and  genera  of  our  bees.  Space  can  be 
taken  here  to  discuss  only  a  few  of  these. 

Haltctus. — Among  the  more  common  of  our  mining  bees  are  those 
of  the  genus  Halictus.  This  is  a  large  genus  including  very  many 
species,  among  which  are  the  smallest  of  our  bees.    The  nests  of  some 


Fig.  1 22 1. — Diagram  of  part  of  a  nest  of  Halictus. 

species  are  excavated  in  level  ground;  other  species  dig  tunnels  in 
the  vertical  sides  of  banks.  These  bees  are  often  gregarious,  hundreds 
of  nests  being  built  near  together  in  the  side  of  a  bank. 

If  these  nests  be  studied  in  midsimimer,  each  will  be  found  to 
consist  of  a  burrow  extending  into  the  bank  (Fig.  1221)  and,  along 
the  sides  of  this  main  burrow  or  corridor,  smaller  short  burrows  each 
leading  to  a  cell,  the  sides  of  which  are  lined  with  a  thin  coating  of 
firm  clay.  In  each  of  these  cells  that  is  closed  will  be  found  either  a 
mass. of  pollen  and  nectar  with  an  egg  upon  it  or  a  larva  feeding  on 
the  food  stored  for  it. 

The  most  striking  feature  of  these  nests  is  the  fact  that  several 
bees  use  the  corridor  as  a  passage  way  to  the  cells  they  are  building 
and  provisioning.  But  this  corridor  is  not  a  public  one;  it  is  con- 
stricted at  its  outer  end  and  is  guarded  by  a  sentinel  whose  head 
nearly  fills  the  opening.  When  a  bee  comes  that  has  a  right  to  enter 
the  sentinel  backs  into  the  wider  part  of  the  corridor  and  allows  it 


IIYMENOPTERA  979 

to  pass  and  immediately  thereafter  resumes  its  j^uardin^  position 
with  its  head  closing  the  opening  of  the  corridor. 

The  explanation  of  this  association  of  several  bees,  in  a  single 
nest  was  worked  out  by  Fabre.  He  found  that  in  the  spring  each 
female  Halictus  that  has  survived  the  winter  makes  a  nest  and  rears 
a  brood.  Then  the  old  bee  and  the  young  ones  together  clean  out 
the  nest,  enlarge  it,  and  use  it  as  a  carefully  guarded  apartment  house, 
each  bee  having  her  own  group  of  cells. 

Halictus  (Augochldra). — A  detailed  account  of  the  habits  of  one 
species  of  this  subgenus,  A.  hunierdlis,  was  given  by  Professor  J.  B. 
Smith  ('oi).  This  species  is  a  mining  bee  which  digs  very  deep 
burrows.  Certain  other  species  of  this  genus  have  very  different 
nesting  habits.  These  burrow  in  decomposing  sap-wood  beneath 
the  bark  of  trees  and  make  their  cells  of  bits  of  decayed  wood  agglu- 
tinated together. 

Anthophora.- — The  genus  Anthophora  is  widely  distributed  and 
includes  many  species,  more  than  eighty  have  been  described  from 
North  America  alone;  but  the  habits  of  only  a  few  of  these  have 
been  described. 

The  nests  of  those  American  species  the  habits  of  which  are  well 
known  are  usually  built  in  steeply  inclined  or  perpendicular  banks  of 
earth,  preferably  in  those  of  compact  clay;  they  are  also  excavated 
in  the  clumps  of  clay  held  between  the  roots  of  stumps  in  stump- 
fences.  In  the  West  a  favorite  nesting  place  of  these  bees  is  in  the 
walls  of  sun-dried  bricks  of  the  adobe  houses.  Like  Halictus  and 
Andrena,  the  bees  of  this  genus  are  gregarious,  hundreds  of  individuals 
building  their  nests  close  together  in  the  same  bank  of  earth. 

A  striking  feature  of  these  nests  is  the  presence  of  a  cylindrical 
tube  of  clay  extending  outward  and  downward  from  the  entrance  of 
the  tunnel  (Fig.  1222).  This  tube  is  rough  on  the  outside  but  smooth 
within.  It  is  composed  of  small  pellets  of  earth  compacted  together. 
These  pellets  when  brought  out  from  the  tunnel  are  wet  and  easily 
molded  into  the  desired  form,  but  soon  become  dry  and  firm.  The 
wetness  of  the  pellets  of  clay  brought  out  from  the  tunnel  in  a  hard  dry 
bank  is  explained  by  the  fact  that  these  bees  when  nest-building  go 
to  some  place  where  water  can  be  had  and  after  lapping  up  a  supply 
of  it  fly  to  their  nest.  This  water  is  obviously  used  for  softening  the 
hard  clay  (Frison  '22). 

The  tunnel  extends  into  the  bank  a  variable  distance  and  leads 
to  a  cluster  of  oval  cells.  The  layer  of  earth  forming  the  wall  of  a  cell 
is  made  firm  by  some  cementing  substance;  this  is  shown  by  the  fact 
that  when  a  lump  of  earth  containing  nests  is  broken  apart  the  cells 
retain  their  form  and  may  be  readily  separated  from  the  earth  sur- 
rounding them.  Nininger  ('20)  in  his  notes  on  the  life-history  of 
Anthophora  stanfordidna  state:  "At  the  bottom  of  a  tunnel  five  to 
seven  inches  deep,  the  bee  excavated  an  oval  chamber  about  three- 
fourths  inch  in  diameter  by  one  inch  deep,  and  then  built  up  within 
this  a  nest-cell  to  fit,  made  of  pellets  of  clay  and  worked  smooth  on 
the  inner  side,  after  which  it  was  coated  with  a  thin  layer  of  water- 
proofing which  seemed  to  be  a  salivary  secretion." 


980 


AN  INTRODUCTION  TO  ENTOMOLOGY 


The  water-proofing  of  the  wall  of  the  cell  is  an  essential  feature 
for  without  it  the  semi-fluid  mass  of  pollen  and  nectar  with  which 
the  cell  is  provisioned  would  be  partially  absorbed  by  the  wall  of 
the  cell. 


Fig.   1222. — Section  of  a  bank  with   nests  of   Anthophora. 
Miss  P.  B.  Fletcher.) 


(Photographed  by 


The  larvae  remain  in  their  cells  throughout  the  winter,  and  trans- 
form to  pupas  in  the  spring.  The  duration  of  the  pupa  state  is  short, 
the  adult  bees  appearing  early  in  the  summer.  The  parasitic  beetles 
Hornia  are  often  found  in  the  nests  of  Anthophora. 

Andrena. — Among  the  larger  of  our  common  mining  bees  are 
certain  species  of  the  genus  Andrena;  some  of  these  nearly  or  quite 
equal  in  size  the  workers  of  the  honey-bee.  They  build  their  nests  in 
road  sides  and  in  fields  that  support  a  scanty  vegetation.  They  sink 
a  vertical  shaft  with  broad  cells  branching  from  it.  These  bees, 
though  strictly  solitary,  each  female  building  her  own  nest,  frequently 
build  their  nests  near  together,  forming  large  villages.  I  once  re- 
ceived from  a  correspondent  a  description  of  a  collection  of  nests  of 
this  kind  which  was  fifteen  feet  in  diameter,  and  in  the  destruction  of 
which  about  two  thousand  bees  were  killed;  what  a  terrible  slaughter 
of  innocent  creatures ! 

The  small  carpenter-bee,  Cerdtina  diipla.- — The  nests  of  this  bee 
are  built  in  dead  twigs  or  stimac  and  in  the  hollows  of  brambles  and 
other  plants.  They  are  more  common  than  those  of  any  other  of  our 
solitary  bees  that  build  in  these  situations.    This  is  a  dainty  httlebee, 


HYMENOPTERA 


981 


about  6  mm.  in  length,  and  of  a  metallic  blue  color.  She  always  selects 
a  twig  with  a  soft  pith  which  she  excavates  with  her 
mandibles,  and  so  makes  a  long  tunnel.  Then  she 
gathers  pollen  and  nectar  and  puts  it  in  the  bottom 
of  the  nest,  lays  an  eg:g  on  it,  and  then  makes  a  parti- 
tion out  of  pith-chips,  which  serves  as  a  roof  to  this 
cell  and  a  floor  to  the  one  above  it.  This  process  she 
repeats  until  the  tunnel  is  nearly  full  (Fig.  1123),  then 
she  rests  in  the  space  above  the  last  cell,  and  waits  for  her 
young  to  grow  up.  The  lower  one  hatches  first ;  and 
after  it  has  attained  its  growth,  it  tears  down  the 
partition  above  it,  and  then  waits  patiently  for  the 
one  above  to  do  the  same.  Finally  after  the  last  one 
in  the  top  cell  has  matured,  the  mother  leads  forth 
her  full-fledged  family  in  a  flight  in  the  sunshine.  After 
the  last  of  the  brood  has  emerged  from  its  cell,  the 
substance  of  which  the  partitions  were  made,  and  which 
has  been  forced  to  the  bottom  of  the  nest  by  the  young 
bees  when  making  their  escape,  is  cleaned  out  by  the 
family,  the  old  bee  and  the  young  ones  all  working 
together.  Then  the  nest  is  used  again  by  one  of  the 
bees.  I  have  collected  hundreds  of  these  nests  and  by 
opening  different  nests  at  different  seasons,  have  gained 
an  idea  of  what  goes  on  in  a  single  nest.  There  are 
two  broods  each  year.  The  mature  bees  of  the  fall 
brood  winter  in  the  nests. 


Fig.  1223.— 
Nest  of  Cer- 
atina  diipta. 


The  large  carpenter-bee,  Xylocopavirginica: — This  is  a  large  insect, 
measuring  from  22  to  24  mm.  in  length  and  resembling  a  bumblebee 
in  size,  and  somewhat  in  appearance.  But  it  can  be  easily  distin- 
guished from  a  bumblebee,  as  the  female  has  a  dense  brush  of  hairs 
on  the  hind  leg,  instead  of  a  basket  for  carrying  pollen.  This  bee 
builds  its  nest  in  solid  wood,  and  sometimes  excavates  a  tunnel  a 
foot  in  length,  which  it  divides  into  several  cells.  The  partitions 
between  the  cells  are  made  of  chips  of  wood,  securely  cemented 
together,  and  arranged  in  a  closely-wound  spiral.  This  arrangement 
of  chips  is  easily  seen  when  the  lower  side  of  a  partition  is  examined ; 
but  the  upper  side  of  a  partition  which  forms  the  floor  of  the  cell  above 
it  is  made  concave  and  very  smooth,  so  that  the  arrangement  of  the 
chips  is  not  visible.  The  nest  of  Monobia  quadridens  described  on  an 
earlier  page  (Fig.  11 88)  was  probably  made  in  a  deserted  tunnel  of 
Xylocopa.   Mowotza,  however,  makes  the  partitions  of  its  nest  of  mud. 

This  species  is  distributed  generally  throughout  the  United  States 
and  is  the  only  species  of  Xylocopa  found  in  the  Northeastern  part 
of  this  country.  Eight  other  species  have  been  described  from  the 
South  and  the  West.  A  monograph  of  the  species  of  Xylocopa  of  the 
United  States  was  published  by  Ackerman  (16). 


982 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Family  MEGACHILID^ 

The  Leaf -cutter  Bees  and  their  Allies 

To  this  family  belong  those  bees  in  which  the  pollen  brush  of  the 
female  is  borne  on  the  ventral  side  of  the  abdomen  and  the  parasitic 
bees  that  are  allied  to  them.  In  this  family  the  tongue  is  long  and 
there  are  only  two  submarginal  cells  of  approximately  equal  size  in 
the  fore  wings.  Among  the  better-known  representatives  of  the 
family  are  the  following. 

The  leaf-cutter  bees,  Megadnk. — The  bees  of  the  genus  Megachile 
have  a  curious  habit  of  making  cells  for  their  young  out  of  neatly-cut 
pieces  of  leaves.  These  cells  are  packed  away  in  such  secure  places 
that  one  does  not  often  find  them ;  but  it  is  a  verv^  easy  thing  to  find 


ts^m;' 


Fig.  1224. — A  leaf-cutter  bee,  Megachila  latimanus,  its  nest,  and  rose-leaves  cut 
by  the  bee. 

fragments  of  leaves  from  which  the  pieces  have  been  cut  by  bees. 
The  leaves  of  various  plants  are  used  for  this  purpose,  but  rose-leaves 
are  used  more  frequently  than  any  other  kind.  In  Figure  1224  there 
are  represented  one  of  these  bees,  its  nest,  and  a  spray  of  rose-leaves 
from  which  pieces  have  been  cut  by  the  bee. 

The  nests  are  made  in  various  situations.  The  specimen  figured 
was  taken  from  a  piece  of  hemlock  timber  in  which  many  of  these  bees 
had  bored  tunnels  to  receive  their  cells.  I  have  also  found  nests  of 
these  bees  in  a  tunnel  in  the  ground  under  a  stone,  between  shingles 


HYMENOPTERA  983 

on  a  roof,  in  the  cavity  of  a  large  branch  of  sumac,  in  the  cavity  of 
a  lead  pipe,  and  in  Florida  in  the  tubular  leaves  of  a  pitcher-plant. 

When  a  suitable  tunnel  has  been  made  or  found  the  bee  proceeds 
to  build  a  thimble-shaped  tube  at  the  bottom  of  it.  For  this  purpose 
it  cuts  from  leaves  oblong  pieces,  each  of  which  forms  a  part  of  a  side 
and  the  bottom  of  the  thimble-shaped  tube.  Two  such  pieces  had 
been  cut  from  the  lower  leaf  on  the  left  side  of  the  spray  figured  here. 
When  the  thimble-shaped  tube  is  completed,  the  bee  partially  fills 
it  with  a  paste  of  pollen  and  honey,  and  then  places  an  egg  upon  the 
supply  of  food.  She  then  cuts  several  circular  pieces  of  leaves,  the 
diameter  of  which  is  a  little  greater  than  the  diameter  of  the  tube, 
and  forces  them  into  the  open  end  of  it,  thus  making  a  tightly  fitting 
plug;  three  of  these  circular  pieces  have  been  cut  from  the  spray 
figured.  Usually  several  cells  of  this  kind  are  placed  end  to  end  in  a 
burrow;  and  sometimes  many  bees  will  build  their  nests  near  to- 
gether in  the  same  piece  of  wood. 

Akiddmea  producta. — Among  the  more  common  members  of  the 
Megachilidee  is  this  species  which  builds  its  nests  in  branches  of  sumac 
and  other  pithy  plants.  I  have  collected  many  of  the  nests  during 
winter,  from  which  the  bees  emerged  the  following  spring.  A  dis- 
tinctive feature  of  the  nest  is  the  fact  that  the  partitions  between 
the  cells  are  composed  of  comminuted  plant  fibers.  The  larva  when 
full-grown  spins  a  silken  cocoon,  which  fills  the  cell.  The  adult  is  a 
black  bee,  7  mm.  long,  with  white  marginal  bands  on  the  abdominal 
segments;  these  are  often  interrupted  on  the  middle  line. 

Trachusa  lateralis.- — This  is  a  parasitic  species  which  is  very  com- 
mon in  the  nests  of  Alcidamea  producta.  This  bee  is  somewhat 
smallerthan  its  host  and  has  on  each  side  of  the  three  basal  abdominal 
segments  a  rather  small  ovate  yellowish-white  spot.  The  cocoons  of 
this  species  are  denser  than  those  of  Alcidamea  producta,  do  not  fill 
the  cell,  and  bear  at  the  apex  a  tiny  nipple. 

Other  illustrations  of  the  habits  of  members  of  this  family  can  be 
referred  to  here  only  briefly. 

The  petals  of  various  flowers  and  especially  those  of  Pelargonium 
often  have  pieces  cut  from  them  shaped  like  those  cut  from  the  leaves 
of  rose  by  the  leaf-cutter  bees.  This  is  probably  the  work  of  some 
species  of  Osmia,  as  certain  European  species  of  this  genus  are  known 
to  build  in  their  burrows  thimble-shaped  tubes  resembling  those  of 
the  leaf-cutter  bees,  except  that  they  are  composed  of  pieces  of 
petals. 

Other  species  of  Osmia  make  their  cells  of  comminuted  vegetable 
fibers.  These  are  placed  in  various  situations.  There  are  in  our 
collection  several  old  cells  of  mud-wasps  in  each  of  which  are  several 
cells  of  this  kind,  from  which  were  bred  a  small  species  of  Osmia. 

Some  species  of  Osmia  make  use  of  empty  shells  of  snails.  Helix, 
in  which  to  build  their  cells,  and  some  European  species  are  known  to 
cover  the  snail  shell  thus  used  with  a  mound  of  fragments  of  grass 
or  of  pine  needles. 


984  AN  INTRODUCTION  TO  ENTOMOLOGY 

Many  bees  make  their  cells  of  a  cement-like  substance  made  of  a 
mixture  of  earth  and  some  fluid  which  is  believed  to  be  secreted  by 
the  salivary  glands.  These  bees  are  commonly  known  as  the  mason- 
bees. 

The  firm-cement-like  nature  of  the  nests  of  some  of  the  mason- 
bees  leads  to  the  belief  that  the  earth  of  which  they  are  made  is  mixed 
with  some  other  fluid  than  water.  They  are  much  firmer  than  are 
the  tubes  built  by  Anthophora,  which  are  made  of  a  mixture  of  earth 
and  water. 

A  remarkable  accumulation  of  the  nests  of  an  Old  World  species 
of  mason-bee,  known  as  the  wall-bee,  Ckalicodoma  nniraria,  was  ob- 


Fig.  1225. — Nests  of  the  wall-bee  on  the  Temple  of  Dendera. 

served  by  the  writer  on  the  walls  of  the  Temple  of  Dendera  in 
Egypt.  This  temple,  which  was  buried  by  drifting  sands  long  ago 
has  been  excavated  by  modern  archaeologists;  but  the  inscriptions 
on  the  walls  of  the  temple  are  being  rapidly  buried  again  beneath  a 
layer  of  the  cement-like  nests  of  the  wall-bee  (Fig.  1225). 

Family  BOMBID^ 
The  Bumblebees 

The  family  Bombidas  includes  the  well-known  nest-building 
btimblebees  and  certain  parasitic  bumblebees,  Pstthyrus,  that  infest 
the  nests  of  the  nest-building  species.     The  members  of  this  family 


HYMENOPTERA  985 

are  large  bees  or  of  medium  size;  they  are  robust  with  oblong  bodies 
and  a  rather  dense  covering  of  hair.  They  are  common,  and  are 
conspicuous  on  account  of  their  noisy  flight  and  striking  coloration, 
which  is  usually  yellow  and  black.  Thev  are  called  bumblebees  on 
account  of  the  sound  they  make  in  flight;  in  England  they  are 
commonly  known  as  bumblebees. 

The  distinctive  characters  of  this  family  are  given  in  the  table  of 
the  Clistogastra  on  page  912.  Most  writers  recognize  only  two 
genera  in  the  Bombidae,  Bomhiis  and  Psithyrus;  but  some  have  sepa- 
rated certain  species  from  Bomhus  and  placed  them  in  a  separate 
genus,  Bomhias.  As  there  is  considerable  doubt  regarding  the  validity 
of  this  genus  it  will  not  be  discussed  here. 

The  nest-building  bumblebees,  Bombiis.- — The  members  of  this 
genus  are  social  insects,  each  species  consisting  as  in  other  social  in- 
sects of  three  castes,  the  queens,  the  workers,  and  the  males.  In 
this  genus  the  queens  as  well  as  the  workers  possess  pollen-baskets  or 
corbiculje  on  the  hind  legs;  as  the  queen  when  founding  a  colony 
must  collect  pollen. 

With  the  bumblebees  the  queens  are  larger  than  either  the  workers 
or  the  males  and,  in  temperate  regions,  are  the  only  ones  that  live 
through  the  winter;  as  in  these  regions  the  colonies,  like  those  of  our 
northern  species  of  social  wasps,  break  up  in  the  autumn  and  all  of 
the  bees,  except  the  young  queens  perish.  These  crawl  away  into 
some  protected  place  and  pass  the  w^inter.  In  the  spring  each  queen 
that  has  survived  the  winter  founds  a  new  colony,  performing,  until 
a  brood  of  workers  has  been  developed,  both  the  duties  of  queen  and 
of  worker.  In  South  America,  where  according  to  von  Ihering, 
bumblebee  colonies  are  perennial,  new  nests  are  formed  by  swarming 
as  among  the  social  wasps  of  the  same  region. 

In  selecting  a  place  for  her  nest  the  queen  usually  chooses  a 
deserted  mouse-nest,  within  which  she  builds  her  nest;  sometimes  an 
old  bird's  nest  is  used  for  this  purpose.  In  certain  European  species 
the  queen,  sometimes  at  least,  constructs  her  nest  entirely  without 
making  use  of  a  nest  of  another  animal.  This  she  does  by  making 
use  of  moss  or  soft  dead  grass,  which  she  combs  together  with  her 
mandibles  and  legs,  for  this  reason  these  species  are  often  known  as 
"carder-bees." 

Many  observers  have  studied  the  founding  and  development  of 
colonies  of  bimiblebees;  among  these  is  Sladen  ('12)  who  has  made 
very  detailed  studies  of  the  species  found  in  England.  The  following 
condensed  summary  is  based  on  the  statements  of  this  author. 

Having  found  a  suitable  nest  the  queen  spends  a  good  deal  of 
time  in  it,  the  heat  of  her  body  gradually  making  its  interior  perfectly 
dry.  She  then  gathers  the  finest  and  softest  material  she  can  find  into 
a  heap  and  in  the  center  of  this  makes  a  cavity  with  an  entrance  at 
the  side  just  large  enough  for  her  to  pass  in  and  out.  In  the  center  of 
the  floor  of  this  cavity  she  forms  a  lump  of  paste  made  of  pollen 
moistened  with  honey.  Upon  the  top  of  this  lump  she  builds  with  her 
jaws  a  circular  wall  of  wax,  and  in  the  little  cell  so  formed  she  lays 


986 


AN  INTRODUCTION  TO  ENTOMOLOGY 


her  first  batch  of  eggs,  and  seals  it  over  with  wax.  The  queen  now 
sits  on  her  eggs  day  and  night  to  keep  them  warm,  only  leaving  them 
to  collect  food  when  necessary.  In  order  tomaintain  animation  and 
heat  through  the  night  and  "in  bad  weather  when  food  cannot  be 
obtained,  it  is  necessary  for  her  to  lay  in  a  store  of  honey.  She  there- 
fore sets  to  work  to  construct  a  large  waxen  pot  to  hold  the  honey. 
This  pot  is  built  in  the  entrance  passage  of  the  nest  (Fig.  1226). 
The  eggs  hatch  four  days  after  they  are  laid.  The  larvae  devour 
the  paste  which  forms  their  bed  and  also  fresh  food  furnished  by  the 
queen.  To  feed  the  larva  the  queen  makes  a  small  hole  with  her 
mandibles  in  the  skin  of  wax  that  covers  them.  While  the  larvae 
remain  small  they  are  fed  collectively,  but  when  they  grow  large  they 
are  fed  individually.  As  the  larvae  grow  the  queen  adds  wax  to  their 
covering,  so  that  they  remain  hidden.  When  the  larvae  are  full- 
grown,  each  one  spins  around  itself  an  oval  cocoon,  which  is  thin  and 


pollen  and  e^^^ 


honey-pot 


Fig. 


honey pol 
poJien  and  eqys 

226. — Honey-pot.     (From  Sladen.) 


papery  but  very  tough.  The  queen  now  clears  away  most  of  the 
brown  wax  covering,  revealing  the  cocoons,  which  are  pale  yellow. 
These  first  cocoons  number  from  seven  to  sixteen,  according  to  the 
species  and  the  prolificness  of  the  queen .  These  cocoons  are  incubated 
by  the  queen,  who  spends  much  time  sitting  on  them,  with  her 
abdomen  stretched  to  about  double  its  usual  length  so  that  it  will 
cover  as  many  cocoons  as  possible. 

The  bees  that  are  developed  during  the  early  part  of  the  summer 
are  all  workers;  these  relieve  the  queen  of  all  duties  except  laying  the 
eggs.  They  feed  the  larvae,  construct  honey-pots  and  special  recep- 
tacles for  pollen  or  store  these  substances  in  cocoons  from  which 
workers  have  emerged.  The  appearance  of  a  nest  in  mid-summer  is 
represented  by  Figure  1227.  Later  in  the  summer  males  and  queens 
are  developed;  and  in  the  autiimn  the  colony  breaks  up. 

The  bumblebees  play  a  very  important  role  in  the  fertilization  of 
certain  flowers,  as  those  of  red  clover,  in  which  the  tubular  corolla 
is  so  long  that  the  nectar  can  not  be  reached  by  bees  with  shorter 
tongues. 

A  monograph  of  the  Bombids  of  the  New  World  was  published 
by  Franklin  ('i2-'i3). 


HYMENOPTERA  987 

The  parasitic  bumblebees,  Pstthyrus. — To  this  j^enus  belong  those 
parasitic  bees  that  infest  the  nests  of  bumblebees.  They  closely  re- 
semble bumblebees  in  aj^pearance  and  in  structure,  except  that,  as 
in  other  parasitic  bees,  the  females  do  not  possess  organs  for  collecting 
and  carrying  pollen.  Although  the  females  of  Psithyrus  are  easily 
distinguished  from  those  of  Bombus  by  the  absence  of  the  pollen- 
baskets  or  corbiculai  in  the  former,  the  males  of  the  two  genera  are 
very  similar.    In  Psithyrus  there  is  no  worker  caste. 

The  conclusions  of  different  observers  as  to  the  extent  of  the 
parasitism  of  Psithyrus  differ  widely.  Sladen  ('12)  from  his  studies 
of  English  species  regards  them  as  the  deadliest  enemies  of  the 


■" 

■' 

bunch  cf  9^1 

^S^^' 

/i  (  nt  u 

-pets 

Old.  cccccn 
con  la  imn  g — 
pollen 

^» 

WSp" ' 

1:^. 

1ji 

'   '-^-.^H 

Hy^^o 

^^MMt 

fi 

hcncypcJs' 

^^^^HB 

r 

-  "^^  W     Oid  cocooTvs Tlllil./ ^^^^^ ^  ^- 
^.  filled,               ^P^-  - 
vuihh  honey 

Fig.  1227. — Nest  in  mid-summer.     (From  Sladen.) 

bumblebees  whose  nests  they  infest.  He  found  "That  it  is  the 
practice  of  the  Psithyrus  female  to  enter  the  nest  of  the  Bombus,  to 
sting  the  queen  to  death,  and  then  get  the  poor  workers  to  rear  her 
young  instead  of  their  own  brothers  and  sisters."  This  conclusion  is 
not  in  accord,  however,  with  those  of  other  European  writers;  and  the 
American  species  of  Psithryus  whose  habits  have  been  studied,  rarely, 
if  ever,  kill  the  host  queen.  For  a  detailed  account  of  the  relations 
of  these  parasites  and  their  hosts  and  for  references  to  the  literature 
of  this  subject  see  Plath  ('22).  For  descriptions  of  the  New  World 
species  see  Franklin  ('i2-'i3). 


988  ^A^  INTRODUCTION  TO  ENTOMOLOGY 

FaxMily  APID^ 
The  Honey-bees 

The  family  Apidas,  as  restricted  here,  includes  only  a  single  genus, 
Apis,  of  which  only  four  species  are  known,  and  one  of  these  is 
doubtfully  distinct.  In  this  country  a  single  introduced  species,  the 
honey-bee,  Apis  mellifica,  is  found.  This  species  has  been  widely 
distributed  over  the  world  by  man.  The  other  species  are  restricted 
to  the  Indomalyan  region;  these  are  A.  dorsdta,  A.  florea,  and  A. 
Indica.  The  last  named  species  is  probably  a  variety  of  Apis  mellifica. 
The  colonies  of  A .  dorsata  and  A .  florea  build  a  single  pendent  comb 
from  the  lower  sides  of  a  branch,  and  are  not  available  for  cultivation. 
A.  mellifica  and  A.  indica  nest  in  cavities,  as  hollow  tree-trunks  and 
caverns,  and  will  make  use  of  hives  prepared  for  them. 

This  family  consists  of  social  bees  in  which  the  hind  tibice  are 
without  apical  spurs;  the  workers  are  furnished  with  pollen-baskets 
or  corbiculae  on  the  hind  legs,  but  the  queens  are  without  functionally 
developed  ones.  Unlike  the  queen  of  the  nest-building  bimiblebees 
the  queen  of  the  honey-bee  is  unable  to  found  a  colony  or  even  to 
exist  apart  from  workers  of  her  own  species. 

The  honey-bee  was  introduced  into  America  more  than  three 
centuries  ago,  and  escaping  swarms  have  stocked  our  forests  with  it ; 
for  when  free,  swarms  almost  invariably  build  their  nests  in  hollow 
trees.  These  nests  include  a  variable  number  of  vertical  combs,  which 
have  cells  on  both  sides,  instead  of  a  single  series  as  is  the  case  in  the 
combs  of  our  native  social  wasps.  The  cells  of  which  the  comb  is 
composed  are  used  both  for  storing  the  food  of  the  colony  and  for 
rearing  the  brood. 

The  three  castes  of  bees  of  which  a  colony  is  composed  are  easily 
distinguished.  The  workers  are  the  well-known  form  that  we  see 
collecting  pollen  and  nectar  from  flowers  and  entering  and  leaving 
the  hive  in  large  numbers.  They  constitute  the  greater  part  of  the 
colony;  an  average  strong  colony  will  include  from  35,000  to  50,000 
workers.  They  are  females  in  which  the  reproductive  organs  are 
imperfectly  developed;  they  do  not  ordinarily  lay  eggs,  and  when 
they  do  the  eggs  develop  only  into  males.  The  workers  do  not  pair 
with  males,  consequently  their  eggs  are  unfertilized,  and  unfertilized 
eggs  of  the  honey-bee  produce  only  males.  The  workers  are  so-called 
because  they  perform  all  the  labors  of  the  colony.  Young  workers 
attend  to  the  inside  work  of  the  hive;  they  take  care  of  the  young 
brood,  and  for  this  reason  are  termed  nurse-bees,  they  build  combs, 
and  protect  the  entrance  of  the  hive  against  robbers.  The  older 
workers  go  into  the  field  to  collect  pollen,  nectar  and  propolis. 

The  drones  are  larger  than  the  workers,  and  are  reared  in  larger 
cells.  If  honeycombs  be  examined,  some  sheets  will  be  seen  to  be 
composed  of  larger  cells  than  those  of  the  more  common  type.  It  is 
in  cells  of  this  kind  that  the  eggs  are  laid  which  are  to  develop  into 
males.    In  shape  the  drones  are  broader  and  blunter  than  the  workers. 


HYMENOPTERA  989 

They  are  few  in  number  and  are  only  present  in  the  hive  during  the 
early  summer.  After  the  swarming  season  is  over,  these  gentlemen 
of  leisure  are  driven  out  of  the  hive  by  the  workers  or  are  killed  by 
them. 

The  queen  is  larger  than  a  worker,  and  has  a  long  pointed  body. 
She  is  developed  in  a  cell  which  differs  greatly  from  the  ordinary 
hexagonal  cell  of  honey- 
comb. This  cell  is  large, 
cylindrical,  and  extends 
vertically.  In  Figure  1228 
the  beginnings  of  two  queen 
cells  are  represented  on  the 
lower  edge  of  the  comb,  and 
a  completed  cell  extends 
over  the  face  of  the  comb 
near  the  left  side.  From 
the  lower  end  of  this  cell 
hangs  a  lid,  which  was  cut 
away  by  the  workers  to  al- 
low the  queen  to  emerge,      pig.  1228.— Comb  of  honey-bee  with  queen- 

The  queen  larva  is  fed         cells, 
with  a  substance  called  royal 

jelly.  This  is  a  substance  which  resem_bles  blanc-mange  in  color  and 
consistency.  It  is  excreted  from  the  mouth  by  the  nurse-bees,  and 
is  very  nutritious  food.  The  origin  of  this  food,  whether  it  is  a 
secretion  from  special  glands  of  the  nurse-bees,  or  is  regurgitated  from 
their  stomachs  is  not  at  present  known.  During  the  first  three  days 
of  the  larval  stage  of  worker  bees  they  are  also  fed  with  royal  jelly 
after  which  they  are  fed  with  honey  and  bee-bread. 

It  has  been  demonstrated  that  in  the  egg  state  there  is  no  differ- 
ence between  a  worker  and  a  queen.  When  the  workers  wish  to 
develop  a  queen  they  tear  down  the  partitions  between  three  adjacent 
cells  containing  eggs  that  under  ordinary  conditions  would  develop 
into  workers.  Then  they  destroy  two  of  the  eggs,  and  build  a  queen- 
cell  over  the  third.  When  the  egg  hatches  they  feed  the  larva  with 
royal  jelly,  and  it  develops  into  a  queen. 

In  early  stimmer  several  queen-cells  are  provided  in  each  colony. 
As  soon  as  a  queen  is  developed  from  one  of  these  the  old  queen  at- 
tempts to  destroy  her.  But  the  young  queen  is  guarded  by  the  work- 
ers, and  then  the  old  queen  with  a  goodly  portion  of  her  subjects 
swarm  out,  and  they  go  to  start  a  new  colony. 

The  swarming  of  the  honey-bee  is  essential  to  the  continued  exist- 
ence of  the  species;  for  in  social  insects  it  is  as  necessary  for  the 
colonies  to  be  multiplied  as  it  is  that  there  should  be  a  reproduction 
of  individuals.  Otherwise,  as  the  colonies  were  destroyed  the  species 
would  become  extinct.  With  the  social  wasps  and  with  the  bumble- 
bees the  old  queen  and  the  young  ones  remain  together  peacefully  in 
the  nest ;  but  at  the  close  of  the  season  the  nest  is  abandoned  by  all 
as  an  unfit  place  for  passing  the  winter,  and  in  the  following  spring 


990  AN  INTRODUCTION  TO  ENTOMOLOGY 

each  young  queen  founds  a  new  colony.  Thus  there  is  a  tendency 
towards  a  great  multiplication  of  colonies.  But  with  the  honey-bee 
the  habit  of  storing  food  for  the  winter,  and  the  nature  of  the  habita- 
tions render  it  possible  for  the  colonies  to  exist  indefinitely.  And  thus 
if  the  old  and  young  queens  remained  together  peacefully  there 
would  be  no  multiplication  of  colonies,  and  the  species  would  surely 
die  out  in  time.  We  see,  therefore  that  what  appears  to  be  merely 
jealousy  on  the  part  of  the  queen  honey-bee  is  an  instinct  necessary 
to  the  continuance  of  the  species. 

The  sting  of  a  queen -bee  is  no  ignoble  weapon,  but  it  is  rarely 
used  except  against  a  rival  queen.  When  several  young  queens  mature 
at  the  same  time  there  is  a  pitched  battle  for  supremacy,  and  the  last 
left  living  on  the  field  becomes  the  head  of  the  colony.  One  morning 
we  found  the  lifeless  bodies  of  fifteen  young  queens  cast  forth  from  a 
single  hive^ — a  monument  to  the  powers  of  the  surviving  Amazon  in 
triiimphant  possession  within. 

The  materials  used  by  bees  are  wax  and  propolis,  which  serve  as 
materials  for  construction;  and  honey  and  bee-bread  used  for  food. 

The  comb  is  made  of  wax,  which  is  an  excretion  of  the  bees. 
When  a  colony  needs  wax,  many  of  the  workers  gorge  themselves 
with  honey  and  then  hang  quietly  in  a  curtain-like  mass,  the  upper 
bees  clinging  to  the  roof  of  the  hive,  and  the  lower  ones  to  the  bees 
above  them.  After  about  twenty-four  hours  there  appear  on  the 
lower  surface  of  the  abdomen  of  each  bee  little  plates  of  wax  that 
are  forced  out  from  openings  between  the  ventral  abdominal  seg- 
ments called  wax-pockets.  Other  workers  attend  to  this  curtain  and 
collect  the  wax  as  fast  as  it  appears,  and  use  it  at  once  in  constructing 
comb. 

Propolis  is  a  cement  used  for  cementing  up  crevices,  and  is  made 
of  a  resin  which  the  bees  collect  from  the  buds  of  various  trees,  but 
especially  of  the  poplar. 

Honey  is  made  from  the  nectar  of  flowers  and  is  taken  into  the 
crop  of  the  bee,  and  there  changed  into  honey,  and  then  regurgitated 
into  the  cells  of  the  comb. 

Bee-bread  is  made  from  the  pollen  of  flowers,  which  the  bees 
bring  in  on  the  plates  fringed  with  hairs  on  the  hind  legs,  the  corbiculae. 

Very  many  books  have  been  written  regarding  the  habits  of  the 
honey-bee;  some  of  these  are  to  be  found  in  most  public  libraries. 
There  are  also  many  manuals  for  the  use  of  those  who  wish  to  keep 
bees ;  among  these  is  a  small  one  for  beginners  by  Mrs.  A.  B .  Comstock 
('20)  and  a  cyclopedia  by  A.  I.  and  E.  R.  Root  ('17).  The  U.  S.  De- 
partment of  Agriculture  has  published  many  bullletins  on  this  subject ; 
one  of  a  general  nature  is  "Farmers  Bulletin  447." 


BIBLIOGRAPHY 

The  following  list  includes  only  the  titles  of  the  books  and  papers  to  which 
references  have  been  made  in  the  preceding  pages. 

Aaron,  S.  F.  ('85).    "The  North  American  Chrysidida.'."    Trans.  Am.  Ent.  Soc. 

Vol.  12,  pp.  209-248. 
AcKERM.\N,  A.  J.  ('16).     "The  carpenter-bees  of  the  United  States  of  the  genus 

Xylocopa."    Jour.  N.  Y.  Ent.  Soc.     Vol.  24,  pp.  196-232. 
Adelung,  N.  von  ('92).    "Beitrage  zur  Kenntnis  des  tibialen  Gehorapparates  der 

Locustiden."    Zeit.  wiss.  Zool.    Vol.  54,  pp.  316-385. 
Aldrich,  J.  M.  ('05).    "A  catalogue  of  North  American  Diptera."    Smithsonian 

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INDEX 


Figures  in  bold-faced  type  refer  to  pages  bearing  illustrations. 


Aaron,  S.  P.,  935 

Abedus,  367 

Acalles,  88 

Acalyptratae,  786,  853 

Acanthaclisis,  304 

Acanthocephala  femorata,  390 

Acanthomyops,  890 

Acanthostichus,  942 

Accessory  cells,  574 

Accessory  circulatory  organs,  122 

Accessory  glands,  162 

Accessory  veins,  68 

Acerentomidae,  26 

Acerentomon  doderoi,  25 

Acetabula,  52 

Achorutes   artnatus,   228;   A.   nivicola, 

228;  A.  maritima,  229;  A.  socialis, 

228 
Acidalia  enudeata,  wings  of,  667 
Acidaliinae,  663,  666 
Acilius,  483 
Ackerman,  A.  J.,  981 
Acoloithus  falsarius,  wings  of,  604 
Acone  eyes,  141 
Acorn-moth,  628 
Acrida  turrita,  134 
Acrididae,  252 
Acroceridas,  786,  789,  837 
Acrolophidas,  581,  589,  611 
Acrolophus,    611;    A.    arcanellus,    611; 

A.  mortipennellus,  61 1;  A.  popean- 

ellus,  611 
Acronycta,  689 
Acroschismus  bruesi,  547 
Acrydiinae,  253,  259 
Acrydtum  arenosiim  obicurum,  260;  A. 

granulatiim,  260 
Aculeae,  573 
Abdomen,  75;  appendages  of  the,  76; 

segments  of  the,  75 
Adalia  bipunctata,  512 
Adaptive  ocelli,  135,  136 
Adela,  598 
Adelges,  429;  A.abietis,  432;  A.  abietis, 

gall  of,  432;  A.  green-winged,  432; 

A.  pine-bark,  432;  A.  pine-leaf,  43 1; 

A .  pinicorticis,  432 ;  A .  pinifolice,  43 1 , 

gall  of,  432;  A.  wings  of,  414,  428 
Adelginise,  429 
Adelinae,  598 
Adelocephala  btcolor,  717 
Adelung,  N.  von.,  150 
Adephaga,  468,  469,  476 
Adipose  tissue,  123 

101 


Adirondack  black-fly,  824 

Adoneta  spintdoides,  wings  of,  608 

Adventitious  veins,  70 

Aedes,   806,   809;  A.   cegypti,   809;   A. 

calopiis,  809 
^geriida;,  582,  584 
Molothrips  fascialus,  344;  A.  nasturtii, 

342 
^olothripidaD,  344 
Molus  dorsalis,  500 
^schna  cyanea,  hind-intestine  and  part 

of  tracheal  system  of  naiad  of,  319 
^schnidae,  320 

Agamic  form?  of  aphids,  415,  416 
Agaoninas,  931 
Agaristida^,  583,  587,  697 
Agdistis  adactyla,  653 
Aglais  milberti,  755 
Agrilus  ruficoUis,  503 
Agrion,  324 
Agrionidas,  324 
Agrionidis,  true,  324 
Agromyzidag,  786,  792,  861 
Agrothereutes  extrematis,  918 
AgroiincE,  695 
A  gratis  c-nigrum,  696 
Ailanthus  webworm,  632 
Ailanthus-worm,  727 
Air-sacs,  118 
Akers,  Elizabeth,  78 
Alabama  argillacea,  686,  687 
Alar  frenum,  783 
Alaus  oculatus,  501 
Alcidamea  producta,  983 
Alder  blight,  421 
Alder-flies,  285 

Aldrich,  J.  M.,  830,  844,  860,  864,  870 
Aleurochiton  forbesii,  437,  440 
Aleyrodes,  439 
Aleyrodidas,  177,  400,  437 
Aleyrodid,  an,  437 
Aleurodothrips  fasciapennis,  346 
Alimentarj'  canal,  107 
Alitnnik,  49 
Alleculidae,  474,  512 
Alsophila  pometaria,  664,  665 
Alternation  of  generations,  923 
Alveolus,  32 
Alula  or  alulet,  776 
Alypia  langtonii,  698;  A.  octomaculata, 

697;  larva,  698 
Alula,  the,  60 
Alulet,  60 
Ambient  vein,  74 
1 


1012 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Amblycera,  337 

Amhlycheila,    477,    478;    A.    cylindri- 

formis,  478 
Amblycorypha,    237;    A.    ohlongifolia, 

236,    237;   A.   rotundifolia,   237;   A. 

uhleri,  237 
Ambrosia- beetle?;,  542,  544 
Ambry sus,  367 
Ametabola,  174 

Ametabolous  development,  174 
Ammophila,  890,  967 
Ampelceca  myron,  659,  660 
AmphiboUps  confluens,  925;  A.  inanis, 

926 
Amphicerus  bicaudatus,  515 
Amphidasis  cognataria,  673 
Amphipneustc,  115 
Amphipyra  pyramidoides,  691 
Amphizoidas,  470,  481 
Ampulicidae,  891,  907,  911,  961 
Anabolia  nervosa,  557 
Anacampsis  tfinocella,  628 
Anacharitinae,  922 
Ancsa,  761;   A.  andria,  761;  A.  morri- 

sonii,  761;     A.  portia,  761 
Anal  angle,  60 

Anal  area,  75;  the  veins  of  the,  65 
Anal  furrow,  73 
Anal  lobe,  888 
Anal  lobes,  445 
Anal  plates,  445 
Anal  ring,  445 
Anal- ring  setae,  445 
Anal  setce,  445 
Anaphothrips  slriatus,  345 
Anarsia  lineatella,  627 
Anasa  iristis,  389 
Anastomosis,  326 
Anastomosis  of  veins,  70 
Anax,  317 

Anaxipha,  242;  A.  exigna,  243,  244 
Anchor  process,  815 
Ancyloxipha  numitor,  738 
Andre,  E.,  937 
Andrena,  980 
Andrenidae,  891,  912,  978 
Andricus  erinacei,  924;  A.  calif orniciis, 

926 
Androconia,  100,  573 
Anepimerum,  51 
Anepistemum,  51 
Angles  of  wings,  60 
Angle-wings,  the,  754 
Angoumois  grain-moth,  626 
Angulifera-mo^h,  726 
Anisandrus  pyri,  545 
Anisolabis  annulipes,  462 ;  A .  maritima, 

462 
Anisomorpha  buprestoides,  262 
Anisopidae,  785,  787,  788,  797 
Anisoptera,  316 


A  nisopiis,  797 ;  wing  of,  797 

Anisota,  717;  A.  rosy,  719;  A.  rubi' 
cunda,  719;  A.  senatoria,  718;  A. 
stigma,  718;  ^.  virginiensis,  718 

Anobiidas,  471,  514 

Anobium,  79 

Anophdes,  808;  head  of,  775 

Anoplura,  214,  217,  347 

Anosa  plexippus,  head  of,  109 

Ant,  see  Ants 

Antecoxal  piece,  54 

Antecubital  cross-veins,  319 

Antelope-beetle,  523 

Antennae,  40,  41;  the  development  of, 
199 

Antenna  cleaner,  886 

Antennal  fossa,  fovea,  or  groove,  779 

Antennal  sclerites,  39 

Antenodal  cross-veins,  319 

Anteonidae,  909,  913 

Anterior  arculus,  72 

Anthicidae,  475,  498 

Anthoboscidae,  891,  910,  935 

Anthocoridas,  356,  358,  377 

Anthocharis  genutia,  748 

Anthomyiidae,  786,  793,  863 

Anthomyioidea,  786 

Anthonomns  grandts,  540;  A.  signatus, 
540;  A.  qtiadrigibbus ,  540 

Anthony,  Maude  H.,  113,  282 

Anthopiwra,  890,  979;  nests  of,  979;  A. 
stanfordiana,  979 

Anthrenus  museorum,  507;  A.  scrophu- 
laricE,  506;  A.  verbasci,  507 

Antispila  pfeifferella,  wings  of,  622 

Antlered  larvae,  677 

Ant-lion,  head  and  mouthparts  of, 
lan^a  of,  282 

Ant-lions,  303 

Antocha,  799 

Ants,  937;  Amazon,  947;  carpenter,946; 
corn  field,  947;  fungus-growing,  945; 
harvesting,  943;  honey,  947;  in- 
quiline  or  guest,  944;  mound-build- 
ing, 946;  slave-maker,  946;  thief, 
943;  typical,  946 

Armraphis  maidi-radicis,  419;  A.  ros- 
eus,  418 

Anurapteryx,  673,  A.  crenulata,  673 

Anurida,  47;  A.  maritima,  post- an- 
tennal organ  of,  226 

Anus,  113 

Aorta,  122 

Apantesis,  701;  A.  virgo,  701 

Apatela,  689;  A.  americana,  690;  A. 
hamamelis,     690;     larva,     691;     A. 
morula,  690 

Apatelinae,  689 

Apatelodes,  707;  A.  angelica,  708;  A. 
torrefacta,  707 

Apex  of  the  wing,  60 


INDEX 


1013 


Aphelininae,  930 

Aphididae,  177,  400,  415,  417 

Aphidinc-e,  bark-feeding,  418;  leaf- 
feeding,  418;  root-fee^'ing,  419;  dif- 
ferent types  of  individuals  in,  416 

A  phidius,' 916,  917 

Aphidoidea,  400,  412 

Aphids,  412;  giant  hickory-,  418; 
strawberry -root,  419;  typical,  415; 
woolly,  420 

Aphis,  com  root,  419;  A.  forbesi,  419; 
A.  gossypi,  413;  A.  melon,  413;  A. 
pomi,  418;  A.  apple-leaf,  418;  rosy 
apple-,  418;  A.  woolly  apple,  421 

Aphis-lions,  299 

Aphodean  dung-beetle,  517 

Aphodius,  517;  A.  fimetarius,  517 

Aphrophora  quadranotata,  403 

Aphycus  emptor,  927 

Apid'ae,  891,  912,  988 

Apis,  988;  A.  dorsata,  988;  A.  florea, 
988;  A.  indica,  988;  wings  of,  884 

Apiocera,  wing  of,  843 

Apioceridae,  786,  789,  842 

Apocrita,  890,  905 

Apodemes,  95,  98 

Apoidea,'972 

Apophyses,  31 

Appendages,  the  development  of,  194 

Apple  fruit-miner,  63 1 

Apple- maggot,  857 

Apple-seed  chalcid,  931 

Apple- worm,  many-dotted,  691 

Apposed  image,  143 

Apterobitlacus,  554;  A.  aptenis,  554 

Apterygogenea,  209 

Apterygota,  209,  214 

Apyrrothrix  araxes,  735 

Aquatic  Hymenoptera,  889 

Aradidaj,  3*57,  358,  359,  388 

Aradiis  acutus,  389 

Arachnid  a,  9 

Araeocerus  fasciculatus,  537 

Archanara,  692 

Archips  argyrospila,  643;  .1.  cerasiv- 
otana,  642;  .4.  ftrvidana,  643;  A. 
rosana,  642 

Arctiidae,  583,  588,  699 

Arctiinae,  700 

Arculus,  72 

Argentine  Ant,  945 

Argidae,  890,  893,  902 

Argynnis  cybele,  751 

Argyresthia  conjugella,  631 ;  A.  thuiella, 

631 

Arilus  cristatiis,  381 
Armored  vScales,  454 
Army-worm,  694 
Arolium,  58 
Arthoceras,  833 
Arthropleona,  228 


Articular  membrane  of  the  setae,  32 
Articular  sclerites  of  the  legs,  53;  of 

the  wings,  54,  55 
Arthromarra  ccnea,  514 
Arthropoda,  i 

Arzama,  692;  A.  obliqua,  692,  693 
Ascalaphidae,  284,  305 
Aschiza,  786,  847 
Ascodipteron,   875, 

Ashmead,   W.    H.    921,  922,  929,  951 
Asilidae,  786,  788,  840 
Asparagus-beetle,  530 
AspiceriniE,  922 
Aspidiotus  perniciosus,  458 
Astaini,  963,  964 

Astatus  bicolor,  964;  A.  unicolor,  964 
Asteiida,  786,  792,  860 
Asterockiton  packardi,  440;  .4.   vapora- 

riorum,  439 
Ateuchus,  88;  yl.  sacer,  516 
Aiherix,  835;  A.  ibis,  835,  836 
AtlanHcus    240;    A.    damn,    240;    A. 

testacens,  240 
AtropidjE,  333 
Atropos  divinaioria,  80;  A.  pulsatoria, 

334 
Atryone  conspicua,  738 
Attelabinte,  538 
Aitelabiis,  538;  A.  aurea,  632 
Attii,  945 
Auditors'  pegs,  147 
Audouin,  J.  V.,  49 
A  ulacaspis  rosce,  458 
Aulacida?,  890,  906,  918 
Aiilacns,  wings  of,  919 
Autographa  brassier,  687;  A.  falcifera, 

687 
Automcrisio,  722 
Axillaries,  54 
Axillary  cord,  60;  A.  excision,  61,  776; 

A.  furrow,  74;  A.  membrane,  60 

Back-swimmers,  362 

Bad-wing,  667 

Bag-worm  Moths,  613;  Abbot's,  613; 

evergreen,  614 
Baker,  A.  C,  419 
Baker,  C.  F.,  880 
Balaninus,    539;   B.   nasicus,    539;   B. 

proboscideiis,  539;  B.  rectus,  539 
Baliosus  rubra,  534 
Balsa  malana,  691 
Baltimore,  the,  752 
Banded  elfin,  770 
Banded  purple,  758 
Banks,  Nathan,  280,  296,  303,  307 
Barber,  H.  S.,  494 
Bark-beetles,      543;     fruit-tree,      544; 

peach-tree,  544 
Barnacle  scale,  454 
Barnes  and  Lindsey,  673 


1014 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Barnes  and  McDunnough,  602 

Basal  anal  area,  320 

Basal  anal  cell,  327 

Basal  or  subbasal  band,  575 

Basement  membrane,  31,  109,  118 

Basilarchia,  750;  B.  archippus,  759;  B. 

archtppus  Jflondensis, 760;  B.anhemis, 

758,  B.  astyanax,  758;  B.  proserpina, 

758 
Basilona  imperialis,  717 
Basswood  leaf -roller,  646 
Bat-ticks,  875 
Bean-weevil,  535 
Bean  leaf- roller,  736 
Bear  animalcules,  11 
Beard,  781 
Beaver  pararite,  486 
Bedbug,  103,  355,  378 
Bedbug,  big,  382 
Bedbug-hunter,  masked,  381 
Bedellia  somnulentella,  616;  wings  of, 

616 
Bee-bread,  990 
Beech-tree  blight,  422 
Bee-flies,  838 
Bee-lice,  876 
Bee-moth,  650 

Beet-  or  Spinach  leaf-miner,  864 
Beetles,  464 

Beetle,  ventral  aspect  of  a,  465 
Bees,    960,    972;    bifid  tongued,    976; 

hairs  of  various,  973;  leaf-cutter,  982 ; 

three     castes  of,  988 
Beggar,  669 
Behdae,  476,  537 
Bella-moth,  700 
Bellesme,  J.,  92 
Bellura,  691;  B.  diffusa,  691,  692;  B. 

gortynoides,  691,  692;  B.  melanopyga, 

691;  B.  white  tailed,  692 
Belostoma,  367;  B.  fliiminea,  367 
Belostomatidae,  356,  357,  365 
Belytidas,  890,  908,  913,  921 
Bembecia  marginata,  636 
Bembicini,  964,  969,  971 
Bembex,  971 

Benacus,  366;  B.  griseus,  367 
Bequaert,  J.,  889 
Berlese,  A.,  25,  106,  113,  128,  132,  133, 

134.  151-  155.398 
Berothidae,  284,  298 
Berotha  insohta,  298 
Bethylidae,  890,  891,  909,  914 
Betten,  Dr.  Cornelius,  559 
Bezzi,  M.,  828,  876 
Bibionidae,  785,  788,  820 
Bibio,  820;  wing  of,  821 
Bibiocephala    doanet,    mouth  parts    of 

female,  826 
Big-eyed  Flies,  849 
Bill-bugs,  540 


Bird-lice,  335 

Bischoff,  H.,  935 

Bttlacomorpha  clavipes,  797 

Bitiacus,  553,  554 

Blackberry  crown- borer,  636 

Black-dash,  738 

Black -flies,  821;  innoxius,  824;  white- 
stockinged,  824 

Black  scale,  453 

Black  witch,  685 

Blastobasidse,  582,  589,  591,  628 

Blaslophaga,  59;  B.  picnes,  932 

Blasturus,  312 

Blatchley,  W.  S.,  236,  502 

Blatchley  and  Leng,  475,  536 

Blatta  orientalis,  266 

Blattella  gormanica,  265,  266 

Blattidae,  234,  263 

Blattoidea,  263 

Blepharocera,  144;  B.  teyiiiipes,  826; 
wing,  825;  section  of  head,  825; 
larva,  826 

Blepharoceridag,  786,  787,  824 

Bhssus  leucopierus,  387 

Blister  Bee-'les,  495 

Blood,  122 

Blood-gills,  114,  120 

Blow-fly,  family,  869 

Blues,  the,  771 

Blue,  tailed,  772 

Bluebottle-fly,  large,  870 

Body-segments,  34 

Body-wall,  29,  34 

Boletoiherns  cornutus,  513 

Bollworm,  pink,  628 

Bombardier-beetles,  479 

Bomb-fly,  868 

Bombias,  985 

Bombidse,  890,  891,  912,  984 

Bombtis,  890,  985,  987;  nest  of,  987 

Bombycidae,  583,  58';,  727 

Bombyliidae,  786,  788,  789 

Bombyliui,,  838 

Bomhyx  mori,  128,  727 

Book-lice,  331,  333 

Book-louse,  mouth-parts  of,  331 

Boophilus  annulatus,  2 

Borboridae,  786,  791,  794,  855 

Boreus,  550,  551,  553 

Boriomyia,  297 

Borner,  C,  430,  432,  876 

Bot-flies,  866;  common,  865;  of  Horses, 
864;  red-tailed,  866;  sheep,  867; 
stomach,  865 

Bothropolys  mullidoniatus ,  21 

Bostrichidae,  471,  515 

Brachelytra,  467,  468;  families  of  the, 
470 

Brachinus,  479,  480 

Brachyacautha,  512 

Brachycentrus  mgrisoma,  570 


INDEX 


1015 


Brachycentrus  nigrisoma,  569 
Brachycera,  786,  828;  Anomalous,  786, 

829!  True,  786 
Brachygastra  lecheguana,  956 
Brachypauropodidae,  19 
Brachyrhinus  ovatus,  539;   B.  sulcalns, 

539 

Bracliystola  magna,  257 

Braconidae,  890,  906,  913,  916 

Bradley,  Prof.  J.  C,  886,  889,  897,  906, 
933.  936,  949,  950,  962 

Brand,  738 

Bra^hinida;,  471,  486 

Brathinus,  486 

Brauer,  F.,  209 

Braula,  876;  B.  cceca,  876;  B.  kohli,  876 

Braulidas,  787,  794,  876 

Braun,  A.  F.,  575,  592,  601 

Breast  bone,  815 

Bremidas,  890 

Bremus,  890 

Breiithis,  752 

Brentidas,  476,  536 

Brephinae,  663,  664 

Brephos  infans,  664 

Brindley,  H.  H.,  172 

Brine-flies,  859 

Bristle-tails,  220 

Bristles,  antipygidial,  879;  the  ab- 
dominal of  Diptera,  785;  the  cephalic 
of  Diptera,  781;  of  the  legs  of  Dip- 
tera, 785;  the  thoracic  of  Diptera, 
783,  784 

Brown-tail  moth,  682 

Briichophagus  funebris,  93 1 

Brues,  C.  T.,  848 

Brychius,  481 

Bubonic  plague,  879 

Bucca,  779 

Bucculaj,  353 

Bucculatrix,  apple,  616;  B.  pomifoliella, 
616;  cocoons  of,  616 

Bucculatrigidae,  617 

Buckley,  938 

Bud-moth,  641 

Btieiioa,  364 

Buffalo- gnat,  Southern,  824 

Bugs,  ambush-,  382;  assassin-,  380; 
burrower-,  391,  392;  chinch-,  386, 
387;  creeping  water-,  367;  flat-,  388; 
fliower-,  377;  four- lined  leaf-,  375; 
giant  water-,  365;  harlequin  cab- 
bage-, 391;  insidious  flower-,  378; 
lace-,  384;  leaf-,  375;  many-combed, 
379;  negro,  391,  392;  shield-backed, 
392;  shore,  369;  squash-,  389;  stilt-, 
388;  stink-,  390;  tarnished  plant-, 
376;  thread  legged,  382;  toad-shaped 
368;  true,  350;  unique-headed,  383 

Bugnion  and  Popoff,  398 

Bullae,  74 


Bumblebees,  984;  parasitic,  987 
Buprestidae,  472,  502 
Buprestid,  Virginian,  503 
Burgess,  E.,  109,  160 
Bursa  copulatrix,  159 
Busck,  A.,  625,  628 
Busck  and  Boving,  594 
Butterflies,  571,  581,  583-  739 
Buzzing  of  flies  and  bees,  91 
Byrrhida;,  471,  508 
Byturidae,  472,  510 
By'turus,  510;  B.  unicolor,  510 

Cabbage-butterfly,    746;   development 

of  the  wings  of,  196 
Cabbage  looper,  687 
Cabbage-root  maggot,  863 
CaccEcia,  642 

Caddice-Flies,  555;  Micro-,  561 
Caddice-worms,  557 
Cadelle,  508 
Caecum,  113 
Ccelioxys,  976 
CcEnis,  309,  312 

Canomyia  ferruginea,  wing  of,  833 
Canurgia,  688;  C.  crassiuscula,  688;  C. 

erechtea,  688 
Calamoceratid^,  559,  560,  567 
Calandra  granana,  541;  C.  oryzcs,  541 
Calendrinas,  540 
Calephelis  borealis,  767;  C.  virginiensis, 

767 
Caliroa  cerast,  902 
Calledapteryx  dryopterata,  709 
CallibcEtis,  312 
Calliceratidae,  890 
Callimoninae,  890 
Calliphora,  869;  C.  erythrocephala,  870; 

C.  vomitoria,  870 
Calliphoridas,  787,  793,  869 
Callosamia  angulifera,   726;    C.   prom- 

e.hea,  724,  725;  cocoon  of,  189 
Callizzia  amorata,  709 
Calocalpe  undtdata,  668,  669;  eggs  and 

nest  of,  669 
Caloptenus  italiciis,  149 
Calopteron  reticulatum,  491 
Calopleryx,  324 

Calosoma   calidum,  479,  480;    C.  scru- 
tator, 479;  C.  sycophanta,  479 
Calypteratse,  786,  862 
Calypteres,  776 
Camcesphecia  tipuliformis,  637 
Camel -crickets,  241 

Campodea,  157,  161 ;  C.  staphylinus,  224 
Campodeidas,  224 
Campodeiform,  184 
Camponotus    hercukanus    pennsylvani- 

cus,  946 
Campsomeris,  937 
Camptonotus  carolinensis,  240 


1016 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Campylenchia  laiipes,  405 
Canaceidae,  786,  792,  859 
Canace  inodgrassi,  859 
Candle-fly,  Chinese,  409 
Canker-worm,   spring,   671;   fall,   664; 

control  of,  665 
Cantharidse,  473,  492 
Caniharis  vtsicatoria,  larva  of,  117 
Canlhon  IcEvis,  517 
Capitate,  41 
Capnia,  179,  330;  C.  pygmcca,  326;  C. 

wine;  of,  330 
Capniidae,  330 
Caprofication,  932 
Caprofigs,  932 
Capsidse,  375 
Carabida?,  470,  478 
Carabus  aura  his,  alimentary  canal  of, 

110 
Cardo,  44 

Caripeta  angustiorata,  wings  of,  662 
Carlet,  G.,  89,  90 
Carolina  locust,  82 
Carpenter,  G.  H.,  17 
Carpenter-bee,  955;  large,  981;  small, 

980 
Carpenter-moths,  601 
Carpenter-moth,  locust-tree,  603 
Carpenter- worm,  lesser  oak,  603 
Carpet  bettle,  506 
Carpocapsa  pomonella,  639 
Carposina  fernaldana,  644 
Carposinidae,  582,  590,  638,  644 
Carriere  and  Burger,  103 
Carrion-Beetles,  487 
Carrot  rust -fly,  859 
Case  bearer,  cigar,  621 
Cat  flea,  882 
Calocata,  688;  C.  fraxini,  wings  of,  684; 

C.  ilia,  688 
Catocalinae,  687 
Catopsilia  eubule,  749 
Cat-tail  moth,  629;  noctuids,  692 
Caudell,  A.  N.,  240,  241,  272 
Caulocampa  acericaulii,,  901 
Cave-crickets,  241 
Cebrionidfe,  473,  499 
Cecidomyia  albovittata,  817 
Cecidomyiidae,  785,  787,  788,  813 
Cecidomyiinae,  816,  817 
Cecropia-moth,  726 
Cedar-beetles,  499 
Cedar  tineid,  631 
Celama  trigueirana,  705 
Celerio  lineata,  660,  661 
Celery  looper,  687 

Cells  of  the  wing,  terminology  of  the,  72 
Celonites  abbreviatui,  950 
Cenchri,  887 
Centipedes,  20 
Cephaloidse,  474,  494 


Cephidae,  890,  893,  898 

Ctphiis  pygmaeiis,  899;  wings  of,  899 

Cerambycidffi,  475,  524 

Cerambycids,  typical,  526 

Ceramb^^cinae,  526 

Ceramtca  picta,  694;  larva,  695 

Ceramiiii,  liisilanicus ,  950 

Cerapachyinae,  941,  942 

Cerapachys,  942 

Ceraphronida;,  890,  908,  913,  921 

Cerasiipsocus  venosus,  331 

Ceratina  dupla,  980;  nest  of,  981 

Ceratocombus,  374 

Ceratophillidae,  882 

Ceratophyllu..  fasciatus,  878;  C.  multis- 

pmosus,  878 
Ceraiopogon,  136 
Ceratubae,  446 
Cercerini,  963,  969 

Cercens  clypeata,  969;  C.  wings  of,  969 
Cerci,  24, '77,  232 
Cercopidae,  400,  402 
Cercyonis  alope,  762;  C.  alope  nephele, 

763;  alope  maritima,  763 
Ceresa  bubalm,,  404;  C.  diceros,  405 
Ceropales,  934 
Cerophytidae,  472,  499 
Cerophytum,  499 

Ceroplastes,  453;  C.  cirripediformis,  454 
Cerores,  446 
Cervncal  sclcrites,  40 
Ceuthophilus,   232,   241;    C.  lapidicola, 

233;  C.  maculams,  241;  C.  uhleri,  241 
Chcrtopsis  anea,  856 
Chain- dotted  geometer,  670 
Chalarus,  850 
Chalastogastra,  890,  891 
Cholcid-flies,  927 
Chalcid-fly,  wing  of,  927 
Chalcididae,  890,  909.  913    929 
Chalcidinae,  929 
Chalcidoidea,  890,  927 
Chalicodoma  muraria,  984;  nests  of,  984 
Chalcophora  virgiiiica,  503 
Chalybion  caruliiim,  967 
Chamaeyidac,  862 
Chamyris  cerintha,  689 
Chapman,  T.  A.,  593 
Charipinae,  922 
Chauliodes,  288;  C.  pectinicornis,  288; 

C.  raslricornis,  288 
Chaidiognathus,    492;    C.    marginatus, 

492;  C.  pennsylvanicus,  492 
Cheeks,  779 
Cheek-grooves,  779 
Cheese-maggot,  858 
Chelonariidae,  471,  506 
Chelonarium  lecontei,  506 
Chelophores,  11 
Chelymorpha  cassidea,  534 
Chemical  sense  organs,  130,  132 


INDEX 


1017 


Chermes,  429;   C.  ahieticolens,  432;   C. 

viridis,  432 
Chermidas,  400,  410 
Cherry-fruit-flies,  857 
Cherrv-tree    ugly-nest    tortricid,    642, 

643 
Cheshire,  F.  R.,  102 
Chiasognathus ,  88 
Chickweed  geometer,  666 
Chigoe,  883 
Child,  C.  M.,  153,  154 
Chilopoda,  20 
Chimarrha  aterrima,  563 
Chinch-bug,  386 
Chin-fly,  866 
China  wax,  102,  441 
Chionaspis  pinifoUcE,  456,  458 
Chio7iaspis  furfura,  441,  457 
Chionea,  799 

Chironomidae,  785,  788,  793,  802 
Chironomus,  120,  147,  148;  wing  of,  803 
Chirotonetes    albomanicattis,     wing    of, 

309,  310 
Chitin,  30 

Chitinized  tendons,  95 
Chloealtis  conspersa,  259 
Chlorion,g6y,    C .  cyaneum ,  gby ;    C.tch- 

nenmoneum,  967 
Chlorippe  celtis,  761 ;  C.  clylon,  760 
Chloropidce,  786,  792,  860 
Chordotonal  ligament,  147 
Chordotonal    organs,    145,    146,    147, 

148;  of  the  Acridiidae,  148,  149;  of  the 

Locustidae  and  of  Gryllidce,  149 
Choreutinas,  633 
Chortophaga  virdifasciata,  257 
Choruses,  93 

Cholodkovsky,  N.  A.,  432 
Chrysalid,  186 
Chrysalis,  186 

Chrysanthemum  gall-midge,  820 
Chrysididas,  891,  909,  934 
Chrysis  nitidula,  935 
Chrysobothris  femorata,  503 
Chrysomelidae,  475,  530 
Chrysomphalus  tenebricostis,   pygidium 

of,  448 
Chrysomyia  macellaria,  870 
Chrysopa,  170,  171,  300;  C.  niger,  830; 

C.  nigricornis,  wings  of,  300,  301,  302 
Chrysopidag,  284,  299 
Chrysops,  830 
Chylestomach,  iii 
Cicada,  head  of,  397,  398;  the  musical 

organs  of  a,  89,  90;  tracheation  of 

wings  of,  395,  396 
Cicadas,  177,  401 
Cicada-killer,  970 
Cicada,  periodical,  402 
Cicada  plebia,  89 
Cicadidse,  400,  401 


Cicadellida?,  400,  406 
Ctcindela,  476,  477,  478;  maxilla  of,  45 
Cicindelidse,  469,  476 
Cicinnus  melsheimeri,  713 
Cigarette-beetle,  515 
Cimhex  americana,  900;  blade  of  ovi- 
positor of,  892 
Cimbicidse,  890,  893,  900 
Cimex,  378;  C.  lectularius,  378,  379;  C. 

pilosellus,  378 
Cimicidas,  356,  358,  378 
Cingilia  catenaria,  670 
Circular-seamed  Flies,  846 
Circulation  of  the  blood,  122 
Circulatory  system,  121 
Circumfili,  814 
Cirphis  unipimcta,  694 
Cisidse,  474,  515 
Citheronia  regalis,  716,  717;  wings  of, 

714 
Citheroniidse,  583,  71s 
Claassen,  P.  W.,  327 
Cladius  isomeriis,  902 
Clambidse,  470,  488 
Clastoptera,    403;    C.  obtusa,    404;    C. 

proteus,  403 
Clavate,  41 
Clavicornia,  467,  469 
Claviform  spot,  575 
Clavigeridae,  470,  490 
Clavola,  41 
Clavus,  350 

Clear-winged  moths,  634 
Clear-wing,  thysbe,  661 
Clemensia  albata,  705 
Clepies,  934 

Cleptidae,  890,  909,  934 
Cleridee,  473,  493 
Click-beetles,  499 
Climacia    dictyona,    2^2;    cocoon    and 

cocoon-cover  of,  292 
Clisiocampa  americana,  170 
Clistogastra,  890,  891,  905 
Cloaked  knotty-horn,  527 
Cloeon,  head  of,  144;  C.  dipt  rum,  312 
Close-wings,  649 

Closing  apparatus  of  the  tracheae,  116 
Clothes-moths,  612;  case-bearing,  612; 

naked,  612;  tube-building,  612 
Clothilla  pulsatoria,  80 
Clothing  hairs,  33 
Clouded  sulphur,  748 
Cloudy- wing,  northern,  737;  southern, 

737 
Clover-flower  midge,  818 
Clover-hay  worm,  649 
Clover-leaf  midge,  818 
Clover-looping-owlets,  688 
Clover-root  borer,  542 
Clover-seed  caterpillar,  641 
Clover-seed  chalcid,  931 


1018 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Clover-worm,  green,  685 

Clusiidag,  786,  790 

Cluster-fly,  870 

Clypeus,  38,  779 

Cnaphalodes  strobilohins,  430 

Cnephia  pecuarum,  824 

Coarctate  pupae,  191 

Coboldia  formicarium,  821 

Coccidas,  177,  400,  401,  440 

Coccid-eating  pyralid,  652 

Coccids,  the  Cochineal,  450;  the  en- 
sign, 450;  the  giant,  449;  metamor- 
phosis of,  448;  mouth-parts  of  a,  443; 
the  pseudogall,  454 

Coccinse,  450 

Coccinella  novemnotata,  512 

CoccinelUdffi,  473,  511 

Cochlidiidse,  608 

Cochineal,  441 

Cockroach,  head  of  a,  38;  head  and 
neck  of,  39;  internal  anatomy  of,  107; 
labium  of  a,  46;  tentorium  of  a,  96; 
the  base  of  a  leg  of  a,  53 

Cockroach,  American,  266,  267;  com- 
mon wood-,  266,  267;  oriental,  266; 
wing  of  nymph  of,  265 

Cockroaches,  263 

Coccus  cacti,  441,  450 

Cocoon,  188;  modes  of  escape  from  the, 
188 

Codlin-moth,  639 

Coenagrionidse,  324 

Coenoymia  ferruginea,  834 

Coenomyiidae,  786,  789,  834 

Coffee-bean  weevil,  537 

Colcenis  julia,  764 

Cole,  F.  R.,  838,  844 

Coleophora,  620;  C.  flelcherella,  621; 
malivorelld,  620,  621 

Coleophoridae,  582,  591,  620 

Coleoptera,  213,  214,  215,  217,  218, 
464;  synopsis  of  the,  467 

CoUeterial  glands,  160 

Colletes,  975,  977;  C.  compacta,  977 

Colletinse,  977 

Collembola,  214,  217,  225 

Collophore,  76,  227 

Collops  guadrimaculatus,  493 

Colonici,  434 

Colopha  eragrostidis,  423;  C.  ulmicola, 
422,  423 

Coloradia,  719;  C.  pandora,  721 

Colorado  potato-beetle,  531 

Colydiidffi,  474;  510 

Colymbetes,  483   ■ 

Comma,  green,  756 

Comma,  gray,  757 

Commisstire,  125 

Complete  metamorphosis,  180 

Compound  eyes,  134,  139;  absence  of, 
135;  dioptrics,  141 


Compton  tortoise,  756 

Comstock,  Mrs.  A.  B.,  990 

Comstpckaspis  perniciosa,  458 

Concave  veins,  73 

Coniopterygidae,  307 

Conjunctiva,  34 

Connectives,  123 

Connexivum,  355 

Conocephalinae,  235,  238 

Conocephalus,    86,    87,    233,    238;    C. 
fasciatus,  233 

Conopidae,  786,  790,  791,  853 

Conops,  854;  wing  of,  60 

Conorhinus,  382 

Conotrachelus  nenuphar,  539 

Contarinia  pyrivora,  819 

Convex  veins,  73 

Cook,  F.  C,  873 

Copidosoma  gelechicE,  889 

Copiphorinae,  235,  239 

Copper,  American,  771;  bronze,  771 

Copper  hindwing,  691 

Coppers,  770 

Copris,  517;  C.  Carolina,  517 

Coptodisca  splendoriferella,  622,  623 

Coquillett,  D.  W.,  823,  845,  871 

Corbicula,  974 

Cordulegaster,  321 

Cordvluridae,  786,  790,  854 

Coreidae,  357,  359,  389 

Corethra,  121,  134;  C.  culiciformis,  154; 
C.  plumicornis,  807 

Corethiinae,  806 

Corisa,  360 

Coriun,  350 

Corixa,  360;  C,  eggs  of,  362;  C.  mer- 
cenaria,  362 

Corixidas,  356,  357,  360 

Corn-borer,  European,  648 

Cornea,  138,  139 

Corneagen,  138 

Corneal  hypodermis,  138,  139 

Corn  ear-worm,  695 

Corneas  of  the  compound  eyes,  36;  of 
the  ocelli,  37 

Corn  stalk-borer,  larger,  650 

Corodentia,  212,  214,  215,  217,  231 

Corrugations  of  the  wings,  73 

Corydalinag,  286 

Corydalus,  62,  iii,  119,  125,  126,  136; 
head  of,  39;  head  of  a  larve  of,  38, 
137;  C,  larva  of,  288;  C.  cornutus, 
287,  288;  wing  of  pupa  of,  287 

Corylophidae,  471,  488 

Corynetidae,  473,  493 

Corythucha  arcuata,  384 

Cosmocoma  elegans,  930 

Cosmoplite,  755 

Cosmopterydidae,  582,  591,  592,  629 
Cosmopteryx,  630 
Cosmosoma  myrodora,  707 


INDEX 


1019 


Cossidae,  582,  585,  601 

Cossinag,  603 

Cossus  ligniperda,  104,  105 

Costa,  64 

Costal  fold,  735 

Costal  margin,  60 

Costal  spines,  575 

Cosymbia  lumenaria,  666 

Cotalpa  lanigera,  519 

Cotinus  nitida,  522 

Cotton-boll  wevil,  540 

Cotton-boll  worm,  695 

Cotton-moth,  maxillae  of  the,  575 

Cotton-stainer,  385 

Cotton-worm,  686 

Cotton}^  maple-scale,  453 

Cow-killer  ant,  937 

"Cow-shed"  built  by  ants,  944 

Coxa,  56 

Coxites,  222 

Coxal  cavities,  52 

Crabro,  972;  C.  singularis,  wings  of, 
971 

Crabronidae,  890 

Crambidia  pallida,  705 

Crambinae,  649 

Crambns,  650;  C.  caliginosellus,  650;  C. 
hortuellus,  650 

Crampton,  G.  C,  40,  47,  49,  52,  233, 
272,  592 

Cranberry  fruit-worm,  652 

Crane-flies,  795;  phantom,  797;  prim- 
itive, 796,  so-called  false,  797;  typ- 
ical, 798 

Crawford,  D.  L.,  860,  921 

Cray-fishes,  6 

Cremaster,  187 

Crematogaster  lineolata,  943,  944 

Creophilus  maxillosus,  489 

Crescent-spots,  752 

Cresson,  E.  T.,  956 

Cricket  head  of  a,  37,  40,  136;  part  of 
the  tentorium  of  a,  96 

Crickets,  242;  ant-loving,  249;  field-, 
247;  house-,  248;  larger  brown  bush-, 
244;  larger  field-,  248;  mole-,  250; 
pigmy  mole-,  251 ;  smaller  field-,  248; 
sword-bearing,  243;  tree-  245;  wing- 
less bush-,  250 

Criocens  asparagi,  530 

Crista  acustica,  152 

Crochets,  578 

Crop,  no 

Crosby,  C.  R.,  377,  391 

Crosby  and  Leonard,  575 

Cross- veines,  64,  71 

Crotch,  88 

Croton-bug,  265,  266 
Crumena,  444 
Crura  cerebri,  123 
Cryptidae,  890 


Cryptochcetum,  861 

Crustacea,  6 

Cryptophagidas,  472,  474,  510 

Cryptoptilum  trigonipalpum,  250 

Crystalline  cone-cells,  140 

Ctenidia,  879 

Ctenocephalus  cams,  882 ;  C.  felts,  878, 

882 
Ctenucha  virginica,  706 
Cuban  termite,  nest  of,  279 
Cubital  area,  320 
Cubito-anal  fold,  73 
Cubitus,  64 

Cuckoo-wasps,  934,  935 
Cucujidas,  472,  474,  509 
Cucujo,  165 
Cucujus  clavipes,  509 
Cucullia,  694;  C.  speyeri,  694 
Cuculliinae,  693 
Cucumber  flea-beetle,  533 
Culex,  153,  806,  807;  larva  of,  805 
Culicidae,  785,  787,  804 
Culicinje,  807 
Cidicoides,  803 
Cupesidae,  471,  494 
Curculio,  apple-,  540 
Curculionida;,  476,  537,  539 
Curculios,  537 
Curicla,  364 

Currant  borer,  imported,  637 
Currant-fruit-fly,  858 
Currant-fruit-worm,  644 
Currant-moth,  pepper-and-salt,  673 
Currant  span-worm,  670 
Currant-stem-girdler,  899 
Currant-worm,  imported,  901 
Cushman,  R.  A.,  903,  904,  905 
Cuticula,  30 
Cuticular  nodules,  31 
Cut  worms,  696 
Cybister,  483 

Cydoplasis  panicifoliella,  634 
Cyclops,  6 
Cyclorrhapha,  786,  846;  with  a  frontal 

suture,  852 ;  without  a  frontal  suture, 

847 
Cydnidas,  357,  359,  391,  392 
Cyladinas,  538 
Cylas  formicaritis,  538 
Cylisticus  convexus,  7 
Cyllene  caryae,  528;  C.  robinae,  527 
Cymatophora  ribearia,  670 
Cynipidae,  890,  908,  913 
Cynipinffi,  922 
Cynipoidea,  890,  922 
Cynomyia  cadaverina,  870 
Cypridopsis,  6 
Cyrtidae,  837 
Cyrtomenus  mirabilis,  392 
Cyrtophyllus  concavus,  93 
Cyrtoxipha  columbiana,  244 


1020 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Dactylopius,  28 

Dactyls,  251 

Dagger,    American,    690;    ochre,    690; 

witch-hazel,  690 
Dalceridag,  582,  585,  605 
Dalcerides  ingenita,  606 
Dalla  Torre,  347,  922 
Damsel-flies,  314,  315,  321;  naiad  of, 

323;    stalked-winged,    324;    tracheal 

gill  of  a,  120;  323 
Danainae,  750,  765 
Danaus  archippiis,  759,  765;  chrysalis, 

766;  larva,  766;  D.  berenice,  766;  D. 

betenice  strigosa,  766 
Dance-flies,  845 
Daphnia,  6 
Darkling  Beetles,  513 
Darwin,  Charles,  88,  181 
Dascillus  cervinus,  505 
Dascyllidae,  472,  505 
Dasymutilla  occidentalis,  937 
Dasyneura  leguminicola,  818;  Z).  trifolii, 

818 
Datana,  28,  675;  D.  ministra,  675,  larva, 

675 
Davidson,  Dr.  Anstruther,  951 
Day-eyes,  142 
Death-watch  family,  514 
Death-watch,  80,  515' 
Decticinae,  235,  239 
Declicus  verrucivorus,  150,  151,  152 
Definite  accessory  veins,  69 
Deltoids,  685 
De  Meijere,  58 
Dendroleon,  304 
Dengue,  810 
Densariae,  447 
Dentes,  228 
Depressaria  heracUana,  624;  wings  of, 

624 
Dermaptera,  212,  214,  215,  217,  460 
Dermestes  lardarius,  506 
Dermestidae,  472,  506 
Dermis,  31 

Derobrachus  brunneus,  526 
Derodontidse,  473,  510 
Desmia  funeralis ,  646 
Desmocerus  palliatiis,  464,  527 
Deutocerebrum,  37,  124 
Development  without  metamorphosis, 

174 
Dewitz,  H.,  loi 
DiabroHca,  532;  D.  duodecimpunctata, 

532;   D.   longicornis,   532;   D.  soror, 

532,  P.  vitata,  532 
Diacrisia  virginica,  703 
Dialeurodes  citri,  440 
Diamond-back  moth,  632 
Diaphania  hyalinata,  647:  D.  nitidalis, 

648 
Diapheromera,  169;  D.  femorata,  261 


Diarlhronomyia  hypogaea,  820 

Diaspidinae,  454 

Diatraea  saccharalis,  650;  D.  zeacolella, 

650 
Dicaelus,  480 
Dicer ca  divaricata,  503 
Dichorda  iridaria,  wings  of,  666 
Digitate  mine,  620 
Digitules,  442 
Digitus,  45 

Dilar  americanus,  297 
Dilaridae,  284,  297 
Dinetini,  963,  965 
Dineutus,  484 
Dione  vanillcp,  764 
Diopsidae,  786,  791,  859 
Dioptidae,  583,  585,  673 
Diploglossata,  269 
Diplolepis  centricola,  926 
Diplopoda,  15 

Diploptera,  948;  The  SoHtary,  950 
Dipsocoridae,  356,  358,  374 
Diptera,  213,  214,  215,  217,  219,  773 
Diptera,  synopsis  of  the,  785 
Discal  cell,  74,  886 
Discal  vein,  74 
Disholcaspis  globulus,  926 
Dissosteira  Carolina,  82,  233,  234,  258 
Distal  retinula  cells,  140 
Divers,  691 
Diver,  black-tailed,  691;  brown-tailed, 

692 
Diverse-line  moth,  668 
Divided  eyes,  144 
Diving-beetles,  the  predacious,  482 
Doane,  Prof.  R.  W.,  951 
Dog-flea,  882,  877 
Dog's  head,  749 
Dolichoderinag,  941,  945 
Dolichopodidas,  786,  789 
Dolichopus  coquilletti,  wing  of,  844;  D. 

lobatus,  843 
Donacia,  530 
Donisthorpea,  890 
Dorcus  parallelus,  523 
Dorsal  diaphragm,  121,  162 
Doru  aculeatum,  463 
Doryhnae,  941 
Douglasiidae,  582,  591,  623 
Doyere,  M.,  12,  13 

DrcECulacephala,  407;  D.  reticulata,  407 
Dragon-flies,  314,  316 
Dragon-fly,  exuviae  of  naiad  of,  319 
Drepana  arcuata,  711,  712 
Drepanidae,  583,  587,  588,  710 
Drone-fly,  851 
Drones,  988 
Drosophila  ampelophila,  861;  D.  melan- 

ogaster,  861 
Drosophilidae,  786,  792,  860 
Dryinidae,  891,  961 


INDEX 


1021 


Drug-store  beetle,  515 

Dryopidae,  471,  504 

Ducke,  A.,  952 

Dufour,  L.,  no 

Dung-beetles,  earth-boring,  517 

Dung-flies,  854,  855 

Dusky- wing,  Martial's,  737 

Dyar,  H.  G.,  33,  173,  579,  610,  807,  810 

Dynastes  grantii,  520;  D.  here  ides,  520; 

D.  suturellus,  385;  D.  tityrus,  520 
Dysodia  oculatana,  654 
Dyspteris  abortivaria,  667;  668,   wings 

of,  668 
Dytiscidae,  470,  482 
Dytiscus,  483 

Dixa,  larva  of,  800;  wing  of,  800 
Dixidae,  785,  788,  800 
Dixiinae,  871 

Earwig,  European,  463;  hind  wing  of 
an,  461;  handsome,  463;  little,  462; 
ring-legged,  462;  seaside,  462;  spine- 
tailed,  463 

Earwigs,  460 

Eaton,  A.  E.,  311 

Ecdysis,  171 

Echidnophaga  gallinacea,  883 

Echidnophagidae,  882 

Eciton,  942 

Ectoderm,  29 

Egg,  166;  -burster,  171;  -calyx,  159; 
-follicles,  15,8;  -tooth,  171 

Egg-masses  of  caddice-flies,  557 

Eggers,  F.,  577 

Ejaculatory  duct,  162 

Elachista  quadrella,  wings  of,  622 

Elachistidae,  582,  591,  621 

Elateridae,  472,  499 

Eleodes,  513 

Elephantiasis,  810 

Elis  {My zinc),  936 

Ellipes  252;  E.  minuta,  2^2 

Elm-gall  colopha,  cockscomb,  422 

Elm-gall  tetraneura,  cockscomb,  424 

Elmidae,  471,  504 

Elophila  fulicalis,  649 

Elytra,  59 

Embia  major,  340;  E.  sabulosa,  338;  E. 
texana,  339 

Embiidina,  212,  214,  216,  218,  338 

Embolemidae,  890,  909,  913,  934 

Embolium,  351 

Etnesa  brevipennis,  382 

Emory,  938 

Emperor,  tawny,  760;  gray,  761 

Empididae,  786,  789,  790 

Empoasca  malt,  407 

Empodium,  58,  778 

Emposa  rosce,  407 

Enchenopa  binotata,  405 

Enchroma  gigantea,  465 


Encoptolophus  sordidus,  257 
Endcrlein,  G.,  338,  823 
Endomychidae,  473,  474,  511 
Endo-skeleton,  95 
Endothorax,  97 
Endrosis  lacteella,  624 
Eneopterinac,  243,  244 
Engraver-beetles,  542,  543 
Enicocephalidae,  356,  358,  383 
Enicocephalus  formicina,  383 
Ennomos  magnarius,  672 
Ensign-flies,  932 
Entomobryidas,  229 
Eosentomidae,  26 
Epargyreus  tityrus,  734;  736 
Epermenia  pimpinella,  631 
Ephemera,  312;  E.  simulans,   312;  E. 

varia,  178,  311 
Ephemerella,  312 
Ephemerida,   180;  ocelU  of,   139,  212, 

214,  215,  216,  308 
Ephemeridae,  312 
Ephestia  kuhniella,  651 
Ephydra,  859 

Eph'ydridaj,  786,  792,  794,  859 
Epiblemidas,  639 
Epiccerus  imbricatus,  538 
Epicauta,    497;    E.    cinerea,    497;    E. 

pennsylvanica,  497;  E.  vitiata,  496 
Epicnaptera  americana,  732 
Epicnemium,  887 
Epidermis,  31 
Epicranial  suture,  37 
Epicranium,  38 
Epilachna   borealis,    512;   E.   corrupta, 

512 
Epimartyria  auricrinella,  593;  E.  pard- 

ella,  593 
Epimerum,  51 
Epinotum,  887 
Epipharnyx,  46 
Epiphysis,  576 
Eoiolemidas,  583,  587,  708 
Epipleuras,  74 
Epiponinae,  949,  956 
Epipyropidae,  582,  610 
Epipyrops  barberiana,  610;  E.  anomala, 

610 
Episternum,  51 
Epistoma,  779 
Epithelium,  109,  118;  of  mid-intestine, 

112 
Epitrix  cucumeris,  533 
Epizeuxis  itibricalis,  685 
Epochra  canadensis,  858 
Epomidiopteron,  936 
Erannis  tiliaria,  671,  672 
Erastriinae,  689 
Erax  apicalis,  841 
Erax,  wing  of,  841 
Erebinae,  685 


1022 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Erebus  odor  a,  685,  686 

Eretmoptera  browni,  802 

Ericerus  pela,  441 

Eriococcinae,  450 

Eriococcus  araucarice,  444 

Eriocraniidae,  581,  584,  593 

Eriosoma  americana,  wings  of,  414 

Eriosoma  lanigera,  421 

Eriosomatinae,  420;  gall-making,  422 

Eristalus,  wing  of,  851;  E.  tenax,  851 

Ermine-moths,  632 

Erotylidae,  472,  474,  509 

Eruciform,  184 

Erythroneura  comes,  406,  407 

Erythrothrips  arizonce,  fore  wing  of,  344 

Estigmene  acraea,  701,  702 

Ethmia,  625 

Ethmiidae,  582,  590,  62,5 

Euchaetias  egle,  larva,  701 

Euchromiidae,  583,  587,  706 

Eucinetidae,  472,  505 

Euclea  delphinii,  609;  scales  of,  571 

Eucleidas,  582,  586,  608 

Euclemensia  basset tella,  634 

Eucnemidae,  472,  502 

Eucoilinae,  922 

Eucone  eyes,  141 

Eucosmidae,  639 

Euctheola  rugicet>s,  520 

Eudeilinia  hermmiata,  711,  712 

Eudule  mendica,  669;  wings  of,  667 

Euglenidae,  475,  499 

Eugonia  j-album,  756 

Eulia  pinatubana,  643 

Eulonchus,  wing  of,  837 

Eumenes,  954;  E.  fraterniis,  954 

EumeninEe,  949,  952 

Eunica,  751 

Eupargia,  950 

Euparagiinas,  949,  950 

Eupeleieria  magnicornis,  872 

Euphoria,  521;  E.  inda,  521 

Euphydryas  phaeton,  752 

Euproctis  chrysorrhoea,  682 

Eupsalis  minuta,  536 

Eupterotidae,  583,  587,  707 

Euptoicia  claudia,  751,  752 

Eurema  enter pe,  749;  E.  nicippe,  749 

Eurosta  solidaginis,  627,  858 

Eurrhypara  urticata,  649 

Eurycyttarus  confederata,  614 

Eurygaster  alternatus,  393 

Eurymus  eurytheme,  748;  E.  philodice, 

748 
Euryophthalmus  s tic cinet us,  2)86;  heme- 

lytron  of,  385 
Etirypauropidae,  20 
Eurypauropus  ornatus,  19;  E.  spinosus, 

19,20 
Eurystethidae,  474,  498 
Eurystethus  subopacus,  498 


Enrytomids,  seed-infesting,  931 

Eurytominae,  930 

Euscelis  exitiosus,  406 

Euschemon  rafflesiae,  733 

Eusternum,  52 

Euthisanotia  grata,  693;  E.  unto,  693 

Euthrips  citri,  345;  E.  fuscus,  345;  E. 

Pyi,  345; -E.  tritici,  345 
Euvanessa  antiopa,  753,  755 
Evania,    933;    E.    appendigaster,    933; 

wings  of,  933 
Evaniidag,  890,  909,  932 
Evanioidea,  890,  932 
Evening  primrose  moth,  695 
Everes  coniyntas,  772 
Evergreen  nepytia,  671 
Evetria,    640;    E.    comstockiatia,    640; 

E.  frustrana,  640 
Evoxysoma  vitis,  931 
Exarate  pupae,  190 
Exner,  S.,  141,  143 
Exuviae,  171 
Eye-cap,  576 
Eyed  brown,  762 
Eyes   of  insects,   two  types  of,    134; 

with  double  function,  143 

Fabre,  J.  H.,  516 

Face,  779 

Facial  depression,  780 

Facialia  or  facial  ridges,  780 

Falcicida  hebardi,  244 

Fall  webworms,  702 

Falx,  877 

Felt,  E.  P.,  814,  815,  816 

Femur,  57 

Fenestra,  274 

Feniseca,  772;  F.  tarquinius,  422,  772 

Ferris,  G.  F.,  875,  876 

Ferton,  Ch.,  950 

Fibula,  62;  of  Corydalus,  63 

Fidia  longpipes,  531 

Fielde,  Miss  A.,  938 

Fiery  hunter,  479 

Fig-eater,  522 

Fig-insects,  931 

Figitinas,  922 

Filaria  bancrofti,  810 

Filariasis,  810 

Filiform,  41 

Fiorinia  fioriniae,  455,  456 

Fire-brat,  224 

Firefly  Family,  491 

Fish-flies,  286 

Fish-moth,  224 

Fixed  hairs,  31,  573 

Flannel-moths,  606 

Flannel-moth,  crinkled,  606 

Flat-headed  apple-tree  borer,  503 

Flat-footed  Flies,  848 

Flask-like  sense-organ,  131' 


INDEX 


1023 


Flea-beetles,  532 

Fleas,  877;  antennae  of,  878;  head  of, 
878;  broken-headed,  881;  unbroken- 
headed,  881 

Fletcher,  Miss  P.  B.,  980 

Flower-beetles,  520 

Flower-beetle,  hermit,  521;  rough,  52X 

Fluvicola,  504 

Follicular  epithelium,  functions  of  the, 
159 

Folsom,  J.  W.,  43,  47 

Fontanel,  274 

Fontanelle,  274 

Footman-moths,  699,  704 

Footman,  banded,  705;  clothed-in- 
white,  705;  painted,  706;  pale,  705; 
footman,  striped,  704;  footman,  two- 
colored,  705 

Forbes,  S.  A.,  419,  61 1 

Forbes,  Wm.  T.  M.,  465,  577,  579,  589, 
6i7>  750 

Ford,  Norma,  929 

Fore-intestine,  108,  109 

Forel,  938 

Forester,  eight-spotted,  697;  Langton's 
698 

Foresters,  697 

Forficula  auricularia,  463 

Forked  fungus-beetle,  513 

Formica  exsectoides,  946;  F.  sa^iguinea, 
946 

Formicidge,  891,  909,  910,  915,  937 

Formicinae,  941,  946 

Four-footed  Butterflies,  750 

Fox,  W.  J.,  937,  96s,  966,  968,  972 

Fracker,  S.  B.,  579,  625 

Fracticipita,  880,  881 

Franklin,  H.  J.,  986,  987 

Frenatas,  582,  596;  Aculeate,  582; 
Generalized,  582,  597;  Non-Aculeate 
Generalized,  582;  Specialized,  582 

Frenulum,  61 

Frenulum-conservers,  583;  Frenulum- 
losers,  583 

Frenulum  hood,  61 

Frenulum-hook,  597 

Frison,  T.  H.,  979 

Frit-fly,  European,  860 

Fritillaries,  751 

Fritillary,  great  spangled,  751;  gulf, 
764;  variegated,  751 

Frog-hoppers,  402 

Frons,  877 

Front,  37,  780;  so-called,  780 

Frontalia,  780 

Frontal  lunule,  775,  780;  orbits,  780; 
suture,  776,  780;  triangle,  780;  vitta, 
780 

Fronto-clypeus,  780 

Froth-glands  of  spittle  insects,  102 

Fruit-tree  ugly-nest  tortricid,  643 


Fucellia,  864 

Fulgoria  candelaria,  409 

Fulgoridag,  400,  408 

Fungus-gnats,  810;  wings  of,  811 

Fungus  weevils,  536 

Funicle,  41 

Furcas,  98 

Furcae  maxillares,  332 

Furcula,  228 

Forrows  of  the  wing,  73 

Gahan,  J.,  88 

Galerita  janus,  480 

Galgulidae,  368 

Galgulus,  368 

Gall-aphid,  vagabond,  424 

Galleria  meUonella,  650 

Galleriinae,  650 

Gall-gnats,  813;  wing  of,  814 

Gallicolae,  434 

Gametes,  809 

Gamogenetic  eggs,  416 

Ganonema  americana,  568 

Garden-flea,  229 

Gartered  plume,  653 

Gaster,  888 

Gasteruption  incertus,  wings  of,  920 

Gasteruptionidae,  890,  906,  919 

Gastric  caeca,  112 

Gastrophilidea,  787,  792,  864 

Gastrophilus,  865;  G.  equi,  865;  G. 
hcEfnorrhoidalis,  866;  G.  intestinalis, 
865;  G.  nasalis,  866,  wing  of,  865 

Gaiirax,  860 

Gelastocoridae,  356,  357,  368 

Gelastocoris  oculatus,  368 

Gelechiidse,  582,  590,  625 

Genacerores,  447 

Genae,  39,  78c,  877;  so-called,  780 

Geniculate,  41 

Genital  appendages,  the  development 
of  the,  201 

Genital  claspers,  76 

Genitalis,  76 

Genovertical  plates,  780 

Geometridse,  583,  584,  587,  589,  663 

•Geometrids,  662;  green,  665 

Geometrinag,  663,  670 

Geometroidea,  583,  662 

Geomyzidae,  786,  792,  861 

Geophilus  flavidus,  21 

Georyssidae,  474,  505 

Georyssus,  505 

Geotrupes,  517 

Germarium,  158 

Gerridag,  356,  357,  370 

Gerris  conformis,  371 

Giraud,  J.,  980 

Glands,  98;  connected  with  setae,  99 

Glandular  hairs,  33 

Glassina  moristans,  873 


1024 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Glenurus,  304 

Glischrochius  (Ips)  fasciatus,  508 

Glossosoma  americana,  Case  of,  561 

Glover's  scale,  457 

Glowworms,  194 

Glutops,  833 

Glycohius  speciosus,  527 

Glyphipterygidae,  582,  590,  633 

Glyphipteryginae,  633 

Glyphipteryx,  633;  G.  thrasonella, 
wings  of,  633 

Glyplocombus  saltator,  374 

Glyptometopa,  935 

Gnathochilarium,  16 

Gnophaela  latipennis,  698,  699 

Gnorimoschema  gallaesolidaginis,  627 

Goat-weed,  butterfly,  761 

Goera  calcarata,  569;  case  of,  569 

Goldenrod-gall,  round,  858 

Gomphines,  318 

Gomphus  descriptus,  wings  of,  318; 
wings  of  naiads  of,  317 

Gonapophyses,  76,  232 

Gonatopus,  961 

Gonin,  J.,  199 

Goniodes  stylifer,  336 

Goniozus,  948 

Goniurus  proteus,  736 

Goose-berry  fruit  worm,  652 

Gortyna  immanis,  691 

Gossamer-winged  butterflies,  768 

Gould,  W.  R.,  938 

Graber,  V.,  146,  149,  150 

Gracilaria,  wings  of,  618 

Gracilariidae,  582,  589,  591,  617 

Gradual  metamorphosis,  175 

Graham,  S.  A.,  466 

Grain-weevils,  540 

Granary- weevil,  541 

Grape-berry  moth,  640 

Grape  flea-beetle,  533 

Grape-leaf  skeletonizer,  605 

Grape  leaf-folder,  646 

Grape  root-worm,  531 

Grape-seed  chalcid,  931 

Grape-vine  epimenis,  693 

Grasshopper,  lubber,  257;  western,  254 

Grasshoppers,  cone-headed,  239;  leaf- 
rolling,  240;  long-horned,  234;  mead- 
ow, 238;  shield-backed,  239;  short- 
horned,  252 

Grassi,  B.,  157,  172 

Grayling,  762;  blue-eyed,  762;  dull- 
eyed,  763;  hybrid,  763;  sea-coast,  763 

Greenbottle,  -fly,  870 

Grimm,  O.,  192 

Ground-beetles,  478 

Gryllacrinae,  235,  240 

Gryllidae,  234,  242 

Gryllinas,  243 

Grylloblalta  campodeiformis,  268 


Grylloblattidae,  218,  268 

Gryllotalpa  borealis,  251;  chirp  of,  93; 
G.  hexadaclyla,  251 

Gryllotalpinae,  243,  250 

Gryllus,  83,  248;  ventral  aspect  of  the 
meso-  and  metothorax  of,  98;  do- 
me sticus,  248,  249 

Guenther,  K.,  132 

Guest  gall-flies,  924 

Guilbeau,  B.  H.,  102,  403 

Gula,  39 

Gynandromorph,  156 

Gypona,  408 

Gyponinse,  407 

Gypsy  moth,  682 

Gyretes,  484 

Gyrinidae,  470,  484 

Gyrinus,  484 

Gyropidas,  337 

Hahrosyne  scripta,  709,  710 

HadeninsB,  694 

Hadwen   S.,  867 

Hamatohia  irritans,  873 

Haematopinidae,  349 

Hcematopinus  asini,  349;  H.  euryster- 

nus,  349;  H.  suis,  349 
Hamatopis  grataria,  666,  667 
Hamatosiphon  inodorus,  378 
Hcemorrhagia  diffinis,  661;  H.  thysbe, 

661 
Hasmozoin,  808 
Hagen,  H.  A.,  113,  171 
Hag-moth,  609 
Hair- streaks,  769 
Hair-streak,   banded,   769;  olive,   769; 

white-m,  770 
Haliclus,  978;  nest  of,  978;  H.  {Augo- 

chlora)  979;  H.  humeralis,  979 
Haliplidae,  470,  481 
Haliplus,  481,  482 
Halisidota,  sp.,  wings  of,  699 
Halobates,    372;    H.    micans,    372;    H. 

sericeus,  372 
Haloptiliidae,  620 
Halteres,  59 
Haltica  chalybea,  533 
Halysidota  carya,  704;  larva,  703 
Hamamelistes  spinosus,  426,  427 
Ham-beetle,  red-legged,  493 
Hamilcara,  603 
Hammar,  A.  G.,  125,  126 
Hamuli,  61 
Handlirsch,    A.,    260,    262,    263,    284, 

289 
Handmaid  moths,  675 
Hansen,  H.  J.,  23,  24,  43 
Hapilhus  agitator,  245 
Haploa,  700;  H.  contigua,  700 
Haploptilia,  620 
Harlequin  milk-weed  caterpillar,  701 


INDEX 


1025 


Ilarmolita,    930:    //.    gratidis,    93 1;    H. 

tritici,  930 
Harpaliis    caliginosus,    480;    head    of, 

468;  labium  of,  45,  52;  prothorax  of, 

468 
Harrisina  americana,  605 
Hartman,  C.  G.,  953 
Harvcstmen,  9 

Hatching  of  young  insects,  171 
Hatching  spines,  171 
Hautsinnesorganc,  130 
Hawk-moths,  655;  larva  of  a,  577 
Hawk-moth,  bumblebee,  661 
Head,  36 

Head  measurements  of  larv.ns,  173 
Hearing,  organs  of,  145 
Heart,  36 

Hebrida;,  356,  358,  359,  372 
Hebnis,  373 
Heel-flv,  868 
Hegner,  R.  W.,  816,  817 
Helichus  lithophilus,  504 
Heliconiinae,  750,  764 
Heliconius  charitonius,  764 
Helicopsyche  borealis,  569 
Heliocharis,  base  of  wing  of,  322 
Heliodinidae,  582,  591,  634 
Heliothis  obsoleta,  695 
Heliothrips  fascial ns,  345;   H.   hcemor- 

rhoidalis,  345 
Heliozelidas,  582,  591,  622 
Helhtla  undalis,  648 
Helodidas,  472,  505 
Helomyzidag,  786,  790,  854 
Heloridae,  890,  907,  921 
Helorus,  g2i 
Hemel\rtra,  59,  350 
Hemerobiidae,  284,  294 
Hemerobius,    301;    larva    of,    297,    H. 

humuli,  wings  of,  295 
Hemerocampa,  679,  680;  H.  leucostigma, 

680;  H.  plagiata,  681;  H.  vetusta,  681 
Hemileuca  tnaia,  720;  H.  olivicE,  721 
Hemimeridai,  269 
Hemimerus,  269 
Hemimetabola,  179 
Hemimetabolous,  development,  178 
Hemiptera,  215,  216,  217,  218,  219,  350 
Hemispherical  scale,  453 
Hemitheinae,  663,  665 
Hendel,  Fr.,  794,  856,  862 
Henicocephalus  culicis,  384 
Henneguy,  L.,  117,  124 
Heodes  epixanthe,  Tjo;H.  heteronea,  770; 

H.  hypophlceas,    771;   H.    thoe,  771; 

wings  of,  768 
Hepialid,  wings  of  a,  62 
Hepialidae,  581,  584,  594,  595 
Hermininae,  685 
Herrick,  G.  W.,  379 
Hesperia,  737;  H.  tessellata,  737 


Hesperiida^  583,  734 

Hesperiina;,  735 

Hes])crioidea,  589,  732 

Hesperortenes  Inugircps,  379 

Hesperophylum  heidemanni,  377 

Hess,  W.  N.,   136,   137,   139,'  146.   147, 

148 
Hessian-fly,  818 

Hetcerina,  324;  base  of  wing  of,  323 
Heterocampa  hilineata,  676;  larva,  676; 

H.  guUivitla,  677;  H.  varia,  6'7'7 
Heterocera,  581 
Heteroceridce,  474,  505 
Heterocerus,  505 
Heterocordylus  maliniis,  376 
Heterogamy,  177,  415 
Heteroj)czina;,  815,  816 
Heteroptcra,  212,  214,  350 
Hewitt,  C.  G.,  202 
Heymons,  R.,  174,  354,  398,  399 
Hexagenia,  312 
Hexapoda,  26 
Hexapoda,   sub-classes  and  orders  of» 

209;  table  of  orders,  213 
Hickory-borer,  painted,  528 
Hickory  horned  devil,  717 
Hicks,  B.,  155 
Hill,  C.  C,  889 

Hilton,  W.  A.,  128,  129,  132,  133 
Hind-intestine,  108,  112 
Hinds,  W.  E.,  341,342 
Hine,  J.  S.,  554,  830 
Hippiscus  apictilahis,  258,  259 
Hippoboscidc-e,  787,  790,  874 
Hispopria  foveicollis,  88 
Histerida?,  470,  490 
Histoblast,  195,  205 
Histogenesis,  204 
Hochreuter,  R.,  155 
Hoeck,  P.  P.  C,  II 
Hofer,  B.,  127 

Hog-caterpillar  of  the  vine,  659 
Holcocera,  wings  of,  629 
Holland,  W.  J.,  739 
Holmgren,  E.,  99,  280 
Holometabola,  180 
Holometabolous  development,  180 
Holorusia  nibiginosa,  197 
Holosphyrum  boreale,  250 
Homaledra  sabalella,  629,  630 
Homochronous  heredity,  181 
Homologizing  of  the  sclerites,  35 
Homoptera,  212,  214,  215,  218,  394 
Honey-bee,  158,  975 
Honey-bees,  988 
Honey-pot,  986 
Hood.  J.  D.,  948 
Hooded  owlets,  694 
Hook-tip  moths,  711 
Hoplopsylltis  anomalus,  882 
Hop-merchant,  756 


1026 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Hop -plant  borer,  691 

Hop  vine  deltoid,  685 

Hormaphidinag,  424 

Hormaphis  hamamelidis,  425 

Hornets,  958 

Hornet,  giant,  960,  white-faced,  960 

Horn-fly,  873 

Horn-tails,  891,  896 

Horse-flies,  829 

Horse-guard,  971 

Horseshoe-crabs,  8 

House-fly,  872;  larva  of  the,  202 

Howard,  L.  O.,  807,  872,  930,  948 

Huber,  P.,  938,  947 

Hiibner,  J.,  620 

Hiibner's  Tentamen,  581 

Human  flea,  882 

Humeral,  angle,  60;  callus,  783;  cross- 
vein,  71;  suture,  274;  veins,  74 

HuniD-backed  Flies,  847 

Hungerford,  H.  B.,  361,  364,  365 

Hutchison,  R.  H.,  873 

Huxley,  T.  H.,  40 

Hyhlcea  piiera,  655 

Hyblaeidffi,  583,  586,  655 

Hybrid  purple,  758 

Hydrometra,  373;  H.  australis,  373;  H. 
martini,  373;  H.  wileyi,  373 

Hydrometridaj,  356,  357,  373 

Hydrophilidae,  471,  473,  485 

Hydrophilus,  486,  egg  sac  of,  170;  em- 
bryo of,  75;  maxilla  of,  44;  H. 
ohtusatus,  486 

Hydropsyche,  562;  net  of,  562 

Hydropsychidae,  560,  562 

Hydroptilidae,  559,  560,  561 

Hydrous,  ^85;  H.  triangularis,  485 

Hylasidae,  890 

Hylaus,  890 

Hylastinus  obscurus,  542 

Hylemyia  antiqua,  864;  H.  brassicae, 
863;  H.  rubivora,  864 

Hymenoptera,  213,  214,  216,  217,  884 

Hymenopterous  wing,  typical,  885 

Hypatus  bachmanni,  766,  767 

Hypeninae,  685 

Hypena  hnmnli,  685 

HypcraescJira  stragida,  wings  of,  674 

Hypenuallus  villosus,  528 

Hypermetamorphosis,  191 

Hyphantria  cunea,  702 ;  H.  textor,  702 

Hypocera  incrassata,  848 

Hypoderma  bovis,  867;  H.  lineaium, 
867,  868 

Hypodermal  structures,  95;  glands,  98 

Hypodermis,  29 

Hyponomeutidae,  631 

Hypopharynx,  47,  400 

Hypopleura,  783 

Hypoprepia  fucosa,  705;  H.  miniata,70i 

Hypoptinas,  603 


Hypopygium,  75 
Hyporhagus,  514 
Hypothetical  tracheation  of  a  wing  of 

the  primitive  nymph,  63 
Hypothetical    type    of    the    primitive 

wing-venation,  62 
Hypsopygia  cos  talis,  649 
Hyptia,  933 
Hyslop,  J.  A.,  501 

Ibaliinae,  922 

Icerya,  449;  /.  purchasi,  449,  512 
Ichneumon-flies,  915,  917 
Ichneumonidae,    890,    906,    913,    915, 

917 
Idiogastra,  890,  891,  903 
mice  unifasiiata,  705 
Imaginal  disc,  195,  205 
Imago,  191 

Imperforate  intestines,  108 
Imperial-moth,  717 
Incisalia  niphon,  770,  753 
Incisurae,  447 

Incomolete  matamorphosis,  178 
Incurvariidse,  582,  589,  590,  598 
IncurvariincB,  598 
Indian-meal  moth,  651 
Inner  margin  of  wing,  60 
Inocellia,  289 
inquilines,  924 
Insects,  26 
Instars,  172 
Integriciuita,  880,  881 
Intercalary  veins,  69 
Interfrontaha,  780 
Intermediate  organ,  152 
Internal  anatomy,  94 
Internal  organs,  the  transformations  of 

the,  204 
Internal  skeleton,  95 ;  sources  of  the,  95 
Intersegmental  plates,  40 
Intima,  109,  117 

Invaginations  of  the  body-wall,  95 
lo-moth,  722 
Iphiclides  marcellus,  743 
Iridomyrmex  humilis,  945 
Isabella  tiger-moth,  702 
Ischnocera,  337 
Ischnopsyllidfe,  881 
Ischnopsyllus,  878 
Isia  isabella,  702 
Isley,  D.,  953 
Isogenus  sp.,  wings  of,  329 
Isometopidae,  356,  359,  374 
Isometopus  pidchellus,  375 
Isoptera,  212,  214,  216,  218,  273 
Isosonia,  930 
Ithobalus,  741 

Ithycerus  noveboracensis,  537 
Ithytrichia  confusa,  562 
Itonididae,  813 


INDEX 


1027 


Jalvsiis  perclavatus,  388;   /.  spinosus, 

388 
Janet,  C,  87 
Janus  integer,  899 

Japanese  beetle,  519;  Laboratory,  520 
Japygidaj,  224 
Japyx,  161,  220,  224;  /.  solifugus,  221; 

ovary  of.  223;  461 
Jigger,  883 
Johannsen,  Oskar  A.,    304,    803,  807, 

811,  823 
Johnston,  Christopher,  152 
Johnston's  organ,  152 
Joint-worm  flies,  grass  and  grain,  930; 

wheat,  930 
Jones,  P.  R.,  342 
Judeich  and  Nitsche,  116 
Jngatae,  581,  584,  592 
Jugates,  haustellate,  593;  mandibulate, 

592 
Jug-builders,  954 
Jugular  sclerites,  40 
Jugum,  61 ;  of  a  hepialid,  63 
Julia  butterfly,  764 
Julus,  16 

June-beetle,  green,  522 
June-bug,  515,  518,  522 
Juniper  web-worm,  643 

Karschomyia  vibiirni,  814 

Katepimerum,  51 

Katepisternum,  51 

Katydid,    chirp    of    the,    93;    angular 

winged,   237;   northern   bush-,    237; 

round-winged,     237;     Uhler's,     237; 

the  false,  236 
Kellogg,  Vernon  L.,  100,  197,  199,  200, 

336,  573,  828 
Kelp-flies,  864 
Kenyon,  F.  C,  18,  19 
Kermes,  454,  455,  634;  K.  ilicis,  441 
Kermesiinae,  454 
Kieffer,  J.  J.,  815,  817,  919,  921,  922, 

.933,  962 
King-crabs,  8 
Kirby  and  Spence,  97 
Kirkaldy,  G.  W.,  362 
Knab,  F.,  807 
Korschelt  and  Heider,  203 
Kowalevsky,  A.,  202 
Krecker,  F.  H.,  443 

Labia  minor,  460,  462 
Labial  palpi,  46 
Labidomera  divicollis,  531 
Labium  or  second  maxillae,  45 
Labrum,  38,  43 
Lac-dye,  441 
Lace-bud,  hawthorn,  384 
Lace-cocoon,  suspended,  632 
Lace-like  cocoon,  188 


Lacewing-flics,  299 

Lacinia,  45 

Lac-insect,  440 

Lacosoma  arizonicum,  713;  L.  chiridota, 
714 

Lacosomidag,  583,  585,  587,  712 

Lady-bugs,  511,  512;  bean,  512;  nine- 
spotted,  512 

LceUus  trogodermalis,  948 

Larlias  philenor,  larva,  741 

Lcetilia  coccidivora,  652 

Lagoa  crispata,  606,  607 

Lagriidas,  474,  514 

Lake-flies,  312 

Lamellate,  41 

Lamellicorn  beetles,  515;  leaf-chafers, 
518;  scavengers,  516 

Lamellicornia,  468,  469;  the  families  of 
the,  475 

Lamiinae,  528 

Lampyridae,  473,  491 

Landois,  H.,  91 

Languria,  510;  L.  mozardi,  510 

Lantern-fly  of  Brazil,  great,  408 

Lapara  bombycoides,  658 

Lappet-caterpillars,    729,    731;    amcri- 
can,  732;  larch,  731;  velleda,  731 

Larder-beetle,  506 

Larentiinae,  663,  666 

Large-intestine,  113 

Larrinae,  964 

Larrini,  963,  964 

Larvae,  adaptive  characteristics  of,  181 ; 
the  different  types  of,  1 83 ;  the  term 
defined,  180 
Lasioderma  serricorne,  515 
Lasiocampidag,  583,  589,  728 
Lasius,  451,  890;  L.  americanus,\jfi(); 

L.  niger  americanus,  947 
Laspeyresia  inlerstinctana,  641 
Lateral  conjunctivae,  35 
Laternaria  phosphorea,  408 
Lathridiidas,  473,  511 
Latzel,  R.,  19,  21,  23,  24 
Laurentiinag,  663 
Leach,  W.  E.,  174,  347 
Leaf-beetles,  530 
Leaf -beetles,  long-horned,  530 
Leaf-chafers,  shining,  519 
Leaf-hoppers,    406;    apple,    407;    de- 
structive, 406;  grape-vine,  406 
Leaf-insects,  260 
Leaf- miner,  morning-glory,  616 
Leather-jackets,  799 
Lebia  grandis,  480 
Lecaniinae,  451 

Lecaninni,  445;  L.  hesperidum,  451,  452 
Legionary  or  Visiting  ants,  941 
Legs,  56;  the  development  of,  197 
Leiby,  R.  W.,  889,  938 
Lenta  trilineata,  530 


1028 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Leng,  C.  W.,  467 

Lentigen  layer,  138 

Leon,  N.,  354 

Leopard-moth,  603 

Lepidoptera,  213,  214,  215,  216,  217, 
218,  219,  571;  frenate,  582;  meta- 
morphosis of,  577 

Lepidosaphes,  445;  L.  gloverii,  457;  L. 
pinncEformis,  456,  457;  L.  ulmi.  457 

Lepisma  saccharina,  48,  78,  224 

Lepismatidas,  224 

Leptidae,  834 

Leptinidae,  470,  487 

Leptinillus  aplodontia ,  487,  L.  validus, 
487 

LeMinotarsa  decemlineata,  531 

Leptinus  testaceiis,  487 

Leptoceridas,  559,  560 

Leptocertis  ancylus,  566;  case  of,  566 

Leptocons   trivittatus,    hemelytrum   of, 

Leptophlebia,  312 

LeptopsylUdse,  881 

Leptothorax  emersoni,  944 

Leptysma  mat ginicollis ,  257 

Lepyronia  quadrangularis ,  403 

Lena,  wing  of,  855 

Lestes  rectangular  is,  wing  of,  321,  322 

Lestremia,  wing  of,  816 

Lestremiinffi,  815,  816 

Lethocerus,    366;   L.    americanus,    366; 

head  of,  352;  last  segment  of  beak  of, 

354 
Leucocytes,  122 
Leucopis,  862;  L.  affinis,  929 
LeucospinEe,  929 
Libel  I  Ilia  luctuosa,  316 
LibelluHdse,  318,  321 
Libytheinse,  750,  766 
Lice,  true,  347;  jumping  plant-,  410 
Lienard,  V.,  125 
Ligament   of  the   ovary,    159;   of  the 

testes,  162 
Light -organs,  164 
Limacodidae,  608 
Lime-tree  winter-moth,  671,  672 
Limnobates,  373 
Limnophilidae,  559,  560,  568 
Limnophilus  combinatus,  568;  case  of, 

569 
Limnoporus,  371 ;  L.  rufoscuHllatus,  371 
Limulus  Polyphemus,  8 
Lincecum,  938 
Lingula,  438 
Lingua,  47 
Lingual  ula,  14 
Linguatulids,  14 
Linnaeus,  209,  252 

Linognathus  pilijerus,  349;  L.  vituli,  349 
Liotheidag,  337 
Liparidae,  679 


Lipoptena  depressa,  875 

Lispa,  wing  of,  863 

Lithocolletis ,  618 

Lithosiidag,  586 

Lithosiinae,  704 

Lloyd,  J.  T.,  559,  564,  567,  570,  649 

Locust  borer,  527 

Locust,  Boll's,  258,  Carolina,  258; 
clouded,  257;  coral- winged,  258;  red- 
legged,  256;  Rocky  Mountain,  254; 
seventeen-year,  402 

Locusta  viridissima,  128 

Locustidas,  234,  252 

Locustinae,  253,  254 

Locusts,  252;  band- winged,  257;  north- 
ern green-striped,  257;  pigmy,  259; 
slant-faced,  259;  spur-throated,  254 

Lomaniyia,  298 

Lonchcea,  856;  L.  polita,  856 

Lonchaeidag,  786,  791,  856 

Lonchoptera,  846;  wing  of,  846 

Lonchopteridae,  786,  789,  846 

Long-beaks,  766 

Long-horned  beetles,  524 

Longistigma  caryce,  418 

Longitudinal  veins,  64 

Long-legged  flies,  843 

Louse,  body-,  348;  crab-,  349;  dog-, 
349;  head-,  348;  hog-,  349;  horse-, 
349;  long-nosed  ox-,  349;  short- 
nosed  OX-,  349 

Louse-flies,  874 

Loxostege  similalis,  648 

Lubbock,  J.,  18,  48,  106,  938 

Lucanus  elaphus,  523 

Lucanidae,  475,  523 

Lucanus  dama,  523 

Lucilia  ccesar,  870 

Luna-moth,  723 

Lyccena  argiolus,  753,  771 

Lycaenidae,  584,  739,  768 

Lycidae,  491 

Lyctidae,  471,  515 

Lycomorpha  pholus,  707 

Lygsidae,  357-  359.  386 

Lygidea  mendax,  377 

Lygris  diver silineata,  668,  669 

Lygiis  pratensis,  376 

LymncEcia  phragmitella,  629 

Lymantriidag,  583,  584,  588,  679 

Lymexylidag,  473,  493 

Lymexylon  navale,  493 

Lyonet,  P.,  104,  105,  106 

Lyonetiidae,  582,  589,  591,  616 

Lyreman,  401 

Lyroda  subita,  965 

McAtee,  W.  L.,  241 
McClendon,  J.  F.,  300 
McCook,  H.  C,  938 
MacGillivray,  A.  D..  458,  886 


INDEX 


1029 


Machilidae,  224 

Machilis,     220;     mandibles     of,    221; 

ovary  of,  223;  M.  alternata,  174,  M. 

ommatidium    of,    139;    leg    of,    57; 

ventral  aspect  of,   77;   tracheae  of, 

116, 117 
Mclndoo,  N.  E.,  155 
Macrohasis,  497;  M.  iinkolor,  497 
Macrocephalus,  383 
^facrochaetae,  779 
Macrodactylus  subspinosus,  519 
Macrofrenatae,  Specialized,  583,  655 
Macrojugatas,  594 
Macrovelia  harrisii,  370 
Macroxyela,  wings  of,  894 
Maia-moth,  720 
Malacosoina  americana,   729,   730;   M. 

californica,  731,   M.  constricta,  731, 

M.  disstria,  730;  M.  fragilis,  731;  M. 

pluvialis,  731 
Malar  space,  887 
Malarial  Infection,  808 
Malloch,  J.  R.,  823,  824,  848,  936 
Mallophaga,  214,  217,  335 
Malpighian     vessels,      113;     as     silk- 
glands,  113 
Mammal-nest  beetles,  487 
Mandibles,  43 

Mandibular  sclerites,  353,  398 
Manidiidas,  583.  587,  673 
Mansonia,  810;  M.  perturbans,  810 
Mantidae,  234,  262 
Mantis  religiosa,  263 
Mantispa.  290;  hypermetamorphosis  of, 

290;  M.  styriaca,  290 
^lantispidae,  289 
Mantoidea,  262 
Manubrium,  228 
Many-plume  moths,  653 
Mapie-borer,  beautiful,  527 
Maple-leaf  cutter,  598 
Marchal,  P.,  431,  815 
:\Iarch-flies,  820 
Marey,  81 

Marginal  accessory  veins,  69 
Marginal  cells,  886 
Margins  of  wings,  59,  60 
:\Iarlatt,  C.  L.,  398 
Masarina%  949,  950 
Mass  provisioning,  962 
Matheson,  R.,  481,  505 
Maxillae,  43;  cross-section  of,  576 
[Maxillary,   palpus,    44;   pleurites,    40; 

sclerites,  353,  398;  tentacle,  599 
Maxillulas,  16,  43 

May-beetle,  heart  of  a,  121;  leg  of  a,  106 
May-beetles,  515,  518 
Mayer,  A.  G.,  572 
May-flies,  308,  312 
May-fly,  metamorphosis  of,  311;  wings 

of  a,  70 


Meadow-browns,  761 

Meadow-maggots,  799 

Meal  snout-mouth,  649 

Meal-worm,  513 

Mealy-bugs,  448,  450 

Measuring-worms,  662 

Mechanical  sense-organs,  130 

Mecoptera,  213,  214,  216,  217,  218,  550 

Media,  64 

Medial  cross- vein,  71 

Median,   caudal  filament,   78;  furrow, 

74;  line,  575;  plates,  55;  segment,  59, 

906;  sutures,  35 
Medio-cubital  cross-vein,  71 
Mediterranean  flour-moth,  651 
Meek,  W.  J.,  398,  399 
Megachile,  982;  M.  latimanus,  nest  of, 

982 
Megachilidae,  891,  912,  982 
Megalodachne,  509;  M.  heros,  510;  M. 

fascial  a,  510 
Megalomus  mcestus,  wings  of,  296 
Alegaloptera,  284 
Megalopyge  opercularis,  607;  cocoon  of, 

189 
Megalopygidae,  582,  585,  606 
Megamelus  notula,  antenna  of,  409 
Megaphasma  dentricus,  262 
Megaprosopidae,  787,  793,  869 
Megaprosopus,  869 
Megarhyssa  lunator,  917,  918 
Megathvmidag,  583,  733 
Megathymus,    733;    M.    streckeri,    733, 

734;  M.  yiicccE,  734 
Meigen,  J.  A.,  794 
Meinert,  347 

Melalopha,  678;  M.  indusa,  678 
Melander,  A.   L.,  339,  340,  845,   856, 

861,  862 
Melandryidae,  474,  475,  514 
Melanin  granules,  808 
Melanoplus,   160;  ental  surface  of  the 

pleurites   of   the   meso-   and   meta- 

thorax  of,  96;  head  of,  97;  tentorium 

of,  97 
Melanoplus    bivittatus,    255,    256;    M. 

differentialis,  256;  M.  femur-rubrum, 

254,  256;  M.  sprelus,  254 
Melittia  satyriniformis ,  637 
Mellinvs,  963 

Meloe,  497;  M.  angusticollis ,  498 
Meloida;,  475,  495 
Melolontha  vidgaris,  larva  of,  185 
Melon-worm,  647 
Melophagus  ovinus,  194,  874 
Melsheimer's  sac-bearer,  713 
Melyrida;,  473,  493 
Membracidae,  400,  404 
Membrane,  350 
Mentum,  46 
Mercer,  W.  P.,  196 


1030 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Merian,  Maria  Sibylla,  408 

Merope,  550,  551,  553;  M.  tuber,  553 

Merozoits,  809 

Merragata,  373 

Mesenteron,  108,  in 

Mesogenacerores,  447 

Mesonotum,  50 

Mesophiagma,  97 

Mesopletira,  783 

Mesothorax,  48 

Mesovelia  douglasensis ,  372;  M.  mul- 
santi,  372 

Mesoveliidas,  356,  358,  372 

Mestra,  751 

Metallic  wood-borers,  502 

Metal-mark,  large,  767;  small,  767 

Metameres,  34 

Metamorphosis  of  insects,  166 

Metanotum,  50 

Metaphragma,  97 

Metapleura,  783 

Metapneustic,  115 

Metathorax,  48 

Methoca  stygia,  936 

Methocinas,  936 

Metrobates,  371;  M.  hesperius,  371 

Miastor  americana,  816 

Microbembex  monodonta,  971 

Microcentrum,  22,7;  M.  retinerve,  237; 
M.  rhombifolium ,  236,  237 

Microdon,  851 

Microfrenatae,  Specialized,  582 

Microfrenatae,  585;  Specialized,  610; 
Families  of  the,  589 

Microgaster,  916 

Micromalthidae,  473,  494 

Micromalthus  debtlis,  494 

Micromus,  297 

Micropezidffi,  786,  791,  858 

Microphthalma,  869;  M.  disjuncta,  869 

Micropterj^gidae,  575,  581,  584,  592 

Microvelia,  370 

Micropteryx,  wings  of,  593 

Micropyle,  167 

Midges,  802 

Mid-intestine,  108,  in 

Migrants,  435 

Milichiidae,  786,  792,  852 

Milkweed-beetles,  red,  529 

Milkweed  Butterflies,  765 

]\Iilk-weed  butterfly,  reproductive  or- 
gans of  the,  160;  transformations  of 
the,  187 

Milk-glands,  875 

Millers,  580 

Millipedes,  15 

Milne-Edwards,  47 

Mindarinae,  419 

Mindarus,  419;  M.  abietinus,  420 

Mineola  vaccinii,  652 

Miridae,  356,  358,  359,  375 


Mischocyttarus,  957;  M.  cubensis,  957; 
M.  flavitarsis,  957;  M.  labiatus, 
wings  of,  956 

Misgomis,  833 

Misopus,  965 

Mites,  9 

Mitoura  damon,  753;  769 

Mnemonica  auricyanea,  594;  M.  cuben- 
sis,   957;    M.    wings   of,    594 

Mocha-stone  moths,  678 

Mocsary,  A.,  935 

Mogoplistinae,  243,  250 

Molanna  angustata,  558 

Molanna,  case  of,  566 

Molannidag,  559,  560,  566 

Molting  fluid,  172;  glands,  99 

Molting  of  Insects,  171 

Mompha  eloisella,  630 

Monarch,  the,  765 

Monarthrum  malt,  Gallery  of,  544 

Moniliform,  41 

Monobia  quadridens,  954,  955,  981 

Monochamus  notatus,  528 

Monommidas,  474,  514 

Monothalamous,  923 

Mononyx,  368;  M.  fuscipes,  368 

Monophlebinae,  449 

Monotomidae,  473,  509 

Mordellidae,  475,  494 

Mordwilkoja  vagabunda,  424 

Morgan,  Miss  A.  H.,  70,  311 

Morrill,  A.  W.,  438 

Morris,  H.  M.,  848 

Mosaic  vision,  theory  of,  141,  142 

Mosher,  Miss  Edna,  580 

Mosquitoes,  804;  antennae  of,  153 

Moth,  pupa  of  a,  580 

Moth-like  Flies,  801 

Moth-like  fly,  wing  of,  801 

Moths,  571 

Mourning-cloak,  755 

A'louth-parts,  42;  the  development  of, 
200 

Mucrones,  228 

Mud-daubers,  967 

Mufflehead,  691 

Muggenburg,  F.  H.,  876 

Muir  and  Kershaw,  398 

MuUer,  Fritz,  181 

Muller,  J.,  141 

MuUer's  organ,  149 

Murgantia  histronica,  391 

Murmidiidae,  474,  511 

Musca  domeshca,  872 

Muscidae,  787,  793,  872;  development 
of  the  head  in  the,  202 

Muscids,  852;  typical,  872 

Muscles,  104 

Muscoidea,  787 

Museum  pests,  507 

Music  of  flight,  80 


INDEX 


1031 


Musical  notation  of  the  songs  of  in- 
sects, 92 

Musical  organs  of  insects,  78 

Mutillidae,  891,  907,  911,  913,  914,  936 

Muttkowski,  R.  A.,  320,  323 

Myceta^ida;,  474,  511 

Myietobia,  798 

Mycctophagidffi,  472,  474,  510 

Mycetophilidse,  785,  793,  810 

jNIydaidae,  786,  788,  842 

Mydas,  wing  of,  842 

Mygetophilidas,  788 

Myiasis  in  man,  871 

Myiomma  cixiiformis,  375 

Mylabridas,  475,  535 

Mylabris  obieckts,  535;  M.  pisorum,  535 

Mymarinae,  930 

Myodaria,  786,  852 

Myriapoda,  15 

]Myrientomata,  24 

Myrmecia,  wings     of,  74 

Myrmecocystits,  947 

Myrmecophila  pergandei,  249 

Myrmecophilinae,  243,  249 

Myrmeleon  immaculatus,  304;  M.  wings 
of,  304 

Myrmeleonidae,  284,  303 

Myrmica  brevinodes,  944;  stridulating 
organ  of,  87 

Myrmicinae,  941,  943 

Myrmosa,  936;  M.  unicolor,  936 

Myrmosinas,  936 

Myrmostda,  936 

Mystacides  sepulchral  is,  567;  case  of, 
566 

Mytilaspis  citricola,  456;  M.  pomonim, 
457 

Nabidae,  356,  358,  380 

Nabis,  380;  A'',  ferus,  380;  N.  subcol- 

eoptratiis,  380 
Xagana,  873 

Xaiad,  the  term  defined,  179 
Nassonow,  X.,  549 
Nasuti,  277 
Nathalis  iole,  749 
Xaucoridse,  356,  357,  367 
Xaupliiform,  185 
Necrobia  rufipes,  493 
Necrophorus,  487 
Xeedham,  J.   G.,    112,    178,  312,  313, 

317.  807 
Needham  and  Lloyd,  561 
Neelus,  229 
Neides  muticus,  388 
Xeididas,  357,  359,  388 
Xemestrinidae,  786,  789,  836 
Nemobiiis,  84,  242,  248;  N.  fasciatus, 

249;  N.  palustns,  249, 
Xemocera,    785,795;  N.  Aanomalous, 

785,  820;  X.  the  true,  785,  795 


Nemognatha,  498 

Nemoura  sjx,  wings  of,  329 

Xemourida;,  330 

Neoconocephalus,  239;  N.  ensiger,  239 

Neohermes,  288;  N.  calif ornicus,  288 

Neophylax,  569 

Neosceleroderma  tarsalis.  948 

Neotcinia,  194 

Neoxabea,  245;  N.  bipunclata,  245 

Neoxyela  alberta,  894 

Nepa  apicidata,  364,  365 

Nepidae,  356,  357,  364 

Nepticulidas,  582,  589,  600 

Nepytia  semiclusaria,  671 

Nerthra,  368;  N.  stygiea,  368 

Xerves,  123 

Xervous  system,  123 

Nestling  birds,  parasites,  870 

Net-winged  midges,  824 

Neuronia,  565;  lateral  aspect  of  the 
mesothorax,  57;  N.  postica,  565 

Neuropore,  130 

Neuroptera,  212,  214,  216,  217,  218, 
281;  X.  mantis-like,  289;  X.  meaty- 
winged,  307 

Neurotoma  inconspicua,  895 

Newcomer,  E.  J.,  326 

Newport,  G.,  106 

Xew  York  weevil,  537 

Xidi,  112 

Niggers,  511 

Xight-eyes,  143 

Nigronia,  288;  N.  fasciatus,  288;  A^. 
serricornis,  288 

Xininger,  H.  H.,  979 

Xitidulidas,  470,  472,  473,  508 

Xoctuid  moth,  Diagram  of  a  fore  wing 
of  a,  575 

Xoctuidae,  583,  586,  588,  683 

Xoctuids,  583 

Xodal  furrow,  74 

Nolinae,  705 

Nomophila  noctiiella,  wings  of,  645 

Nosodendridae,  471,  508 

Nosodendron,  508 

Notauh,  887 

Notched-wing  geometer,  672 

Notiothauma,  551 

Notodontidae,  583,  587,  674 

Notolophus,  679,  680;  N.  antiqua,  681 

Notonecta  undulata,  362 

Notonectidae,  356,  357,  362,  363 

Notopleura,  782 

Notostigma,  22 

Notoxus,  498 

Notum,  49 

Noyes,  Miss  Alice  A.,  563,  564 

Nurse  cells,  158 

Nycteribiidae,  787,  794,  875 

Nymph,  the  term  defined,  176 

Nymphahdae,  584,  739,  760 


1032 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Nymphalinae,  750 
Nymphon  hispidum,  11 
Nymphs,  750 
NymphulinEe,  648 
Nyssonini,  963,  969 

Oak-apples,  925;  large,  925;  large 
empty,  926;  smaller  empty,  926 

Oak-bullet  gall,  926 

Oak-coccid  blastobasid,  629 

Oak-gall,  giant,  926 

Oak  hedgehog  gall,  924 

Oak-leaf  miner,  white-blotch,  618 

Oak-pruner,  528 

Oak-slug,  spiny,  609 

Oak- worm,  orange-striped,  718;  rosy- 
striped,  718;  spiny,  718 

Oak  ugly-nest  tortricid,  643 

Oberea  bimaculata,  529 

Oblique  vein,  319 

Obrussa  ochrefasciella,  Wings  of,  574, 
601 

Obtected  pupae,  191 

Occiput,  39,  780,  877 

Ocellar  triangle,  780;  plate,  780 

OcelH,  134,  135 

Ochteridae,  356,  357,  368 

Ochterus,  368;  0.  americanns,  369 

Ochthiphilidas,  786,  791,  862 

Ocular  sclerites,  39 

Odonata,  180,  212,  214,  215,  216,  314 

Odontoceridas,  560,  567 

Odontomachus,  942 

Odontomyia,  puparium  of,  831 

Odynerus,  953,  934;  0.  geminus,  953; 
O.  tropicalis,  953 

Qicanthinae,  243 

CEcanthus,  84,  85,  86,  242,  245;  table  of 
species,  246;  CE.argentinus,  246;  CE. 
calif ornicus,  246;  (E.  nigricornis, 
247;   CE.  niveus,  93;  (E.  vicarius,  378 

CEcophoridffi,  582,  590,  624 

Qi^demeridas,  474,  494 

CEdipodinae,  253,  257 

(Eneis  katahdin,  764;  ffi.  semidea,  763 

CEnochrominae,  663,  664 

CEnocytes,  163 

CEsophageal,  sympathetic  nervous  sys- 
tem, 125,  127;  valve,  in 

CEsophagus,  no 

CEstridas,  787,  792,  866 

(Estrus   ovis,  867 

Ohr-Wurm,  460 

Oiketicus  abboti,  613 

OinophiHdae,  582,  589,  617 

Olene,  680 

Olethreutidae,  582,  590,  639 

Olfactory  pores,  131,  154;  pore  of  Mc- 
Indoo,  155 

Olfersia,  wing  of,  874;  O.  americana,  875 

Oligotoma  saundersi,  fore  wing  of,  339 


Ommatidium,  135;  structure  of,  139 

Omophronidae,  470,  481 

Omus,  478 

Oncometopia,  407,  0.  undata,  407 

Onion  maggot,  864 

Oniscoida,  7 

Ontholestes  cingulatus,  489 

Onychii,  58 

Onychophora,  4 

Oocyst,  809 

Ookinete,  migratory,  809 

Ootheca,  170;  of  a  cockroach,  264 

Operculum,  438 

Ophion,  918 

Opostega,  bij 

Opostegidas,  582,  589,  617 

Opthalmochlus  duryi,  547 

Oral  hooks,  201 

Orange-tips,  The,  747;  falcate,  748; 
olympia,  748 

Orasema  viridis,  929 

Orbicular  or  round  spot,  57 ■> 

Orbits,  780 

Orchelimum,  238;  O.  indgare,  238 

Orchesella,  22() 

Or  eta  rosea,  wings  of,  712 

Organs  of  sight,  130 

Ormenis,  410;  O.  septentrionalis,  410 

Orneodes  hexadactyla,  653;  0.  hubneri, 
653 

Orneodidas,  583,  584,  653 

Ornix,  618 

Orocharis  mltator,  245 

Orphnephilidas,  828 

Ortalidas,  786,  791,  856 

Orthezia,  102,  448,  450 

Ortheziinse,  450 

Orthoptera,  212,  214,  215,  218,  230 

Orthopteroid  insects  of  uncertain  kin- 
ship, 267 

Orthorrhapha,  785,  794;  short-horned, 
828 

Oryssidas,  903 

Oryssus,  905;  ovipositor  of,  904;  0. 
abietinus,  wing  of,  904;  0.  occidental- 
is,  905;  O.  sayi,  903 

Osborn,  H.,  337,  349 

Oscinidae,  860 

Oscinis  frit,  860 

Osmeteria,  101 

Osmia,  976,  983 

Osmoderma  eremicola,  521;  O.  scabra, 
521 

Osmylus  hyalinatus,  wings  of,  68,  69 

Ostia  of  the  heart,  121 

Ostomidae,  472,  508 

Othniidag,  474,  498 

Othnius,  498 

Otiocerus,  409;  0.  coquebertii,  409 

Otiorhynchinag,  538 

Oudemans,  J.  T."",  n7,  880 


INDEX 


1033 


Outer  margin,  60 

Ovarian  tubes,  157,  158 

Ovaries,  156 

Oviduct,  156,  159 

Ovigerous  legs,  1 1 

Ovipara,  416 

Oviparous,  191 

Ovipositor,  76 

Owlet-Moths,  683 

Ox-warble-flies,  867 

Oxvbclini,  963,  972 

Oxyhelus,  972 

Oxyptilus  periscelidactylus ,  653 

Oyster  shell  scale,  457 

PaJhysphinx  modesta,  657 

Pachypsylla  celtidis-mamma,  411 

Packard,  A.  S.,  149,  189 

Packardia  geminata,  Wings  of,  609 

PcEcilocapsus  lineatus,  375,  376 

Paedogenesis,  192,  816 

Paedogenitic,  larvae,  192;  pupae,  192 

Painted  beauty,  754 

Palae,  361 

Palaeostracha,  8 

Paleacrita  vernaia,  671 

Palloptera,  856 

Palmetto-leaf  miner,  629 

Palpicornia,  467,  469 

Palpifer,  44 

Palpiger,  46 

Palpognaths,  21 

Pamphila  sassacus,  wings  of,  738 

Pamphiliidas,  890,  893,  894 

Pamphilinas,  737 

Pamphilius,  persicus,  895;  wings  of,  67, 

896 
Pa?iorpa,  552;  Head  of,  550;  wings  of, 

551 
Panorpodes,  553 
Pantarbes  capita,  wing  of,  838 
PantograPha  limata,  646,  647 
Pantomoriis  fulleri,  539 
Papilio     glaucus,     742;     larva,     742; 

glaiicus  glaucus,  742;  glaucus  turnus, 

742;     polyxenes,     741;     larva,     742; 

wings  of,  740;  P.  thoas,  173;  larva  of, 

101 ;  P.  zolicaon,  742 
Papilionidae,  583,  739,  740 
Papilionoidea,  589,  739 
Papilioninas,  740 
Papirius,  229 

Paraclemensia  acerifoliella,  598,  599 
Parafacials,  780 
Parafrontals,  780 
Paraglossae,  43 

Paragnatha,  43 ;  of  Machilis,  222 
Paralechia  pinifoliella,  626,  627 
Parallelia  histnaris,  689 
Parandra,  469,  524,  525;  P.  brunnea, 

526 


Paraphyses,  448 

Paraprocts,  232 

Parapsidal  furrows,  887 

Parapsides,  51,  887 

Parasites,  Respiration  of,  120 

Parasitoid,  915 

Parasymmiclus  clausa,  wing  of,  836 

Paratenodera  sinensis,  263 

Paraptera,  51 

Parcohlntta  pennsylvanica,  266 

Parectopd  mbiniella,  620 

Parhan)io)iia  pini,  637 

Parker,  J.  B.,  971 

Parnassiinae,  744 

Parnassius,  744;  P.  smintheus,  Cross- 
section  of  scales  of,  572 

Parsnip  web  worm,  624 

Parthenogensis,  889 

Paraxenos  eberi,  Wing  of,  548 

Passalidas,  475,  524 

Passalus,  cornutus,  524;  stridulating 
organ  of  a  larva  of,  89 

Patagia,  50,  576 

Patch,  Dr.  Edith,  422,  432 

Paurometabola,  176 

Paurometabolous  development,  175 

Pauropodidas,  20 

Pauropoda,  18 

Pauroptis  huxleyi,  18 

Peach  sawfly,  895 

Peach-tree  borer,  636;  lesser,  636; 
Pacific,  636 

Peach  twig-laorer,  627 

Pear-blight  beetle,  545 

Pear-midge,  819 

Pear-slug,  902 

Pea-weevil,  535;  family,  535 

Peckham  and  Peckham,  953,  964,  965 

Pecten,  628 

Pectinse,  448 

Pectinate,  41 

Pectinophora  gossypiella,  628;  wings  of, 
626 

Pedicel,  41 

Pedilidae,  475,  498 

Pegomyia  hyoscyami,  864 

Pelecinidae,  890,  907,  921 

Pelicinus  polyturator,  921 

Pediculid^e,  348 

Pediculus,  capitis,  348;  P.  corporis,  34S 

Pe-la,  441 

Pelidnota  punctata,  519 

Pelobius,  120 

Pelocoris,  367 ;  P.  femoratus,  367 

Pelogonus,  368 

PelopcEus,  967 

Peltodytes,  481,  482 

Pemphigus  acerfolii,  422 

Pcmphrcdonini,  963,  968 

Penis,  162 

Pentastomida,  14 


1034 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Pentatomidae,  103,  357,  359,  390 

Penthe,  514;  P.  obliguata,  514;  P. 
pimelia,  514;  prothorax  of,  53 

Penthima  americana,  408 

Pentozocera  australensis,  547 

Pepsis,  934 

Perceoreille,  460 

Perez,  J.,  92 

Pericardial,  cells,  164;  diaphragm,  163 

Pericopidae,  583,  588,  698 

Perilampus  hyalnius,  928,  929 

Peripatoides  novae-zealandiccE,  4 

Pert  pat  us,  i,  4 

Peripheral  sensory  nervous  system, 
I2"8,  129 

Penplaneta  americana,  266;  P.  orien- 
tal is,  107,  127 

Peripneustic,  ll.S 

Peripodal,  cavity,  197;  membrane,  197 

Peristome,  780 

Peritoneal  membrane,  109 

Peritremes,  52 

Peritrophic  membrane.  111,  112 

Perkins,  R.  C.  L.,  962 

Perhdae,  328 

Peterson,  A.,  341 

Petiole,  938 

Petroleum-flv,  859 

Pettit,  R.  H;,  365 

Phceoses  sabinella,  617 

Phagocyte,  164,  204 

Phagocytic  organs,  164 

Phagocytosis,  164,  204 

Phalacridse,  472,  511 

Phalonia  rutilana,  643 

Phaloniidae,  582,  590,  639,  643 

PhancEUS,  517;  P,  carnifex,  517 

Phaneropterinae,  235,  236 

Pharsalis,  917 

Pharynx,  109 

Phasgonuridae,  234 

Phasiidae,  787,  793,  868 

Phasma,  121 

Phasmidse,  234,  260 

Phasmoidea,  260 

Pheidole  pilifera,  943 

Phengodida?,  473,  492 

Pheosia  rimosa,  674 

Philagraida,  709 

Philanthini,  963,  969 

Philopotamidse,  559,  560,  563 

Philopteridae,  337 

Philosamia  cynthia,  727 

Phlebotomus,  802;  P.  vexator,  802 

Phloeothripidae,  346 

Phobetron  pithecium,  609,  610;  larva, 
610 

Pholisora,  -jiT,  P.  catullus,  737 

Pholus  pandorus,  660 

Phonapate,  88 

Phora,  wing  of,  848 


Phoridas,  786,  789.  793,  847 

Photinus  marginellus,  165 

Phragmas,  97 

Phryganea,  565;  P.  pilosa,  pupa  of, 
558;  P.  vestita,  565 

Phryganeidae,  559,  560,  564 

Phryganeids,  Cases  of,  565 

Phryganidia  californica,  673 

Phthirius  pubis,  349 

Phthorophlceus  liminaris,  542,  544 

Phyctodes,  752;  P.  nycteis,  752 

Phycitinae,  651 

Phycodromidae,  786,  791,  855 

Phyllium,  261 

Phyllonorycter,  618;  P.  cincinnatiella , 
619;  P.  hamadryadella,  618,  619 

Phyllophaga,  518 

Phylloscyrtus  pulchellus,  244 

Phyllofreta  vittata,  532 

Phylloxera,  433;  gall-inhabiting  form, 
436;  gall  of,  434;  grape,  433;  root- 
inhabiting  form,  43 s;  436;  P.  vast- 
atrix,  433 ;  wings  of,  429 

Phylloxeridas,  400,  428 

Phylloxerinae,  433 

Phymata,  383;  P.  erosa,  383 

Phymatidae,  356,  358,  382 

Physocephala  affinis,  wing  of,  853 

Physonota  unipiinctata,  534 

Phytomyza  aquilegia,  861;  mine  of,  861 

Phytophaga,  468,  469;  families  of  the, 
475 

Phytophaga  destructor,  818 

Pickle- worm,  648 

Pieces  jugulaires,  40 

Pierce,  W.  Dwight,  548,  549 

Pierida;,  584,  739,  744 

Pieris  natn,  747;  P.  protodice,  747; 
wings  of,  745;  rapae,  746 

Piesma  ctnerea,  385 

Piesminas,  385 

Pigeon  horn-tail,  897 

Pigment  cells,  accessory,  138,  140;  iris, 
140 

Piliferous  tubercles  of  larvae,  35 

Pill-beetles,  508 

Pinacate-bugs,  513 

Pinconia  coa,  606 

Pine  clear-wing  moth,  637 

Pine-cone  willow  gall,  817;  guest, 
817 

Pine-leaf,  miner,  627;  scale,  458;  tube- 
builder,  643 

Pine-pest,  Zimmermann's,  652 

Pine-twig  moths,  640 

Pinipestis  zimmermanni,  652 

Piophila  casei,  858 

PiophiUdae,  786,  792,  858 

Pipunculidae,  786,  790,  849 

Pipunculus,  849;  wing  of,  850 

Pistol  case-bearer,  620 


INDEX 


103;: 


Planidium,  928;  oi  perilam pus,  928;  g2g 

Planta.  578,  974 

P]ant-licc,  412;  jumping,  410 

Plasma,  122 

Plasmodium,  808 

Plastoceridae,  473,  499 

Plates,  448 

Plathemis  lydia,  314 

Platygaster  keimales,  889 

Platygasteridas,  890,  907,  913,  921 

Plathypena  scabra,  685 

Platypeza,  wing  of,  849 

Platypezidas,  786,  789,  848 

Platypodidae,  476,  541 

Platypsvllidae,  470,  486 

Platypus,  541 

Platvsomidas,  476,  536 

Plea,  364 

Plecoptera,  136,  212,  214,  216,  325 

Pleura,  34 

Pleurites,  35 

Pleurostigma,  21 

Plodia  interpunctella,  651 

Plum-curculio,  539 

Plume-moths,  652 

Plum  web-spinning  sawfly,  895 

Plusiinae,  687 

Plutella  maculipennis ,  632 

Plutellidae,  582,  589,  591,  632 

Pocock,  R.  I.,  17,  21 

Podalirius,  890 

Podical  plates,  232 

Podisiis,  391 ;  P.  maculiventris,  391 

Podura  aquatica,  229 

Poduridae,  115,  228 

Polistes,    546,    957;    nest    of,    957;    P. 

Uneatus,  957 
Polistinae,  949,  957 
Pollen  brushes,  974 
Pollen ia  rudis,  870 
Pomocenis   aquatica,    ommatidium   of, 

225 
Ponerina;,  941,  942 
Ponitia  rapa,  195 
Polycentropidae,  559,  560,  563 
Polycentropiis,  564 
Polychrosis  viteana,  640 
Polyctenidffi,  356,  379,  359 
Polyembryony,  168,  889 
Polyergus,  947;  P.  hicidus,  947 
Polyformia,  467,  469 
Polygonia,  756 
Polygonia  comma,  753,  756;  P.  comma 

comma,  757;  P.  comma  dryas,  756; 

f aunts,  753,  756;  P.  interrogationis, 

753,  757;  progne,  757 
Polymitarcys,  312 
Polyphaga,  467,  468,  486 
Polyphemus-moth,  722 
Polystcechotes    punctatus,    299;    P.    vil- 

tatus,  299 


Polystocchotidae,  284,  298 

Polythalamous,  923 

Polyxenus,  16,  17 

Pomace-flies,  860,  861 

Pomocerus  plumbens,  225 

Pompilida;,  890,  910,  915,  933 

Popillia  japonic  a,  519 

Poplar-leaf  gall  aphid,  424 

Pore-plate,  131 

Porocephalus,  14 

Porlhetria,  dispar,  682 

Postalar  callus,  783 

Postantennal  organ,  227 

Postcubital  cross- veins,  319 

Postembryonic  molts,  number  of,  172 

Posterior  arculus,  72 

Posterior  lobe,  776;  of  the  wing,  61;  of 

the  pronotum,  887 
Postgenacerores,  447 
Postgenae,  39,  781 
Postnodal  cross-veins,  319 
Postnotum,  50 
Postpetiole,  938 
Postphragma,  98 
Postscutellum,  50 
Poststernellum,  52 
Powder-post  beetles,  515 
Praetarsus,  58 
Pratt,  H.  S.,  874 

Praying  mantes,  262;  eggs  of,  170 
Prealar  callus,  783 
Preanal  area,  75 
Preanal lobe,  888 
Preaxillary  excision,  888 
Preepisternum,  51 
Pregnacerores,  447 
Prepectus,  887 
Prephragma,  98 
Prepupa,  185 
Prescutum,  50 
Presternum,  52 
Presultural  depression,  783 
Pricer,  938 
Primarv  oceUi,  135;  structure  of,  137, 

138  ' 
Primitive  weevils,  536 
Primordial  germ-cells,  158 
Prionid,  straight-bodied,  526 
Prioninae,  525 
Prionoxystus  macmurtrei,  603;   P.  rob- 

iniae,  603;  wings  of,  70,  596,  602 
Prionus,    broad-necked,    526;    P.    im- 

bricornis,  526;  P.  laticollis,  526 
Prociphilus  imbricator,   422;   P.   tessel- 

latus,  421,  422 
Proctodaeum,  108 
Proctotrupidag,  890,  908,  914,  921 
Proctotrupoidea,  890,  920 
ProdoxinjE,  599 
Prodoxus,  600 
Progrediens  type,  431 


1036 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Progressive  provisioning,  962 
Prolabia  pulchella,  463 ;  P.  burgessi,  462 
Prolegs  of  larvae,  78;  the  development 

of,  182 
Prolimacodes  badia,  610 
Promethea-moth,  725 
Prominent,  two-lined,  676 
Prominents,  674 
Pronotum,  50 
Pronuba  yuccasella,  599 
Prophragma,  97 
Propleura,  782 
Propneustic,  115 
Propodeum,  49,  887,  906 
Propolis,  990 
Propupa,  343 
Propygidium,  75 
Prosimulium  hirtipes,  824 
Prosopidae,  890,  891,  912,  976 
Prosopinae,  976 

Prosopis,  890,  973,  974,  975,  976 
Prothorax,  48 
Protocalliphora,  870;  P.  azurea,  870;  P. 

chrysorrhea,  870 
Protocerebrum,  47,  124 
Protoparce  quinquemaculata,  658;  pupa, 

659;  wings  of,  656;  P.  sexta,  659 
Protoplasa,    796;    P.    ntchii,    796;    P. 

vanduzeei,  796;  P.  vipio,  796 
Protosialis  americana,  286 
Protura,  26 

Proventri cuius,  no,  111 
Psacaphora  terminella,  630 
Psammocharidae,  890 
Psectra,  294;  P.  diptera,  294 
Pselaphidae,  470 
Pseninae,  967 
Psenini,  964,  968 
Psephenidae,  471,  503 
Psephenus,  503;  P.  lecontei,  504 
Pselaphidae,  409 
Pseudagenia,  934 
Pseudococcus    citri,     451;    P.    (Dacty- 

lopius)  destructor,  eyes  of,    443;    P. 

longispinosus,  451;  wing  of,  442 
Pseudocone  eyes,  141 
Pseudo-cubitus-one,  301 
Pseudo-halteres,  59 
Pseudohazis,  721;  P.  eglanterina,  721; 

P.  hera,  721 
Pseudomasaris,     950,     951,     952;     P. 

vespoides,  951;  nests  of,  952 
Pseudo-media,  301 
Pseudomyrma,  942 
Pseudomyrminae,  941,  942 
Pseudophyllinae,  235,  238 
Pseudothyatira  cymatophoroides ,  710 
Pseudova,  191,  416 
Psila  roscB,  859 
Psilidae,  786,  792,  859,  890 
Psilogaster  fasciiventris,  929 


Psilopa  petrolei,  859 

Psilopodius  sipho,  wing  of,  844 

Psilotreta  frontalis,  567 ;  case  of,  567 

Psithyrus,  976,  984,  985,  987 

Psocid,  wings  of,  332 

Psocidae,  333 

Psocids,  331 

Psychidffi,  582,  584,  585,  586,  613 

Psychodidae,  785,  787,  801 

Psychomorpha  epimenis,  693 

Psychomyidae,  560,  564 

Psyllia,  floccosa,  410;  pear-tree,  41 1 ;  P. 

pyricola,  411 
Pterodontia  flavipes,    837;   P.    misella, 

837 
Pterombus,  936 
Pteronarcella,  328;  P.  badia,  wings  of, 

328 
Pteronarcidas,  328 
Pteronarcys,  120,  328;  head  of,  136;  P. 

dorsata,  325 
Pteronidea  ribesi,  901;  P.  trilineata,  901 
Pterophoridae,  582,  584,  652 
Pterophylla  camellifolia,  237,  238 
Pteropleura,  783 
Pterostigma,  74,  327 
Pterygogenea,  209 
Pterygota,  209,  214 
Ptilinum,  190,  776,  781 
Ptinidae,  471,  514 
Ptiniis  fur,  514 
Ptychopteridae,  785,  787,  796 
Pulex  irritans,  882 
Pulicidae,  882 

Pulsations  of  the  heart,  122 
Pulvilii,  58 
Pulvinaria,  453;    P.  acericola,  453;  P. 

innumerabilis,  170;  P.  vitis,  453 
Punkies,  803 

Pupa,  186;  of  a  beetle,  466 
Pupae,  active,  187;  the  different  types 

of,  190 
Puparium,  190,  815 
Pupipara,  193,  787;  873 
Pycnogonida,  10 
Pygidial  area,  888 
Pygidium,  75,  445;  diagram  of  a,  446, 

'447 
Pyralididae,  582,  585,  587,  644 
Pyralidinag,  649 
Pyralidoidea,  582,  644 
Pyralids,     582,     644;     aquatic,     648; 

typical,  649 
Pyralis  farinalis,  649 
Pyrausta  nubilalis,  648 
Pyraustinas,  646 
Pyrochroidag,  475,  498 
Pyromorpha,   604;    P.  dimidiata,   604; 

wings  of,  605;  P.  marteni,  wings  of, 

605 
Pyromorphidae,  582,  585,  586,  604 


INDEX 


1037 


Pyrrhocoridae,  357,  359,  385 
Pyrrhopydinae,  735 
Pythidae,  474,  498 

Quadrangle,  322 
Queen,  the,  766,  989 

Radial  cross-vein,  71 

Radicicola;,  434 

Radio-medial  cross- vein,  71 

Radius,  64 

Ramphocorisa  acuminala,  362 

Ranatra,  365 

Range-caterpillar,  New  Mexico,  721 

Raphidia,  289 

Raphidiida;,  289 

Raphidioidea,  289 

Raspberry  fruit-worm,  510;  geometer, 
665,  root-borer,  636 

Raspberry-cane  maggot,  864 

Rasping  organs,  87 

Rat-flea,  Indian,  882 

Rath,  O.  vom,  132 

Rat-tailed  maggots,  851 

Ran  and  Rau,  953 

Reaumur,  R.  A.  F.  de,  572,  876 

Rectum,  1 13 

Red  admiral,  754 

Red- bug,  385;  apple-,  376;  false  apple-, 
377;  hop-,  377 

Red-humped  apple-worm,  677 

Redikorzew,  W.,  137 

Red-necked  agrilus,  503 

Red  spotted  purple,  758 

Reduviidas,  356,  358,  380 

Reduvius  personatus,  381 

Regal-moth,  716,  717 

Regions  of  the  body,  36 

Reicherklla  collaris,  wing  of,  821 

Reighardia,  14 

Reniform  spot,  575 

Reproduction  of  lost  limbs,  173 

Reproductive  organs,  156;  of  the  fe- 
male, 157;  of  the  male,  160,  161 

Resin-gnat,  819 

Respiratory  organs,  the  closed  or 
apneustic  types  of,  119;  the  open  or 
holopneustic  types  of,  114 

Respiratory  system,  113 

Resplendent  shield-bearer,  622,623 

Reticulitermes,  2-jg;  R.  {Leucoiermes) 
flavipes,  278 

Retina,  138 

Retinodiplosis  resinicola,  819 

Retinula,  138,  140 

Rhabdom,  137 

Rhabdomere,  137 

Rhabdophaga  strobiloides,  817 

Rhachicerus,  832;  R.  nitidus,  833 

Rhagio,  wing  of,  835 

Rhagionida;,  786,  789,  834 


Rhagium  lineatum,  526 

Rhagolelis    cingulata,    857;    R.   fausta, 

857;  R.  pomonella,  857 
Rhagovelia,  370;  R.  obesa,  370 
Rhamphomyia,  wing  of,  845 
Rhaphidophorinae,  235,  241 
Rheumai?tera  hastata,  669 
Rheumatobaies,  372 
Rhinoceros-beetles,  520 
Rhinomacerinae,  537 
Rhipiceridae,  472,  499 
Rhipiphoridae,  475,  494 
Rhizophagidae,  472,  474,  508 
Rhizophagus,  508 
Rhodites  rosae,  926,  927 
Rhodophora  florida,  695 
Rhopalocera,  581 
Rhopalomyia,  814 
Rhopalosoma  poeyi,  948 
Rhopalosomidae,  891,  911,  948 
Rhyacophila,  555;  R.  fuscula,  555,  561; 
wings  of,  556 

RhyacophiHdae,  559,  560 

Rhynchiies  bicolor,  538 

Rhynchitinae,  537 

Rhynchophora,  468,  469,  535;  families 
of  the,  475 

Rhvnchophorus,  head  and  prothorax  of, 
469 

Rhysodidae,  470,  508 

Ribbed  pine-borer,  526 

Rice-weevil,  541 

Riley,  C.  V.,  171,  177,  187,  496,  599 

Riley  and  Johannsen,  378 

Ring-joints,  41 

Riodinidae,  584,  739,  767 

Ripersia,  451 

Ripipteryx,  252 

Roadside  butterfly,  748 

Robber-flies,  840 

Rodolia  cardinalis,  511 

Rohwer,  S.  A.,  889,  903,  904,  905 

Rolleston,  107 

Root,  A.  I.,  and  E.  R.,  990 

Root-cage,  501 

Roproniidge,  890,  907,  921 

Rose-beetle,  Fuller's  539 

Rose-bugs,  519 

Rose-gall,  mossy,  926,  927 

Rose-slug,  902 

Rose  ugly-nest  tortricid,  642 

Roubaud,  E.,  953 

Round-headed  apple-tree  borer,  529 

Rove-beetles,  488 

Royal  jelly,  989 

Royal-moth,  two-colored,  717 

Royal-moths,  715 

Rut  or  povi,  171 

Sabine  stimulea,  609 

Sacred  beetle  of  the  Egyptians,  516 


1038 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Saddle-back  caterpillar,  609 

Saissetia  hemisphcerica,   453;    S.    ohcE, 

452,  453 
vSaldidae,  356,  358,  369 
Salivary  glands,  103,  104 
Saltatorial  orthoptera,  177 
Salt-marsh  caterpillar,  701 
Samia  cecropia,  726;  pupa,  726;  cocoon, 

727;  wings  of,  720;  S.  Columbia,  726; 

5.  gloven,  726;  S.  rubra,  727 
vSand-crickets,  242 
Sandflies,  803 
San  Jose  scale,  458 
Saperda  Candida,  529 
Sapromyza,  856 
SapromyzidcB,  786,  791,  856 
Sapygid'ae,  891,  911,  935 
Sarcophaga  hcBtnorrhoidalis ,  871 
Sarcophagida;,  787,  793,  870 
Saturniidae,  583,  719 
Saturnoidea,  583,  589,  714 
Satyrinse,  750,  761 
Satyrodes  canthus,  762 
Saussure,  H.  de,  952 
Saw-flies,    argid,    902;    cimbicid,    900; 

leaf -rolling,  894;  stem,  898;  typical, 

900;  web-spinning,   894;  xiphydriid, 

897 
Sawfly,  American,  900;  locust,  901 
Sawyer,  528 

Scale-insects,  440;  control  of,  459 
Scales,  873 
Scalloped  owlet,  686 
Scallop-shell  moth,  668,  669 
Scape,  40 

Scaphidiidffi,  470,  490 
Scapulae,  887 
Scarabaeidffi,  475,  515 
Scarabeiform,  184 
Scatophaga,  854 
Scatopsidas,  785,  788,  821 
Scelionidae,  890,  907,  908,  913,  921 
Sceliphron  cemeniarium,  966;  wings  of, 

966,  967 
Scenopinidae,  786,  789,  839 
Scenopiniis,    840;    wing    of,    840;    5. 

fenestralis,  840 
Scent-glands  of  females,  100 
Scepsis  fulvicollis,  706,  707 
Schierbeek,  A.,  580 
Schindax,  709 
Schiodte,  J.  C,  88,  185 
Schistocera  americana,  256 
Schizoneura  americana,  421 ;  5.  pinicola, 

420;  5.  rileyi,  421;  S.  iilmi,  421 
Schizont,  808 
Schizophora,  786,  852 
Schizopteridas,  356,  358,  373 
Schizura,  679;  5.  concinna,  larva,  677; 

5.  ipomeae,  larva,  679 
Schmiedknecht,  O.,  929 


vSchneider,  A.,  192 

Schreckensteinia  erythriella,  634;  5. 
festaliella,  634 

Schwabe,  J.,  150,  151 

Sciara,  eyes  of,  812;  wing  of,  812 

Sciara-army-worm,  813 

Sciaridas,  813 

Sciarinag,  812 

Sciomyzidag,  786,  791,  855 

Sclerites,  35 

Scolia,  937 

Scoliidae,  891,  911,  937 

Scoliopteryx  libatrix,  686 

Scolopale,  146 

Scolops,  409 

Scolus,  578 

Scolytidas,  476,  542 

Scolytus  rugiilosus,  544 

Scopae,  974 

Scorpion,  9 

Scorpion-flies,  550,  552 

Scorpions,  lateral  ocelli  of,  137 

Screw-worm  fly,  870 

Scudder,  S.  H.',  92,  235 

Scudderia,  237;  S.  mexicana,  237;  3'. 
septentrionalis,  237 

Scurfy  scale,  457 

Scutellar  bridge,  783 

Scutelleridae,  357,  359,  392 

Scutellum,  50 

Scutigera  forceps,  22 

Scutigerella,  24 

Scutum,  50 

Scydmsenidae,  470,  488 

Sc>'thrididae,  582,  592,  631 

Scythris  eboracensis,  631 ;  5.  magnatella, 
631 

Searcher,  the,  479 

Seaton,  Frances,  139 

Second  antecoxal  piece,  54 

Secondary  sexual  characters,  157 

Sectorial  cross- vein,  71 

Segmentation  of  the  aopendages,  34; 
of  the  body,  34 

Segments  of  the  head,  47,  48 

Seller,  W.,  139 

Semidalis  aleurodiformis,  306 

Seminal  vesicle,  162 

Sense-cones,  131 

Sense-domes,  154,  155 

Sense-hairs,  33 

Sense-organs,  classification  of  the,  129; 
cuticular  part  of  the,  130;  oi  un- 
known functions,  154 

Sensillum,  ampuUaceum,  131;  basi- 
conicum,  131;  choeticum,  131;  coelo- 
conicum,  131;  placodeum,  131;  tri- 
chodeum,  130,  132 

Sepsidae,  786,  790,  791,  858,  859 

Sepsis,  858 

Serial  veins,  67 


INDEX 


1039 


Sericostomatidac,  559,  560,  569 

Serphidae,  890 

Serrate,  41 

Seryda  conslans,  scale  of,  572 

Setae,  32;  classification  of,  33;  primary, 

578;    subprimary,    578;    secondary, 

578;  taxonomic  value  of,  33 
Setiferous  sense-organs,  130 
Setiferous   tubercles,   arrangement   of, 

579;  types  of,  578 
Setodes  grandis,  566;  case  of,  566 
Sexuales,  436 
Sexuparae,  435 
Sharp,  David,  87,  88,  89,  144,  194,  301, 

505,  506,  950,  977 
Sheep-tick,  874 
Shellac,  441 
Sialidae,  284 

Sialis  infumata,  285,  286;  larva  of,  286 
Siebold,"C.  T.  von,  92,  145 
Siebold's  organ,  152 
Sierolomorpha  ambigna,  935 
Sigalcessa  flaveola ,  860 
Sight,  organs  of,  134 
Silk-glands,  cephalic,  103 
Silk- Worm,  114, 727;  sense  hairs  of  the, 

133 
Silk- Worms,  giant,  719 
Silpha,  488 

Silphidffi,  470,  471,  487 
Silvanns  surinamensis,  509 
Silverfish,  224 
Silvestri,  F.,  16,  25,  113 
Simaethis  fabriciana,  wings  of,  633 
Simuliidae,  786,  788,  821 
Simulium,  120;  head  of  larva  of,  200; 

larva  of,  1 1 1 ;  wing  of,  822 
Simulium  meridionale,  824;  5.  pictipes, 

824;  S.  venustum,  824 
Siphlurus    alternatus,    caudal    end    of 

abdomen  of,  308 
Siphonaptera,  214,  217,  877 
Siphunculata,  347 
Sirex  juvencus,  wings  of,  897 
Siricidae,  890,  893,  896 
Sistens,  431 
Sisyra  flavicornis,  292;  5.  umbrata,  291; 

larva  of,  292;  silk-organs  of,  282,  283 
Sisyridse,  284,  291 
Sitodrepa  panic ea,  515 
Sittroga  cerealella,  626 
Skiff -caterpillar,  610 
Skimmers,  321 
Skin-beetles,  522 

Skipper,  least,  738;  silver-spotted,  736 
Skippers,  571,  583,  732;  common,  734; 

giant,  733 
Skippers  with  a.  costal  fold,  735 
Skippers  with  a  brand,  737 
Sladen,  F.  W.  L.,  985,  987 
Sleeping  sickness  of  man,  873 


Slingerland,  M.V.,  417,  459,608,644,647 

Slingcrland  and  Crosby,  459 

Slug-caterpillar  moths,  608 

Small-headed  flies,  837 

Small-intestine,  113 

Smell,  organs  of,  132 

Smerinihtis  geminatus,  657,  658 

Sminthuridae,  229 

Sminthurus,  229;  S.  hortensis,  229 

Smith,  J.  B.,  398,  977,  979 

Smith,  R.  C,  300,  302 

Smoky  moths,  604 

Smynthurus,  115 

Snake  flies,  289 

Snipe-flies,  834 

Snodgrass,  R.  E.,  49,  50,  55,  57,  98 

Snout-beetles,  535;  imbricated,  538; 
pine-flower,  537,  scarred,  538,  tooth- 
ed-nose, 537,  typical,  537 

Snout-butterfiv,  767 

Snow-flea,  228 

Snow-flies,  799 

Snyder,  T.  E.,  280 

Soldier-beetles,  492 

Soldier-flies,  830 

Solenobia,  wings  of,  615;  5.  wal,shella,6i^ 

Solenopsis  molestus,  943 

Solidago  gall-moth,  627 

Solitary-midge,  828 

Solpugida,  9 

Somites,  34 

Soothsayers,  262 

Sooty-wing,  737 

Sovereigns,  the,  757 

Sow-bugs,  7 

vSpear-marked  black,  669 

Spear-winged  flies,  846 

Spermatazoa,  160 

Spermatheca,  159 

Spermathecal  gland,  160 

Spermatophores,  162 

Sphaeriidae,  471,  490 

Sphcerites  glabratus,  490 

Sphasritidae,  470,  490 

Spharagemon  bolli,  258 

Sphecidae,  891,  911,  962 

Sphecinas,  966 

Sphecini,  963 

Sphecius  speciosus,  970;  wings  of,  970 

Sphecodes,  975 

Sphecoidea,  891,  960 

Spechoid-wasp,  head  and  thorax  of,  960 

Sphecoid- wasps,  960,  961 ,  typical,  962 

Sphenophorus,  540;  S.  maidis,  540 

Sphex,  890,  967 

Sphindidas,  474,  515 

Sphingidffi,  583,  586,  655 

Sphinx,  657;  chersis,  657,  658;  Harris's, 
658;  modest,  657,  pandorus,  660, 
pen-marked,  658;  twin-spotted,  657; 
white-lined,  660 


1040 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Sphinxes,  655 

Sphyracephala  brevicornis,  859 

Spiders,  9 

Spider- wasps,  933,  934 

Spines,  32,  445 

Spiracles,  52,  113,  114;  structure  of,  116 

Spiracular  musical  organs,  91 

Spirostreptus,  16 

Spittle-insects,  402 

Spondylidse,  525 

Spondylis,  469,  524 

Spongilla-flies,  291;  labia  of,  293 

Spongophorus  ballisla,  404;  S.  querini, 

404 
Sporoblasts,  809 
Sporozoite,  808,  809 
Spotted  pelidnota,  519 
Spring  azure,  771 
vSpring  of  the  Collembola,  76 
Spring-tails,  225 
Spuler,  A.,  859 
Spurious  vein,  70 
Spurs,  32 
Squama,  776 
Squamae,  60 

Squash-bug,  egg-mass  of  the,  170 
Squash-vine  borer,  637 
Stable-fly,  873 
Stadia,  172 
Stag-beetles,  523 
Stagmatophora  gleditschiaella,  630 
Stagmomatis  Carolina,  263 
Staphylinidse,  470,  488 
Staphylinus    mactdosus,    489;    5.    vid- 

pinus,  489 
Stegomyia  calopus,  809 ;  5.  fasciata,  809 
Stelis,  976 
Stem-eyed  fly,  859 
Stem-mother,  415 
Stenelmis  bicarinatus,  505 
Stenobothrus ,  82 
Stenogaster,  950 
Stenoma,  625;  S.  schlcegeri,  625 
Stenomidse,  582,  591,  625 
Stenopelmatinas,  235,  242 
Stenopelmatus,  242;  ventral  aspect  of 

the  metathorax,  98 
Stephanidae,  890,  907,  919 
Sterictiphora,  903 
Sternal  spatula,  815 
Sternellum,  52 
Sternites,  35 
Sternopleura,  783 
Sternum,  34,  52 
Sthenopis,    595;    5.   argenteomaculahis, 

596;   5.   piipurascens,   595,   596;   5. 

thule,  596 
Sicta  Carolina,  971 
Sticktight  flea.  883 
Stigma,  74 
Stigmata,  1 13 


Stigmus  fralernus,  968;  S.  prodagricus, 
wings  of,  968 

Stiletto-flies,  839 

Stink-bugs,  source  of  odor,  355 

Stink-glands,  102,  462 

Stipes,  44 

Stizini,  970,  974 

Stizus  unicinctus,  970 

Stomach,  iii 

Stomodaeum,  108 

Stomoxus  cakitrans,  873 

Stone-flies,  325 

Stone-fly,  naiad  of,  327 

Stratiomyia,  831;  wing  of,  831 

Stratiomyiidas,  786,  788,  830 

Straus  Durckheim,  40,  106,  121 

Strawberry  crown-girdler,  539 

Strebhdas,'787,  790,  794,  875 

Strepsiptera,  194,  213,  214,  215,  546 

Stridulating  organs,  81;  of  corixidae, 
362;  of  the  locustidae,  82;  of  the 
gryllidas  and  the  tettigoniidae,  83; 
of  Ranatra,  356 

Strigilis,  886 

Striped  flea-beetle,  532 

Sturtevant,  A.  H.,  861 

vStyU,  56,  76,  222 

Stylopidas,  546 

Stylopids,  546,  958;  mouth-parts  of 
male,  547 

Stylus,  442 

Subcosta,  64 

Subcostal  fold,  73 

Subgalea,  44 

Subimago,  312 

Subcesophageal  commissure,  125;  gan- 
glion, 123,  124 

Submarginal  cells,  886 

Submentum,  46 

Subnodus,  319 

Subquadrangle,  323 

Subterminal  band,  575 

Sugar-cane,  beetle,  520;  borer,  650 

Sulphur,  cloudless,  749;  dainty,  749; 
little,  749;  orange,  748 

Sumac  bobs,  634 

Superimposed  image,  143 

Superlingua?,  43,  226 

Supertriangle,  319 

Supplements,  70 

Surpa-alar  groove  or  cavity,  783 

Supra-anal  plate,  231 

Supra-tympanal  or  subgenual  organ, 
151 

Suspensoria  of  the  viscera,  162;  thread- 
like, 163 

Sutures,  35;  the  thoracic  of  Diptera, 
782,  783 

Swallow-tail,  black,  741;  larva,  742; 
tiger,  larva,  742;  zebra,  743 

Sweet-fern  geometer,  666 


INDEX 


1041 


Sweet-potato  root-borer,  538 
Swifts,  594,  595 

Symmerista  nlbifrons,  larva,  676 
Symphasis  varia,  291 
Sympherobiidas,  284,  293 
Sympherobius,  294;  5.  amiculus,  wings 

'of,  294 
Symphoromyia,  835 
Symphyla,  23 
Symphypleona,  229 
Symphyta,  891 
Synanthedon  exiliosa,  636;  wings  of,  635; 

5.  opalescens,  636;  S.  pictipes,  636 
Synchloe  olympia,  747,  748 
Synchlora  cerata,  665 
Synergus  erinacei,  924 
Syntomaspis  druparum,  931 
Syntomidse,  706 
Syrphidag,  786,  790,  850 
Syrphus,  851 
Syrphus-fiies,  850 
Syslelloderus  biceps,  383 

Tabanidae,  786,  788,  829 

Tabamis,    830;   atratus,    830;    wing   of, 

66,  829 
Tachardia  laica,  440 
Tachina-flies,  871 
Tachinidae,  787,  793,  871 
Tachininaj,  871 
Tachyst>hex  terminatus,  964;  wings  of, 

964 
Tceniopteryx,  326;  T.  pacifica,  326 
Tafalisca  lurida,  245 
Tangle-veined  flies,  836 
Tanyderida?,  785,  787,  796 
Tanypeza,  858 
Tanypezidae,  786,  791,  858 
Tapestry-moth,  612 
Tapetum,  144 
Tarachidia  candefacta,  689 
Tarantula  hawks,  934 
Tardigrada,  11,  12 
Tarsal  claws,  58 
Tarsus,  57 

Taste  and  smell,  organs  of,  132 
Tegeticula,  599;  T.  alba,  599,  600 
Tegmina,  59,  230 
Tegula,  54 
Telamona,  405 

Telea  polyphemiis,  722;  larva,  723 
Telson,  75 
Tenaculum,  228 

Tenagogonus,  371;  T.  gillettei,  371 
Tenebrio  molitor,  466,  513 
Tenebrionidae,  474,  513 
Tenebroides  mauritanicus,  508 
Tenent  hairs,  58,  100,  101 
Tent-caterpillars,  729;  apple-tree,  729, 

730;    California,    731;    forest,    730; 

Great  Basin,  731 


Tenthredinidae,  890,  893,  900 

Tentorium,  96 

Terebrantia,  344 

Tergites,  35 

Tergum,  34 

Termatophylidae,  356,  359,  377 

Termes  gilvus,  276 

Terminal  band,  575 

Terminal  filament,  158 

Termite,  queen,  276 

Termites,  158,  194,  273 

Termuoxinia,  156 

Termopsis  angusticollis ,  wings  of,  274 

Testes,  160 

Testicular  foUicle,  structure  of  a,  161 

Tetanoceridae,  856 

Tetracha,  478 

Tetraneura  colophoides,  424;  T.  gra- 
minis,  424 

Tetraopes,  529;  T.  letraophthalmus,  529 

Tettigoniidas,  234 

Thalessa  lunator,  169,  918 

Thanaos,  737;  T.  martialis,  735,  737 

Thaumalea  americana,  828;  wing  of, 
828 

Thaumaleidae,  786,  788,  828 

Thecabius  populicaiilis,  424 

Thecla  calanus,  769;  T.  m-album,  770 

Thecodiplosis  mosellana,  819 

Thereva,  wing  of,  839 

Therevidae,  789,  786,  839 

Thermobia  domestica,  224 

Thick-headed  flies,  853 

Thompson,  C.  B.,  278 

Thorax,  48;  diagram  of,  50,  51 

Thorybes  daunus,  737;  T.  pylades,  737 

Thre'ad-waisted  wasps,  966 

Three-lined  lema,  530 

Thripidae,  344 

Thrips,  341;  banded,  344;  bean,  345; 
grass,  345;  greenhouse,  345;  imma- 
ture forms  of  citrus-,  343;  onion,  345; 
orange,  345;  pear,  345;  strawberry, 
345;  tabaci,  345;  tobacco,  345 

Throat-bot,  866 

Throscidae,  472,  502 

Thyatiridae,  583,  586,  709 

Thynnidae,  891,  910,  914,  935 

ThyreocorinEe,  392 

Thvreocoris  ater,  392;  T.  pulicariiis,  392 

Th'yrididas,  583,  586,  587,  653 

Thyridopteryx  ephemeraeformis,  614; 
wings  of,  61,  613 

Thyris  lugubrius,  654;  T.  maculata,  654; 
wings  of,  654;  T.  mournful,  654;  T. 
spotted,  654 

Thysanoptera,  178,  212,  214,  215,  218, 

341 
Thysanura,  214,  217,  220 
Tibia,  57 
Tibican  linnei,  401 


1042 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Tibicina  septendecim,  402 

Tiger-beetles,  476 

Tiger-moths,     699,     700;     tiger-moth, 

hickorv',  704 
Tigrioides  bicolor,  705 
Tillyard,  R.'J.,  300,  593 
Timber-beetles,  544 
Tinagma    obscurofasciella,    624;    wings 

of,  624 
Tinea,    612;    T.   parasitella,   wings   of, 

612;  T.  pellionella,  612 
Tineidae,  582,  589,  590,  611 
Tineola  biselliella,  612 
Tingidffi,  357 
Tinginae,  384 

Tiphia,  936;  T.  inornata,  936 
Tiphiidas,  891,  910,  911,  914,  936 
Tiphiinae,  936 
Tipiila,  799;  7".  abdominalis,  larva  of, 

2;  wing  of,  799 
Tipulidse,  785,  787,  793,  798 
Tipuloidea,  78.^,  795 
Tischeria,  615;  T.  malifoliella,  615;  T. 

marginea,  wings  of,  615 
Tischeriidse,  582,  591,  615 
Tlascala  redvclella,  wings  of,  645 
Tmetocera  ocellana,  641 
Tobacco-worm,  659 
Tolype  lands,  731,  T.  velleda,  731 
Tomato-worm,  658 
Tool -using  wasps,  967 
Tormae,  781 
Tortoise-beetles,  534;  scales,  451 ;  -shell, 

American,  755 
Tortricidas,  582,  590,  639,  642 
Tortricids,  638;  typical  642 
Tortricoidea,  582,  638 
Tortrix,  638 
Toryminas,  931 
Touch,  organs  of,  131 
.Tower,  W.  L.,99,  172,  354,  573 
Townsend,  Miss  A.  B.,  165 
Townsend,  C.  H.,  872 
Toxicognaths,  21 
Tracheae,    113,    116;   the   structure   of 

the,  117 
Tracheal  gills,  119;  the  development  of, 

182 
Tracheation    of    wing    of    imago    of 

Calosoma,  466 
Tracheation    of    wing    of    imago    of 

Dytiscus  verticalis,  466 
Tracheoles,  113,  118 
Trachusa  lateralis,  983 
Tramea,  317 

Transverse,   anterior  band,   575;   con- 
junctivae, 34;  cord,  326;  impression, 

781 ;  posterior  band,  575 
Treat,  Mrs.  938 

Tree-hoppers,  404;  buffalo,  404;  two- 
horned,  405;  two-marked,  405 


Tremex  columba,  169,  896,  897,  918 

Trepobates,  372;  T.  pictus,  i-j2 

Tricenodes,  565,  567;  case  of,  566 

Triangle,  319 

Triatoma  sanguisuga,  382 

Trichocera,  798 

Trichodectes  equi,  336;  T.  latus,  336;  T. 

scalaris,  336;  T.  spherocephalus,  336 
Trichodectidae,  337 
Trichodes  nuttali,  493 
Trichodezia  albovittata,  667 
Trichogens,  30 
Trichophaga  lapetiella,  612 
Trichopore,  32,  130 
Trichootera,  213,  214,  216,  555 
Trichopterous  Larvae,  table  of,  560 
Trichopterygidae,  471,  490 
Tridactylin'ae,  243,  251 
Tridactylus,  252;  T.  apicalis,  252 
Trigonahdae,  890,  907,  918 
Trigonidiinag,  243 
Triphelps  insidiosus,  378 
Tritocerebrum,  47,  124 
Tritoxa  flexa,  856 
Triungulin,  495 
Triungulinid,  548 
Triungulins,  548 
Trochanter,  57 

Trochantin,  53 ;  of  the  mandible,  40 
Trades  divinatoriiis,  33 1 ,  333 
Trogidae,  475,  522 
Tropcea  luna,  723,  724 
Trophallaxis,  956 
Tropisternus,  485;  T.  calif ornicus,  485; 

T.  glabra,  48=; 
Trox,  522 

Trumpet-leaf  miner  of  apple,  615 
Truxalinae,  253,  259 
Trj^petidae,  786,  791,  856 
Trypoxylon,  965;  T.  albitarsis,  966;  T. 

albopilosum,  965;   T.  frigidum,  965; 

T.  rubrocinctum,  965;  nest  of,  965 
Trypoxyloninae,  965 
Trypoxylonini,  963 
Tsetse-fly,  873 
Tubulifera,  345 
Tumble-bugs,  516 
Tunga  penetrans,  883 
Turkey-gnat,  824 
Tiu-ner,  938 
Tussock-moth,    679;    California,    681; 

old,  681;  well-marked,  681 
Twisted-winged  insects,  546 
Two-spotted  oberea,  529 
Tylus,  353 
Tympana,  146,  577 
Typhoid-fly,  872 

Udamoselis,  wings  of,  437 
Ululodes  hyalina,  305;  larva  of,   306; 
wings  of,  305 


INDEX 


1043 


Underwings,  687 
Ungues,  58 
Unguiculus,  227 
Unguis,  227 
Urodus  pannda,  632 
Utetheisa,  700;  U.  bella,  700 

Vagina,  159 

Valentinia  glandulella,  628 

Valvulas,  232 

Van  der  Weele,  284,  285,  306 

Van  Duzee,  E.  P.,  362,  844 

Van  Dyke,  E.  C,  498 

Vanessa  atalanta,  754;  V.  cardui,  755; 
V.  huntera,  755;  V.  virgmiensis,  754 

Vanhornia  eucnemidarum,  921 

Vanhorniidae,  890,  907,  921 

Van  Rees,  202 

Vas  deferens,  156,  162 

Vasiform  orifice,  438 

Vedalia  cardinalis,  512 

Velia,  370 

Veliidae,  356,  357,  369 

Velvet-ants,  936 

Venomous  setae  and  spines,  100 

Ventral  diaphragm,  163;  heart,  163; 
sacs,  222;  sympathetic  nervous  sys- 
tem, 127;  tube,  227 

Ventriculus,  iii 

Verhoeff,  49 

Vermiform,  185 

Verruca,  578 

Verson,  114,  199 

Vertex,  39,  781 

Vertical  triangle,  781 

Vespa,  958;  V.  arctica,  950;  V.  austraca, 
960;  V.  consobrina,  960;  V.  crabro, 
960;  V.  diabolica,  960;  wings  of,  949; 
V.  macidata,  960;  nest  of,  958,  959; 
V.  rufa,  960 

Vespidse,  891,  910,  948 

Vespinae,  907,  949,  958 

Vespoidea,  933,  890 

Vespoid-wasp,  head  and  thorax  of,  960 

Vespoid-wasps,  933 

Vespida,  960 

Viallanes,  47 

Vibrissae,  782 

Vibrissal  angles,  781;  ridges,  781 

Vice-reine,  760 

Viceroy,  the,  759 

Viereck,  H.  L.,  929 

Violet  tip,  757 

Visual  cell,  structure  of  a,  137 

Vitellarium,  158 

Vitreous  layer,  138 

Viviparit3%  192,  193 

Viviparous  insects,  191;  adult  agamic 
females,  192 

Vogel,  R.,  155 

Volucella,  851 


Wagner,  Nicholas,  192,  816 

Walker,  E.  M.,  233,  252,  268 

Walking-sticks,  260 

Wall-bee,  984;  nests  of,  984 

Wanderer,  the,  772 

Warble-flics,  866 

Wasps,  social,  955,  typical,  948 

Water-beetles,  the  crawling,  481 

Water-boatmen,  360,  361 

Water-bues,  giant,  365 

Water  measurers,  373 

Water-pennv,  504 

Water-scavenger  beetles,  485 

Water-scorpions,  364 

Water-striders,  370;  broad-shouldered, 
369 

Water-tigers,  483 

Wax,  990 

Wax-glands,  102;  outlets  of,  445 

Web  worms,  648;  burrowing,  6ii;  cab- 
bage, 648;  garden,  648 

Wedge-shaped  leaf-beetles,  533 

Weevil,  black  vine-,  539;  strawberry-, 
540 

Weevils,  leaf-rolling,  538 

Weisman,  A.,  202,  203 

Wheat-midge,  819 

Wheat-sawfly-borer,  899 

Wheat  straw- worm,  931 

Wheeler,  W.  M.,  280,   524,  937,  938, 

944.  945 

Whirligig-beetles,  484 

White-ants,  273 

White,  checkered,  747 

White  flies.  437 

White  fly,  citrus,  440;  greenhouse,  439; 

maple,  440;  strawberry,  440 
White,  gray-veined,  747 
White-grubs,  518 
White  marked  tussock-moth,  680 
White  Mountain  butterfly,  763 
White-striped  black,  667 
Whites,  the,  745 
White-tipped  moth,  676 
Williams,  F.  X.,  950,  952,  964 
Williston,  S.  W.,  852 
Window-flies,  839 
Window-winged  moths,  653 
Wings  of  the  heart,  121,  162 
Wings,   58;  the  development  of,   182, 

195;  specihzation  of,  212 
Wing-veins,  reduction  of  the  number 

of,  65;  the  chief  branches  of  the,  64; 

the  increase  of  the  number  of,  68  ; 

the  principal,  64 
Winnerlzia  calciequina,  814 
Wire-worms,  500 
Witch-hazel  cone-gall,  425 
Witch-hazel-gall,  the  spiny,  426 
Wohlfahrtia  vigil,  871 
Wollaston,  88 


1044 


AN  INTRODUCTION  TO  ENTOMOLOGY 


Wood-nymph,    beautiful,    693;    pearl, 

693 

Workers,  988 
Wyeomyia  smithii,  810 

Xenopsylla  cheopis,  882 
Xenos  vesparum,  549 
Xestobium  rufovillosum,  515 
Xiphidium,  238 
Xiphosura,  8 

Xiphydria  maculata,  wings  of,  898 
Xiphydriidae,  890,  893,  897 
Xyelidae,  890,  893,  894 
Xylocelia  {Diodontus),  968 
Xylocopa  virginica,  955,  981 
Xylomyia,  832;  X.  pallipes,  832 
Xylomyiidffi,  786,  788,  832  -.. 
Xylophagidae,  786,  789,  833  . 
Xylophagus,  833 ;  wing  of,  833 

Yellow-bear,  703 
Yellow-fever  mosquito,  809 
Yellow-jackets,  960,  958 
Yellows,  the,  748 


Yellow,  sleepy,  749 
Yponomeuta,  632;  Y.  padella,  633 
Yponomeutidae,   580,    582,    590,    591, 

631 

Yucca-borer,  734 
Yucca-moths,  599;  bogus,  600 

Zale  lunata,  689 

Zebra,  the,  764 

Zebra-caterpillar,  694,  695 

Zenodochium  coccivorella,  629 

Zethinae,  949,  951 

Zethus,  951;   Z.   cyanopterus,   952;  Z. 

lobulatus,  952;  Z.  roniandinus,  952; 

Z.  slossoncB,  951;  Z.  spinipes,  951 
Zerene  casonia,  749 
Zeuzera,  pyrina,  603 
Zeuzerinse,  603 
Zophodia  grossularia,  652 
Zoraptera,  214,  216,  218,  270 
ZorotypidEe,  270 
Zorotypus,  270;  Z.   hubbardi,  271;  Z. 

snyderi,  271 
Zygoptera,  321 


